Pathological changes of stomach in ringed seal (Pusa hispida) from Arviat (North Canada) caused by anisakid nematodes

Abstract

This is a report of lesions associated with the nematodes (Anisakidae) from the stomach of ringed seals (Pusa hispida). On thirty one examined ringed seals from Arviat, thirteen were infected by 1 to 24 anisakids. Identification of nematodes from their stomachs showed two species; Contracaecum osculatum (sensu lato) (79 specimens) and Pseudoterranova decipiens (sensu lato) (11 specimens). In the gastric sections with parasites, larvae and adults of nematodes were present mainly in the fundic portion of the stomach. The anterior parts of the nematodes were embedded in mucosa and submucosa. Anisakids were associated with ulcerous gastric lesions and raised inflammatory areas in the stomachs. The histological examination of a sample taken from the tissue surrounding anisakids revealed the presence of more or less confluent focal necrotic areas. Most small petechial hemorrhages were located in the mucosal layer of the gastric wall and were surrounded by inflammatory mononuclear cells such as lymphocytes, histiocytes, eosinophils and fibroblasts. The Anisakidae larvae in the stomach caused atrophy of glands, hemorrhaging and eosinophilic infiltrations that consequently healed, creating fibrotic scars.

A Review of Circumpolar Arctic Marine Mammal Health—A Call to Action in a Time of Rapid Environmental Change

“…Numerous roundworms have been documented in AMMs in the lungs of ringed seals [ 200 ], the stomachs of bearded seals [ 201 ], and in multiple organs in ribbon and spotted seals [ 202 ]. Common nematodes in AMMs include Ascaroids such as Anisakis , Spirurids such as Crassicauda , Filaroids such as Acanthocheilonema , hookworms such as Uncinaria, and Metastrongyloids (lungworms) such as Otostrongylus circumlitus [ 203 , 204 , 205 , 206 , 207 ]. Zoonotic Anisakis is well documented in both people and AMMs [ 208 ].…”