title: Invasive snails and an emerging infectious disease: results from the first national survey on Angiostrongylus cantonensis in China.
abstract: BACKGROUND
  Eosinophilic meningitis (angiostrongyliasis) caused by Angiostrongylus cantonensis is emerging in mainland China. However, the distribution of A. cantonensis and its intermediate host snails, and the role of two invasive snail species in the emergence of angiostrongyliasis, are not well understood.
  
  
  RESULTS
  A national survey pertaining to A. cantonensis was carried out using a grid sampling approach (spatial resolution: 40x40 km). One village per grid cell was randomly selected from a 5% random sample of grid cells located in areas where the presence of the intermediate host snail Pomacea canaliculata had been predicted based on a degree-day model. Potential intermediate hosts of A. cantonensis were collected in the field, restaurants, markets and snail farms, and examined for infection. The infection prevalence among intermediate host snails was estimated, and the prevalence of A. cantonensis within P. canaliculata was displayed on a map, and predicted for non-sampled locations. It was confirmed that P. canaliculata and Achatina fulica were the predominant intermediate hosts of A. cantonensis in China, and these snails were found to be well established in 11 and six provinces, respectively. Infected snails of either species were found in seven provinces, closely matching the endemic area of A. cantonensis. Infected snails were also found in markets and restaurants. Two clusters of A. cantonensis-infected P. canaliculata were predicted in Fujian and Guangxi provinces.
  
  
  CONCLUSIONS
  The first national survey in China revealed a wide distribution of A. cantonensis and two invasive snail species, indicating that a considerable number of people are at risk of angiostrongyliasis. Health education, rigorous food inspection and surveillance are all needed to prevent recurrent angiostrongyliasis outbreaks.
authors.affiliation: National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, People's Republic of China.
authors.forename: Shan
authors.initials: S
authors.lastname: Lv
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: He-Xiang
authors.initials: HX
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Hu
authors.forename: Kun
authors.initials: K
authors.lastname: Yang
authors.forename: Peter
authors.initials: P
authors.lastname: Steinmann
authors.forename: Zhao
authors.initials: Z
authors.lastname: Chen
authors.forename: Li-Ying
authors.initials: LY
authors.lastname: Wang
authors.forename: Jürg
authors.initials: J
authors.lastname: Utzinger
authors.forename: Xiao-Nong
authors.initials: XN
authors.lastname: Zhou
mesh_terms: D017185:Angiostrongylus cantonensis / Q000502:physiology*; D000818:Animals; D002681:China / Q000453:epidemiology; D003625:Data Collection; D005843:Geography; D006801:Humans; D012908:Snails / Q000469:parasitology*; D017206:Strongylida Infections / Q000453:epidemiology* / Q000635:transmission*