Comparative serological diagnosis of toxoplasmosis in horses using locally isolated Toxoplasma gondii

A total of 420 serum samples collected from horses of different ages, sexes and breeds, located at some horse farms in Egypt, were used for serological studies. A crude antigen of the locally isolated Toxoplasma gondii tachyzoites from horse tissues (LA) was used for the detection of T. gondii antibodies in horses. It showed good diagnostic efficiency (38.1%) by Enzyme Linked Immunosorbent Assay (ELISA). To increase this efficiency, an affinity purification process was performed. Two fractions were obtained from LA by CNBr-Sepharose 4B affinity column chromatography named; unbound (LAunb) and bound (LAb). LAb showed the highest diagnostic potency (51.7%), while LAunb showed the lowest value (31.7%) using ELISA. The electrophoretic profile of LA (12 bands), LAb (6 bands) and LAunb (6 bands) showed molecular weights ranged from 25.1 to 184.3 kDa. The immunoreactive bands of each of the three antigens were identified with infected horse sera by immunoblot assay. Four immunogenic bands of 155.8, 115.1, 83.2 and 66.2 kDa were identified in LAb and probably were responsible for the highest diagnostic potency. Examination of horse sera by Indirect Fluorescence Antibody Test (IFAT) at a dilution of 1: 64 and Modified Agglutination Test (MAT) at a dilution of 1: 25 revealed that 170 (40.5%) and 202 (48.1%) had antibodies against T. gondii, respectively. The current research introduces crude and purified fractions (bound and unbound) obtained from the locally isolated tachyzoites (equine origin), which are utilized globally for the first time in detection of T. gondii antibodies in horses. Furthermore, this study recommended utilization of the bound fraction in diagnosis of toxoplasmosis using indirect ELISA which proved better diagnostic potency compared with IFAT and MAT.