A Novel Procedure for Precise Quantification of Schistosoma japonicum Eggs in Bovine Feces

Abstract

Schistosomiasis japonica is a zoonosis with a number of mammalian species acting as reservoir hosts, including water buffaloes which can contribute up to 75% to human transmission in the People's Republic of China. Determining prevalence and intensity of Schistosoma japonicum in mammalian hosts is important for calculating transmission rates and determining environmental contamination. A new procedure, the formalin–ethyl acetate sedimentation-digestion (FEA–SD) technique, for increased visualization of S. japonicum eggs in bovine feces, is described that is an effective technique for identifying and quantifying S. japonicum eggs in fecal samples from naturally infected Chinese water buffaloes and from carabao (water buffalo) in the Philippines. The procedure involves filtration, sedimentation, potassium hydroxide digestion and centrifugation steps prior to microscopy. Bulk debris, including the dense cellulosic material present in bovine feces, often obscures schistosome eggs with the result that prevalence and infection intensity based on direct visualization cannot be made accurately. This technique removes nearly 70% of debris from the fecal samples and renders the remaining debris translucent. It allows improved microscopic visualization of S. japonicum eggs and provides an accurate quantitative method for the estimation of infection in bovines and other ruminant reservoir hosts. We show that the FEA-SD technique could be of considerable value if applied as a surveillance tool for animal reservoirs of S. japonicum, particularly in areas with low to high infection intensity, or where, following control efforts, there is suspected elimination of schistosomiasis japonica.

Real-time PCR Demonstrates High Prevalence of Schistosoma japonicum in the Philippines: Implications for Surveillance and Control

“…Twenty samples were randomly selected for further microscopic examination using a modification of the FEA-SD technique [ 26 , 29 ]. After processing using this procedure, S. japonicum eggs were found in 16 samples by microscopy ( Table 4 ).…”

“…Validation of the qPCR by microscopy . A random selection of 20 human stool samples that were: qPCR-positive and KK-negative; qPCR- and KK-positive; or qPCR- and KK-negative were re-examined by microscopy after processing, using a modification of the formalin-ethyl acetate sedimentation-digestion (FEA-SD) technique developed recently for the precise quantification of S. japonicum eggs in bovine stool [ 26 , 29 ]. The remaining volume of stool not used for DNA extraction was used for the microscopic examination.…”

Advances in the Diagnosis of Human Schistosomiasis

“…The sensitivity of the test can be improved by using multiple stool samples over several consecutive days, but this can compromise its simplicity and cost-effectiveness, and this modified approach can suffer from low compliance due to the reluctance of individuals to provide more than one stool sample for examination (57). While modifications to the KK test to improve the test efficacy have been suggested (65,66), the inherent drawbacks have yet to be resolved.…”

Road to the elimination of schistosomiasis from Asia: the journey is far from over

“…A study by Wu et al in Leyte, using a polymerase chain reaction (PCR)-based diagnostic method, showed the S. japonicum prevalence in carabao was 52% [13]. Another recent study of bovines in Samar province in 2010 using real time quantitative PCR (qPCR) showed similar results with greater than 90% of bovines being infected with S. japonicum [14,15]. Thus, there is a little question that bovines play a major role in the transmission of S. japonicum in the Philippines and should thus be targeted for the treatment and vaccination.…”