Investigation of <i>Fasciola gigantica</i> in freshwater snail <i>Radix</i> (<i>Lymnaea</i>) spp. In the highly parasite-prevalent area of Nakhon Ratchasima Province, Thailand

This study investigates the distribution of the <i>Lymnaea</i> (<i>Radix</i>) spp. in Pak Chong district, Nakhon Ratchasima province, northeast Thailand, where a vast cattle farming area is located and has a high prevalence of <i>Fasciola</i> spp. in the cattle. By random selection, 1,414 snails were collected from the natural and man-made ponds. The snails were recorded for morphology and processed for DNA isolation. The snail species were investigated by conventional PCR using a 16S rDNA-specific primer. The result demonstrated that all collected snails were <i>R</i>. (<i>L</i>.) <i>rubiginosa</i>. Moreover, the infection of <i>Fasciola</i> gigantica in the snails was investigated by PCR using a cytochrome c oxidase I (COX1)-specific primer. The results illustrated that the overall prevalence was 22.5% (318/1414), with the highest prevalence in the Nong Sa Rai subdistrict at 73.6% (81/110), which is the highest prevalence of <i>Fasciola gigantica</i> in the snail host that has ever been reported. The lowest prevalence existed in the Pong Ta Long subdistrict at 3.7% (4/109). Our results corresponded to the previous report on the <i>Fasciola</i> spp. infection in the cattle from this area, and the geographical analysis revealed that the most suspected factor would be the earth dam located in these subdistricts, where many animals live freely during the day. Our findings could be helpful for further parasite control and could trigger the study of the biology and associated factors in the future.