1The Marine Mammal Center, Sausalito, CA, USA; 2 Veterinary Pathology, Microbiology and Immunology, Veterinary Medicine Teaching Hospital, University of California, Davis, CA, USA; 3Gulf of the Farallones National Marine Sanctuary, San Francisco, CA, USA
An eastern Pacific gray whale (Eschrichtius robustus) that stranded off Pelican Point, Tomales Bay, California, USA, was euthanatized due to its emaciated condition and the logistic difficulties associated with rescue. It was examined for ingested prey, parasites, and associated pathology.
The animal was a 2-year-old male on the northward migration, and was severely emaciated, with prominent transverse processes of the vertebrae, and atrophy of the blubber and nuchal fat pad. Hematology and serum biochemical analyses indicated an elevation in hematocrit, serum sodium and potassium values, and hypoglycemia and hypoalbuminemia. The stomach was distended with prey and masses of parasites. The prey taxa identified indicated the whale was feeding on hard bottom communities prior to death. Multifocal transmural abscesses were observed along the first 75 m of the ileum. Within each abscess was an encapsulated proboscis of the acanthocephalan, Bolbosoma balaenae (Gmelin, 1790). Culture of the abscesses using routine bacterial culture methods produced Edwardsiella tarda, Escherichia coli, and Clostridium perfringens. Acanthocephalans also were observed free in the lumen of the ileum, but these were bodies only without attachment organs. The lumen of the ileum was reduced in diameter due to thickening of the wall. Histologic examination also revealed severe acute lung congestion, minimal, multifocal, lymphocytic, interstitial myocarditis, and mild hepatocellular and Kupffer cell hemosiderosis.
Parasites recovered included five species, one ectoparasite (Cyamus scammoni), and four helminths (Anisakis simplex, Ogmogaster antarcticus, Ogmogaster pentalineatus, Bolbosoma balaenae) with the latter causing the multifocal transmural abscesses in the intestine.
From this case, it is unclear whether the state of malnutrition of this whale was the cause or consequence of the heavy parasite burden detected.