Zoonoses

• Zoonoses


  Diseases that can be transmitted from animals to humans
• Food borne diseases (FBD)


  Acute illnesses associated with the recent consumption of food
• The food involved is usually contaminated with a disease pathogen or toxicant
• Such food contains enough pathogens or toxicant necessary to make a person sick
• Classification of food borne diseases

  • Food borne infections
  • Food borne intoxications
• Food borne infections


  Caused by the entrance of pathogenic microorganisms contaminating food into the body, and the reaction of the body tissues to their presence
• Types of food borne infections

  • Fungal
  • Bacterial
  • Viral
  • Parasitic
• Food borne infections


  • Tend to have long incubation periods and are usually characterized by fever
• Bacterial food borne infections


  • Cholera
  • Salmonellosis
  • Typhoid fever
  • Shigellosis
  • Yersiniosis
  • Escherichia coli infection
  • Campylobacteriosis
  • Vibrio parahemolyticus
  • Listeriosis
• Mycotic food borne infections

  • Candida spp.
  • Sporothrix spp.
  • Wangiella spp.
• Viral food borne infections

  • Hepatitis A
  • Norwak virus
  • Poliomyelitis virus
• Salmonellosis


  A group of organisms with over 2000 different serotypes that are capable of causing disease in animals and man when taken into the body in sufficient numbers
• Many salmonella species have a wide host range and commonly cause food poisoning
• Some salmonella serotypes are associated with human disease and are not known to affect animals
• Salmonellae are ubiquitous in the gut of human and animals and act as sources of food contamination
• People who are carriers of the salmonellae contaminate the food
• A heavy dose up to 10,000 -1,000,000 organisms per gram of food is required to cause salmonella infection
• Common food poisoning salmonella serotypes

  • Salmonella typhimurium
  • Salmonella enteritidis
  • Salmonella dublin
  • Salmonella softenburg
  • Salmonella virchow
  • Salmonella montevideo
  • Salmonella infantis
  • Salmonella newport
• Salmonellae


  • Killed by temperatures attained in commercial pasteurization
  • Can remain alive in moist earth for one year and in dry earth for 16 months
  • Not destroyed in carcasses or offal maintained at chilling or freezing temperatures, or in the usual pickling solutions
• Forms of salmonella food poisoning outbreaks

  • Sporadic cases involving only one or two persons in a household
  • Family outbreaks in which several members of the family are affected
  • Large outbreaks caused by a widely distributed infective food item
  • 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
• Ways salmonellae reach food

  • Directly from slaughter animals to food
  • From human excreta, and transferred to food through hands, utensils, equipment, flies etc.
• Food poisoning is more likely to occur if the total number of microorganisms present is high
• Foods commonly involved in salmonella food poisoning

  • Meat and meat products
  • Milk and milk products
  • Egg and egg products
• Salmonella food poisoning symptoms

  • Abdominal pain
  • Headache
  • Diarrhea
  • Fever
  • Vomiting
  • Prostration and malaise
  • In severe cases: septicaemia with leucopenia, endocarditis, pericarditis
• Severe cases are encountered in babies, young children, the sick and in elderly persons, with a mortality up to 13%
• Salmonella food poisoning 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)


  Caused by Salmonella typhi and Salmonella paratyphi A, B and C respectively
• Enteric fevers


  • Incubation period usually 2 weeks, but might vary between 3 and 28 days for typhoid fever and between 1 and 15 days for the paratyphoid fevers
  • Generalized septicaemic infections with a frequent, if not constant bacteraemia during the first two weeks of the disease
  • Abdominal symptoms are severe, while fever and illness may continue for 4-6 weeks
• The typhoid and paratyphoid bacilli are essentially human parasites and are acquired mostly from human sources, namely, patients and carriers
• Only a few organisms are needed to cause enteric fever disease
• Enteric fever control measures

  • Hygienic control of food and water supplies
  • Detection and treatment of chronic carriers
  • Vaccination using TAB-vaccine
• Campylobacteriosis


  Food poisoning caused by Campylobacter jejuni and Campylobacter coli
• Campylobacter


  • Tiny strictly micro-aerophilic curved or spiral gram negative rods
  • Campylobacter jejuni occur in large numbers in cattle feces, and poultry as normal flora
  • Campylobacter coli are commonly associated with human diarrhoea, and enteritis in pigs mostly in association with Treponema hyodysenteriae
• Campylobacter disease in man


  • Characterized by diarrhoea, abdominal pain, fever, nausea, vomiting, and abdominal complaints
  • Primarily affects the jejunum, ileum and colon resulting in acute inflammation and occasionally, abscess formation
  • Self-limiting
• Campylobacter clinical signs


  • Incubation period ranges between 2-11 days with an average of 3-5 days
  • Preceded by fever, followed by foul smelling and watery diarrhea, which runs for 3-4 days
  • Diarrhea may sometimes contain blood and mucus in feces
  • Abdominal pain is associated with backache, and a high mortality
  • Condition is self-limiting but may last for up to 10 days
• Foods involved in campylobacter infection

  • Meat from infected animals
  • Unpasteurized milk
  • Cross-contamination from these sources to foods eaten uncooked or unrefrigerated
• Poultry constitutes the greatest potential source of campylobacter infection to humans
• Pork is a major source of Campylobacter coli
• Campylobacter prevention 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
  • Maintenance of high standard of hygiene