Survey on the Focus of Angiostrongylus cantonensis in Guangdong Province

Objective To understand the distribution of Angiostrongylus cantonensis foci in Guangdong Province for making surveillance program.Methods Survey sites were chosen by strata sampling according to different geographic locations.Totally 22 survey sites were selected in four regions:East Guangdong,West Guangdong,North Guangdong and the Pearl River Delta.One or two administrative villages in each site were randomly selected for the investigation.Pomacea canaliculata and Achatina fulica collected from fields and other species of freshwater or terrestrial snails obtained in the restaurants and wet markets were examined for the third stage larvae by tissue grinding or lung examination.Rats were captured in the fields,and their hearts and lungs were dissected for adult worms.Rat feces were also collected for the detection of first stage larvae by water precipitation.Results Large number of P.canaliculata was found in all sites.A.fulica was found in most surveyed sites.Totally 2 929 P.canaliculata and 1 354 A.fulica were collected with a larva infection rate of 5.9%(172/2 929) and 16.5%(223/1 354),respectively(P0.01).The average prevalence among the regions was different(P0.01) with the highest prevalence in Pearl River Delta(15.6%,152/975),especially in Dongguan City of the Delta(34.7%,78/225).114 Cipangopaludina sp.and 252 Bellamya sp.were bought from wet markets of 9 sites.Larvae were found only in Bellamya snails from Luoding and Kaiping cities with an infection rate of 1.4%(1/70) and 3.3%(3/91),respectively.Totally 491 rats were captured in 9 sites including Rattus norvegicus,R.flavipectus,Suncus murinus,Mus musculus,Bandicota indica,R.losea and R.rattus,with an average infection rate of 11.4%(56/ 491).Adult worms were found in R.norvegicus,R.flavipectus and B.indica with a prevalence of 19.8%(52/263),2.5%(3/118) and 10.0%(1/10),respectively.Thirty-four rodent fecal samples were collected in 7 sites and examined with a larva positive rate of 44.1%(15/34).Conclusion Foci of Angiostrongylus can to nensis are widely distributed in Guangdong Province as natural infection has been found in its intermediate and definitive hosts.