Sensitivity of artificial digestion and enzyme immunoassay methods of inspection for trichinae in pigs

Forty-seven pigs were infected with varying doses of Trichinella spiralis and tested for evidence of infection by serology, using an enzyme immunoassay (EIA), and by artificial digestion methods. Using a l-g sample, as prescribed in accordance with European Union (EU) directives, the sensitivity of the pooled-sample artificial digestion method was between three and five larvae per gram (LPG) of tissue. Using a 5-g sample size, in accordance with methods described in the U.S. Code of Federal Regulations, and as required for the inspection of horses exported to the EU, the sensitivity of the test was increased to approximately 1 LPG. Serological testing by EIA detected pigs with as few as 0.02 LPG, but detection times varied from 4 to 8 weeks after infection. Mean postinoculation times for detection by serology were 32 to 42 days. On the basis of these results, it is clear that digestion testing using a 5-g sample size is the only method of those tested here that is completely reliable for detection of trichinae infection at a level that will protect public health. Both digestion testing using a 1-g sample and EIA have drawbacks. However, EIA remains a highly effective tool for epidemiological purposes and for monitoring trichinae infection on the farm.