Role of goat in transmission of schistosomiasis japonica II Effect of tempera-ture and humidity on survival of eggs in goat feces and egg survival in natural environ-ments / 中国血吸虫病防治杂志

ABSTRACT

Objective To investigate the survival of Schistosoma japonicum eggs in goat feces in natural marshlands and the factors affecting its survival,so as to provide evidences for understanding of the role of eggs in goat feces in the transmission of schistosomiasis and the development of the interventions pertaining to disease control and elimination. Methods The goat ani?mals of schistosomiasis japonica were modeled in laboratory,and the feces of infected goat were collected. In laboratory,the ef?fects of environmental temperature and water content in goat feces on egg hatching were evaluated,and in the field,the effect of duration of goat feces on marshland on egg hatching and the effect of direct sunshine on egg survival were evaluated. Results At 25℃in laboratory,the hatching rate of eggs in goat feces was high?positively correlated with the water content in goat feces (r=0.87). If the water content reduced to 7.6%in goat feces,the eggs in goat feces lost the ability to hatch. Under the same wa?ter content in goat feces,the hatching rate of eggs gradually decreased with the extension of the duration of exposure of goat feces to-5℃,which reduced to 0 following 5 h exposure. At 5,15 and 25℃,the hatching rates of eggs gradually decreased with the extension of the duration of exposure of goat feces,and the miracidium hatching rates of eggs were 2.3%,5%and 0.9%respec?tively following the exposure for 52 d. At 35℃,the hatching rate of eggs gradually decreased with the extension of the duration of exposure,which reduced to 0 following 13 d exposure. In winter(-2?10℃),the hatching rate of eggs gradually decreased with the extension of the duration of exposure of goat feces on marshlands,which reduced to 0 after 21 d of exposure,and in spring(16?19℃),the hatching rate of eggs gradually decreased with the extension of the duration of exposure of goat feces on marshlands,which reduced to 0.9%after 5 d of exposure. At the same time point on the same marshland,the hatching rate of eggs in goat feces exposed to marshlands with direct sunshine was lower than that without direct sunshine. Conclusion The sur?vival of S. japonicum eggs in goat feces is associated with environmental temperature and water content(humidity)in goat feces, and the temperature and humidity are major natural factors affecting egg hatching.