Accuracy of indirect haemagglutination and western blot assays for the detection of anti-Schistosoma antibodies in non-severe febrile patients in two Tanzanian hospitals

Background: The diagnosis of schistosomiasis is usually based on clinical data associated with the detection of eggs in stool, urine, and/or rectal and bladder biopsy specimens. However antibody detection can be useful to indicate Schistosoma infection in those for whom eggs cannot be demonstrated. The aim of this study was to assess the seroprevalence of schistosomiasis and to evaluate the accuracy of indirect haemagglutination (IHA) and Western blot (WB) assays for the detection of anti-Schistosoma antibodies in 2 peripheral hospitals of the United Republic of Tanzania. Methods: Between February and March 2007 blood samples were collected from 297 non-severe febrile outpatients who attended Chake Chake Hospital, Pemba Island and Tosamaganga Hospital, Iringa region in Tanzania. The samples were processed for Schistosoma antibodies by IHA and WB assays in Italy. Results: Two hundred and sixty-two of 297 patients were schistosomiasis antibody-positive by IHA (88.2%). Of 142 patients positive by IHA, only 22 (12.4%) cases were confirmed by WB assay. The WB assay confirmed all 35 negative cases previously identified by IHA. The seroprevalence of Schistosoma at Chake Chake Hospital was lower than in Tosamaganga Hospital (9/97, 9.3% vs 13/80, 16.2%). Conclusions: Schistosomiasis is endemic in Tanzania, being more prevalent on the mainland than on Pemba Island. The implications of this study are of public health relevance and suggest the need for increased efforts in large-scale chemotherapy-based morbidity control programmes, integrated with those for other soil-transmitted helminthiases, in these 2 peripheral areas of the United Republic of Tanzania.