Comparison of a commercial ELISA, an in-house indirect ELISA, and a dot-ELISA developed for the serodetection of <i>Toxoplasma gondii</i> antibodies in farm animals

<i>Toxoplasma gondii</i> is a widespread intracellular protozoan that can infect humans and animals. We isolated <i>T. gondii</i> strains from sheep, goats, cattle, buffaloes, and camels to develop and evaluate a modified in-house dot-ELISA for the detection of <i>Toxoplasma</i> antibodies in farm animals, and compared the results with a commercial ELISA (IDvet; gold standard). Animal tissue samples (<i>n</i> = 430) were examined microscopically, and infected tissues were bioassayed in mice as a viability test. Egyptian <i>Toxoplasma</i> strains were isolated from sheep, cattle, and camels and identified via PCR using the <i>B1</i> gene (GenBank OR837022.1, OR837021.1, OR837020.1 from sheep, cattle, and camels, respectively). A <i>T. gondii</i> tachyzoite antigen from a sheep strain had the highest potential for the detection of specific <i>T. gondii</i> antibodies. We characterized this antigen using SDS-PAGE and separated it into 10 polypeptides of 96-12 kDa. Our modified in-house dot-ELISA detected <i>T. gondii</i> seropositivity in 172 of 430 (40%) farm animals with a sensitivity of 96.6% and specificity of 100%. The results of our dot-ELISA were confirmed in comparison with those of our indirect ELISA and the commercial ELISA. In a western blot, a predominant immunogenic reactive antigen band of 65 kDa was detected in <i>T. gondii</i>-positive sera of sheep, cattle, buffaloes, and camels; no cross-reaction occurred with antibodies to other parasitic infections or samples from healthy controls. Our modified in-house dot-ELISA is a rapid and simple test that showed promise for the detection of <i>Toxoplasma</i> antibodies in farm animals.