zoonoses and communicable diseases common to ... - PAHO/WHO

STAPHYLOCOCCAL FOOD POISONING 253Purulent staphylococcal synovitis is a disease that causes appreciable losses inchickens and turkeys. In the former Czechoslovakia, one of the principal sources ofstaphylococcal food poisoning is thought to be infected poultry (Raska et al., 1980).Staphylococcal strains isolated from poultry farms in that country and others produceenterotoxin D. Many researchers have isolated S. aureus from the nasal passagesand skin of 100% of the birds examined, as well as from the nose and skin of72% of swine (Genigeorgis, 1989). These data indicate that meat- and milk-producinganimals may make a significant contribution to contamination of the food chain.The Disease in Man: The incubation period is short, generally three hours afteringestion of the food involved. The interval between ingestion and the first symptomsmay vary from 30 minutes to 8 hours depending on the amount of toxiningested and the susceptibility of the individual.The major symptoms are nausea, vomiting, abdominal pain, and diarrhea. Somepatients may show low fever (up to 38°C). More serious cases may also show prostration,cephalalgia, abnormal temperature, and lowered blood pressure as well asblood and mucus in the stool and vomit. The course of the disease is usually benignand the patient recovers without medication in 24 to 72 hours.There are patients who require hospitalization due to the severity of the symptoms.It is assumed that these are people who have ingested foods with high dosesof the enterotoxin, who were not exposed to the enterotoxin in the past, or who maybe debilitated due to other causes.Source of Infection and Mode of Transmission: The principal reservoir of S.aureus is the human carrier. A high proportion of healthy people (30% to 35%) havestaphylococci in the nasopharynx and on the skin. A carrier with a respiratory diseasecan contaminate foods by sneezing, coughing, or expectorating. Similarly, hemay contaminate food he handles if he has a staphylococcal skin lesion. However,even if not sick himself, the carrier may contaminate food by handling different foodingredients, equipment, utensils, or the finished product. According to variousauthors, the proportion of enterotoxin-producing S. aureus strains of human originvaries from 18% to 75% (Pulverer, 1983). The proportion of toxigenic strains isolatedfrom various sources (humans, animals, and food) is very high.Strains of human origin predominate in epidemics, but animals are also reservoirsof the infection. Milk from cow udders infected with staphylococci can contaminatenumerous milk products. Many outbreaks of staphylococcal poisoning have beencaused by the consumption of inadequately refrigerated raw milk or cheeses fromcows whose udders harbored staphylococci. The largest outbreak affected at least500 students in California (USA) between 1977 and 1981 and was traced to chocolatemilk (Holmberg and Blake, 1984). Another outbreak occurred in the US inwhich 850 students became ill after drinking chocolate milk. The average amount ofenterotoxin A in the milk was 144 ng per half-pint carton (Evenson et al., 1988).Goat milk is implicated more rarely. A small outbreak occurred in Israel amongBedouin children who drank semna, goat milk that is skimmed, sweetened, andheated. The milk came from a goat with mastitis caused by S. aureus enterotoxin B(Gross et al., 1988).Small outbreaks and sporadic cases occurred in a town in Scotland betweenDecember 1984 and January 1985, in which cheeses made from sheep milk wereimplicated. Bacteriological examination of the various samples of the cheese was