Detection of specific hydatid antigens and antibodies in serum and urine of experimentally infected sheep

Immunodiagnostic confirmation of cystic human hydatidosis is frequently required before surgical intervention or of chemotherapy. However, it remains inadequate to detect specific antibodies or antigens in some confirmed cases of echinococcosis. This study was carried out to investigate the accuracy of three different immunodiagnostic tests for detection of specific circulating antigens or antibodies in the serum and urine of 13 experimentally infected sheep. For this purpose, Echinococcus granulosus were collected from small intestine of experimentally infected dogs, and 2000 taenid eggs were orally administered to each of the 13 sheep. There were six other sheep, which were kept as the control group. Biweekly serum and urine samples were collected from all the sheep for 4 months after infection. The sera were subjected to indirect hemagglutination test and the concentrated urine samples were subjected to coagglutination and counter immunoelectrophoresis tests. The results revealed that the sensitivity of these tests in detecting the hydatid antigens in the urine or antihydatid antibodies in the serum of the infected sheep reached their maximum in 12th and 13th week after infection; then it decreased in the following weeks. Examination of the non-infected sheep samples throughout the experiment showed that the aforesaid findings were specific only to the infected sheep. It seems that the appearance of specific hydatid antigen in urine and its antibodies in the serum were simultaneous. Although these tests are highly specific, false negative outcomes were encountered in their detection of cystic echinococcosis. In general, it seems rational to establish some series of diagnostic procedures in order to reveal antibodies and antigen of metacestode in serum and urine of the patients.