Frequent carriage of invasive Salmonellae amongst patients infected with schistosomiasis in Sudan

Bacteria-parasite association has been documented as a factor that is responsible for continued and prolonged bacterial infection, such as typhoid and paratyphoid fever in schistosomiasis patients. This work aimed to determine the presence of typhoid and paratyphoid Salmonella among schistosomiasis patients and to evaluate the efficacy of Widal test on such population. A cross sectional descriptive study was conducted between November 2005 and May 2006 in Managil region, Gezira State, Sudan. A total of 203 males participated in the study. Urine, stool and blood samples were collected and processed for the investigation of schistosomiasis and Salmonella infection based on standard methods. Widal test was performed to estimate diagnostic cut-off value of enteric fever. Of the 203 studied subjects, 42 (20.7%) were diagnosed with Schistosoma haematobium, whereas eight (3.9%) had Schistosoma mansoni infection. Of these, Salmonella species were detected in 30 (60%) cases, of which Salmonella typhi represented 63.3%, followed by Salmonella paratyphi A and B (16.7%, each) and Salmonella paratyphi C (3.3%). Based on the culture results (n=30) as a diagnostic method used for enteric fever, Widal test was positive in 12 cases, with a sensitivity of 40% and specificity of 75%. Of the Widal positive cases, titers of 1:160, 1:320, 1:640 were detected in 58.3, 33.3 and 8.3% of samples, respectively. In schistosomiasis endemic regions, enteric fever was associated with schistosomiasis, which requires investigation of both infections concomitantly. Regardless of the low sensitivity of Widal test, titer of ≥1/160 is a diagnostic value for enteric fever in this study group.