Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/1998
Publication Date: N/A
Interpretive Summary: The presence of the parasite Trichinella spiralis in pork has resulted in consumer avoidance of fresh pork products and has impeded access to international markets. Unlike many other countries, the U.S. has no slaughterhouse inspection program for trichinae in pigs. To make U.S. pork safer and more acceptable to consumers and to maintain or enhance international sales, the USDA along with the National Pork Producers Council has initiated a series of studies to test the feasibility of an on farm program to certify pigs free from trichinae. In this study, USDA scientists used a serology test to determine the prevalence of trichinae in pigs in the northeastern U.S. and to determine what risk factors were associated with transmission to pigs. The suitability of the serology test for monitoring trichinae-free status was also evaluated. The presence of trichinellosis in pigs in New England and New Jersey has declined during the past 12 years when compared with previous prevalence studies. In addition, infected pigs harbored fewer worms. Waste feeding had no statistically significant association with seropositivity for trichinellosis in pigs; significant associations were found with exposure to live wildlife and wildlife carcasses, suggesting biosecurity is a major factor in transmission of trichinellosis to pigs. The serology method was found to be highly sensitive for identifying infected animals. Based on these studies a certification pilot to test methods for the production of trichinae free pork was initiated in Iowa.
Technical Abstract: The objectives of this study were to determine the efficacy of EIA for detecting trichinellosis in farm raised pigs, to determine prevalence of swine trichinellosis in endemic areas, and to determine risk factors associated with transmission of trichinellosis to pigs. We tested 4078 pigs of various ages and mixed sex from 156 farms in New England and New Jersey raised under a variety of management conditions. Farms were selected based on feed type (grain, regulated waste, non-regulated waste). Serum was tested by enzyme-linked immunoassay for antibodies to Trichinella spiralis. Seropositive pigs were tested by digestion at slaughter (when possible) for the presence of Trichinella larvae. Questionnaires, completed at the time of serum collection, were used to develop descriptive statistics on farms tested and to determine measures of association for risk factors for the presence of Trichinella-seropositive pigs. A total of 4078 pigs were tested dfrom 156 farms in New England and New Jersey. A total of 15 seropositive pigs on 10 farms were identified, representing a prevalence rate of 0.37% and a herd prevalence rate of 6.4%. A total of 9 seropositive pigs and one suspect pig from 6 farms were tested by digestion; 4 pigs (representing 3 farms) harbored Trichinella larvae at densities of 0.003 - 0.021 larvae per gram of tissue; no larvae were found in 6 pigs. Risk factors which were significantly associated with seropositivity included access of pigs to live wildlife and wildlife carcasses on the farm.