Woodyard

American Alligators Infected With the Trematode Odhneriotrema incommodum and the Isolation of Aeromonas veronii From the Associated Lesions

1Ethan T. Woodyard, 1Lorelei M. Ford, 1Divya Rose, 2Wes A. Baumgartner, 3Orion S. Rivers, 4Scott A. Rush, 5Celene M. Slifka, 5Jonah A. Nguyen, 6Derek H. Marshall, 1Matt J. Griffin, 4Thomas G. Rosser

1Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi 39759; 2Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Illinois, Urbana, Illinois 61802; 3Institute for Imaging & Analytical Technologies, Mississippi State University, Mississippi State, Mississippi 39759; 4Department of Wildlife, Fisheries and Aquaculture, College of Forest Resources, Mississippi State University, Mississippi State, Mississippi 39759; 5Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi 39759; 6Mississippi State University Libraries, Mississippi State, Mississippi 39759

ABSTRACT

The American alligator Alligator mississippiensis is an ecologically and economically important game animal in Mississippi, particularly since the inception of the states’ alligator hunting permit system in 2013. Inconsistencies in the literature regarding the identity and pathogenicity of alligator parasites warrant further investigations into both parasite systematics and associated disease processes. To this end, carcasses of A. mississippiensis have been collected from a commercial alligator processor from 2016–2021 for use in an ongoing survey of parasites of A. mississippiensis in Mississippi. Trematodes collected from the tongues were morphologically identified as Odhneriotrema incommodum. Molecular characterization, using tissue sections excised from individually identified worms, confirms the identification as O. incommodum. Genes included in the multi locus sequence analysis were the 18S small subunit ribosomal, ITS1, 5.8S, ITS2, 28S large subunit ribosomal sequence data as well as cytochrome c oxidase subunit 1 and NADH dehydrogenase subunit 1 mitochondrial sequence data. Histologically, parasite-induced lesions on the tongue were associated with hemorrhage, necrosis, and secondary bacterial infections. Scanning electron microscopy allowed direct observation of bacteria associated with these lesions. Bacteria isolated from these lesions were identified as Aeromonas veronii by 16S rRNA and gyrase A, gyrase B and RNA polymerase sigma 70 gene sequencing. Together, these data reveal lesions associated with attachment sites of O. incommodum on alligators can create portals of entry for A. veronii and other potentially pathogenic bacteria present in the environment, leading to opportunistic secondary infections. The implications of these infections on alligator health are unclear but suggest O. incommodum in high numbers may have ancillary negative impacts on alligator health beyond mechanical irritation at the attachment site.