To assess pathological changes associated with natural infections of the trematode Odhneriotrema incommodum in wild-caught American alligators Alligator mississippiensis and assess potential first intermediate hosts.
Materials and methods
Tongues from two wild-caught alligators were obtained from a commercial alligator processor in Port Gibson, Mississippi, USA. Tongues were subjected to gross parasitological examination and routine histological assessment. Eggs were expressed from adult trematodes collected from these tongues into distilled water, where they hatched into infectious miracidia. The snails Planorbella trivolvis, Physa gyrina, and Biomphalaria havanensis were exposed to these miracidia and observed for cercarial emergence for 200 days post-exposure.
Histological assessment of alligator tongues revealed marked hemorrhage, necrosis, presence of bacteria, and inflammation at sites of Odhneriotrema incommodum attachment, differing from previous histological reports from controlled experimental studies. Cercarial emergence was not observed in snails exposed to infectious miracidia.
Wild-caught alligators infected with Odhneriotrema incommodum exhibit more severe pathology than was previously noted from experimentally infected alligators. This adverse pathology may be associated with microbes present in eutrophic natural habitats that are absent from controlled environments used in experimental exposures. Impacts of this parasite in wild alligator populations are likely underestimated and damage associated with parasite attachment could increase host susceptibility to secondary infections. Given the importance of alligators as game animals and sustained demand for alligator products, further study into the role of O. incommodum on alligator health is warranted. Results of snail exposures to miracidia suggest these snail species are not suitable first intermediate hosts for this trematode and the true first intermediate host of O. incommodum remains unknown.
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We would like to thank Mr. Woodrow Cain and Mrs. Vecie Cain of Port Gibson, Mississippi for providing us with alligators for study. This work would have been impossible without their generosity. We also acknowledge Ricky Flynt and the Mississippi Department of Wildlife, Fisheries and Parks for the issuance of hunting permits that allowed for the collection of wild alligators used in the present study. This project was supported by the College of Veterinary Medicine at Mississippi State University, the College of Forest Resources at Mississippi State University, and the IUCN-SSC Crocodile Specialist Group Fritz Huchzermeyer Veterinary Science Student Research Assistance Scheme awarded to ETW.
Conflict of Interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
The corresponding author declares on behalf of all authors that alligators collected in the present study were collected under hunting permits issued to hunters as part of the Mississippi Department of Wildlife, Fisheries and Parks Alligator Program. Alligator tongues were opportunistically collected after processing, and no alligators were killed for the purposes of this study. Ethical standards for the treatment and euthanasia of snails were followed.
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Woodyard, E.T., Baumgartner, W.A., Rush, S.A. et al. Pathology associated with Odhneriotrema incommodum infection in wild-caught American alligators Alligator mississippiensis and assessment of potential first intermediate snail hosts. Acta Parasit. 65, 144–150 (2020). https://doi.org/10.2478/s11686-019-00142-9
- Alligator mississippiensis
- Biomphalaria havanensis
- Odhneriotrema incommodum
- Planorbella trivolvis