DAO 111:93-106 (2014)  -  DOI: https://doi.org/10.3354/dao02762

Surveillance for zoonotic and selected pathogens in harbor seals Phoca vitulina from central California

Denise J. Greig1,9,*, Frances M. D. Gulland2, Woutrina A. Smith3, Patricia A. Conrad3, Cara L. Field4, Michelle Fleetwood5, James T. Harvey6, Hon S. Ip7, Spencer Jang8, Andrea Packham3, Elizabeth Wheeler2, Ailsa J. Hall

1Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews KY16 8LB, UK
2The Marine Mammal Center, Sausalito, California 94965, USA
3Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, California 95616, USA
4Mystic Aquarium & Institute for Exploration, Mystic, Connecticut 06355, USA
5New Hampshire Veterinary Diagnostic Laboratory, University of New Hampshire, Durham, New Hampshire 03824, USA
6Moss Landing Marine Laboratories, Moss Landing, California 95039, USA
7US Geological Survey, National Wildlife Health Center, Madison, Wisconsin 53711, USA
8William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, California 95616, USA
9Present address: The Marine Mammal Center, Sausalito, California 94965, USA
*Corresponding author:

ABSTRACT: The infection status of harbor seals Phoca vitulina in central California, USA, was evaluated through broad surveillance for pathogens in stranded and wild-caught animals from 2001 to 2008, with most samples collected in 2007 and 2008. Stranded animals from Mendocino County to San Luis Obispo County were sampled at a rehabilitation facility: The Marine Mammal Center (TMMC, n = 175); wild-caught animals were sampled at 2 locations: San Francisco Bay (SF, n = 78) and Tomales Bay (TB, n = 97), that differed in degree of urbanization. Low prevalences of Salmonella, Campylobacter, Giardia, and Cryptosporidium were detected in the feces of stranded and wild-caught seals. Clostridium perfringens and Escherichia coli were more prevalent in the feces of stranded (58% [78 out of 135] and 76% [102 out of 135]) than wild-caught (42% [45 out of 106] and 66% [68 out of 106]) seals, whereas Vibrio spp. were 16 times more likely to be cultured from the feces of seals from SF than TB or TMMC (p < 0.005). Brucella DNA was detected in 3.4% of dead stranded harbor seals (2 out of 58). Type A influenza was isolated from feces of 1 out of 96 wild-caught seals. Exposure to Toxoplasma gondii, Sarcocystis neurona, and type A influenza was only detected in the wild-caught harbor seals (post-weaning age classes), whereas antibody titers to Leptospira spp. were detected in stranded and wild-caught seals. No stranded (n = 109) or wild-caught (n = 217) harbor seals had antibodies to phocine distemper virus, although a single low titer to canine distemper virus was detected. These results highlight the role of harbor seals as sentinel species for zoonotic and terrestrial pathogens in the marine environment.


KEY WORDS: Campylobacter · Leptospira · Influenza · Morbillivirus · Neospora · Sarcocystis · Toxoplasma · Vibrio


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Cite this article as: Greig DJ, Gulland FMD, Smith WA, Conrad PA and others (2014) Surveillance for zoonotic and selected pathogens in harbor seals Phoca vitulina from central California. Dis Aquat Org 111:93-106. https://doi.org/10.3354/dao02762

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