title: [Longitudinal observation on a schistosome-infected snail spot as a source of infection in a mountainous village of Dali city].
abstract: OBJECTIVE
  To observe longitudinally the changes in survival and infection rate of Oncomelania snails in a positive snail spot in Yunnan.
  
  
  METHODS
  A positive snail spot in a ditch in Shalimuzhuang Village, Dali City, was continually observed on the changes in the density of snail population and natural infection rate of the snails by random environmental sampling for 8 times in 4 successive years.
  
  
  RESULTS
  During the 8 times of snail survey, living snails were found relatively stable in the ditch, in which positive snails were obtained in 6 occasions, the average infection rate being 3.99%.
  
  
  CONCLUSIONS
  The density and the positive rate of snails in the mountain region remains relatively stable as a source of human infection. Elimination of the positive snail spots is necessary for controlling schistosomiasis.
authors.affiliation: Department of Parasitology, Kunming Medical College, Kunming 650031.
authors.forename: F
authors.initials: F
authors.lastname: Li
authors.forename: D
authors.initials: D
authors.lastname: Xia
authors.forename: C
authors.initials: C
authors.lastname: Ma
authors.forename: X
authors.initials: X
authors.lastname: Jia
authors.forename: X
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002681:China; D006790:Host-Parasite Interactions; D008137:Longitudinal Studies; D012547:Schistosoma / Q000302:isolation & purification*; D012552:Schistosomiasis / Q000517:prevention & control; D012908:Snails / Q000469:parasitology* / Q000502:physiology