Horsemeat-Associated Trichinosis -- France

In August and October 1985, two outbreaks of trichinosis associated with consumption of horsemeat occurred in France. Brief reports follow.

Outbreak 1. During the week of August 12, 1985, several cases of trichinosis were diagnosed in Melun, a town located 30 miles southeast of Paris. Shortly thereafter, several more cases were diagnosed from a southern district of Paris in the 14th arrondissement. An investigation was undertaken to determine the extent and source of this outbreak. Cases of trichinosis were identified through review of medical records from private and public laboratories and contact with local physicians in the two areas where the initial cases were identified. Three hundred seventy-five (92%) of 409 persons with potential trichinosis were interviewed. A case was defined as an individual with (1) a Trichinella-positive muscle biopsy, with recent signs and symptoms suggestive of trichinosis; (2) positive indirect immunofluorescence test (titer greater than 1:100) for Trichinella antibodies, with recent signs and symptoms suggestive of trichinosis; or (3) at least three of the following signs and symptoms suggestive of trichinosis: eosinophilia, fever, myalgia, and/or periorbital edema.

Three hundred twenty-five individuals met the case definition. One hundred fifty-nine (49%) of the patients were from the 14th arrondissement of Paris, and 166 (51%) were from Melun. Patients' ages ranged from 2 years to 86 years (mean 41 years). One hundred sixty-six (51%) were male. Age distribution by sex was similar.

Diagnosis was made by a positive muscle biopsy in one patient, positive serology in 234 (72%), and clinical presentation in 90 (28%). Of the symptoms compatible with trichinosis, myalgia was reported among 306 (94%) of the patients; fever, among 293 (90%); facial edema, among 189 (58%); diarrhea, among 169 (52%); and rash, among 137 (42%). Twenty percent of the patients complained of neurologic symptoms, including paresis, oculomotor dysfunction, visual field changes, dyaesthesia, and dizziness. Onset of symptoms, known for 288 (89%) patients, occurred between July 29, and September 15, 1985 (Figure 3). Two patients died--an 86-year-old man, and a 65-year-old man with a history of heart disease. Four patients were pregnant; one had a miscarriage during the sixth week of pregnancy. Examination of fetus and placenta revealed no larva. The other three women delivered healthy babies.

The investigation implicated horsemeat as the source of the outbreak. All 325 patients reported consuming horsemeat--99% of whom ate it raw or rare--before onset of illness, compared with 38% of a random sample of 198 people questioned on a street in the 14th arrondissement of Paris. Family members of patients who did not eat any horsemeat but shared other food with the patients did not become infected with trichinosis. Similarly, a case-control study in a Melun prison showed that all cases and no controls had ingested horsemeat. Although several butchers in Paris and Melun sell horsemeat, all patients purchased their horsemeat exclusively from one of two shops between July 22 and August 5. The butchers from these two shops and their families were also infected with trichinosis. Records indicated that each shop received half of a single horse carcass on July 22. The carcass had been shipped as "fresh meat" to France from a slaughterhouse in Connecticut, which ships 8,000-9,000 horses to Europe each year. The establishment is inspected by the U.S. Department of Agriculture, but inspection did not include examination of meat samples for trichinae. Because horses are obtained by the slaughterhouse from multiple sources and are not individually identified on leaving the processing plant, the implicated horse could not be traced to farm of origin. No meat from the implicated horse was available for inspection.

Outbreak 2. Although not fully investigated at this time, a second outbreak of trichinosis occurred in France beginning October 3, 1985. Preliminary reports from physicians and hospitals suggest that up to 900 individuals were infected with trichinosis, most coming from three foci in Paris and its surroundings: Paris 12, Nogent/Marne, and Vitry/Seine. Six provincial foci were also involved but with smaller numbers of patients.

Imported horsemeat was again implicated as the source of the infection. All patients reported eating horsemeat purchased from one shop in each of the foci. Five of nine butchers selling the horsemeat at these shops and their families were infected. Records indicate that all of the implicated shops received portions of the same horse imported from West Germany. Three quarters of the horse were sold as fresh meat in the three main foci of the outbreak on September 12. The remaining quarter was deboned and vacuum-packed in 5- to 20-kg portions and was delivered to the six secondary provincial foci over the next 2 weeks. Reported by T Ancelle, MD, J Dupouy-Camet, MD, F Heyer, MD, C Faurant, MD, J Lapierre, MD, Dept of Parasitology, Cochin Hospital, Paris, France; G Parham, DVM, W Leese, JC Leighty, DVM, Food Safety and Inspection Svc, US Dept of Agriculture, Beltsville, Maryland; Helminthic Diseases Br, Div of Parasitic Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note:Horsemeat has rarely been implicated as a source of trichinosis. The first reported outbreaks due to this meat source occurred in Italy in 1975 (1) and in France in 1976 (2). In both instances, the infected horsemeat had been imported from Eastern Europe. How horses become infected with trichinosis is unknown. Horses are commonly observed to be herbivorous; however, experimental studies prompted by the outbreak in Italy indicate that horses will ingest meat placed in their feed and will become infected with trichinosis when fed infective larvae (3). The unusually large numbers of cases involved in the two 1985 outbreaks are related to the size of the implicated animal species (the carcass of the horse associated with outbreak 1 was 278 kg) and the preference among French consumers for raw or lightly cooked horsemeat, prepared as steaks, in soups, or ground ("steak tartare"). At the time of the second outbreak, the French Ministry of Agriculture temporarily banned importation of horsemeat from all countries and will currently accept it only if certified trichinae-free by an approved inspection procedure.

Little is known about Trichinella infection in horses in the United States, but it is assumed to be extremely rare. Between late October and December 31, 1985, samples from 20,000 horses killed in the United States were examined for Trichinella, with negative results. Trichinosis in horses in the United States would presumably represent an unlikely public health hazard because few citizens eat horsemeat, and those who do probably cook it. Since 1975, 30 to 289 U.S. trichinosis cases have been reported per year, approximately 80% of which were associated with the ingestion of pork (4).

References

1. Mantovani A, Filippini I, Bergomi S. Indagini su un' epidemia di trichinellosi umana verificatasi in Italia. Parassitologia 1980;22:107-34.

2. Bouree P, Bouvier JB, Passeron J, Galanaud P, Dormont J. Outbreak of trichinosis near Paris. Br Med J 1979;1:1047-9.

3. Bellani L, Mantovani A, Pampiglione S, Filippini I. Observations on an outbreak of human trichinellosis in northern Italy. In: CW Kim, ZS Pawlowski, eds. Proceedings of the Fourth International Conference on Trichinellosis. University Press of New England, 1976:535-9.

4. Schantz PM. Trichinosis in the United States--1947-1981. Food Tech 1983;37:83-6.

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