Investigation Of Infectious Sources Of Schistosomiasis Japonica And Observation Of Cercarial Shedding Patterns From Infectious Snails In Marshland And Hilly Regions

Objective To understand species of infectious sources of schistosomiasis japonica andtheir roles in the disease transmission in two different endemic areas (marshland andhilly regions).Methods Shankouzhen village in Anqing City (the marshland region) and Du village inShitai County (the hilly region) were selected as field investigation sites. Stool sampleswere collected from human and domestic animals and examined with parasitologicalmethods, kato-katz and miracidium hatching test (MHT), and wild animals were trappedand examined with autopsy and MHT. Infection rates, infection intensity (EPG) and thenumber of eggs excreted per day (EPD) of infectious species were calculated for theidentification of roles of infectious sources of schistosomiasis japonica in diseasetransmission.Results Water buffaloes were the major infectious source of schistosomiasis japonica,and human ranked the second at Shankouzhen village. The infection rate and infectionintensity of water buffaloes were27.27%,2.97EPG, respectively. The EPD of waterbuffaloes was178182, which accounted for97.88%of total EPD of all infectioussources. The infection rate and intensity of human were2.81%,0.54, respectively. TheEPD of human was3867, accounting for2.12%of total EPD. Wild mice, human anddogs were main infectious sources of schistosomiasis japonica in Du village. Theinfection rate of wild mice, human and dogs were12.24%,1.25%and7.69%,respectively. The infection intensity of wild mice, human and dogs were65.14,0.26and 0.09, respectively. The EPD of human, dogs and wild mice were315154,1007,45,respectively. Wild mice accounted for99.67%of total EPD of all infectious sources, thehuman for0.32%, and the dogs for0.01%.Conclusion Water buffaloes are still the main infectious source in the marshland regionwith schistosomiasis. Since the removal of bovine and the stable breeding of pigs, wildmice are possible to become the main reservoir host of schistosomiasis in hilly region. Objective To understand cercarial shedding patterns of infectious snails in marshlandand hilly regions by the observation of snails naturally infected in the fields and theother artificially infected in laboratory.Methods Snails were collected from Shankouzhen village in Anqing City (themarshland region) and Du village in Shitai County (the hilly region). By cercariaeshedding, the snails infected with schistosoma japonicum were selected and randomlydivided into three groups in which snails were put into water at6:00,12:00and18:00,respectively. The cercarial shedding patterns were observed24hours under25℃withillumination in the daytime and no illumination at night. Meanwhile, the miracidia fromthe marshland region and the hilly region were used to infect the local snails and onesfrom another endemic region, respectively. The cercarial shedding patterns of artificiallyinfectious snails were carried out at the same method as natural infectious snails. Results The number of cercariae shedding from natural infectious snails of themarshland region reached a peak two to four hours after being put into water underillumination. Furthermore, there were two cercariae shedding peaks at18:00group, thefirst peak from18:00to22:00, and another peak from8:00to10:00in the next day. Thecercariae shedding from natural infectious snails of the hilly region mainly began at16:00to18:00, with a peak from20:00to22:00. The cercariae shedding from theartificially infectious snails, miracidia from the marshland infecting the snails from themarshland region and the hilly region, reached the peak two to four hours after beingput into water under illumination at6:00and12:00groups, and there were two cercarialpeaks (from20:00to22:00; from8:00to10:00in the next day) at18:00group. Theartificially infectious snails, miracidia from hilly region infecting the snails from themarshland region and the hilly region, had a shedding peak from20:00to22:00at threegroups.Conclusion The observation of both natural and artificially infectious snailsdemonstrates that there are significant differences in cercarial shedding patternsbetween schistosoma japonicum from the marshland and the hilly regions, namely, theschistosoma japonicum from the marshland region shows quick cercarial shedding, andthat from the hilly region shows cercarial shedding at night.