EPIZOOTIOLOGY OF BRUCELLA INFECTION IN AUSTRALIAN FUR SEALS Michael Lynch, 1,2,7 Pa ´ draig J. Duignan, 3 Trevor Taylor, 4 Ole Nielsen, 5 Roger Kirkwood, 6 John Gibbens, 2 and John P. Y. Arnould 2 1 Veterinary Department, Melbourne Zoo, PO Box 74, Parkville, Victoria 3052, Australia 2 School of Life and Environmental Sciences, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia 3 Faculty of Veterinary Science, University of Melbourne, 250 Princes Highway, Werribee, Victoria 3030, Australia 4 CSIRO Animal Health, Australian Animal Health Laboratory, Private Bag 24, Geelong, Victoria 3220, Australia 5 Department of Fisheries and Oceans, Central Arctic Region, 501 University Crescent, Winnipeg, Manitoba, Canada R3T 2N6 6 Phillip Island Nature Parks, PO Box 97, Cowes, Victoria 3922, Australia 7 Corresponding author (email: mlynch@zoo.org.au) ABSTRACT: Novel members of the bacterial genus Brucella have recently emerged as pathogens of various marine mammal species and as potential zoonotic agents. We investigated the epizootiology of Brucella infection in Australian fur seals (Arctocephalus pusillus doriferus) by establishing demographic and temporal variations in antibody prevalence, attempting isolation of the causative agent, and determining whether this potential pathogen is involved in frequent abortions observed in this pinniped species. Two competitive enzyme-linked immunosorbent assays (cELISAs), an indirect ELISA, and a fluorescence polarization assay (FPA) were used to test sera for Brucella antibodies. The FPA and cELISA proved suitable for use in this species. Significant differences in antibody prevalence were found between age classes of seals sampled between 2007 and 2009 at one colony. Pups sampled at this site (n5134) were negative for Brucella antibodies by all serologic tests but 17 of 45 (38%) of juveniles were antibody-positive. Antibody prevalence in adult females was significantly higher than in juveniles (P50.044). Antibody prevalence for adult females between 2003 and 2009 varied significantly over time (P50.011), and for individuals sampled between 2003 and 2005, the likelihood of pregnancy was greater in individuals positive for Brucella antibodies (P50.034). Inflammatory lesions suggestive of infectious agents were found in 14 of 39 aborted Australian fur seal pups, but pathologic changes were not uniformly consistent for Brucella infection. Culture and PCR investigations on fetal tissues were negative for Brucella. Culture and PCR on selected fresh or frozen tissues from 36 juvenile and adult animals were also negative. We suspect that the prevalence of active infection with Brucella in Australian fur seals is low relative to antibody prevalence. Key words: Abortion, Australian fur seals, Brucella, disease, epizootiology, gestational failure, pinniped, serology. INTRODUCTION Brucella infections of terrestrial animals are a well-recognized cause of abortion and infertility and, consequently, of high economic concern to the domestic live- stock industry (Van Campen and Rhyan, 2010). Infection of marine mammals with Brucella spp. has been recognized since the mid-1990s (Ross et al., 1994). Subse- quently, serologic evidence of exposure to bacteria of this genus has been found in many species from various geographic areas (Nielsen et al., 2001; Tryland et al., 2005). Marine strains of Brucella are genetically and biochemically distinct from other species in this genus, and isolates from cetaceans and pinnipeds have been proposed recently as two new species, respectively, Brucella ceti and Brucella pinnipedialis (Foster et al., 2007; Dawson et al., 2008b). Although serology shows evidence of exposure to Brucella spp. in cetaceans and pinnipeds in the Southern Hemisphere, no isolates have been made from marine mammals in this region (Blank et al., 2002; Dawson, 2005; Abalos et al., 2009). However, isolates from humans with severe brucellosis who were resident in South America and New Zealand were characterized as marine mammal types (Sohn et al., 2003; McDonald et al., 2006; Dawson et al., 2008b), further supporting Journal of Wildlife Diseases, 47(2), 2011, pp. 352–363 # Wildlife Disease Association 2011 352 Downloaded from http://meridian.allenpress.com/doi/pdf/10.7589/0090-3558-47.2.352 by guest on 15 December 2021