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Title: SENSITIVITY OF ARTIFICIAL DIGESTION AND ENZYME IMMUNOASSAY METHODS FOR INSPECTION OF TRICHINELLOSIS IN PIGS

Author
item GAMBLE, HOWARD

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Trichinellosis, caused by the human pathogen Trichinella spiralis, is a significant cause of public health concern worldwide. Most developed countries, with the exception of the United States, inspect pork and horses at slaughter for the presence of this parasite. Currently used methods for inspection are based on several variations of the pooled sample digestion method. The requirements for testing pigs include the use of a 1 gram tissue sample, while the testing of horses requires a five gram sample. Since these methods obviously have different sensitivities, the present study was undertaken to determine the actual sensitivity. Using a large group of pigs, the pooled sample digestion method using a one gram sample had a sensitivity of 3-5 larvae per gram of tissue, while using a five gram sample this sensitivity was reduced to 1 larvae per gram. Since parasite infection levels of greater than 1 larvae per gram are sufficient to cause human disease, the first method is not suitable for detecting all animals of public health significance. The use of serology testing was highly sensitive, but positive animals were not detected until 3 to 7 weeks following infection. Both direct (digestion) and indirect (serology) methods both have limitations, but are each useful in an integrated program for control of trichinellosis.

Technical Abstract: 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 1-gram sample, as prescribed in accordance with EU directives, the sensitivity of the pooled- sample artificial digestion method was between 3 and 5 larvae per gram (LPG) of tissue. Using a 5-gram 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. Serology 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 32-42 days. Based on the results obtained here, it is clear that digestion testing using a 5-gram sample size is the only method, of those tested here, that is completely reliable for detection of trichinae infection at a level which will protect public health. Both digestion testing, using a 1- gram sample, and EIA have drawbacks. However, the EIA remains a highly effective tool for epidemiological purposes and for monitoring trichinae infection on the farm.