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.
Highlights
Schistosoma japonicum, the causative agent of Asian schistosomiasis, is endemic to the People’s Republic of China, the Philippines and small pockets of Indonesia [1,2,3,4,5,6,7]
The range of mammalian hosts complicates schistosomiasis control efforts and, as well as the public health considerations, the disease adds to the economic burden of communities as S. japonicum infection debilitates domestic livestock that are used for food and as work animals [9,10]
Schistosomiasis japonica, a chronic human parasitic disease in the People’s Republic of China, the Philippines and areas of Indonesia, is a zoonosis with over 40 different mammals, including a number of ruminants, that can act as reservoir hosts for the infection
Summary
Schistosoma japonicum, the causative agent of Asian schistosomiasis, is endemic to the People’s Republic of China, the Philippines and small pockets of Indonesia [1,2,3,4,5,6,7]. Water buffaloes (Bubalus bubalis), have been shown to be major reservoir hosts for schistosomiasis japonica in the lake areas and marshlands of southern the People’s Republic of China [11,12,13,14,15,16]. Their role in schistosome transmission has yet to be fully determined in other endemic areas, notably the Philippines, due partly to inconsistent results obtained with the different methods used for identifying and quantifying S. japonicum eggs in mammalian hosts [17,18,19,20]. The presence of bulk debris, including cellulosic fibrous material, in the feces of ruminants often obscures the eggs and impairs their visualization across all current copro-parasitological methods that involve microscopy
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