First report of a trematode (Microphalloidea: Phaneropsolidae) infection in an invasive Pomacea maculata population with recommendation methods for future surveillance

Authors: NGUYEN, JONAH - Mississippi State University; T0LLEY-JORDAN, LORI - Jacksonville State University; SLAYTON, ANNIE - Jacksonville State University; Richardson, Bradley; ROSSER, THOMAS - Mississippi State University

Submitted to: Parasitology International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2025
Publication Date: 11/27/2025
Citation: Nguyen, J.A., T0lley-Jordan, L., Slayton, A.P., Richardson, B.M., Rosser, T.G. 2025. First report of a trematode (Microphalloidea: Phaneropsolidae) infection in an invasive Pomacea maculata population with recommendation methods for future surveillance. Parasitology International. 112:1-13. https://doi.org/10.1016/j.parint.2025.103203.
DOI: https://doi.org/10.1016/j.parint.2025.103203

Interpretive Summary: Giant apple snails are an invasive species from South America that is considered a pest in several agricultural industries. The large size and high reproductive rates make the snails easy to find, but difficult to eradicate. Additionally, the snails are known to serve as a host for at least one parasite that is a human health concern; however, information on parasite prevalence within apple snails is still lacking. Here, scientists from the USDA-ARS Warmwater Aquaculture Research Unit in Stoneville, MS, along with researchers at Mississippi State University and Jacksonville State University collected giant apple snails from a municipal park in Mobile, Alabama to evaluate differences in parasite prevalence based on size and sex. A total of 284 snails were collected and dissected across 2 years. At smaller sizes, females were more likely to be infected with parasites than males; however, the risk of infection increased faster for males as they grew, than in females. The methods and results of this study show the utility of field-based dissections as a rapid method for parasite prevalence screening in giant apple snails. This method can be paired with molecular techniques to enhance detection and identification of trematode parasites collected during snail sampling.

Technical Abstract: Giant apple snails, Pomacea maculata (Caenogastropoda: Ampullariidae), are native to South America, but are now invasively established in subtropical freshwater habitats worldwide. In May 2017, P. maculata from an urban pond in Mobile, Alabama, USA were collected and infections with a larval trematode were observed on microscopic examination. This prompted further collections to determine infection prevalence and investigate effects of infection by snail sex and size. In total, 284 snails (n = 184 female, n = 104 male) were collected in May, August, and October of 2017 and 2018. Of these, 60 females and 23 males were infected with prevalence per sampling event ranging from 4–67% in females and 0–47% in males. Chi-square analysis revealed that parasitized snails were detected at significantly higher frequencies than expected during multiple sampling events and ANOVA results showed that infection occurred in larger snails, regardless of sex, as compared to smaller individuals. Partial 28S ribosomal DNA sequence data were obtained from a subsample of infected snails to conduct phylogenetic analyses used to putatively identify the trematode parasites. These results suggest the larval trematode isolates infecting the Mobile apple snails were members of Phaneropsolidae (Microphalloidea), a family that infects ampullariid snails in their native range. Further detailed comparisons of cercarial morphology against published descriptions complement the molecular results. These methods and initial findings demonstrate the utility of simple tissue screening and partial 28S rDNA sequence data in the rapid detection and molecular identification of larval trematodes collected from invasive populations of apple snails.