Parker, C., J. K. Gaydos, S. Raverty, A. D. McIntosh, A. L. Traxler, and P. Harner. 2013. Vertical transmission of internal parasites in harbor seal (Phoca vitulina richardsi) pups in San Juan County, Washington. Annual Conference of the International Association of Aquatic Animal Medicine, San Francisco, CA, April 2013.
Type: Technical report or proceeding
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Vertically transmitted nematodes can be a significant case of morbidity and mortality in some pinnipeds. Examples include the transmammary transmission the infective L3 of Uncinaria lucasi in Northern fur seals (Callorhinus ursinus) and Uncinaria spp. in California sea lions (Zalophus californianus) and in Juan Fernandez fur seals (Arctocephalus philippi).
To the best of our knowledge, transmammary or transplacental transmission of nematodes has never been documented in harbor seals (Phoca vitulina). Four deceased and six live stranded harbor seal pups collected between June and August 2012 in San Juan County, Washington, were studied for evidence of vertical transmission of internal parasites. Samples evaluated included lungs, liver, and gastrointestinal tracts collected from pre-weaned pups at necropsy and fecal samples from live stranded pups in rehabilitation. Tissue samples were evaluated by rinsing through a sieve and resultant material was examined for evidence of parasites. Fecal samples were examined via centrifugal float using zinc sulfate solution. Samples from the live pups showed no evidence of parasite infestation or shedding. However, a single necropsy sample revealed a developing adult male Phocanema decipiens nematode in the gastrointestinal tract of a three-day-old male harbor seal pup, suggesting vertical transmission of this parasite can occur in harbor seals. Infestation with P. decipiens has been widely reported in adult harbor seals in the Salish Sea but this is the first known documentation of infestation in a pre-weaned pup. The prevalence of P. decipiens in pre-weaned pups should be further studied, as should the potential clinical significance of this infection in harbor seal pups.