Abstract

Parasitic infections are common in wild harbor porpoises (Phocoena phocoena), and the pathology associated with prevalent nematode and trematode parasites has been characterized in Europe^1,2,3,4,5 but little data exist for harbor porpoises in Washington State. We retrospectively examined necropsy records for harbor porpoises that stranded in San Juan County, Washington between 2006 and 2016 to identify common parasites and their associated pathology. Stranded porpoises received complete necropsy examinations that included gross examination, histopathology, and ancillary testing, including bacteriology. Parasites collected were fixed in ethanol and set to the University of Florida for definitive identification. Occasionally, parasites were not identified grossly but were found during histopathology and could occasionally be identified to genus. Overall, five distinct species of nematode within six different genera (Anisakis, Crassicauda, Halocercus, Stenurus, Tonyurus and Pseudoterranova) and three species of trematode within two genera (Campula and Hadwenius) were identified in 19 individuals. Verminous bronchopneumonia (multi-focal granulomatous, eosinophilic with edema) was identified in all 19 cases and the associated parasites included Anisakis larvae (n=1) as well as adult Halocercus invaginatus (n=3), Stenurus minor (n=3) and Tonyurus sp. (n=1) nematodes. Definitive parasite identification could not be made in the other 11 cases with bronchopneumonia and scattered to florid intralesional nematodes. Granulomatous inflammation and hemorrhage of the peri-bullar area was identified in 5 of 7 animals with Stenurus minor infection. Anisakis simplex and Anasakis sp. were identified in the gastrointestinal tracts of 12 animals. Parasites often were associated with gastritis (mild to moderate, multifocal, granulomatous and eosinophilic) and occasionally with gastric ulceration in cases with significant worm burdens. Crassicauda sp. infection was identified in the subcutaneous adipose tissue of 10 animals and was most commonly associated with granulomatous steatitis, dystrophic mineralization and variable numbers of Langhan’s type multinucleate giant cells. We found one case of Crassicauda sp.-associated mastitis (mild, focal, granulomatous), which may suggest an alternative route of transmission to perinates. Campula oblonga was the only trematode identified (n=13) and infection always was associated with cholangiohepatitis (mild to moderate, multifocal and often with biliary ductular hyperplasia and ductular cholestasis). Also, the trematode Hadwenius mironovi was associated with cholangiohepatitis in one animal and enteritis in another (moderate, multifocal eosinophilic, subacute). Interestingly, eosinophilic lymphadenitis was identified microscopically in 63% of cases with parasites (n=12) and was associated with polyparasitism in all cases except one. Anecdotally, intercurrent disease and nutritional status impacted the extent and severity of parasitism. Our findings are consistent with parasites and associated pathology found in harbor porpoise from Europe^1,2,3,4,5 and continued efforts should focus on better understanding potential sub-lethal effects of parasites on harbor porpoises in the Salish Sea.

Acknowledgements

We thank the numerous volunteers of the San Juan County Marine Mammal Stranding Network and private citizens who reported stranded harbor porpoise. Much of this work was funded through John H. Prescott Marine Mammal Rescue and Assistance Grants.

Table 1. Summary of parasites and associated pathology identified in stranded harbor porpoises from San Juan County, Washington between 2006 and 2016

* Presenting author

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