Histopathological Impact Of Nematodes On The Gastric Mucosa Of The American Alligator (Alligator Mississippiensis)

Abstract

Nematodes are adapted to inhabit a vast array of niches. They have evolved tremendous strategies to survive and succeed in a variety of hosts and host tissues. Intestines represent an ideal habitat for a large number of parasites, compared to the stomach. In the present study we examined the stomach of 14 sub‐adult, wild‐caught American alligators (Alligator mississippiensis) from the coastal region of Louisiana. Nematodes were found in four of the alligators (~29%). Two different parasites were found; Dujardiascaris waltoni (Nematoda: Heterocheilidae) and Ortleppascaris sp.? (Nematoda: Ascaridoidea). D. waltoni was found loose among the stomach contents, whereas Ortleppascaris sp.? was found embedded in the stomach wall. Ortleppascaris was associated with multifocal lesions in the gastric mucosa. These lesions were roughly 4 mm in diameter and housed multiple parasites. The lesions caused a clearly visible penumbra of mucosal damage. As the parasites invaded the gastric mucosa, they induced a granulomatous inflammation of the mucosa and submucosa. There was a marked eosinophilic necrosis, a cellular response that produces the penumbra around the invasive nodules. The impacted worms burrowed into the mucosa, and were surrounded by an eosinophilic exudation, resulting in an elevated nodule of worms and mucosa. This presumably represent proliferating host mucosal tissue responding to the parasitic challenge. Alligators have “typical” vertebrate gastric pits and glands in the stomach mucosa. Mucosal burrows of the nematodes led to a loss of the gastric pits in the infected zone and digestive efficiency of the host. Previous studies have described keratitis and enteritis associated with nematode infections in crocodilians, but similar reports are lacking from Alligator mississippiensis. Alligators and crocodiles have remarkably effective immune systems, which enable them to fight against microbial infections and allow quick wound healing. We hope to expand our understanding of host‐parasite relations in this important species.Host response/eosinophil exudation in infected gastric mucosaFigure 1Nematodes burrowed in to the stomach mucosaFigure 2