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United States Department of Agriculture

Agricultural Research Service

Title: Sensitiviity and Specificity of Various Serologic Tests for the Detection of Toxoplasma Gondii Infection in Naturally Infected Sows

Authors
item Dubey, Jitender
item Thulliez P, - INST DE PUERICULTURE, FR
item Weigel R M, - DEPT VET PATHOBIO, UN IL
item Andrews C D, - FSIS
item Lind P, - MINISTRY AGRI, DENMARK
item Powell E C, - IOWA STATE UNI, AMES, IA

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 1995
Publication Date: N/A

Interpretive Summary: Infection by the protozoan parasite Toxoplasma gondii is widespread in humans and livestock. Infection by this parasite causes abortion in livestock and mental retardation and loss of vision in children. Humans because infected by ingesting Toxoplasma encysted in tissues of animals or by ingesting food and water contaminated with resistant Toxoplasma (oocysts) from infected cat feces. Pork is considered the major meat source of Toxoplasma for humans. Approximately 25% of swine in the U.S. have antibodies to T. gondii. However, the specificity and sensitivity of different serologic tests for the diagnosis of T. gondii infection are unknown. Scientists at the Beltsville Agricultural Research Center and the University of Illinois compared sentivity and specificity of several serological tests and found that the modified agglutination test had the highest sensitivity and specificity for the diagnosis of T. gondii infection in pigs using the isolation of viable T. gondii as the standard.

Technical Abstract: The sensitivity and specificity of various serologic tests for antibodies to Toxoplasma gondii were compared in 1,000 naturally exposed sows using the isolation of viable T gondii as the definitive test. Serum samples from the heart of 1,000 sows from Iowa were examined for T gondii antibodies by the use of the modified agglutination test (MAT), the latex agglutination test (LAT), the indirect hemagglutination test (IHA), and an ELISA. Toxoplasma gondii was isolated from 170 hearts of 1,000 sows by bioassays in mice and cats. The percentage of samples diagnosed as positive for each of the serologic tests was: MAT = 22.2% (titer > 1:20), IHA = 6.4% (titer > 1:64), LAT = 10.4%(titer > 1:64), and ELISA = 24.1%(OD > 0.360) The sensitivity and specificity of these tests were calculated respectively to be: 82.9% and 90.29% for MAT, 29.4% and 98.3% for IHA, 45.9% and 96.9% for LAT and 72.9% and 85.9% for ELISA. The dye test was run at 1:20 dilution on only 893 sera because of bacterial contamination and the presence of anticomplement substances. Dye test antibodies were found in 17.8% of the sera and its sensitivity and specificity were 54.4% and 90.8%, respectively. Thus, the MAT had the highest sensitivity among all serologic tests used.

Last Modified: 10/25/2014
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