Study On Biology And Natural Focus Of Trichobilharzia Sp.

The present article deals with the biology of duck Trichobilharzia from Gaotang Lake districts of Anhui, China, which causes human cercarial dermatitis, and the epidemic status of human cercarial dermatitis and investigate natural focuses of Trichobilharzia sp. in this area.The collection processes of the various stages of life cycle of Trichobilharzia sp. were contrasted and studied. the valid separation and collection method of imagoes, cercarie and miracidiums were perfusion of hepatic portal vein and vena mesenterica , method of bottle drop away from light and narrow neck flask push pipe method respectively.The various stages of life cycle of Trichobilharzia sp. were observed with viviperception, microscope and scanning electron microscope(SEM). Their morphological characteristic were carefully described and photographed. The species of Trichobilharzia from Anhui area were discussed, and so the author recognized the Trichobilharzia sp. in Anhui area was not confirmed.This article reports the results of an investigation on the general medical mollusks in Huainan, Anhui. The ecology of Radix auricularia that is intermediate host of Trichobilharzia sp. was studied carefully through field observation and laboratory raising. There are 8 specieses medical mollusks in Huainan section, which belonging to 4 families 7 genera of Gastropoda. The Radix auricularia distributes widely over this locality,snails began to come out of clod and act in the first ten days of March, its crest-time of oviposition is from the last ten days of March to the first ten days of April, they hibernates at the beginning of November. Radix auricularia propagates 3 generations in one year, its highest breed density is 468 individuals per square meter.Cercarial biology of Trichobilharzia sp. was studied especially, the author discovered the detection rate of cercarie varies with air temperature, its rise and fall shows visible seasonality. The cercaria can be detected from April to October, and the highest detection rate is 1.12% in July. The cercaria has strong phototaxis, its lifetime is 52 hours. The cercaria can infects host before the age of 40 hours, and then its infectant power will be lossed. The snails emit cercarie concerns with environmental factors such as temperature, illumination and so on. the cercaria can be emitted between 20～25℃at the condition of illumination.The investigation shows there exist definitive hosts of Trichobilharzia sp. in Gaotang Lake, the infection rate of home duck and wild duck are 35.20%, 56.25% respectively. There exists intermediate host which is Radix auricularia, its infection rate is 1.03%. Cercarial dermatitis of Trichobilharzia sp. happened among peasant and fisherman who lived and worked at Gaotang Lake area, frequency of cercarial dermatitis is 79.37%, the happeness of dermatitis has nothing to do with gender. The natural focuses of Trichobilharzia sp. were extensively distributed in the Gaotang Lake districts of Anhui, China.