Abstract

Using novel diagnostic techniques for detection of infection with, or exposure to, marine-origin Brucella, including indirect and competitive ELISA, real-time PCR, bacteriologic culture and immunohistochemical staining, >6,000 blood or tissue samples have been tested. These samples represent >4,250 individuals, including wild and captive cetacean, pinniped, and marine carnivore species from Atlantic, Pacific, and Arctic regions of North America. In preliminary results, seropositivity by cELISA averages 41% in cetaceans, 42% in pinnipeds, 10% in sea otters and 12% in manatees, but there is significant variation between species and populations in different geographic regions. In >900 animals tested, culture- or PCR-confirmed cases occur uncommonly (<5%) in both cetaceans and pinnipeds. In pinnipeds, predictive value of a positive serologic test to indicate active Brucella-associated disease is low, but the predictive value of a negative serologic result is high; these data reflect high seroprevalence and low rates of active disease, as well as a few cases of active disease without seroconversion. Immunohistochemical staining of positive cases suggests a carrier state in pinnipeds, with little evidence of inflammatory reactions to resident bacteria in many cases; however, Brucella-associated abortion has recently been found in one population of California sea lions. PCR detection of Brucella in feces and lungworms of pinnipeds suggests fecal-oral or dietary exposure as potential routes of transmission, in addition to transplacental infection. Our data highlight widespread distribution of Brucella spp. infections in marine mammals, and the necessity of using multiple testing techniques to determine effects of these pathogenic bacteria on marine mammal populations.

Acknowledgments

The authors thank the many individuals and institutions who contributed samples to this extensive survey, including Dyanna Lambourn of the Washington Department of Fish and Wildlife, Joe Gaydos of the SeaDoc Society, Stephen Raverty of the British Columbia Ministry of Agriculture and Food, David Rotstein of the NOAA Center for Marine Animal Health, Frances Gulland and Tracey Goldstein of The Marine Mammal Center, Carrie Goertz and Anne Hoover-Miller of the Alaska SeaLife Center, Terry Spraker of Colorado State University, Cheryl Rosa and Cyd Hanns of the North Slope Borough Department of Wildlife Management, Lena Measures of the Canada Department of Fisheries and Oceans, Judy St. Leger of SeaWorld, Greg Bossart of Harbor Branch Oceanographic, Patricia Fair of the National Ocean Service, Randy Wells of the Chicago Zoological Society, Grace Egeland and Brian Ward of McGill University, Melissa Miller and Dave Jessup of the California Department of Fish and Game, Angela Doroff and Verena Gill of the US Fish and Wildlife Service, Stephanie Venn-Watson and Cynthia Smith of the US Navy Marine Mammal Program, and Lizabeth Kashinsky of NOAA. This research was supported by a NOAA Oceans and Human Health Initiative grant (NA04OAR4600209), NOAA Fisheries Prescott Grant (NA03NMF4390408) and by a Bernice Barbour Foundation grant (000342006).