Dot-ELISA for diagnosis of caprine schistosomosis

Dot-ELISA was developed for diagnosing caprine schistosomosis using Schistosoma spindale somatic antigen, its excretions and secretions and cercarial antigen of S. incognitum. The cercarial antigen @ 1 mu l (protein 1.5 mg/ml) per nitrocellulose membrane strip, 1: 200 serum dilution, 1: 800 rabbit-anti-goat IgG HPRO conjugate and reaction with DAB substrate for 10-15 sec provided optimum results with 85.3% sensitivity and 63.6% specificity. The parasitological methods incorporating faecal examination (formal -ether, alkaline digestion, hatching method), mesenteric and intestinal scraping examinations in 200 goats revealed cumulatively 58% prevalence of caprine schistosomosis, whereas dot-ELISA, in the same animals, exhibited it to be 70%. The least sensitive parasitological method provided highest sensitivity but least specificity to the screening test. Therefore, it proved erroneous to compare results of dot-ELISA with faecal alkaline digestion and/or formal-ether methods as they provided 100% sensitivity but 30-31% specificity. A simple method of dot-ELISA using nitrocellulose combs, ELISA plate and electric vertex shaker was developed which facilitated processing of 96 cases simultaneously thus making it possible to detect schistosomosis in 96 samples within 4-5 h. It is possible to undertake surveillance of domestic animals for schistosomosis under field conditions by supplying antigen loaded nitrocellulose strips to less developed veterinary laboratories.