Epidemiological Investigation of Schistosomosis in Domestic Cattle in Bangladesh

Abstract

Bovine schistosomiasis is a disease of great economic importance in cattle production resulted from infection by helminth parasite of the genus Schistosoma. An epidemiological study of bovine schistosomiasis was conducted in Mymensingh, Netrokona, Kishorgonj, Chittagong and Sirajgonj areas of Bangladesh. On farm and abattoir survey were done to find out the risk factors associated with epidemiology, abundance of vectors and their relationship with temperature and rainfall during September 2009 to August 2011. Epidemiological data were collected from five different agro-ecological zones and schistosomiasis was found as one of the major bovine parasitic diseases. Among the different areas Sirajgonj district, male, adult animal and rainy and summer seasons were identified as significant risk factors for bovine schistosomiasis by egg (egg per gram of feces) count in Bangladesh. Among the three species of mostly common schistosomes in Indian sub-continent two species of were recorded during this period. Schistosoma indicum (29.9%) were the most common species than Schistosoma Spindale (10.6 %). Based on fecal egg examination a significant variation in the prevalence of bovine schistosomiasis were observed according to districts, ages, breeds, sexes, physical conditions, fecal consistency, sanitations, grazing, diets, de-worming, farming systems and seasons. Mesenteric blood vessels examination showed higher prevalence (48.0%) than fecal examination (33.2%). A significant variation in the prevalence of bovine schistosomiasis was observed according to regions and seasons. The highest number of total schistosomes counted from one mesenteric blood vessel was 322 and lowest was 18. In the study of intensity 27.4% of the mesenteric blood vessels showed moderate intensity (21-100 pair) which were statistically significant than low and heavy worm intensity. In order to find out the role of vector host snails were examined and 3.8% were found positive for cercariae of schistosomes of cattle with seasonal variation. Among the three different types of snails Indoplanorbis exustus played the dominant role followed by Lymnaea luteola and L. auricularia for shedding of Furcocercus cercariae. The shedding of Schistosoma spp. carcariae was significantly higher (P<0.01) during rainy season. The miracidial hatchability study clearly showed that miracidia hatching increases with the decreasing age of cattle. This observation clearly indicates that young animal plays an important role in the transmission cycle. Though clinical signs were not observed but histopathology of liver, small intestine and large intestine showed slight to moderate parasitic granulomas produced by the S. indicum eggs and adult parasites. Two simple methods such as egg detection method and miracidia hatching test was of great help in performing a proper diagnosis and fair assessment of schistosomiasis in the field. It may be concluded that schistosomiasis in cattle could be listed among the infectious diseases with special care because of climate change in the future which will severely affect the disease transmission dynamics. This study indicated that treatment of the infected animal with proper anthelmintic at the end of summer and restrict their movement nearer to water reservoirs could reduce the infection rate to a greater extent.