Food and Waterborne Diseases PDF

CHAPTER FIVE 5. FOOD AND WATERBORNE DISEASES At the end of this chapter, students will be able to:  Differentiate food born infection and food born intoxication  Identify types and transmission of food borne illnesses  Understand bacterial and viral food borne infections, and the...

CHAPTER FIVE 5. FOOD AND WATERBORNE DISEASES At the end of this chapter, students will be able to:  Differentiate food born infection and food born intoxication  Identify types and transmission of food borne illnesses  Understand bacterial and viral food borne infections, and their prevention and control measures.  Understand food borne intoxications (bacterial, fungal, chemical and biotoxications), and their prevention and control measures.  Understand water-borne, water-washed, water-based and water-related diseases; their transmission and prevention and control measures. 5.1. Introduction to food and waterborne diseases (FWBD)  FWBDs are illness caused by ingestion of food and water contaminated by pathogenic microorganisms (bacteria, viruses, parasites and fungi).  FWBD tend to be most severe in the young and elderly, those with weakened immune system, those with chronic diseases, and pregnant women.  According to WHO (2020),  Annually about 7.5% of all deaths (56 million people) are attributed to foodborne diseases, where 30% of these deaths occur in children under the age of 5 year.  Each year about 829,000 people die from diseases caused by unsafe water, poor hygiene, and inadequate sanitation. Food Borne Diseases (FBDs)  Are acute illnesses associated with the recent consumption of food  The food involved is usually contaminated with a disease pathogen or toxicant which are enough to make a person sick. Water Borne Diseases  Result either from ingestion of contaminated water or contact with water (e.g., bathing, wading, swimming, ocular exposure), or inhalation of aerosols generated from water that contains etiologic agents/infectious substances. 5.2. Classification of food and water borne diseases 1. Food/water borne infections: infections caused by microorganisms that produce enterotoxins. 2. Food/water borne intoxications: caused by either chemical substances or preformed toxins produced by microorganisms.  5.2. 1. Food borne infections  Food borne infections are caused by the entrance of pathogenic microorganisms contaminating food into the body, and the reaction of the body tissues to their presence.  These can either be fungal, bacterial, viral or parasitic  Food borne infections tend to have long incubation periods and are usually characterized by fever.  Incubation period: time between exposure to a pathogen, chemical, or radiation and the first appearance of symptoms. Food borne infections include:  Bacterial food borne infections include Cholera, salmonellosis, typhoid fever, shigellosis, Yersiniosis Escherichia coli infection Campylobacteriosis, Vibrio parahemolyticus and Listeriosis  Mycotic food borne infections include Candida spp., Sporothrix spp., Wangiella spp. etc.  Viral food borne infections include hepatitis A, Norwak virus and poliomyelitis virus  Bacterial food borne infections 1. Salmonellosis  The salmonellae constitute a group of organisms with over 2000 different serotypes.  These organisms are capable of causing diseases in animals and man when taken into the body in sufficient numbers.  Many salmonella species have a wide host range. However, some are restricted to a single host species e.g. Salmonella abortus ovis causing abortion in ewes, and Salmonella gallinarum the cause of fowl typhoid.  Conversely, some salmonella serotypes are associated with human disease and are not known to affect animals e.g. S. typhi and Salmonella paratyphi.  Salmonellae are ubiquitous in the gut of human and animals and act as sources of food contamination.  A heavy dose up to 10,000 -1,000,000 organisms per gram of food is required to cause infection.  Salmonellae grow well on food and can exist for a considerable period in feces, and on pastures.  Salmonella food poisoning outbreaks Outbreaks occur in different forms: a. Sporadic cases involving only one or two persons in a household b. Family outbreaks in which several members of the family are affected c. Large outbreaks caused by a widely distributed infective food item d. Institutional outbreaks which may be caused by a contaminated single food item. Factors associated with Salmonella food poisoning outbreaks  Consumption of inadequately cooked or thawed meat or poultry,  Cross-contamination of food from infected food handlers.  Presence of flies, cockroaches, rats, in the food environment that act as vectors of the disease. Transmission  Salmonellae reach food in many different ways; a) Directly from slaughter animals to food b) From human excreta, and transferred to food through hands, utensils, equipments, flies etc.  Food poisoning is more likely to occur if the total number of microorganisms present is high. A smaller number may have no ill effect. Foods involved  Any food contaminated with salmonellae may be involved. However, foods commonly involved are animal derived foods such as: o meat and meat products, o milk and milk products, o egg and egg products Clinical symptoms  The ordinary symptoms include abdominal pain, headache, diarrhea, fever, vomiting, prostration (state of extreme physical exhaustion, weakness or collapse) and malaise (a feeling of discomfort, a feeling like you have an illness).  In severe cases there is septicaemia (presence of bacteria in the bloodstream asymptotically) with leukopenia (a condition where the body doesn’t have enough disease-fighting leukocytes in the blood), endocarditis (an inflammation of the inside lining of the heart chambers and heart valves), pericarditis (an inflammation of the lining around the heart).  Severe cases are encountered in babies, young children, the sick and in elderly persons. The mortality is up to 13 %. Control measures  Efficient refrigeration and hygienic handling of food.  Consumption of properly cooked meat.  Complete thawing of frozen meats and adequate cooking.  Heat processing of meat, milk, fish and poultry to destroy salmonella organisms in food.  Typhoid and Paratyphoid fever (Enteric fevers)  Enteric fevers include typhoid and paratyphoid fevers caused by Salmonella typhi and Salmonella paratyphi A, B and C respectively.  The serotypes are similar to other salmonella bacteria, but unlike them, they are essentially parasites of man.  S. typhi possesses capsular (vi). antigen in addition to the usual O and H antigens found in other serotypes. Disease symptoms  The incubation period is usually 2 weeks, but might vary between 3 and 28 days for typhoid fever and between 1 and 15 days for the paratyphoid fevers.  The enteric fevers are generalized septicaemic infections with a frequent, if not constant bacteremia (an infection caused by large amounts of bacteria entering the bloodstream that leads to fever and mental state change) during the first two weeks of the disease.  The abdominal symptoms are severe, while fever and illness may continue for 4-6 weeks. Transmission  The typhoid and paratyphoid bacilli are essentially human parasites and are acquired mostly from human sources, namely, patients and carriers.  The bacteria can be transmitted by the contamination of water, milk or food by flies.  Only a few organisms are needed to cause disease. Control measures  Hygienic control of food and water supplies  Detection and treatment of chronic carriers  Vaccination using TAB-vaccine. The vaccine contains a mixed culture of S. typhi, and S. paratyphi. The vaccine protects for 5-7 yrs. 2. Campylobacteriosis  Campylobacter are a group of tiny strictly micro-aerophilic curved or spiral gram negative rods  Campylobacter jejuni and Campylobacter coli cause food poisoning and are associated with acute enterocolitis (inflammation of small and large intestine) in man.  Campylobacter jejuni occur in large numbers in cattle feces, and poultry as normal flora.  Campylobacter coli are commonly associated with human diarrhoea, and enteritis (inflammation of small intestine) in pigs mostly in association with Treponema hyodysenteriae. Disease in man Campylobacter jejuni and C. coli cause illness characterized by diarrhoea, abdominal pain, fever, nausea, vomiting, and abdominal complaints. The jejunum, ileum and colon are primarily affected resulting in acute inflammation and occasionally, abscess formation (a painful collection of pus).. Mode of infection  Infection occurs by ingestion of campylobacter organisms in contaminated foodstuffs.  Foods involved includes meat from infected animals, unpasteurized milk and possibly cross-contamination from these sources to foods eaten uncooked or unrefrigerated.  Among the meats, poultry constitutes the greatest potential source of infection to humans.  Microorganisms are present in poultry gut and feces upto 1,000,000 organisms/g of feces.  Carelessness in the kitchen e.g. cutting chickens with the same knife used to cut other foods without proper cleaning prior to use.  Pork is a major source of Campylobacter coli.  Contamination of pork occurs during slaughter. Clinical signs  Incubation period ranges between 2-11 days with an average of 3-5 days.  It is preceded by fever, followed by foul smelling and watery diarrhea, which runs for 3-4 days.  The diarrhea may sometimes contain blood and mucus in feces.  Abdominal pain is associated with backache, and a high mortality.  The condition is self-limiting but may last for up to 10 days. Preventive measures  Thorough cooking of all foodstuffs derived from animal sources.  Prevention of re-contamination after cooking.  Proper refrigeration of foods.  Recognition, control and prevention of campylobacter infections in animals, and  Maintenance of high standard of hygiene. 3. Escherichia coli food borne infection  Escherichia coli are potential food poisoning pathogens which are widely distributed in low numbers in food environments.  E. coli strains involved in food borne infection fall into the following groups: 1. Enteropathogenic E. coli 2. Enterotoxigenic E. Coli 3. Enteroinvasive E. coli 4. Enterohemorrhagic E. coli Clinical symptoms  Cause illness that is characterized by watery diarrhea in most patients.  In addition, there is fever, nausea, and abdominal cramps.  Bloody diarrhea may occur in fewer than 10 % of patients.  Illness is usually self-limiting, lasting for 2 to 3 days. Control measures  Proper cooking of meats  Avoidance of cross-contamination of foods in the kitchen, and  Good personal hygiene. 4. Shigellosis (Bacillary dysentery)  Shigellosis is caused by members of the genus Shigella.  The species involved include Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonei.  All strains of shigella posses potent exotoxins which are carbohydrate-lipid protein complexes.  The infective dose is smaller than that of salmonellae, except S. typhi. Clinical symptoms  The illness begins 1 to 4 days after ingestion of bacteria and may last 4 to 7 days.  Symptoms include watery or bloody diarrhea, fever, stomach cramps, nausea or vomiting, dehydration and prostration in severe cases and convulsions in young children.  The diarrhea which starts as a thin watery discharge quickly looses its fecal character to be composed of nothing but pus, mucus threads and blood.  Death from bacillary dysentery is uncommon when efficient treatment is provided.  However, S. dysenteriae infections have been reported to have a case fatality rate of 20 % and the mortality rate is higher in children than adults. Transmission  Spread is by fecal-oral route, and person-to-person transmission is common. Bacteria leaves the body in stool of an infected person and infects another person through contaminated hands, food, water, or objects.  Flies can spread shigella germs when they get into contact with infected stool and then contaminate drinking water or food.  Shigella organisms may remain viable in tap water for as long as 6 months, and in sea water for 2 to 5 months. Preventive measures  Practice good hygiene and sanitation.  Wash hands well with water and soap each time you use the ablution.  Home and surroundings should be kept clean to prevent contamination of food and water supply.  Proper disposal of human waste or sewage.  Keep kitchen work surfaces clean.  Use boiled or chlorinated water  Eat properly cooked of food 5. Cholera  Cholera is caused by Vibrio cholera bacterium.  Cholera vibrios are ingested in drink or food.  The organism multiply in the small intestine to produce a very potent enterotoxin, which stimulates a persistent out pouring of isotonic fluid by the gut mucosal cells. Transmission  Man is the only natural host of the cholera vibrios  Spread of infection is from person-to-person, through contaminated water or foods.  Shrimps and vegetables are the most frequent carriers.  Cholera is an infection of crowded poor class communities  Cholera outbreaks occur either as explosive epidemics usually in non-endemic areas or as protracted epidemic waves in endemic areas Clinical symptoms  Sudden onset of effortless vomiting and profuse watery diarrhea.  Patients may produce up to 20-30 stools per day, losing many litres of water and electrolytes, o Very rapid dehydration (body loses more fluid than take in leading to the upsets of the mineral balances) and hypovolemic shock (an emergency condition in which severe blood or other fluid loss makes the heart unable to pump enough blood to the body causing many organs to stop working). Urine is suppressed, the skin becomes wrinkled, the eyeballs are sunken and the voice becomes weak Blood pressure falls, the heart sounds become barely audible and the pulse become rapid and weak just before death. Death may occur in 12 to 24 hrs due to rapid dehydration Control measures  Provision of potable water  Proper sewage disposal  Proper cooking and hygienic handling of food  Observation of personal hygiene  Vaccination -The heat killed, phenol preserved vaccine has protection that lasts for 3 to 6 months.  Viral Food borne infections Characteristics of viral food borne infections  Only a few viral particles are necessary for the disease to develop  High numbers of viral particles are further transmitted via feces of infected persons (up to 1011 particles per gram of feces).  Specific lining cells are necessary for virus replication. Accordingly they cannot multiply in foods or water.  Food borne virus are stable and acid resistant outside host cells  Hepatitis A and Norwalk-like virus (Novovirus) are the most important viral food borne pathogens. Highly infectious and may lead to widespread outbreaks Hepatitis A  The incubation period is long, being an average of 30 days (range 15-50 days).  Systemic infection characterized by gastrointestinal manifestations and liver injury, fever, malaise, anorexia, nausea, abdominal discomfort, bile in urine and jaundice.  The duration of the disease could be from a few weeks to several months. Norwalk-like virus (Novovirus) food borne infection  Novovirus infection is relatively mild with an incubation period of 3 days.  Clinical manifestations/symptoms include vomiting and diarrhea, and rarely convulsions.  Asymptomatic infection are common and may contribute to the spread of the infection.  Infections have resulted from consumption of raw oyesters.  5.3. FOOD BORNE INTOXICATIONS These are diseases caused by consumption of food containing: 1. Biotoxicants – toxins from certain plants and animals. 2. Metabolic products (toxins)- formed and excreted by microorganisms while they multiply in food, or in gastrointestinal tract of man. 3. Poisonous substances- intentionally or unintentionally added to food during production, processing, transportation or storage.  Food borne intoxications have short incubation periods (minutes to hours) and are characterized by lack of fever. Food borne intoxications can be classified into: a. Bacterial intoxications b. Fungal intoxications c. Chemical intoxication d. Plant toxicants, and e. Poisonous animals. 1. Bacterial food borne intoxications 1. Staphylococcus aureus intoxication 2. Bacillus cereus intoxication 3. Clostridium perfringens intoxication 4. Clostridium botulinum intoxication i. Staphylococcus aureus food borne intoxication  Caused by consumption of food contaminated with staphylococcal enterotoxins produced by certain strains of Staphylococcus aureus while growing in food. Vehicle foods  Milk and milk products including pasteurized milk, yoghurt, chocolate milk, fermented milk, cream filled pastries, poultry, fish, shellfish, meat and meat products, non meat salads, egg and egg products, vegetables and cereal products Disease symptoms in man  Incubation period is 1-6 hrs after consumption of food contaminated with at least 1.0 µg of enterotoxin.  Clinical signs include salvation, nausea, vomiting, abdominal cramps, sometimes diarrhea with prostration.  It has an attack rate of 5-100%, but fatalities which occurs in children, the old and debilitated victims are rare.  Duration of illness is 24-72 hrs. Preventive measures  Practice good personal hygiene including good personal conduct in food establishment and when handling food.  Use of spoons when serving foods to prevent contamination of cooked foods  Fast cooling of cooked food and keeping such foods at low temperatures  Discourage consumption of left-overs ii. Bacillus cereus food borne intoxication  Caused by consumption of enterotoxins produced by some strains of Bacillus cereus. Vehicle foods  Bacillus cereus is a common soil saprophyte and is easily spread to many types of foods, especially of plant origin,  It is frequently isolated from meat, eggs and dairy products,  Cereal dishes e.g. rice, spice, mashed potatoes, herbs, vegetables, minced meat, cream and milk. iii. Clostridium perfringens intoxication  Caused by Clostridium perfringens enterotoxin produced in the gastrointestinal tract by enterotoxigenic strains of C. perfringens.  The organism is found in the soil, dust, water, sewage marine sediments, decaying materials, intestinal tracts of humans and other animals.  This organism is a spore-forming, anaerobic, gram positive bacillus.  The food poisoning strains are heat resistant and survive heating at 100oC for 1 hr). Vehicle foods  The food involved are those that are prepared one day and served the next day.  Foods that have been involved include red meats, chickens, fish, pork, fruits, vegetables, spices etc.  The heating of such foods is inadequate to destroy heat resistant endospores. Symptoms of disease in man  Symptoms appear 6-24 hours after ingestion  Symptoms include nausea, intestinal cramps, pronounced diarrhea Prevention  Proper cooking of food and eating freshly prepared foods.  Thorough washing and sanitation of containers  Hygiene handling of cooked food  Fast cooling of cooked food. Storing food in small quantities will enhance cooling.  Proper reheating of cold cooked food before consumption iv. Clostridium botulinum food borne Intoxication  Botulism is a type of food poisoning caused by consumption of enterotoxins produced by strains of Clostridium botulinum.  C. botulinum is an obligate, spore-forming anaerobe, and Gram positive bacilli  The strains are divided into proteolytic and non-proteolytic types according to whether they hydrolyze proteins or not. Characteristic of Botulinal toxins  Neurotoxins, that are highly toxic, heat labile (inactivated by heating at 80oc for 10 min), unstable at alkaline pH (but stable below pH 7.0) but resistant to pepsin and acidic environment.  The toxins can resist the action of the gastric and intestinal juices.  Botulinus toxin is one of the most lethal poisons known. The calculated lethal dose for an adult person is 10 µg.  Uncooked fresh foods are safe because they are eaten before the toxin has had time to develop, while, if foods are cooked, the toxin is destroyed. Symptoms of the disease in man  Symptoms include nausea, vomiting, fatigue, dizziness, headache, dryness of skin, mouth and throat, constipation, lack of fever, nerve paralysis and great muscular weakness, double vision, respiratory failure and death.  Duration of illness 1-10 days and mortality is high up to 60- 100% of affected persons. The earlier the appearance of symptoms, the higher the mortality rate.  2. Fungal intoxications  Caused by consumption of metabolites produced by fungi, when growing in food. These metabolites are called mycotoxins. E.g. Aflatoxicosis caused by aflatoxins produced by the fungi (most public health significance)  Grains, oilseeds, fruits and vegetables are mostly involved if they are stored at high humidity (≥ 0.75) or if they are not properly dried before storage. Aflatoxicosis  Caused by aflatoxins produced by the fungi, e.g. Aspergillus flavus.  When consumed in large doses, they are lethal in causing acute hemorrhagic syndromes  Sub-lethal doses cause histotoxic changes Prevention of aflatoxicosis  Proper drying and storage of grains and other affected foods  Use of fungicides as seed dressings to protect stored cereals and other foods like pulses and potatoes against fungal invasion.  3. Chemical food borne intoxication  Arising from consumption of food containing poisonous chemicals  These may be intentionally or unintentionally added to foods as a result of producing, processing, transporting or storage. Chemical substances involved  Heavy metals e.g. mercury, arsenic, flouride, lead, cadmium, cyanide etc.  Pesticides and insecticides e.g. DDT, Organochlorines and organophosphates.  Herbicides and Fungicides e.g. organomercurials  Preservatives e.g. nitrites, nicotinate, etc How chemicals enter foods  Accidental contamination- e.g. Heavy metals, Pesticides, and radionuclides.  Intentional addition- e.g preservatives such as nitrite and sodium nicotinate for color preservation and fungicides used as dressing during storage.  Leaching from containers- e.g zinc galvanized containers by acid foods, copper surfaces, lead pipes, asbestos roofs.  Usage: Presence of such chemicals in food as a result of use of their use in animal and crop husbandry  Maliciously -added to cause harm (is rare). Preventive measures  Do not use utensils or containers that are able to leach chemicals such as antimony, cadmium, zinc, copper, etc.  Prevent contamination of foods when using insecticides.  Prevent misuse or avoid use of dangerous additive e.g. sodium nicotinate.  Education of persons preparing food (e.g. possibility of Zn poisoning).  Ensure that withdrawal periods are observed after use of pesticides and antibiotics in animal and crop husbandry.  4. Biotoxications  These are disorders resulting from ingestion of a poisonous substance (a biotoxin) present in the body of a plant or animal.  Such substances are derived from plants or animals presumably as a result of metabolic activities. Animals biotoxications Animal tissues may be rendered poisonous by bacterial and enzymatic decomposition, but some are naturally toxic. Prevention of animal biotoxications  Eating of unknown meats from vertebrates or invertebrates sources is always a threat to the consumer.  Local eating customs should be followed and local quarantine regulations strictly adhered to in order to reduce the risk.  Avoid sea foods and always heat foods to above 100oC to denature the inherent heat labile toxins that may be present in animal tissues. 5.3. Water Borne Diseases  Water borne diseases also are viral, bacterial and parasitic (Protozoa and Helminths) diseases which use water as a common means of transmission.  Diarrhoeal diseases are the leading cause of mortality and morbidity of children under five years of age;  Because their immune systems are not fully developed and their resistance may be further impaired by malnutrition Etiology of water Borne Diseases 1. Bacterial  Shigellosis, Typhoid Fever, Cholera, Acute Gastroenteritis (E.coli) 2. Viral  Infectious hepatitis, poliomyeltis, Rota Virus 3. Protozoan  Amaebiasis, Giardiasis 4. Helminths  Drancunculiasis (Guinea worm), Bilharzia Prevention and Control  There is abundant evidence that improving only water quality or only latrines will have little or no effect on the incidence of water borne diseases. Thus there has to be a holistic intervention approach to these problems. The prevention and control measures include:  Sanitary disposal of human waste.  Protecting public water supplies from fecal contamination.  Treatment of suspected water supplies, both rural and urban, before consumption.  Keeping fetched water at home safe during storage.  Mass treatment during epidemic outbreaks, e.g. at schools, in prisons etc.  Treatment of surface water supplies.