Summary of Pathological Findings from Subsistence Hunting of the Pacific Walrus (Odobenus rosmarus divergens) in Alaska from 1995-2004
A subsistence hunt of the Pacific walrus (Odobenus rosmarus divergens) is conducted annually by Alaska Natives. Lesions found during processing of the meat are submitted through the United States Fish and Wildlife Service Marine Mammals Management Division (USFWS-MMM) to the Armed Forces Institute of Pathology (AFIP) for histological evaluation. Purposes of the evaluation include determination of the suitability of the carcasses for human consumption and detection of disease. Reproductive tracts are occasionally collected to assess the reproductive condition of the animal. From 1995-2004, specimens from 107 Pacific walruses were submitted to the USFWS-MMM and the AFIP. The samples were from 57 adult males, 41 adult females, three subadult females, one female calf, and five walruses of unspecified age and sex. Body condition was described as robust in 25 adults, fair in 21 adults, and emaciated in seventeen adults, one subadult and one calf. Neoplasia was diagnosed in eighteen of the walruses, and consisted of five uterine leiomyomas, one uterine and ovarian leiomyoma, one mesenteric leiomyoma, two thoracic cavity peripheral nerve sheath tumors, two gastric gastrointestinal stromal tumors, two ovarian dysgerminomas, one intestinal hemangioma, one hepatic hemangioma, one simple mammary adenoma, one thoracic fibrohistiocytic neoplasm, and one scirrhous adenocarcinoma within the lung, liver and mesentery. All of the neoplasms occurred in adult walruses, except for one dysgerminoma in a subadult female. In addition to the neoplasms, common gross findings included white hepatic foci, trauma, multiorgan congestion, and malodor. The white hepatic foci were often associated with histological findings of cholangiohepatitis and fibrosis, likely due to parasitism or ascending bacterial infection from the intestines. Hepatic trematodes were described in three animals. Trauma associated lesions included fibrosis, abscesses and cystic necrotic lesions, and was frequently located on the chest. Multiorgan congestion is a nonspecific terminal change. Malodor was often associated with superficial cutaneous bacterial or fungal infection. Additional common histological findings, often not grossly apparent, included mild cardiac fibrosis, mild chronic interstitial nephritis, chronic pancreatitis that is often periductular and fibrotic, and hepatic glycogenosis. Myocardial fibrosis and chronic interstitial nephritis are common findings in adults of many species, and when mild are usually clinically insignificant. The pancreatitis is likely associated with parasitism or an ascending bacterial infection from the intestinal tract. The hepatic glycogen accumulation is probably a normal physiological change in the walrus.