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Trichinosis -- Hawaii

In January 1986, three cases of trichinosis were reported to the Hawaii Department of Health. The cases occurred among persons who had eaten wild boar meat given to them by a local Hawaiian who had killed the animal. Because the meat had been distributed among several family members and friends of the hunter, an investigation was conducted to determine the extent of the outbreak.

Among all of those who had received some of the wild boar, health officials identified 28 persons who had eaten the meat. Seven of them were not available for follow-up; the remaining 21 persons were interviewed on February 21 and 22, 1986. Seven (33%) of these had illnesses that met the standard case definition for trichinosis (1). All seven patients had at least four of the following symptoms: myalgia (7), malaise (7), fever (6), headache (6), diarrhea (4), nausea (4), periorbital edema (4), vomiting (2), and trunk and limb edema and cutaneous rash (1). The patients ranged from 13 to 55 years of age (mean = 32 years); five (71%) were male. All were of Hawaiian or Asian decent. Dates of ingestion ranged from January 9 to January 22; dates of onset of symptoms ranged from January 31 to March 1. The median incubation period was 26 days, and the median duration of illness was 14 days. One patient was hospitalized; three were treated with mebendazole, and two were treated with thiabendazole. All patients recovered.

Serum was drawn from all seven patients during a time period that ranged from 50 and 81 days after ingestion of the implicated meat. There was serological evidence of infection in five of these patients (titers greater than or equal to 40 by the bentonite flocculation test). Laboratory studies of four patients seen by a physician during acute illness revealed eosinophilia ranging from 8% to 55%.

Samples of the implicated wild boar meat were sent to the Centers for Disease Control for study. An artificial digestion procedure performed on the meat revealed from 2 to 9 Trichinella larvae per gram of the frozen meat.

Four of the 21 persons interviewed ate the meat after it had been microwaved at high heat for 2 minutes; the remaining 17 persons ate the meat fried. All four of those eating microwaved meat became ill; and three (18%) of those who had eaten fried meat became ill (p = 0.01, RR = 5.7). Inadequate recall and incomplete responses prevented investigators from looking at dose response for illness. However, the two people with the most severe illness had eaten the largest amounts of wild boar meat.

All remaining portions of the wild boar meat were confiscated. In addition, all persons who had eaten the meat were instructed in the proper handling and preparation of pork products. Reported by EL Lyons, DVM, MS, CK Wakida, AP Liang, MD, MPH, State Epidemiologist, Hawaii Dept of Health; Helminthic Diseases Br, Div of Parasitic Diseases, Center for Infectious Diseases, Div of Field Svcs, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Trichinella spiralis continues to be a persistent public health problem in the United States. During the period 1975-1985, pork (including wild boar) was implicated in 78.7% of the reported cases in which the implicated meat item was identified. Other wild animal meat was implicated in 13.8% of the reported cases, and ground beef, in 6.7%. During the same time period, only 19 (1.6%) of the reported cases of trichinosis were associated with wild boar meat. Hawaii reported nine cases, eight of which were associated with consumption of wild boar meat (1,2).

In the present outbreak, three cases were associated with fried wild pork sausage that was undercooked. Four cases were associated with wild pork sausage prepared in a microwave oven; however, the procedures used were not compatible with those generally recommended by microwave oven manufacturers or pork interest groups for safe microwave cooking of pork (3). The U.S. Department of Agriculture has recommended cooking pork in a microwave oven until it attains a temperature of 76.7 C (170 F) throughout. Improper cooking of meat in a microwave can result in variability of internal temperatures in the meat, with the result that there will not be proper inactivation of bacteria and other potentially disease-producing organisms (4,5).

References

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

  2. CDC. Trichinosis surveillance, 1984. MMWR 1986;35:11SS-15SS.

  3. Zimmerman WJ. Evaluation of microwave cooking procedures and ovens for devitalizing trichinae in pork roasts. J Food Sci 1983;48:856-60, 899.

  4. Zimmerman WJ. An approach to safe microwave cooking of pork roasts containing Trichinella spiralis. J Food Sci 1983;48:1715-8, 1722.

  5. Zimmerman WJ. Power and cooking time relationships for devitalization of trichinae in pork roasts cooked in microwave ovens. J Food Sci 1984;49:824-6.

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