Detection of Trematodes from the Host Exotic Aquatic Snail Melanoides tuberculata in an Urban Stormwater System

The red-rimmed melania or Malaysian Trumpet Snail, Melanoides tuberculata, is a common exotic freshwater snail that has been invading an increasing number of water bodies in North America. As a well-known host for trematodes causing human and animal diseases, the pattern of invasion and parasitic infection for this species is of great concern. Snail specimens were collected from an urban stream in Los Angeles that drains into a fragile, protected wetland ecosystem. Molecular analysis identified four trematode species: Haplorchis pumilio, Fasciola jacksoni, Parorchis sp. TH-2019, and an unclassified trematode species, Trematoda distomecercaria WN-2016. H. pumilio is responsible for haplorchiasis infections, previously considered endemic to Asia. F. jacksoni infection is a significant cause of mortality in Asian elephants. This study represents the first occurrence of F. jacksoni in North America and a novel occurrence of that trematode in association with M. tuberculata. This study also represents new occurrences of Parorchis sp. TH-2019 and an unclassified trematode species, Trematoda distomecercaria WN-2016, within California and North America. Parorchis sp. TH-2019 has previously only been documented in a marine whelk. This identification of these trematodes in association with M. tuberculata further exemplifies the need for ongoing monitoring and detection, especially considering the significance of H. pumilio and haplorchiasis to public health.