Role of goat in transmission of schistosomiasis japonica III Environmental contamination by goat feces and prediction of environments at high risk of S. japonicum infection

Abstract

To quantitatively estimate the range and area of environmental contamination by the feces of Schistosoma japonicum-infected that were freely grazed, so as to provide the theoretical evidence for the scientific assessment of the role of the freely grazed goat in the transmission of schistosomiasis japonica and development of control strategy. All the fecal samples excreted by the infected goat at daytime (12 h) were collected by using a self-made goat fecal collector, weighed and counted. The quantity and dispersal of the feces excreted by the freely grazed goat at daytime under a natural condition were investigated, and the walking route and speed of the freely grazed goat at daytime were recorded with a multifunction GPS data logger. The maximum range and area of the environment contaminated by the feces of the freely grazed goat at daytime were estimated, and the maximum range and area of the Oncomelania hupensis snails that may be infected by the schistosome miracidium released from the eggs in the fecal samples of the freely graze goat at daytime were calculated. During the walking along the marshland at daytime (12 h), the quantity of the feces execrated by the freely grazed infected goat was (232.8 ± 39.8) g per goat, and the fecal samples were composed of (819.2 ± 152.1) pellets. The goat had a mean walking speed of (0.522 7 ± 0.099 7) km/h, and the longest distance, largest radius and largest range of walking activity were (6.272 4 ± 1.195 8) km, 3.136 2 km and (3 191.113 0 ± 1 189.709 4) hm2 at daytime, respectively. The area of the snails that may be infected by the miracidium released from the eggs in the fecal samples of the freely graze goat (range of key regions for infected snails detection and control) at daytime was estimated to be (3 210.717 5 ± 1 190.907 3) hm2. The intensity of environmental contamination by the eggs in the fecal samples of the freely grazed goat is linked to the number of infected goat. The contamination range caused by the feces of the freely grazed goat with fixed fences is relatively stably kept within the walking range at day-time, and the range and area of goat fecal contamination is associated with the number of households that breed goat and the distribution of goat fence. The area of the snails that may be infected by the miracidium released from the eggs in the fecal samples of the freely graze goat is larger than the area of setting contaminated by the eggs in the goat feces, indicating that the range of infected snail examination and control is larger than the range of goat feces detected.