Population genetic diversity of invasive Pomacea snails and surveillance of Angiostrongylus cantonensis in Shanghai, East China.

BACKGROUND

Golden apple snails (Gastropoda: Ampullariidae: Pomacea) were introduced into China in the 1980s for aquaculture and have since become widespread agricultural pests across East Asia. In addition to their invasive impact, they are a key intermediate host of the rat lungworm Angiostrongylus cantonensis (Secernentea: Angiostrongylidae) in China, the causative agent of eosinophilic meningitis in humans.

METHODS

We conducted a malacological survey of 55 freshwater sites across Shanghai and neighboring East China provinces to assess Pomacea distribution, genetic diversity, and A. cantonensis infection status. A total of 700 Pomacea snails were examined for A. cantonensis using traditional lung microscopy and molecular xenomonitoring (PCR and LAMP). Mitochondrial COI barcoding was performed on 200 individuals from 20 high-density sites to assess species composition and genetic diversity.

RESULTS

Pomacea snails were found at 81.8% (45/55) of sites surveyed. No A. cantonensis infections were detected by microscopy or molecular assays. Genetic analyzes revealed three Pomacea species (P. canaliculata, P. maculata, and P. occulta) and nine distinct COI haplotypes. Pomacea canaliculata was the most common and genetically diverse species, with four unique haplotypes (H5-H8) occurring only in Shanghai, indicative of recent introductions. Overall, populations showed moderate haplotype diversity (Hd = 0.73) and population structure (FST = 0.24).

CONCLUSIONS

Although no A. cantonensis infections were detected in the snails examined in this survey, these negative findings do not preclude the possibility of low-prevalence or newly emerging infections. The wide distribution and high genetic diversity of Pomacea populations across Shanghai and East China highlight that suitable hosts are already well-established, emphasizing the ongoing risk of parasite introduction and spread into currently nonendemic regions. Continued molecular surveillance, public awareness, and strengthened biosecurity measures remain essential to effectively manage invasive snail populations and mitigate future public health threats.