Foodborne diseases

The definition of food poisoning by the World Health Organisation is “any disease of an infectious or toxic nature caused by or thought to be caused by the consumption of food and water”. This definition includes all food and waterborne illnesses regardless of the presenting symptoms and signs; it thus includes not only acute illnesses characterised by diarrhoea and/or vomiting, but also illnesses presenting with manifestations not related to the gastrointestinal tract, such as botulism and listeriosis and illnesses caused by toxic chemicals. Illnesses due to know allergies and intolerances are excluded.

Poultry and eggs are recognised as a source of a number of bacterial pathogens which cause food poisoning in humans.

Causative agents reported for foodborne outbreaks, 2005
  N %
of total
Outbreaks
General Family
N Human cases
No. admitted
to hospital

No.
of deaths

Bacillus spp. 74 1.4 62 12 1,18 28 -
Brucella spp. 2 <0.1 1 1 15 - -
Campylobacter spp. 494 9.2 338 156 2,478 150 1
Clostridium spp. 79 1.5 60 19 1,633 38 1
Cryptosporidium spp. 7 0.1 7 - 195 0 0
Flavivirus 3 0.1 1 2 46 33 -
Foodborne viruses 312 5.8 280 32 6,812 255 0
Giardia 16 0.3 14 2 34 0 -
Histamine 40 0.7 34 6 326 28 -
Listeria 5 0.1 5 - 26 3 0
Path. Escherichia coli 60 1.1 44 16 796 125 0
Salmonella spp. 3,406 63.6 1,577 1,829 25,76 3,554 16
Scrombrotoxin 10 0.2 7 3 69 2 -
Shigella spp. 47 0.9 29 18 322 82 1
Staphylococcus spp. 164 3.1 106 58 1,692 365 1
Trichinella spp. 12 0.2 5 7 142 62 -
Yersinia spp. 9 0.2 5 4 22 7 -
Multiple agents 12 0.2 9 3 276 43 0
Other2 30 0.6 22 8 260 7 2
Unknown 573 10.7 467 106 5,699 557 2
Total 5,355 100 3,073 2,282 47,783 5,339 24


1. Including all outbreaks from Germany and Sweden with no distinction on type (general or family outbreak).
2. Include Aeromonas and Francisella


Role of poultry


Poultry is seen as an important source of paratyphoid Salmonellae which can cause foodborne illness in humans. More than 99 percent of all identified Salmonellae don’t cause clinical disease in poultry. Salmonellae can be acquired by the laying hen through two possible ways: horizontal and vertical transmission.
The ingestion of Salmonellae is the major route for infection in mature chickens. Chickens can be infected with Salmonellae through eating contaminated particles, feed, drinking water or manure. Eggs can be infected by an environment contaminated with Salmonellae. This can lead to an infected day-old chick at the time of hatching. This type of transmission is called horizontal transmission.

S. enteritidis can be egg transmitted due to deposition in the egg yolk prior to lay. Therefore, day-old chicks can be infected at the time of hatching. This type of transmission is called vertical transmission. When Salmonellae are acquired through the intake of contaminated food or water they have to survive the acid environment of the stomach before they adhere and enter the cells lining the epithelium of the intestine. Salmonellae have to survive in blood and replicate in the macrophages of the liver and spleen. For full expression of pathogenicity it is necessary for Salmonellae to replicate within host cells. Chickens can be vaccinated against Salmonellae and vaccination is reducing both egg content and shell contamination. Also the number of tissues positive for Salmonellae is lower for vaccinated birds. Vaccination is an important tool to reduce the number of infections with Salmonellae. Several researchers investigated factors of influence on the prevalence of Salmonella contamination for broiler farms. The factors: equipment, the presence of rodents and having had a disease leading to a treatment in the previous flock are increasing the prevalence of Salmonella contamination. Factors reducing the prevalence of Salmonellae contamination are cleaning, hygiene, disinfection and gravel alongside the broiler house.
Clinical salmonellosis usually only occurs in young chicks until the age of three weeks and most frequently is associated with S. enteritidis and S. typhimurium.

Human Salmonellosis

Eggs are playing a major role in the distribution of Salmonellae. In the period 1994 to 1998 almost 40 percent of all cases of human salmonellosis were associated with eggs. In contrast to other European countries, in The Netherlands, the total number of laboratory diagnosed infections with Salmonellae seems to lower from the mid eighties. This reduction is almost only caused by the reduction in the incidence of Salmonellae in the group of children of 0-5 years and in the group of persons over 70 years. The greater the number of Salmonellae cells present within an egg the greater the chance of infection. Differences between the different serotypes of Salmonellae are present. Symptoms of an infection with S. typhimurium DT104 are believed to be more severe than those due to S. enteritidis PT4. Infants, elderly people and immunocompromised hosts are most susceptible to infections with Salmonellae. Different symptoms can occur when clinical Salmonellosis is present. Symptoms include: diarrhoea sometimes with blood, vomiting, sickness, cramps, bellyache, lack of appetite, loss of weight and fever (>38˚C). The disease is usually self-limiting and a few days to a week after the first signs of illness recovery follows. Carriage of Salmonellae for more than one year after disease is possible.
Zoonoses are diseases that are transferable between animals and humans. Zoonoses can be transmitted from animals to humans in different ways. Foodstuffs of animal origin are the most important source of zoonoses in humans.