Abstract
Vertically transmitted nematodes can be a significant cause 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).3,4,7 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 flotation 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 that vertical transmission of this parasite can occur in harbor seals. Infestation with Phocanema 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.
Acknowledgements
This work was funded by the John H. Prescott Marine Mammal Rescue and Assistance Grant. The authors would like to thank the staff and volunteers of the San Juan County Marine Mammal Stranding Network, the SeaDoc Society, the Whale Museum, and Wolf Hollow Wildlife Rehabilitation Center. The authors would also like to thank Katie Haman, Lauren Rust, Dr. Richard Evans, and Karisa Tang for their contributions to the project.
* Presenting author
+ Student presenter
Literature Cited
1. Gerber, J.A., Roletto, J., Morgan, L.E., Smith, D.M., and Gage, L.J., 1993. Findings in pinnipeds stranded along the Central and Northern California coast, 1984–1990. J Wildl Dis 29(3):423–433.
2. Irvine, R.J. 2006. Parasites and the dynamics of wild mammal populations. Anim Sci 82:775–781.
3. Lyons ET. 1994. Vertical transmission of nematodes: emphasis on Uncinaria lucasi in northern fur seals and Strongyloides westeri in equids. J Helminthol Soc Wash 61:169 178.
4. Lyons ET, DeLong RL, Spraker TR, Melin SR, Tolliver SC. 2003. Observations in 2001 on hookworms (Uncinaria spp.) in otariid pinnipeds. Parasitol Res 89:503–505
5. Meyers, B.J. 1960. On the morphology and life history of Phocanema decipiens. Can J Zoo 38: 331–344.
6. Ross, P.S., Pohajdak, B., Bowen, W.D., and Addison, R.F. 1993. Immune function in free-ranging harbor seal (Phoca vitulina) mothers and their pups during lactation. J Wildl Dis 29(1):21–29.
7. Sepúlveda MS, Alcaíno H. 1993. Fauna helminthologica en el lobo fino de Juan Fernandez, Arctocephalus philippi (Peters, 1866). Parasitol Día 17:19–24.
8. Steiger, G.H., Calambokidis, J., Cubbage, J.C., Skilling, D.E., Smith, A.W., and Gribble, D.H., 1989. Mortality of harbor seal pups at different sites in the inland waters of Washington. J Wildl Dis 25(3):319–328.