Public health 4

1. Role of nutrition in prevention of cardiovascular diseases

  • Most important behavioural (modifiable) risk factors for heart disease and stroke are unhealthy diet, physical inactivity, tobacco use and harmful use of alcohol.
  • Behavioural risk factors are responsible for about 80% of coronary heart disease and cerebrovascular heart disease
  • 2018 study in British Medical Journal (BMJ): Healthy dietary patterns can decrease the effect of genetic factors that would otherwise predispose to obesity. Also, improved diet quality had a more significant effect on people with high genetic risk for obesity.
  • 2012 Cochrane review: Reducing saturated fat in diet decreases risk for cardiovascular disease by 14%
  • 2014 study in BMJ: Replacing saturated fat in diet with polyunsaturated fat did not decrease risk for cardiovascular disease (later studies contradict this, but those studies are not mentioned in the lecture)
  • Oslo diet heart study: Diet low in saturated fat, cholesterol and high in polyunsaturated fat -> reduced serum cholesterol, reduced cardiovascular disease
  • Lyon diet heart study: Diet low in saturated fat, high in unsaturated fat -> reduced cardiovascular mortality
  • Stanford coronary risk intervention project (SCRIP): Low fat, saturated fat, cholesterol diet + exercise -> decreased dyslipidaemia, decreased cardiovascular disease

Cardiometabolic risk

  • The risk for developing diabetes, heart disease or stroke (basically metabolic syndrome)
  • Risk factors:
    • Hypertension
    • Inflammation
    • Age
    • Race
    • Gender
    • Family history
    • Dyslipidaemia
    • Overweight
    • Insulin resistance
    • Smoking
    • Physical inactivity
    • Unhealthy eating

Benefits of fish oils:

  • Fish oils contain omega-3 (n-3, ω-3) polyunsaturated fatty acids (PUFAs)
  • DART trial: Men with cardiovascular disease who increased intake of fish or used fish oil tablets had reduced cardiovascular mortality
  • GISSI trial: Men and women with cardiovascular disease who took 1 g omega-3 daily decreased the number of cardiovascular events

Other nutrients

  • Nurses health study: Increased nut intake -> decreased risk for cardiovascular events
  • PREDIMED study: Increased nut intake -> decreased cardiovascular mortality
  • Zhaoli meta-analysis: Increased soy intake -> decreased cardiovascular risk
  • Phytosterol-supplemented foods intake -> decreased LDL-cholesterol
  • Increased intake of garlic -> decreased total cholesterol

Recent changes in the view of associated between diet and cardiovascular disease

  • Dietary cholesterol is not the major determinant of blood cholesterol
  • Individual nutrients may not be responsible for risk, but rather complex foods
    • Example: Increased consumption of fish is better than omega-3 fat supplementation

Vitamin D

  • High serum vitamin D concentration -> decreased cardiovascular events
  • Hypovitaminosis D leads to:
    • Decreased anti-inflammatory cytokines
    • Increased pro-inflammatory cytokines
    • Increased inflammation -> increased atherosclerosis
    • Increased angiotensin II activity -> increased myocardial remodelling
    • Increased insulin resistance

Therapeutic lifestyle changes (TLC)

Nutrients Recommended intake
Saturated fat < 7% of total calories
Polyunsaturated fat < 10% of total calories
Monounsaturated fat < 20% of total calories
Total fat 25 – 35% of total calories
Carbohydrate 50 – 60% of total calories
Fibre 20 – 30g daily
Protein 15% of total calories
Cholesterol < 200mg/day
Total calories Balanced so that body weight is stable or reached desirable levels

TLC can reduce LDL levels by 20 – 30%

Summary:

  • Reducing LDL levels is beneficial for preventing cardiovascular disease or events
  • Decreased saturated fat intake
  • Decreased total fat intake
  • Decreased trans fat intake
  • Increased fibre intake
  • Sufficient vitamin D intake
  • Increased fish consumption
  • Decreased weight
  • Increased intake of plant sterols
  • Decreased dietary cholesterol
  • Increased physical activtiy
  • See also Mediterranean diet, DASH diet

2. Role of nutrition in prevention of cancers

  • 35% of cancer cases are related to nutrition – nutrition is the most important behavioural risk factor for cancer – more than smoking, infections
  • Underfeeding -> decreased risk of cancer
  • Overfeeding (obesity) -> increased risk of cancer

β-carotene supplementation and cancer:

  • ATBC – huge study in Finland -> daily β-carotene supplementation increased risk for lung cancer in smokers
  • CARET – huge study in USA -> daily β-carotene supplementation increased risk for lung cancer in smokers

Tea and cancer

  • Green tea consumption decreased risk of oesophageal cancer
  • Study: People who drank hotter tea in Iran -> increased risk for oesophageal cancer

Energy intake and cancer

  • Possible mechanisms of increased cancer risk
    • Increased insulin and IGF-1
      • These hormones stimulate cell proliferation and inhibit apoptosis
    • Increased oestrogen
    • Increased leptin
    • Increased inflammatory cytokines
    • Increased oxidative stress
    • Decreased DNA repair capacity

Fat intake and cancer

  • Possible mechanisms of increased cancer risk
    • Associated with high energy intake (see above)
    • Presence of lipid soluble carcinogens
    • Peroxidation of lipids
    • Membrane composition of cells can be influenced by diet intake
    • Prostaglandin synthesis
      • Fatty acids are precursors to prostaglandins and prostacyclins
      • Certain prostaglandins are pro-metastatic
    • Fats can have direct cytotoxic effect
    • Diacylglycerol is an intracellular second messenger -> activates protein kinase C
  • Flax seed oil -> high in omega-3 fats, low in saturated fats

Other macronutrients and cancer

  • Proteins probably don’t influence carcinogenesis
  • Carbohydrates probably don’t directly influence carcinogenesis, but their increased intake means increased energy intake

Meat intake and cancer

  • Saturated fat in red meat. Less in poultry
  • Increased meat consumption -> increased colorectal carcinoma
    • Increased meat consumption -> increased presence of N-nitroso compounds in stool
  • N-nitroso compounds in cured and processed meats
  • Heterocyclic amines in meat prepared at high temperature (especially grilling, frying)

Secondary bile acids and cancer

  • Bile acids produced by the liver are primary. When these enter the intestines, bacteria will convert them into secondary bile acids
  • Secondary bile acids are a risk for colorectal cancer
  • Increased consumption of red meat and saturated fat have increased levels of secondary bile acids in the intestine, perhaps these foods change the microbiome of the intestines to bacteria that produce more secondary bile acids

Fibre intake and cancer

  • Decreased fibre intake -> increased colorectal carcinoma
  • Suggested intake: 30g/day
  • Types of fibre
    • Water soluble (like pectin)
    • Water insoluble (like cellulose, hemicellulose)
  • Cancer preventative effects of fibre
    • Takes more time to chew -> increased sense of fullness -> decreased energy intake
    • Fibre binds carcinogenic substances and secondary bile acids
    • Fibre increases faecal transit time -> Intestines are less exposed to carcinogens
    • Fibre dilute bowel content
    • Fibre modifies the enteric bacterial flora, decreasing the production of secondary bile acids

Other dietary factors and cancer:

  • Grilled, smoked, cured foods
  • Hot foods and drinks
  • Decreased vitamin D intake
  • Inadequate fluid intake
  • Food additives, preservatives, artificial sweeteners
    • Nitrites
    • Nitrates

Phytochemicals and cancer

  • Phytochemicals are chemical compounds of plant origin
  • Examples
    • β-carotene
    • Lycopene
    • Lutein
    • Glucosinolates
    • Flavonoids
    • Quercetin
  • Mechanisms of cancer prevention
    • Antioxidant effect
    • Inhibit phase I biotransformation in liver
    • Induce phase II biotransformation in liver
    • Induction/inhibition of COX, LOX
    • Anti-inflammatory effect
    • Stimulate immune system
    • Induce apoptosis
    • Regulate intracellular signalling
    • Arrest cells in the cell cycle
    • Competitively inhibit oestrogen
    • Inhibit DNA synthesis
    • Inhibit angiogenesis
    • Changes enteric bacterial flora
    • Decrease expression of oncogenes
    • Increase DNA repair
    • Inhibit NF-κB

Alcohol consumption and cancer

  • Pro: red wine contains phytochemicals (resveratrol)
  • Cons:
    • Irritation
    • Fat soluble carcinogens in alcohol
    • Alcohol itself is carcinogen
    • Alcohol induces biotransformation enzymes
    • Acetaldehyde is carcinogen
  • Net effect of alcohol (even red wine) consumption: increased risk for cancer!

Summary (recommendations by American institute for cancer research)

  • Be as lean as possible without being underweight
  • Be physically active for at least 30 minutes every day
  • Avoid sugary drinks
  • Limit consumption of energy-dense foods
    • Especially processed foods with much added sugar or fat
  • Eat a variety of vegetables, fruits, whole grains, legumes
  • Limit consumption of red meats and avoid processed meat
  • Alcohol shouldn’t be consumed, or at least limited to 2 units (men) or 1 unit (women) per day
  • Limit consumption of salty foods and foods processed with salt
  • Don’t use supplements to protect against cancer
  • Cancer survivors should follow recommendations for cancer prevention
  • Mothers should exclusively breast feed for 6 months, and only after that can they add other liquids and foods

3. Principles of healthy diet

Component of diet

  • Nutrients
    • Macronutrients
      • Lipids
      • Proteins
      • Carbohydrates
    • Micronutrients
      • Vitamins
      • Minerals
  • Dietary fibre
  • Bioactive components
    • Alkaloids
    • Flavonoids
    • Carotenoids
  • Food additives
    • Spices
    • Preservatives
    • Colouring
    • Sweeteners
    • Thickeners
    • Stabilizing agents

Macronutrients

  • Proteins should be 12 – 15% of the total calorie intake
  • Carbohydrates should be 55 – 60% of the total calorie intake
  • Fat should be 25 – 30% of the total calorie intake

Calories

  • Males 19-30 years – 2500 kcal/day
  • Females 19-30 years – 1900 kcal/day
  • Requirements increased with increased level of activity

Lipids

  • 25 – 30% of total calorie intake
  • Sources of lipids
    • Monounsaturated fats (oleic acid)
      • Olive oil
      • Almonds
      • Butter
      • Avocado
    • Omega-3 (α-linoleic acid, DHA, EPA)
      • Flax seeds
      • Linseed oil
      • Walnuts
      • Olive oil
      • Fish oil
    • Omega-6 (linoleic acid)
      • Grapeseed oil
      • Corn oil
      • Walnuts
      • Soybean oil
      • Margarine
    • Saturated fat (palmitic acid)
      • Butter
      • Meat fat
      • Palm oil
      • Coconut oil
    • Trans fatty acids
      • Industrially produced
      • Naturally in beef, lamb, diary
  • Lipid-free diet -> dermatitis, coagulopathy, avitaminosis of lipid soluble vitamins
  • Excess lipids in diet -> obesity, atherosclerosis, hypertension
  • Essential lipids are necessary in the diet
    • Linoleic acid – an omega-6 acid – precursor for arachidonic acid
    • α-linoleic acid – an omega-3 acid – precursor for EPA and DHA
    • Arachidonic acid is pro-inflammatory
    • EPA, DHA are anti-inflammatory
    • Omega-6:Omega-3 ratio is important. Optimal is 4:1. Ratio in western diet: 15:1 (too much omega-6)
  • Saturated fatty acid intake -> increased serum cholesterol
  • Monounsaturated fatty acid intake -> no change in serum cholesterol
  • Trans fats intake -> increased risk for cardiovascular disease, serum cholesterol and cancer

Dietary cholesterol

  • Found in egg yolk, milk fat, animal fat, meat
  • Intake increases serum cholesterol concentration (only according to POTE. This is not the consensus anymore)

Proteins

  • 12 – 15 % of total calorie intake
  • Increased need in:
    • Childhood
    • Pregnancy, lactation
    • Tissue regeneration (infection, burns, postoperative)
    • Exercise
  • Essential amino acids are necessary in the diet
    • Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine
    • “Complete proteins” – proteins containing essential amino acids in sufficient amounts
      • Proteins of animal origin
    • “Incomplete proteins” – proteins not containing all essential amino acids, or containing all essential AAs but not in sufficient amount
      • Proteins of plant origin
  • Biological value of protein = how much of ingested protein is incorporated into proteins in the body
    • Determined by which essential amino acid is present in the lowest quantity
Food Biological value
Breast milk 100%
Egg 100%
Milk 90%
Beef 90%
Chicken 80%
Potatoes 70%
Rice 60%

Carbohydrates

  • 55 – 60% of total calorie intake
  • Low carb intake -> gluconeogenesis, lipid metabolism
  • High carb intake -> obesity, diabetes mellitus type 2, caries
    • Carbs taste good (high palatability) -> excessive calorie intake
    • Empty calories – foods with many carbs usually don’t contain many nutrients
  • Types
    • Monosaccharides
      • Glucose
      • Fructose
      • Galactose
    • Disaccharides
      • Sucrose
      • Lactose
      • Maltose
    • Oligosaccharides
      • Maltotriose
      • Fructotriose
    • Polysaccharides
      • Starch
      • Glycogen
      • Cellulose
  • Glycaemic index (GI) = the increase in blood glucose in the 2 hours after ingestion, compared to glucose
    • Diets high in carbs with high GI -> diabetes mellitus, dyslipidaemia
      • Causes glucose spike and insulin spike after eating
      • Dates
      • Instant rice
      • Corn flakes
      • Whole wheat bread
    • Diets high in carbs with low GI -> decreased cholesterol and triglyceride
      • Peanuts
      • Soymilk
      • Apple, pear
      • Long-grain rice

Dietary fibres

  • 25 – 35 g/day
  • = Large and complex mixtures of polysaccharides that aren’t digested and absorbed
  • Types
    • Cellulose
    • Gums
  • Effect on health
    • Increases satiety
    • Slow down glucose absorption
    • Increase stool mass

4. Epidemiology of malnutrition and nutritional deficiencies

  • Micronutrient deficiency is widespread in developing countries, affecting 2 billion people worldwide
  • Deficiency affects the most vulnerable groups most commonly
  • Most common deficiencies
    • Iron
    • Vitamin A
    • Iodine
  • Malnutrition = inadequate or excess intake of a nutrient, leading to infections and disorders
  • Underweight malnutrition – large problem in the developing world
    • Affects mainly children and women
    • Malnutrition increases risk for children to die from malaria, meningitis, pneumonia, gastroenteritis

Epidemiology of malnutrition

  • Epidemiology is the study of the distribution and determinants of diseases and other health outcomes in human populations
  • Types of studies in nutritional epidemiology
    • Descriptive studies – an observational study that describes the characteristics of a population
      • Describes the nutritional state of a population
      • National surveys are often used
    • Ecological studies – an observational study that measures the incidence of a disease in a population
      • Can compare how the incidence of a disease in a population changes over time
      • Can study whether certain populations have higher incidence of disease (like certain ethnicities, religions)
      • Can study immigrants to assess the contributions of genetic and environmental factors
    • Case-control studies – a retrospective observational study that compares people with a disease and without a disease and looks for possible risk factors
    • Cohort studies – a prospective study that compares two groups, one group with a risk factor and another group without and compares their incidence of disease
    • Intervention trials – a double blind experimental study where random subjects are assigned into two groups. One group receives a treatment, the other not. Health outcomes are compared.

Kwashiorkor

  • Severe protein malnutrition but without total calorie deficiency
  • Symptoms
    • Oedema
    • Pigmentation changes of skin and hair
    • Impaired growth and development
    • Ascites
    • Liver disease

Marasmus

  • Severe protein and calorie malnutrition
  • Symptoms
    • Growth retardation
    • Wasting of subcutaneous fat, muscle

Cachexia

  • = a complex metabolic syndrome characterised by loss of muscle with or without loss of fat, due to an underlying illness
  • Frequently seen in COPD, chronic kidney disease, cancer
  • Causes weight loss
  • Anorexia, inflammation, insulin resistance and protein catabolism as associated with cachexia
  • Not the same as starvation!
  • Increases morbidity

Iron deficiency

  • Most common nutritional disorder – 2 billion people worldwide
  • Causes anaemia
  • Very prevalent in pregnant women and preschool children in developing countries
  • Aggravated by parasite infection, malaria, HIV, TB
  • Health effects
    • Fatigue
    • Poor pregnancy outcome
    • Impaired physical and cognitive development
    • Increased morbidity in children
  • Prevention
    • Increase iron intake
    • Control infection
    • Improve nutritional status

Vitamin A deficiency

  • Major cause of blindness in Africa, south-east Asia
  • Affects mostly children and pregnant women
  • Prevention
    • Supplementation
    • Increased breastfeeding
    • Promotion of vitamin A-rich diet
    • Fortification of food
      • Golden rice – a type of rice fortified with vitamin A

Intervention of malnutrition and nutritional deficiencies

  • Determine etiology of malnutrition
    • Parasite
    • Infection
    • Increased demand
    • Poor diet
  • Effective measures
    • Supplementation
      • When deficiency is severe
      • Can be used as preventative measure in high-risk populations
      • Cost-effective
    • Fortification of foods (adding nutrients to foods)
      • Not appropriate in severe deficiency
      • Requires participation of the food industry
    • Diversify the diet
      • Introduce nutrient-rich foods in the diet
      • Change dietary habits
    • Change agricultural habits

5. Dietary guidelines

General dietary guidelines (according to the 2015-2020 American dietary guidelines)

  • Increased intake of whole grain, vegetables and fruits
    • Decreases weight gain
  • Reduced intake of sugar-sweetened beverages
    • These are a large source of calories while containing few essential nutrients
  • Increased intake of 100% fruit juice
  • Decrease alcohol intake
    • Alcohol intake is associated with weight gain, cancer and liver disease
  • Decrease total number of calories consumed
  • Monitor food intake
    • By monitoring intake of the various nutrients, individuals become more aware of what and how much they eat and drink
  • Eat more meals at home rather than eating out
  • Prepare and serve smaller portions
    • People eat and drink less when the portions are smaller
  • Eat a nutrient dense breakfast
  • Limit screen time
    • Screen time is associated with overweight
  • Reduce sodium intake (< 2300 mg/day)
  • Reduce cholesterol intake
    • Dietary cholesterol intake alone is no longer believed to increase serum cholesterol, however foods high in cholesterol are often also high in saturated fats
  • Reduce daily trans fat and saturated fat intake
    • Saturated fats should be replaced by unsaturated fats, preferably polyunsaturated fats
  • Increase intake of vegetables of different colours, especially dark green

Specific population groups

  • Pregnant women
    • Should consume more folic acid (400 µg daily)
    • Should consume more iron
    • Limit intake of tuna, shark and swordfish (due to methyl mercury content)
  • Older individuals
    • Should consume more B12

6. Special nutritional considerations: vegetarianism

Vegetarian diet

  • No meat, poultry, fish or other seafood is consumed
  • Animal products like milk and eggs can be consumed
  • Not all plant products contain all essential nutrients. Thus, a vegetarian diet must be well-planned to meet the daily recommended intake of all nutrients
  • The vegetarian diet contains more than enough of
    • Vitamins B, E, C
    • Minerals
    • Dietary fibre
    • Unsaturated fatty acids
    • Carbohydrates
    • Plant sterols
  • The vegetarian diet often brings other health benefits with it
    • Vegetarians are usually generally health conscious
      • Have decreased consumption of tobacco, alcohol, drugs
      • Live a physically active life
    • Have decreased intake of sugar
    • Have decreased intake of calories
    • Consume more potassium than sodium -> decreased risk for hypertension

Special nutritional considerations

  • Many plant foods are poor sources of protein or are incomplete proteins
    • Thus, multiple plant sources of protein should be consumed to ensure all essential amino acids are consumed
    • Protein deficiency is usually not a problem, though
    • Sources of protein for vegetarians
      • Soy
      • Legumes
      • Grains
  • Vegetarians tend to have smaller iron stores than meat eaters
    • Plant foods contain iron in ion form and not in heme form (which is found in meat)
    • Sources for vegetarians
      • Eggs
      • Pulses (beans, chickpeas)
      • Dark green vegetables
  • B12-containing foods should be consumed regularly
    • Sources for vegetarians
      • Milk
      • Cheese
      • Eggs
  • Omega-3 fatty acids are mostly found in oily fish
    • Sources for vegetarians
      • Flaxseed oil
      • Rapeseed oil
      • Soya oil
      • Walnuts
      • Fortified eggs

Well-planned vegetarian diet contains

  • Dark green vegetables
  • Red and orange vegetables
  • Legumes (beans and peas)
  • Starchy vegetables (potatoes)
  • Whole grains
  • Fruits
  • Eggs
  • Soy products
  • Nuts
  • Seeds

7. Special nutritional considerations: Mediterranean diet, DASH- (Dietary Approaches to

Stop Hypertension) diet

Mediterranean diet

  • Based of food patterns typical of Greece, Crete and southern Italy
  • Not only a diet, rather a lifestyle
    • Contains regular physical activity and enjoying meals with families and friends
  • Lower rates of multiple conditions in the region, which can be attributed to the diet
    • Obesity
    • Diabetes mellitus type 2
    • Cancer
  • Characterised by
    • Abundant plant foods (fruits, vegetables, breads, cereals, potatoes, beans, nuts, seeds)
    • Olive oil as the principle source of fat
    • Dairy products (mainly cheese and yoghurt)
    • Low-moderate consumption of fish and poultry
    • Low consumption of meat
    • Low consumption of wine, often with meals
  • The diet is low in saturated fat (< 7% of calories)
  • Total fat 30% of calories

How to change to a Mediterranean diet

  • Consume whole grains rather than non-whole grains
  • Consume more nuts
  • Switch out butter and margarine with olive oil
  • Use herbs and spices rather than salt and fat
  • Eat more fish
  • Limit consumption of red meat to just a few times a month
  • Consume more low-fat diary and less high-fat diary

DASH – Dietary Approaches to Stop Hypertension

  • Been proven to reduce blood pressure, LDL cholesterol and therefore cardiovascular risk
  • Characterised by
    • Eating more vegetables, fruits and whole grains
    • Including fat-free or low-fat dairy products
    • Eating more fish, poultry, nuts, beans and vegetable oils
    • Limiting foods high in saturated fat, like fatty meats, full-fat dairy products and oils like coconut and palm oil
    • Limiting sugar-sweetened beverages and sweets
    • Limiting red meat
    • Limiting sodium
    • Limiting saturated and trans fats

8. Special nutritional considerations: trendy diets

Palaeolithic diet (paleo diet)

  • Tries to replicate the diet of hunters and gatherers during the stone age
    • Assumes that people in the stone age didn’t consume starchy carbohydrates like potatoes and grains
    • (Recent studies have shown that people in the stone age did actually consume starchy carbohydrates)
  • Diet is characterised by eating
    • Fish
    • Grass-fed pasture-raised meats
    • Eggs
    • Vegetables
    • Fruit
    • Fungi
    • Roots
    • Nuts
  • The following are not consumed
    • Grains
    • Legumes
    • Dairy products
    • Potatoes
    • Refined salt
    • Refined sugar
    • Processed oils
  • The diet is generally
    • Low in calories
    • Rich in micronutrients
    • Rich in fruits and vegetables
    • Low in salt
  • Special nutritional considerations
    • Calcium
      • Lack of diary can lead to calcium deficiency and is commonly seen
    • Iodine
      • Lack of table salt and dairy products can lead to iodine deficiency

Atkins diet

  • Characterised by:
    • High protein
    • Very high fat
    • Very low carbohydrate
    • Unrestricted calories
  • Forbidden foods
    • Grains
    • Vegetables
    • Fruit
  • Promoted foods
    • Meat
    • Cheese
    • Eggs
    • Fats
  • Disadvantages
    • High saturated fat intake
    • Low fruit and vegetable intake
    • High meat intake

9. Assessment of nutritional status, nutritional screening

Tools in the assessment of nutritional status – anthropometric measurements

  • Advantages of anthropometry
    • High specificity, high sensitivity
    • Many variables are acquired and measured
    • Data can be graded on charts and compared to healthy subjects
  • Disadvantages of anthropometry
    • Difference in measurements depending on the observer
    • Gives limited information on specific nutritional state
  • Body mass index – BMI
    • Defined as the weight (kg) divided by the height squared (m2)
    • High BMI – associated with type 2 diabetes and mortality
    • Classification
      • BMI < 18.5 – underweight
      • BMI 18.5 – 25 – normal range
      • BMI 25 – 30 – overweight (pre-obesity)
      • BMI 30 – 35 – obese (grade 1 obesity)
      • BMI 35 – 40 – severely obese (grade 2 obesity)
      • BMI > 40 – morbidly obese (grade 3 obesity)
    • Proportion of obese vs non-obese people in the western world has increased the last decades
  • Waist circumference
    • Predicts mortality better than any other anthropometric measurement
    • Can be used to assess obesity
    • Measured at the level of the umbilicus, rounded to nearest 0.5 cm
    • Two risk levels exist according to waist circumference
      • Level 1 – males – circumference > 94 cm
      • Level 2 – males – circumference > 102 cm
      • Level 1 – females – circumference > 80 cm
      • Level 2 – females – circumference > 88 cm
  • Hip circumference
    • Measured at the point of greatest circumference around the hips, rounded to nearest 0.5 cm
  • Waist/hip ratio
    • Waist circumference divided by hip circumference
    • Defined as central obesity if ratio > 0.95 in males or > 0.80 in females
  • Skin fold thickness
    • A special tool measured the thickness of a fold of skin
    • Can be used to estimate the body fat percentage
    • Very cheap, not very accurate
    • Common sites to measure skin fold thickness:
      • Triceps
      • Abdomen
      • Frontal thigh
      • Chest
  • Hydrostatic weighing
    • By lowering a person into a pool of water and measuring how much water is displaced, we can find out the volume and therefore the density of the person
    • The density can be used to estimate the body fat percentage
    • Expensive, time-consuming, but very accurate
  • Bioelectrical impedance analysis
    • A machine measures the resistance (impedance) of the body and estimates the body fat percentage
    • Not time-consuming, relatively expensive but not very accurate

Biochemical methods of assessment of nutritional state

  • Advantages of biochemical methods
    • Can detect changes early, perhaps before clinical symptoms
    • Accurate measurements
  • Disadvantages of biochemical methods
    • Time consuming
    • Expensive
    • Requires trained personnel
  • Serum haemoglobin
    • Decreased in anaemia, protein deficiency or mineral deficiency
  • Stool examination
    • Presence of intestinal parasites can be seen
  • Urine dipstick
    • Can detect blood, sugar, albumin
  • Urinary levels of minerals like potassium, sodium, fluoride, chloride, iodide
    • Reflects the recent intake of minerals
  • Level of nutrients in RBCs, adipose tissue, nails, hair
    • Reflects dietary intake over weeks or months
  • Cholesterol esters in RBC membrane
    • Reflect recent lipid intake
  • Transferrin levels
    • Reflect protein intake in last week
  • HbA1c
    • Reflects average blood glucose level last 3 months

Clinical assessment of nutritional state

  • Advantages of clinical assessment
    • Simple, most practical method
    • Non-invasive
  • Disadvantages of clinical assessment
    • Can’t detect early
    • Detected signs aren’t specific to certain dietary component
  • Examination of areas like
    • Hair
      • Abnormal in protein, zinc, vitamin A, vitamin C deficiency
    • Nails
      • Abnormal in iron, protein deficiency
    • Skin
      • Abnormal in iron, folate, vitamin C, vitamin B2, vitamin A, zinc deficiency
    • Angle of mouth
      • Abnormal in iron, vitamin B deficiency
    • Gums
      • Bleeding in vitamin C deficiency
    • Tongue
    • Eyes
    • Thyroid gland
      • Enlarged in iodine deficiency
    • Muscles
    • Bones
      • Abnormal in vitamin D and vitamin C deficiency

Dietary assessment of nutritional state

  • Methods
    • Dietary recall – subject is asked to list foods consumed during a certain period of time, usually in the last 24 hours
      • Quick, simple
      • Depends on short term memory
      • Doesn’t represent usual intake
    • Food diary – subject writes a record of their intake as they eat
      • Needs cooperation of the individual
    • Food frequency questionnaire – subject is given a questionnaire that ask how often they consume a certain food
      • Example: How many times a week do you eat bread?
      • It’s easy to forget or underreport certain food habits
    • Diet histories – subject is simply asked open-ended questions regarding their usual food habits
      • Time consuming
      • It’s easy to forget or underreport certain food habits
    • Observed food consumption
  • Interpreting results
    • Quantitative interpretation – calculating the amount of energy and specific nutrients the patient consumes and compare it to the recommendations
      • Time-consuming
    • Qualitative interpretation – comparing the different food groups the patient eats with the food groups of a recommended diet

10. Epidemiology of obesity

Obesity

  • Epidemiology
    • Worldwide obesity has more than doubled since 1980
    • In 2014 more than 1.9 billion (39%) adults were overweight. 600 million (13%) were obese
    • North Africa, the Middle East and Latin America are almost as overweight as Europe
    • Obesity is growing in the developing world. Here the number of overweight adults has more than tripled since 1980
    • In Europe
      • Romania, Italy least obese
      • Hungary, Great Britain most obese
  • Definition of obesity – according to WHO
    • BMI 25 – 30 – overweight (pre-obese)
    • BMI 30 – 35 – Obese (type I obesity)
    • BMI 35 – 40 – Severely obese (type II obesity)
    • BMI > 40 – Morbidly obese (type III obesity)
    • Other tools in measurement of obesity:
      • Hip-waist ratio
      • Skinfold thickness
      • Waist circumference
    • Types of obesity
      • Hyperplastic obesity – number of adipocytes is increased
        • Often seen in prepubertal obese people and people who have been obese since a young age
        • Often peripheral obesity
      • Hypertrophic obesity – adipocytes are hypertrophic
        • Often seen in people who become obese in adulthood
        • Often central obesity
        • Male type (“android”)
          • Associated with cardiovascular disease, cancer
        • Female type (“gynoid”)
          • Associated with varicose veins, thrombosis
  • Central obesity
    • Chronic inflammatory state
    • Insulin resistance
    • Dyslipidaemia
    • Diabetes mellitus type 2
  • Causes of obesity
    • Genetic factors
      • GLUT4
      • IRS-1
      • Adiponectin
      • Leptin
      • Genetic differences in metabolic rate
    • Excessive energy intake
    • Physical inactivity
    • Pregnancy
    • Secondary obesity
      • Medical treatment
      • Hormonal imbalance
        • Cushing syndrome
        • Polycystic ovary syndrome
  • Consequences of obesity
    • Increased mortality
    • Increased risk for diabetes mellitus type 2
    • Obstructive sleep apnoea
    • Metabolic syndrome
    • Cardiovascular disease
    • Arthritis
    • Cancer
      • Breast cancer
        • Excess amount of oestrogen produced by adipose tissue
      • Colorectal cancer
      • Oesophageal cancer
      • Endometrium
        • Excess oestrogen
      • Pancreas
      • Renal cell cancer
    • Mechanism of cancer development
      • Increased level of hormones who stimulate cell proliferation
        • Insulin
        • Insulin-like growth factor
        • Leptin
      • Chronic inflammation
      • Oxidative stress
      • Activation of NF-κB
      • Excess amount of oestrogen

Obesity in childhood

  • Tripled in last 30 years
  • Lifelong lifestyle habits are established during childhood
  • Much study time, television -> mild obesity -> too tired for sports or activity -> moderate obesity -> bullying causes obese child to eat comfort foods -> severe obesity

11. Dietary supplements and functional foods

Dietary supplementation

  • Definition: A manufactured product intended to supplement the diet when taken by mouth as a pill, capsule, tablet or liquid
  • Can provide natural or synthetic nutrients
  • $37 billion industry in 2015
  • 50% of Americans take dietary supplements
  • Common types
    • Multivitamins
    • Sport nutrition supplements
    • Calcium
    • B-vitamins
    • Vitamin C
    • Glucosamine
    • Fish oil
    • Collagen
    • Ginseng
    • Glucosamine
    • Probiotic
    • Folic acid
  • Medically indicated uses for dietary supplementation
    • Changing diet to treat nutrient deficiencies is always preferred to dietary supplementation
    • Folic acid in pregnancy
    • Fish oil (omega-3 fatty acids have cardioprotective effect)
    • In diseases with malabsorption (Crohn’s, chronic pancreatitis)
  • Supplementing nutrients in patients who are not nutrient deficient has no effect!
  • A balanced diet eliminates the need for dietary supplement! (which it’s required by law to be written on the nutritional label)
    • Dietary supplements can’t make up for poor eating habits
  • Food safety
    • Most supplements are safe even in case of overdose, but some (like fat-soluble nutrients) are not
    • Vitamin K supplementation can impair the function of blood thinners
    • St. John’s wort speeds up the metabolism of many drugs, decreasing their effectiveness
    • Antioxidants can reduce the effectiveness of chemotherapy
    • Overdosing iron causes severe intestinal bleeding
    • Overdosing vitamin A can cause birth defects

Functional foods

  • Definition: Foods that have a potentially positive effect on health beyond providing nutrition
    • Claimed to have health-promoting or disease-preventing effects
    • Fruits and vegetables are functional foods as they contain molecules that are not nutrients but still beneficial
  • Includes
    • Fortified foods – foods with nutrients added to them
      • Omega-3 added to butter
      • Vitamin D added to milk
      • Iodine added to salt
      • Probiotics added to yoghurt
    • Phytonutrients/phytochemicals = Molecules in fruits and vegetables that are not nutrients or vitamins
      • Lycopene
      • Anthocyanin
      • β-carotene
      • Lutein
    • Wild fish
      • Contains omega-3 fats
    • Grains
      • Contain dietary fibre

12. Food additives

Food additives

  • Definition: Substances added to food to preserve flavour or enhance its taste, appearance or other qualities
  • Examples:
    • Preserving foods with vinegar or salting
    • Sweetening foods
    • Adding taste enhancers like monosodium glutamate (MSG) – enhances umami taste
    • Adding antioxidants to prevent oxidation of the food
    • Adding nitrites to preserve the food longer
    • Adding sulphur dioxide to wine to preserve it
  • All food additives in Europe have a unique “E number”
    • E100 – E199 – food colours
    • E200 – E299 – preservatives
      • E250 – sodium nitrite
    • E300 – E399 – antioxidants, acidity regulators
    • E400 – E499 – Thickeners, stabilizers, emulsifiers
    • E500 – E599 – Acidity regulators, anti-caking agents
    • E600 – E699 – flavour enhancers
    • E700 – E799 – antibiotics
    • E900 – E999 – Glazing agents, gases, sweeteners
    • E1000 – E1599 – additional additives
  • Approval of new food additives in the EU
    • Takes 10+ years in total
    • At least 5 years of safety testing
  • Potential negative health effects
    • Nitrites are used to preserve cured meat. They can react with amines in food in the acidic environment of the stomach to form nitrosamine, a known carcinogenic compound
    • Some people have allergies to certain food additives

13. Food safety, food safety testing

Food safety

  • Definition: The scientific discipline describing handling, preparation and storage of food in ways that prevent food-borne illness
  • Five key principles of food hygiene (according to WHO)
    1. Prevent contaminating food with pathogens
    2. Separate raw and cooked foods
    3. Cook foods for appropriate length of time and at appropriate temperature to kill pathogens
    4. Store food at the proper temperature
    5. Use safe water and safe raw materials
  • Food-borne illness
    • Bacteria
      • Campylobacter jejuni
      • Salmonella
      • Enterohaemorrhagic E. coli
    • Bacterial toxins
      • Staphylococcus aureus toxin
      • Clostridium botulinum toxin
      • Bacillus cereus toxins
      • Clostridium perfringens toxin
    • Fungal toxins
      • Aflatoxin – produced by Aspergillus species
        • Causes cirrhosis and hepatocellular carcinoma
        • Only produced in warm, humid environments
    • Viruses
      • Enterovirus
      • Hepatitis A
      • Norovirus
      • Rotavirus
    • Parasites
      • Helminths (flatworms)
        • Taenia
      • Nematodes (roundworms)
        • Trichinella
      • Protozoa
  • In Hungary: National Food Chain Safety Office is responsible for national food safety
  • Labelling
    • “Best before” – a date after which the food may lose quality, but does not imply any serious health problems
    • “Use by” – a date after which it’s no longer legal to sell the product due to serious risk of food-borne illness
  • Taenia solium/saginata
    • Pigs/cows eat eggs -> we eat pork/beef -> flatworms grow to multiple meters in the small intestine
  • Trichinellosis – trichinella spiralis
    • Trichinella adults invade intestinal wall of pig -> enter pig muscles -> lay larvae in the muscles -> pork is consumed by humans -> larvae grow to adults -> invade intestinal wall of human -> enter human muscles
    • Symptoms: GI symptoms, myalgia, facial oedema. Symptoms resolve after 4 – 7 weeks
    • Prevention
      • Trichinoscope – a special device for detecting trichinella larvae in meat
      • Appropriate heating of food – 20-30 min at 60℃

14. Chemoprevention

  • Definition: Chemoprevention refers to the use of natural compounds to try to reduce the risk of or delay the development or recurrence of cancer
  • Vitamin E supplements actually increase the risk for prostate cancer
  • Green or black tea may be chemopreventative
  • Resveratrol is being investigated as a possible chemopreventative agent
  • Recent research has determined several potentially chemopreventative natural compounds

Potentially chemopreventative natural compounds

  • Most of these have proven effect in vitro but not in vivo
  • Many of these are phytochemicals, chemical compounds of plant origin that are not nutrients
  • Types
    • Carotenoids
      • β-carotene
      • Lutein – red carrots, watermelon, tomatoes
      • Lycopene
    • Flavonoids
      • Catechin
    • Alkaloids
    • Resveratrol – found in red wine, grapes, blueberries
    • Curcumin
  • Possible mode of action
    • Antioxidant effect
    • Inhibit phase I biotransformation enzymes
    • Activate phase II biotransformation enzymes
    • Anti-inflammatory effect
    • Immune stimulatory effect
    • Induction of apoptosis
    • Anti-angiogenesis
    • Regulation of cyclooxygenase
    • Regulation of intracellular signalling pathways (like PKC, PKB, JAK)
    • Modification of epigenetics
    • Stimulate DNA repair
    • Inhibition of NF-κB

15. Genetically modified organisms

Genetically modified organisms – GMO

  • Definition: An organism whose genetic material has been altered using genetic engineering techniques.
  • Genes can have been transferred within the same species, across different species and even across biological kingdoms. New genes can be introduced, or endogenous genes can be enhanced, altered or disabled
  • Examples
    • Spider goat – a GMO goat that received a spider-silk producing gene. They produced spider silk in their milk
    • Crops are genetically modified to give higher yields, need fewer antibiotics or be more resistant to infections
      • Almost all crops in the western world today is genetically engineered in some way
        • Especially corn, soy, potato, rice
    • E. coli are genetically modified to produce insulin and growth hormone for pharmaceutical companies
    • Oxitec – a company that produced GMO mosquito that bred with natural mosquito, but their offspring died due to a lethal gene
      • This could decrease the population of mosquitoes
    • Yeast modified to produce opioids
    • AquAdvantage salmon – a GMO salmon with excessive growth hormone, grows much faster than normal salmon
    • Golden rice – Rice plants genetically modified to produce rice with more β-carotene
      • Invented to reduce vitamin A deficiency is deficient populations
  • Certain vaccines are recombinant, i.e. the DNA for an antigen is inserted into a yeast, which produces many copies of the antigen, which can be used in a vaccine
  • Edible vaccines
    • Crops like potatoes can be genetically engineered to produce (non-harmful) antigens from infections, which the immune system can create immunity against

Potential harmful effects

  • Eosinophilia-myalgia syndrome – a condition that affected many people who took GMO-produced tryptophan supplements
    • The tryptophan supplements were contaminated with an unknown toxin, causing eosinophilia and myalgia
    • Shows how GMO can be dangerous
  • Many crops are genetically engineered to produce Bt toxin, a toxin that kills insects that feast on the crops
    • This is used to decrease the amounts of pesticides necessary to maintain a crop
    • Bt toxin may be toxic to humans
      • May damage intestinal cells
      • May promote growth of H. pylori

Labelling of GMO

  • Not labelled in the USA
  • In EU – all intentional GMO must be labelled
    • If genetically modified ingredients account for less than 0.9% of the food and this modification is unintentional or unavoidable, labelling is not mandatory

Horizontal gene transfer

  • Exchange of genetic material between organisms without producing a new offspring
  • Examples
    • The 2016 World Food Prize – genes were horizontally transferred from a bacterium to the genome of a sweet potato
    • Amflora – a GMO potato which produced only amylopectin and no amylose, unlike normal potatoes
      • It also contains a gene for antibiotic resistance. If consumed, bacteria in our gut could acquire these resistance gene by horizontal gene transfer

16. Interaction of environmental and genetical factors in disease development

  • Most diseases are due to a combination of genetic and environmental factors
  • We cannot change the genetic factors but we can change environmental factors
  • Certain genes can increase the risk of disease after exposure to certain environmental factors
    • Exposure + susceptible genotype -> high risk
    • Exposure + not susceptible genotype -> moderate risk
    • No exposure + susceptible genotype -> low risk
    • No exposure + not susceptible genotype -> low risk
  • Concept is demonstrated by an epidemiological study of oven workers
    • Oven workers at a steel company are exposed to PAH emissions from the ovens. The amount of exposure depends on where they work
    • Result of study: workers who smoked on their free time had more chromosomal damage as a result of oven emission exposure
    • Conclusion: Smoking reduced DNA repair capacity, increasing the susceptibility to PAH
  • Individual single nucleotide polymorphisms (SNPs) = point mutations in a single nucleotide
    • Basically means small variations in genes between individuals
    • Certain SNPs are associated with increased risk of diseases
      • SNPs of GSTM1 – increased risk for colorectal cancer
      • SNPs of NAT2 – increased risk for colorectal cancer
      • A1 variant of DRD2 – increased risk for cervical cancer

17. Genomics and epigenetics in public health. Nutrigenomics

  • Most diseases with a genetic component can not be traced back to a single gene but rather multiple
    • Exceptions: Cystic fibrosis, Huntington disease
  • Genomics = the interactions of all genes and their combined influence on the organism
    • Genetics = the study of heredity. The effect of single gene mutations on the organism
  • Genomics in public health – Using genome-based discoveries for health benefits of the population
  • How to start:
    • Genome-wide association studies = Identify genetic differences between patients and controls
  • Single nucleotide polymorphisms (SNPs) can alter protein function and increase susceptibility to certain diseases in response to environmental factors
  • In future: Use genetic testing to find treatment that is best suited for the patient (personalized/precision medicine)
    • Genetic information of nicotine metabolism can be used to personalize smoking cessation
    • Genetic information can give indication for screening, if high-risk genotypes are present

Epigenetics

  • Definition: Instructions for the cell on how and when to read DNA
  • Epigenetics changes gene expression
  • Genetically identical organisms can have different phenotype due to different epigenetics
  • Types
    • Acetylation of histones
    • Methylation of DNA
    • Presence of miRNA
    • Chromatin remodelling
  • Environmental factors can change epigenetics of an individual, and therefore the expression of the DNA
  • Folic acid necessary for DNA methylation -> deficiency could theoretically cause hypomethylation and carcinogenesis
  • Drugs affecting epigenetics “Epi-drugs” -> chemotherapeutical drugs
    • Demethylates DNA
    • Acetylates histones

Nutrigenomics

  • Definition: The relationship between nutrition and genomics
  • How nutrition can change epigenetics
    • Deficiency of certain nutrients (folate, B12, C, E) can cause DNA changes similar to those seen after radiation

18. Molecular basics of carcinogenesis

Carcinogenesis

  • DNA damage to normal cell -> mutations in genome -> altered gene product -> Tumor suppressors ↓ or oncogenes ↑
  • Protective mechanisms against carcinogenesis
    • DNA repair enzymes
    • Tumor suppressors
  • Characteristics of cancer cells
    • Inhibition of apoptosis + lack of response to inhibitory factors -> capable of self-maintained replication, long survival
    • Mutagenic agents/defective DNA repair -> genetic instability -> more mutations
    • Capable of angiogenesis
    • Capable of invasion and metastasis
  • Theories of carcinogenesis
    • Somatic mutation theory (classic theory): cancer results from accumulation of mutations in susceptible cells
      • Largely disproven: the stroma of the cancer is not mutated but highly influences tumor development, either positively or negatively
        • Healthy cells transplanted to certain cancer stromas will become cancerous
        • Cancer cells transplanted to other cancer stromas will not become more malignant
      • Also, many tumors don’t have any mutations
    • Cancer stem cell theory: most cancer cells arise from stem cells that accumulate damage as they divide

19. Primary and secondary factors of epidemic process (virulence, source of infection, means of transmission, susceptible host)

  • Epidemic process = the process of spreading of infectious diseases among people
  • Characteristics of infectious diseases
    • Caused by infectious agent
    • Has a well-defined incubation period
    • Has an acute course
    • After resolution the immune system has developed immunity
  • Anthroponosis = an infectious disease that is transmissible from human to human
  • Zoonosis = An infectious disease that is transmissible from vertebrate animals to humans
    • Brucellosis
    • Anthrax
    • Plaque
    • Trichinosis
    • Tularaemia
    • Rabies

Virulence

  • Infectivity = out of 100 people exposed to a certain infectious agent, how many will be infected?
  • Pathogenicity = out of 100 people exposed to a certain infectious agent, how many will not only be infected but also sick?
    • Measles, varicella – close to 100%
    • Diphtheria – 30%
    • Poliomyelitis – 1%
  • Lethality = out of 100 people who got the disease, how many died=

Primary (direct) factors of epidemic process

  • Those factors that directly influence the spreading of the disease
    • The source of the infection
      • The reservoir is the habitat in which the infectious agent normally lives, grows and multiplies
      • Can be humans, animals or the environment
      • The reservoir may or may not be the source from which an agent is transferred to the host (it may be reservoir -> environment/animal -> human)
      • Environmental reservoirs
        • Plants, soil, water
        • Many fungal agents have reservoir in soil
        • Legionella pneumophila has reservoir in stale waters
      • Source = the location from which the infectious agent is immediately transmitted to the host (not the same as reservoir)
      • Carriers = a person with inapparent infection who can transmit the infectious agent to others
        • Asymptomatic/healthy carrier = carrier who never experience symptoms themselves
        • Incubatory carrier = carrier who can transmit the agent during the incubation period before the clinical symptoms begin
        • Convalescent carrier = carrier who has recovered from the illness but can still transmit the infectious agent
      • Carriage may be
        • Transient = organism can be transmitted only for a short period of time
        • Intermittent = organism can be transmitted sporadically
        • Chronic = organism can be transmitted for a long time
          • Hepatitis B, salmonella typhi
    • The route of transmission
      • Direct transmission
        • Contact
        • Sexually
        • Transplacental
        • Transplantation
        • Respiratory droplets (> 5µm)
      • Indirect transmission
        • Airborne
          • Droplets (< 5µm)
          • May be suspended in air for a long time and can travel great distances
        • Waterborne
          • Through drinking water, bathwater
          • Water can be contaminated with human/animal discharge, sewage
        • Foodborne
          • Food can be infected by improper handling
          • Microorganisms can multiply in food
        • Soil
        • Personal objects
          • Bed
          • Clothes
          • Door handle
        • Insect-borne
          • Mosquitoes, fleas, ticks
          • Infectious agent can be carried on the inside of or outside of the insect
    • The susceptible population
      • Susceptibility = a feature of a person that makes it possible for an infectious agent to cause illness in him
        • Individual susceptibility – depends on the immune system of the individual
        • Population susceptibility – depends on the proportion of susceptible and non-susceptible individuals

Secondary (indirect) factors of epidemic process

  • Those factors that help the spreading of infections and affect the spread and duration of epidemics
    • Living and working environment
    • Weather
    • Nutritional status
    • Social factors
    • Status of health care

20. Nosocomial infections. Sterilization, disinfection

  • Nosocomial disease = disease which is the result of treatment in a hospital
  • Nosocomial infection (hospital-acquired infection) = infection which is the result of treatment in a hospital
  • Nosocomial epidemic = nosocomial infection that affects two or more patients, and there is a connection between the cases
  • Problems with nosocomial infections
    • Many people in small area
    • Hospitalized people often have impaired immunity or condition
    • Microorganisms in the hospital often have increased resistance to antibiotics
  • Source of nosocomial infection
    • Other patients
    • Staff
    • Visitors
  • Pathogens
    • Bacteria
      • Staph. saprophyticus and Staph. epidermidis infect IV lines
      • E. coli cause UTI
      • Clostridium causes gangrene
      • Staph. aureus – MRSA
      • Pseudomonas – likes wet and damp areas
    • Viruses
      • Hepatitis B, C
      • RSV
      • Rotavirus
      • Enterovirus
    • Parasites
      • Giardia
      • Scabies
    • Fungi – often cause infections in immunosuppressed patients
      • Candida albicans
      • Aspergillus
      • Cryptococcus
      • Cryptosporidium
  • Route of transmission
    • Direct contact
    • Indirect
      • Airborne
      • Waterborne
      • Foodborne
      • Objects, instruments
        • Clothing
        • Bedsheets
  • Susceptible population
    • Infants
    • Elderly
    • Immunocompromised
      • Diabetes
      • Cancer
      • Polytrauma
      • Surgical patients
  • Secondary factors
    • Crowded rooms
    • Insufficient number of cleaning and nursing staff
    • Lack of medical staff’s preventive approach
  • Respiratory tract infections and sepsis are the most common cause of mortality in hospitals
  • Catheters, surgical wounds, intubation, artificial ventilation are common foci where infection can originate

Preventing nosocomial infections

  • Surveillance
  • Limit overuse of antibiotics
  • Education and training of medical staff
  • Asepsis, antisepsis, isolation of patients
  • Disinfection = reduce the number of microorganisms, killing most harmful microorganisms
  • Sterilization = kill all microorganisms
  • Disinfection of hands
    • Before, during and after patient contact
  • Personal hygiene
  • Sterilization of equipment
    • Thermal – autoclave
    • Radiation
    • Chemical

Multi-resistant bacteria

  • MRSA
    • In the ICU
    • Infects skin, wounds, urinary tract, respiratory tract
  • ESBL – extended spectrum beta lactamase
    • Resistant to cephalosporins, penicillins and aztreonam
    • Treatment: carbapenems
    • Often in E. coli or Klebsiella pneumoniae

21. Infectious diseases worldwide

  • Sporadic case = case not connected to other cases
  • Endemic = many cases of a disease within a given geographical area or population
  • Outbreak = a small, localized group of people infected with the disease
  • Epidemic = a region in a country, or multiple countries infected with the disease
  • Pandemic = global disease outbreak
  • Types
    • Seasonal outbreaks – number of cases increase in a certain season
      • Influenza – winter
      • Diphtheria – autumn
    • Cyclic outbreaks – number of cases increase at a certain interval
      • Pandemic flu – every 30-40 years
      • Diphtheria – every 12 years
  • Infectivity
  • Pathogenicity

Important worldwide diseases

  • Influenza
  • Pertussis
  • Tuberculosis
  • Neisseria meningitidis
  • HIV

Recently emerging pathogens

  • Vancomycin-resistant S. aureus (VRSA)
  • SARS – coronavirus
  • Carbapenem-resistant Klebsiella

22. Prevention of infectious diseases: vaccination, chemoprophylaxis

  • Vaccination prevents 2-3 million deaths every year
    • An additional 1.5 million deaths could be avoided with further vaccination
  • Immunogenicity = the ability of a vaccine to provoke an immune response
    • Can be measured by measuring circulating antibodies
  • Protectivity = how well the vaccine protects against the disease
    • Must be measured with long-term observational studies
  • Reactogenicity = how many adverse reactions the vaccine produces
  • “Ideal” vaccine
    • 100% efficiency for all ages
    • Only needs a single administration
    • Does not cause side effects
    • Stable under various environmental conditions
    • Easily administrated (preferably oral)
    • Low price
    • Obviously doesn’t exist

Types of vaccines

  • Live, attenuated vaccine
    • The pathogen is attenuated, meaning that it is manipulated to become much less pathogenic
    • The attenuated pathogen has limited ability to reproduce in humans
    • Advantages
      • The closest vaccine to a natural infection
      • Provokes both humoral and cellular immune response
      • Long-term effective protection with only one or two doses
    • Disadvantages
      • Can’t be given to immune compromised patients
      • Need to be continuously refrigerated
      • Small risk of the pathogen turning virulent
      • Currently very hard to make for bacteria
    • Examples
      • MMR
      • Chickenpox (varicella)
      • BCG (Tuberculosis)
      • OPV (oral polio vaccine, Sabin)
  • Inactivated vaccine
    • The pathogen is killed with chemicals, heat or radiation
    • Advantages
      • No risk of the pathogen turning virulent (as it is dead)
      • No refrigeration needed (as it is dead)
    • Disadvantages
      • Stimulates weaker immune response
      • Several doses and booster shots are necessary, requiring regular access to healthcare
    • Examples
      • IPV (Salk polio vaccine)
      • HAV (Hep A)
      • Rabies
  • Toxoid vaccine
    • Can be made for bacteria who produce toxins
    • Toxin is extracted from the bacterium and inactivated with formalin, so that it is no longer pathogenic -> now called a toxoid
    • Used when the illness is caused by the toxin and not the bacterium itself
    • Advantage
      • Rarely causes side effects
      • Stable, doesn’t require refrigeration
      • No risk of acquiring the disease
    • Disadvantage
      • Several doses may be needed
      • Stimulates weak immune response
    • Examples
      • Diphtheria
      • Tetanus
  • Subunit vaccine
    • Protein antigens from the pathogens are given in a vaccine
    • Examples
      • Hepatitis B (HBsAg)
      • Acellular pertussis (aP)
  • Conjugate vaccine
    • Polysaccharides are weak antigens, meaning that they stimulate weak immune responses
    • For bacteria protected by a polysaccharide capsule
    • The polysaccharide antigen of a bacterium is conjugated (attached to) a highly immunogenic protein antigen, which stimulates a strong immune response against both the polysaccharide antigen and the protein antigen
    • Advantages
      • Give a strong immune response with long-term protection
    • Disadvantages
      • Multiple shots or booster shots may be necessary
    • Example
      • Haemophilus influenzae type b
      • Meningococcus (Neisseria meningitidis)
  • DNA vaccine
    • Only experimental
    • Genes for antigens are inserted into bacteria, which produce plasmids (circular DNA) of these antigen genes
    • Plasmids are inserted into the body. Cells of the body will take up the plasmids and start synthesizing the antigen from the plasmid
    • The immune system recognizes the antigen produced as foreign and triggers immune response
  • Recombinant vector vaccines
    • Only experimental
    • Genes for antigens are inserted into bacteria, which synthesize large amounts of the antigen
    • Antigen is then purified and given as a vaccine

Who gets vaccines:

  • Age-specific compulsory vaccines
    • BCG
    • Haemophilus influenzas type b
    • IPV (Salk polio)
    • MMR (measles, mumps, rubella)
    • Hepatitis B
    • Pneumococcus
    • HPV
  • Compulsory vaccines for at-risk groups
    • Tetanus
    • Rabies
    • Diphtheria
    • DTaP (diphtheria, tetanus, acellular pertussis)
    • Hepatitis A
  • Non-compulsory vaccines for at-risk groups, free of charge
    • Influenza
  • Job-related vaccines
    • Rabies
    • Meningococcus
    • Tick-borne encephalitis
  • Travel-related vaccines
    • Yellow fever
    • Cholera
    • Typhoid fever
    • Japanese encephalitis
  • Other non-compulsory vaccines

Chemoprophylaxis

  • Definition: Administering drugs for the purpose of preventing disease or infection
  • Can be given
    • Preexposure – before the exposure to the pathogen
    • Postexposure – after the exposure to the pathogen but before symptoms develop
  • Examples
    • Giving antiretroviral drugs to people at high risk for HIV right after being exposed to HIV
      • Like health care workers who come in contact with HIV
    • Giving antimalaria drugs to people before, during and after travelling to malaria-prone areas
    • Giving antibiotics to people who travel to areas where Traveller’s diarrhoea (ETEC) is common
    • Giving antibiotics to people who have been exposed to bacillus anthracis
    • Giving antibiotics to people who have been exposed to Neisseria meningitidis

23. Epidemiology and prevention of vaccine-preventable diseases, mandatory immunisation for children

Vaccination program for Norway (as of 2017)

Age Vaccination against
Infancy (only for children with parents from high-risk countries) Tuberculosis (BCG)
6 weeks Rotavirus
3 months Rotavirus

Diphtheria, tetanus, pertussis, poliomyelitis, Haemophilus influenzae-type B- and hepatitis B (DTP-IPV-Hib-Hep B)

Pneumococcus (PKV)

5 months DTP-IPV-Hib-Hep B and PKV
12 months DTP-IPV-Hib-Hep B and PKV
15 months Measles, Mumps, Rubella (MMR)
7 years DTP-IPV
11 years MMR
12 years Human papillomavirus (HPV), 2 doses
15 years dTP-IPV

24. Epidemiology and prevention of airborne bacterial infections

Airborne infections:

  • Inhalation of organisms suspended in the air on water droplets or dust particles
  • Prevention:
    • Handwashing
    • Vaccines

Bacterial airborne infections:

  • Diphtheria
  • Haemophilus influenzae
  • Pertussis
  • Neisseria meningitidis (meningococcus)
  • Tuberculosis
  • Streptococcus pneumoniae (pneumococcus)
  • Legionnaire disease

Diphtheria

  • Corynebacterium diphtheriae
  • Produces toxin
    • Affects myocardium
    • Peripheral nerves
    • Nephritis
  • Produces pseudomembrane in the pharynx
  • Global reported cases down since vaccine was introduced in the 80s
  • Very rare in countries with high coverage with vaccine
  • Vaccine
    • Toxoid vaccine – toxin is inactivated with formalin
    • DTaP vaccine at 3, 5 and 12 months, 7, 15 years (in Norway) + booster (Tdap) every 10 years
    • Vaccine lasts 10 years
    • Intramuscular vaccine
    • Because vaccine doesn’t protect against the infection itself, only the (toxin-mediated) disease, there is no herd immunity!

Pertussis

  • Bordetella pertussis
  • Whooping cough – paroxysmal coughing
  • Causes pneumonia
  • Important cause of infant death worldwide
  • Vaccine
    • Acellular pertussis (DTaP)
    • Given at 3, 5 and 12 months, 7, 15 years (in Norway) + booster (Tdap) every 10 years

Tuberculosis

  • Mycobacterium tuberculosis
  • Risk factors
    • HIV (or other immune suppression)
    • Severe disease (DM, renal failure)
  • TB is prevalent among
    • Migrants
    • Homeless
    • Poor people
    • Drug abusers
  • 9th leading cause of death worldwide
  • 27 000 new cases every day
  • Leading cause of death in HIV-positive
  • Incidence and mortality dropping in the last 20 years
  • Vaccine
    • BCG vaccine
    • Live attenuated Mycobacterium bovis
    • Unchanged since 1921
    • Good protection against childhood TB meningitis and miliary TB
    • Poor protection against adult pulmonary TB
    • Intradermal injection in the deltoid

Streptococcus pneumoniae (pneumococcus)

  • Common cause of community-acquired pneumonia, bacterial meningitis, bacteraemia, otitis media
  • Colonizes nasopharynx
  • Often in fall, winter
  • Vaccine
    • Conjugate vaccine
    • Given at 3, 5 and 12 months

Haemophilus influenzae

  • Colonizes nasopharynx
  • Causes otitis media, meningitis, epiglottitis, sinusitis
  • Vaccine
    • Conjugate vaccine
    • Only for H. flu type b – the only type with a capsule and therefore only pathogenic type
    • 3, 5 and 12 months

Legionellosis

  • Legionella pneumophila
  • Inhalation of contaminated aerosol
  • Two forms
    • Non-pneumonic form – causes Pontiac disease (influenza-like illness)
    • Pneumonic form – causes Legionnaire disease – severe pneumonia
  • No vaccine available

Neisseria meningitidis

  • Serotype B and C account for most cases in western world
  • Serotype A accounts for most cases in Africa
  • Asymptomatically colonizes nasopharynx
  • Mainly affects children and infants
  • Vaccine
    • Polysaccharide vaccine used during outbreaks
    • Conjugate vaccine used for prevention
  • Chemoprophylaxis
    • Antibiotic prophylaxis for people in close contact to infected

25. Epidemiology and prevention of airborne viral infections

Airborne viral infections

  • Influenza
  • Measles
  • Mumps
  • Rubella
  • Varicella zoster
  • Epstein Barr virus

Measles

  • Highly contagious, serious disease
  • 300 deaths every day
  • Vaccination caused an 80% drop in cases from 2000 to 2017
  • Spread by coughing and sneezing
  • Can cause otitis media, pneumonia, diarrhoea, subacute sclerosing panencephalitis
  • No specific treatment
  • Vaccination
    • MMR vaccine

Rubella

  • Rubella virus
  • Generally mild illness
  • Part of TORCH – serious for pregnant women
  • No specific treatment

Influenza

  • Type A and B exists – type A is most pathogenic
  • Very hard to vaccinate against – antigens change constantly
    • Antigenic drift – point mutations in the Haemagglutinin (H) and neuraminidase (N) genes
    • Antigenic shift – two different strains combine to form a new strain with different surface antigens
  • Pandemics in history
    • Spanish flu (1918)
    • Asian flu (1957)
    • Hong Kong flu (1968)
    • Swine flu (2009)
  • Seasonal epidemics during winter
  • Can cause severe illness in high risk populations
    • Small children
    • Elderly
    • Pregnant women
    • Chronically ill
  • Vaccination
    • Contains killed virus
    • Recommended for at-risk populations
    • The serotype of the influenza virus changes all the time -> WHO must try to predict which serotype will cause epidemic every year and produce vaccine against that type
    • For every year the vaccine is taken the more efficient it becomes
  • Preventative measures
    • Hand hygiene
    • Covering mouth and nose when sneezing, use tissues
    • Self-isolation when symptoms occur
    • Avoid close contact with sick people

26. Characteristics, types, occurrence and prevention of enteric infections

Gastrointestinal infections

  • Caused by viruses, bacteria, protozoa and helminths
  • Symptoms can be caused by the organisms themselves or by toxins they produce
  • If small intestine is affected:
    • Watery diarrhoea
    • Abdominal cramps
    • Vomiting
  • If large intestine is affected
    • Bloody diarrhoea
    • Lower abdominal pain
    • Fever
  • Infection acquired from contaminated food or drinking water, or from person-to-person as a result of poor hygiene
  • Diarrhoeal disease is the second leading cause of death in children under five
  • Very common in developing countries
  • Treatment: clean water, salt, sugar, zinc tablets
  • Risk factors
    • Children
    • Elderly
    • Pregnant
    • Malnutrition
    • Immunosuppression
    • Working with infected people
  • Socioeconomic risk factors
    • Poverty
    • Overcrowding
    • Poor sanitation
    • Water contamination
    • Poor food hygiene

Types of foodborne illness

  • Intoxication – ingestion of a toxin, which causes the illness
  • Toxico-infection – ingestion of a microorganism which produces toxin in the human body. The toxin causes the illness
  • Infection – ingestion of a microorganism which itself causes illness

Prevention of foodborne illness

  • Most foodborne illness is caused by food being improperly prepared or handled at home
  • Sick people should not handle food
  • Vegetables and fruits should be rinsed under water
  • Five keys to safer foods
    • Keep hands, surfaces and equipment clean. Wash hands before handling food
    • Separate raw and cooked foods – don’t use same equipment for both
    • Cook thoroughly – especially meat, eggs and seafood
    • Keep food at safe temperatures
      • Don’t leave cooked food in room temperature for more than 2 hours
      • Refrigerate cooked food as soon as possible
      • Do not store food too long
      • Do not thaw frozen food at room temperature, rather in the fridge
    • Use safe water and raw materials

27. Epidemiology and prevention of enteric bacterial infections

Enteric bacterial infections

  • Non-inflammatory diarrhoea (often watery)
    • Preformed toxin
      • Staphylococcus aureus
      • Bacillus cereus
      • Clostridium perfringens
    • Bacteria that produce toxin in the intestines
      • Enterotoxigenic E. coli (ETEC)
      • Vibrio cholerae
  • Inflammatory diarrhoea (often bloody)
    • Bacteria that produce cytotoxins
      • Enterohaemorrhagic E. coli (EHEC)
      • Clostridium difficile
    • Bacteria that invade the mucosa
      • Shigella
      • Salmonella
      • Campylobacter
      • Enteroinvasive E. coli
      • Yersinia enterocolitica

Staphylococcus aureus

  • Lives in salads, ham, eggs, dairy products
  • Produces toxin which is ingested

Clostridium perfringens

  • Toxin is found in meat which is not sufficiently cooked

Bacillus cereus

  • Produces spores which survive cooking
  • Food left too long in room temperature -> spores start to proliferate and produce toxin
  • Often associated with rice stored at room temperature

Campylobacter jejuni

  • Bacteria ingested through contaminated food or water, or undercooked meat
  • Causes bloody diarrhoea
  • May cause Guillain-Barré syndrome
  • Outbreaks during summer
  • Prevention: thoroughly cooking the food

Salmonella

  • Most commonly salmonella enteritidis
  • Lives in poultry, pigs, cattle
  • Ingested through undercooked meat
  • Acid labile bacteria
    • Healthy adults need to ingest many bacteria to be infected

Enterohaemorrhagic E. coli (EHEC)

  • Most important serotype – O157:H7
  • Very similar: Shiga-toxin producing E. coli (STEC)
  • Lives in cattle
  • Ingested through undercooked ground meat, raw milk
  • Heat-sensitive bacterium
  • Causes bloody diarrhoea
  • May cause haemolytic uraemic syndrome in weak populations

Enterotoxigenic E. coli (ETEC)

  • Causes traveller’s diarrhoea
  • Major cause of infantile diarrhoea
  • Self-limiting
  • Ingested through contaminated food or water
  • Can cause dehydration in young children

Shigella

  • Causes dysentery
  • Uncommon in EU, common in developing countries
  • Major cause of death in children < 5
  • Transmitted faecal-oral or via contaminated food or water
  • Symptoms
    • Short period of watery diarrhoea
    • Later bloody or mucopurulent stool
    • Haemolytic uraemic syndrome

Cholera

  • Vibrio cholerae
  • Affects both children and adults
  • Can kill within hours
  • Risk factors
    • Unsafe water
    • No proper sanitation
    • Poor waste management
  • 80% of cases can be treated with oral rehydration + salts
  • Providing safe water and sanitation is the most important factor in preventing cholera

Typhoid fever

  • Salmonella typhi or paratyphi
  • Absent from industrialized countries, big problem for poorer countries
  • Spread faecal-orally
  • Symptoms
    • Fever
    • Headache
    • Abdominal pain
    • Constipation
  • Can cause GI bleeding
  • Vaccines exist for salmonella typhi but not for paratyphi

28. Epidemiology and prevention of enteric viral infections

Viral enteric infections

  • Rotavirus
  • Norovirus
  • Poliovirus

Rotavirus

  • Rotavirus is the leading cause of severe diarrhoeal disease in infants and children worldwide
  • Most common cause of diarrhoeal deaths in developing countries
  • Most common during the winter in temperate climates
    • Year-round in tropical climates
  • Virtually all children in developing countries are infected before they reach age 3
  • Transmission
    • Faecal-oral
    • Respiratory droplets
    • Contaminated objects
  • RV can also infect adults
    • Especially institutionalized and hospitalized
  • Symptoms
    • Watery diarrhoea
    • Vomiting
    • Abdominal pain
  • Vaccine
    • Live attenuated oral vaccine
    • Childhood vaccine
      • At week 6 and month 3

Norovirus

  • A calicivirus
  • Causes diarrhoea in children and adults
  • Most common during the winter (stomach flu)
  • Causes gastroenteritis
  • Common cause of non-bacterial acute gastroenteritis in western countries
  • Virus can be shed after two weeks of no symptoms
  • Virus can survive freezing and heating to 60 degrees
  • Self-limiting
  • Symptoms
    • Vomiting
    • Abdominal cramp
    • Diarrhoea
    • Fever
  • Transmission
    • Faecal-oral
    • Person-to-person
  • No vaccine

Poliovirus

  • Causes poliomyelitis
  • Faecal oral transmission
  • Mainly affects children
  • Symptoms
    • Often very mild, flu-like
    • 1% may develop aseptic meningitis, myalgia
    • 0.3% develop paralytic poliomyelitis
  • Often self-limiting
  • No cure, but vaccine
    • Oral polio vaccine (Sabin)
      • Live attenuated
    • Inactivated polio vaccine (Salk)
      • Killed virus

29. Epidemiology and prevention of enteric helminth and protozoon infections

Enteric helminth and protozoa infections

  • Pinworms
  • Giardia
  • Amebiasis
  • Ascariasis
  • Tapeworms
  • Whipworm

Pinworms

  • Parasite: Enterobius Vermicularis
  • Outbreaks common in schools
  • Faecal-oral transmission
  • Key symptom: itching at the rectum
  • Parasites leaves the anus at night, leaves eggs around the anus
  • Diagnosis: Put tape at the anus, look for eggs in the morning
  • Treatment:
    • Vermox
    • Antiminth

Giardiasis

  • Parasite: Giardia lambila
  • Faecal-oral transmission
  • Lives in the upper GI tract
  • Very common water-borne infection
  • Symptoms
    • Diarrhoea
    • Abdominal pain
    • Flatus
    • Steatorrhea
  • Diagnosis: Microscopy of stool to look for cysts

Amebiasis

  • Entamoeba histolytica
  • Found in 4% of the population
  • Faecal-oral transmission
  • Invades the mucosa of coecum and ascending colon
  • Symptoms
    • Can be asymptomatic
    • Diarrhoea
    • Abdominal pain
    • Flatus
  • Can travel to liver, causing hepatitis

Ascariasis

  • Ascaris lumbricoides (the large intestine round worm)
  • Transmitted by contaminated food
  • Penetrate the intestine, invades liver, lung, heart
  • Symptoms
    • Can be asymptomatic
    • Invasion of lungs -> causes Loeffler syndrome

Tapeworms

  • Taenia solium
  • In raw or undercooked pork or beef
  • Can be 25 meters in length
  • Cysticercosis -> cysts of larvae in any organ, especially in the brain

Whipworm

  • Trichuris trichiura
  • Very common parasitic infection in the US
  • Worm lives in coecum and appendix
  • Female produces thousands of eggs every day
  • Faecal-oral transmission
  • Symptoms
    • Allergic reactions
    • Anaemia
    • Diarrhoea

30. Epidemiology and prevention of viral hepatitides

Risk factors for hepatitis viruses

  • Low socioeconomic status
  • Crowding
  • Poor sanitation
  • Lack of safe water
  • IV drug users
  • People with many sexual partners
  • People who receive regular blood transfusions

Hepatitis A

  • Faecal-oral transmission or direct contact
  • Young children are asymptomatic
    • In developing countries most children are affected before age of 10
  • Adults are commonly symptomatic
  • Self-limiting, low mortality
  • Cannot progress to chronic hepatitis
  • Vaccine
    • For travellers to endemic areas

Hepatitis B

  • Causes many deaths worldwide
  • Low prevalence in Europe
  • Can progress to chronic hepatitis
    • Occurs more commonly in children and infants
  • Transmission
    • Vertical
    • Blood transfusion
    • Sexually
    • Between IV drug users
  • Diagnosis
    • Serology – HBsAg, antibodies
  • Vaccine
  • Post-exposure chemoprophylaxis
    • Passive immunization (immunoglobulins)

Hepatitis C

  • Commonly progresses into chronic hepatitis, cirrhosis and HCC
  • Mostly found in Africa, East Asia
  • Transmission
    • Same as Hep B
  • Antiviral medication can cure 95% of infected people
  • No vaccine, no postexposure prophylaxis
  • Screening
    • IV drug users
    • Patients with HIV
    • Health care workers after needlestick injury
    • Children of HCV-infected mothers
    • Sexual partners of HCV-infected persons

Hepatitis D

  • Requires hepatitis B for expression and replication
  • Superinfection of Hep D on hep B causes more severe acute illness and more often chronic hepatitis
  • Can be prevented with hepatitis B vaccination

Hepatitis E

  • Very similar to hep A
  • Cannot progress to chronic hepatitis
  • Can cause fulminant hepatitis in people with liver disease or pregnant women
  • No vaccine available (only in China)

31. Epidemiology and prevention of haematogenic and lymphogenic infections

Vector-borne diseases

  • Infections transmitted by the bite of infected arthropods like:
    • Flies
      • Sleeping sickness
    • Mosquitoes
      • Malaria
      • Yellow fever
      • Zika
      • Dengue fever
      • West Nile fever
    • Ticks
      • Lyme disease
      • Tick-borne encephalitis
      • Q fever
      • Tularaemia
    • Lice
    • Fleas
      • The plague
  • The infection can be located inside the vector or outside
  • Arthropods are cold-blooded and are therefore very sensitive to changes in the climate
    • Climate change changes their habitat -> can make areas previously spared from these diseases become affected

Lyme disease

  • Borrelia burgdorferi, afzelii and garinii
  • Transmission by bite of the Ixodes tick
  • Reservoir: many small mammals
  • Endemic in most of Europe, most in central and eastern European countries
  • Symptoms
    • Target-shaped rash
    • Neurological complications
    • Arthritis
  • Prevention
    • No vaccine
    • Avoiding tick bites
    • Early removal of attached ticks

Tick-borne encephalitis

  • Arbovirus
  • Reservoir: small rodents
  • Transmission by bite of the Ixodes tick
  • Endemic in areas of Europe and Asia
  • Most cases occur during the summer
  • Few infected people get sick
  • Illness is worst in elderly
  • Symptoms
    • Neurological complications
  • Prevention
    • Vaccine exists
    • Avoiding tick bites
    • Early removal of attached ticks

Malaria

  • Parasites of the genus plasmodium
    • Plasmodium falciparum – most severe
  • Transmission by mosquitoes
  • No animal reservoir: only lives in humans
  • Most cases are in Africa, especially Nigeria
  • Major cause of death in developing countries
  • Risk groups
    • Pregnant women
    • Children and infants
    • HIV infected
  • Entomologic inoculation rate = how many infectious mosquitoes bites per person per year
    • A measure of transmission intensity
    • High if above 50
    • The higher the EIR, the greater the burden of malaria
  • Chemoprophylaxis:
    • For travellers to malaria endemic countries
    • For high-risk residents of endemic countries
  • Prevention
    • Kill mosquitoes
    • Insect nets
    • Clothes that cover the body
    • Mosquito repellent
  • Vaccine
    • Name: RTS,S
    • Very recent (2019)
    • Against plasmodium falciparum

Crimean-Congo haemorrhagic fever (CCHF)

  • CCHF virus
  • Endemic in Africa, Balkans, Middle East, Asia
  • Transmission by tick
  • Symptoms
    • Fever
    • Petechiae

Tick-borne relapsing fever

  • Transmission by tick
  • Symptoms
    • Relapsing fever
    • Headache

West Nile virus

  • A flavivirus
  • Reservoir: birds
  • Transmission by mosquitoes
  • Originated from Africa, now present worldwide
  • Symptoms
    • Often asymptomatic
    • Flu-like symptoms
    • Rarely meningitis or encephalitis
  • Prevention
    • Protect against mosquito bites

Japanese encephalitis

  • Japanese encephalitis virus
  • Reservoir: birds
  • Transmission by mosquitoes
  • Symptoms
    • Often asymptomatic
    • Rarely encephalitis and neurological sequelae
  • Vaccine exists

Zika virus

  • A flavivirus
  • Transmission by mosquito
  • Symptoms
    • Often asymptomatic
    • Congenital zika causes CNS malformations
  • Prevention
    • Protect against bites

Yellow fever

  • A flavivirus
  • Transmission by mosquito
  • Occurs in Sub-Saharan Africa and South America
  • Infants and children are at highest risk
  • Prevention
    • Vaccine
    • Protection against mosquito bites

Lymphatic filariasis

  • Also called elephantiasis
  • Filarial parasites transmitted to humans through mosquitoes
  • Causes severe lymphoedema

32. Epidemiology and prevention of infections transmitted through the skin

Wound infections

  • Pathogen enters through a wound
  • Local inflammation at site
  • Risk factors
    • Diabetes
    • Immunosuppression
    • Old or young age
    • Foreign material in wounds
    • Crowded conditions
    • Poor hygiene

Tetanus

  • Clostridium tetani
  • Produces spores
  • Spores enter wounds and thrive in the anaerobic environment there
  • Toxins
    • Tetanolysin – haemolyses. No pathological activity
    • Tetanospasmin – causes symptoms of tetanus
  • Reservoir: Soil, dust, animal GI tract
  • Transmission – Contaminated objects in contact with wounds or ulcers
    • No person-to-person
  • More common in rural communities and agricultural regions
  • Fatality 10 – 20% with therapy (without: 50%)
  • Dakar score system – gives prognosis of tetanus
  • Four types of tetanus
    • Generalized tetanus
      • Most common form
      • Descending muscle rigidity
      • Risus sardonicus – smiling grin
      • Opisthotonus – spasm of the back muscles
    • Localized tetanus
      • Rare, very good prognosis
    • Cephalic tetanus
      • Rare, poor prognosis
      • Dysfunction of cranial motor nerves
    • Neonatal tetanus
      • Very poor prognosis
  • Treatment
    • Supportive care
    • Protection of the airways
    • Neutralization of toxins (passive immunization)
  • Prevention
    • Vaccine (DTaP)
    • Clean birth

Gas gangrene

  • Clostridium perfringens
  • Spores enter wounds and thrive in anaerobic environment
  • Often seen after trauma (accidents) or postoperative
  • Prevention
    • Clean any skin injury thoroughly
    • Remove foreign objects from wounds
    • Give post-exposure antibiotics

Epidemic keratoconjunctivitis

  • Adenovirus
  • Transmission
    • Direct contact with eye secretions

Trachoma

  • Chlamydia trachomatis in the eye
  • Causes eye infection
  • Major cause of blindness in developing countries
  • Transmission
    • Direct contact with eye discharge
    • Spread by flies
  • Repeated eye infections can cause blindness
  • Prevention
    • Sanitation of the face
    • Antibiotics

Pediculosis – lice infestation

  • Transmission
    • Direct contact
    • Indirect – via sharing objects like combs, clothes, hats
  • Three types
    • Pediculus capitis – head louse
      • Grow in hair
      • Lay eggs at the scalp
    • Pediculus corporis – body louse
      • Lives in clothing, not in body hair
    • Pthirus pubis – pubic louse
      • Grow in pubic hair
      • STD
  • Symptom: itching
  • Prevention
    • Don’t share stuff
    • Avoid head-to-head contact
    • Wash clothes at 60

Scabies

  • A mite that burrows into the epidermis, where they live and deposit eggs
  • Reservoir: humans
  • Transmission: Direct contact
  • Often affects children and sexually active adults
  • Symptoms
    • Itching
    • Pimple-like rash
    • Burrows in the skin
  • Prevention
    • Avoid direct contact with infected
    • Objects an infected person has used should be washed

33. Epidemiology and prevention of zoonotic helminth and bacterial infections

Zoonoses

  • A disease that is naturally transmissible from vertebrate animals to humans and vice versa
  • > 60% of all infectious disease are zoonoses
  • Bacterial
    • Listeria monocytogenes
    • Brucella
    • Leptospirosis
    • Bacillus anthracis
    • Tularaemia
    • Q fever
    • Salmonella
    • Plague
    • Shigella
  • Helminth
    • Trichinella spiralsis
    • Taenia solium
    • Echinococcus

Listeriosis

  • Listeria monocytogenes
  • Animals are often asymptomatic but have the bacteria in their feces -> faecal-oral
  • Also found in processed meat, soft cheese
  • Can cause abortion in pregnant women
  • Prevention
    • Pasteurizing dairy products
    • Pregnant women should avoid soft cheeses and pre-packed salads
    • Hand-washing

Brucellosis

  • Caused by brucella bacteria
  • Reservoir: Cattle, dogs, sheep, goats, pigs (farm animals)
  • Prominent in Mediterranean region
  • Transmission
    • Direct or indirect contact with animals
    • Contaminated animal products
  • Symptoms
    • Fever
    • Arthritis
  • Prevention
    • Vaccination of animals
    • Pasteurization

Leptospirosis

  • Leptospira bacteria
  • Most common in tropical areas
  • Reservoirs: many wild animals (rat, mouse)
  • Transmission
    • Direct contact with urine of infected animals
    • Indirect contact with urine
  • Prevention
    • Controlling rodent populations

Anthrax

  • Bacillus anthracis
  • Reservoir: grass-eating animals (sheep)
  • Transmission: exposure to spores
    • Eating contaminated meat
    • Through skin
  • Prevention
    • Vaccination of animals
    • Protective equipment in workers

Tularaemia

  • Francisella tularensis
  • Reservoir: rabbits, hares, squirrels
  • Transmission
    • Bite of infected insects (ticks, mosquitoes, flies)
    • Contact with infected animal
    • Eating undercooked infected meat
  • Symptoms
    • Fever
    • Lymphadenopathy

Q fever

  • Coxiella burneti
  • Reservoir: sheep, goat, cattle
  • Transmission
    • Inhalation of aerosols with the bacterium
  • Symptoms
    • 50% asymptomatic
    • Headache
    • Fever

34. Epidemiology and prevention of zoonotic protozoon and viral infections

Viral zoonoses

  • Rabies
  • Hantavirus
  • Influenza
  • Crimean-Congo haemorrhagic fever
  • Ebola
  • Rift valley fever

Protozoan zoonoses

  • Toxoplasma

Rabies

  • Very few cases in Europe
  • 95% of death occur in Asia and Africa
  • Reservoir: Dogs, bats, wolves, foxes
  • Transmission:
    • Bite or direct contact with saliva of infected animal
  • Incubation period – 1-3 months – depending on how far from the CNS the infection occurred
  • Two types
    • Encephalitic rabies (most common)
      • CNS symptoms
      • Agitation
      • Confusion
      • Hypersalivation
    • Paralytic rabies
      • Flaccid paralysis spreading from the bite wound
    • Both
      • Hydrophobia
  • Retrograde transport from nerves at bite site to the CNS
  • Prevention
    • Human vaccine
      • For travellers spending much time outdoors
      • For high-risk occupations, like veterinarians
    • Oral immunization of animals – releasing baits containing oral vaccine into high-risk areas
    • Teaching children to avoid animal bites
    • Post-exposure prophylaxis
      • Washing wound for 15 minutes
      • Giving rabies vaccine soon after bite
      • Administration of rabies antibodies if needed

Hantavirus

  • Bunyaviruses
  • Reservoir: rodents
  • Transmission
    • Inhalation of infected rodent urine or droppings
    • Bites
  • Risk groups
    • Forest workers
    • Farmers
  • Clinical features
    • Haemorrhagic fever with renal syndrome
    • Hantavirus cardiopulmonary syndrome
  • Prevention
    • Avoidance of dust
    • Minimizing contact with rodents

Toxoplasmosis

  • Toxoplasma gondii (a helminth)
  • Reservoir: cats
  • Transmission
    • Ingestion of cysts
    • Direct through cat faeces
    • Indirect through food or water contaminated with cat faeces
  • A part of TORCH – causes perinatal death or congenital infection – neurocognitive deficit

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