In this study, we investigated oysters, Crassostrea virginica, from Laguna Madre in South Texas, where a 45-yr old study recorded metacercarial infections of the echinostomatid trematode, Acanthoparyphium spinulosum, an Asian relative of which, Acanthoparyphium tyosenense, has been associated with human infections via the ingestion of raw mollusks. In an effort to examine the base-line infection parameters of Acanthoparyphium sp. in oysters, we examined the effect of distance from the shoreline, which is the habitat of the first intermediate host snail, Cerithidea pliculosa, as well as temporal changes in oyster infection levels, by conducting quarterly collections of oysters during a year. We found that almost all oysters (prevalence = 97.8–100%) were infected regardless of distance to the shoreline and season. However, the abundance of metacercariae was significantly higher close to the shoreline, while no significant temporal changes could be detected. In addition to the echinostomatid, we found a high abundance of the metacestode Tylocephalum sp. and the presence of 4 other metazoan parasites. None of the infections seemed to incur significant tissue damage to the oysters. Our study shows that at least locally, recreational harvesters of oysters may be exposed to Acanthoparyphium sp. Future studies should examine oysters from snail host habitats in the Gulf of Mexico, and the potential zoonotic risk of Acanthoparyphium sp. should be evaluated using experimental infections of animal models.

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