EVALUATION OF A SEROLOGICAL TEST SYSTEM FOR THE DIAGNOSIS OF SARCOCYSTIS-CRUZI INFECTION IN CATTLE USING S-CRUZI MEROZOITE ANTIGEN

Fifty serum samples were examined by enzyme-linked immunosorbent assay (ELISA) for antibodies directed against crude antigens isolated from cystozoites and merozoites of Sarcocystis cruzi and Sarcocystis tenell a/Sarcocystis arieticanis and merozoites of Toxoplasma gondii. Of thes e 50 samples, 2 5 were from cattle originating from an area where the prevalence of S. cruzi was found to be very low (9%) and in which no c ystozoites were detected, and 25 were from cattle which were found by a digestion method to be heavily infected with S. cruzi.A very high co rrelation was observed between the parasitological data and the result s obtained from the serological assays which used antigens from either cystozoites or merozoites of S. cruzi. The assay using the antigen de rived from merozoites provided the best result for discriminating infe cted and non-infected animals. There was some cross-reactivity between the antigen derived from cystozoites of heterologous species of Sarco cystis and S. cruzi antibodies, and some cross-reactivity between anti gen of T. gondii and antibodies to S. cruzi. The reproducibility of th e assays was found to be high and similar results were observed when t he sera were tested on two separate occasions. The unpurified S. cruzi merozoite antigen produced in vitro is relatively accurate in discrim inating positive and negative animals and may be used for diagnosis in economically important hosts such as cattle and sheep.