title: [Studies on negative conversion of schistosome-infected snails in mountainous region of Yunnan].
abstract: The monthly cercaria shedding of 90 artificially infected Oncomelania snails was observed under a field condition in mountainous region, Shitoudi Village, Weishan County, Yunnan Province. The results showed that 20% of teh snails shed cercaria monthly, 42.2% could shed irregularly and 37.8% stopped releasing cercariae after several times of shedding. Final direction of the snails showed that none cercaria or sporocyst could be found in part of the snails. A total of 304 naturally infected snails were observed individually every month. Samples were taken each month from the snails which did not shed cercaria, then dissected and examined. The negative conversion rate was calculated in the second, third, fourth, fifth and sixth month after the first shedding, which were 36.1, 50.0, 41.0, 39.8 and 2.6% respectively.
authors.affiliation: Institute of Parasitic Disease, Chinese Academy of Preventive Medicine, Shanghai.
authors.forename: F X
authors.initials: FX
authors.lastname: Xie
authors.forename: G L
authors.initials: GL
authors.lastname: Yin
authors.forename: X Q
authors.initials: XQ
authors.lastname: Zhang
authors.forename: J Z
authors.initials: JZ
authors.lastname: Wu
authors.forename: R F
authors.initials: RF
authors.lastname: Xu
authors.forename: W S
authors.initials: WS
authors.lastname: Yang
authors.forename: J
authors.initials: J
authors.lastname: Yang
authors.forename: Y R
authors.initials: YR
authors.lastname: Duan
authors.forename: K
authors.initials: K
authors.lastname: Qian
authors.forename: J
authors.initials: J
authors.lastname: Zheng
mesh_terms: D000818:Animals; D002681:China; D007814:Larva; D012549:Schistosoma japonicum; D012908:Snails / Q000469:parasitology*