Antibodies to marine-origin Brucella have been detected in marine mammal species worldwide, however most of these studies used testing methodologies designed to detect terrestrial Brucella species. We utilized a competitive enzyme-linked immunosorbent assay (cELISA), developed from a whole-cell suspension from a harbor seal Brucella isolate, to detect antibodies to marine Brucella. This technique was found to be more sensitive for marine Brucella than traditional terrestrial Brucella-based tests on samples from bottlenose dolphins (Tursiops truncatus).3
Currently, we recognize three distinct subspecies of sea otters: southern (Enhydra lutris nereis), Alaskan (Enhydra lutris kenyoni) and Russian (Enhydra lutris lutris). The three subspecies ranges do not overlap, restricting any potential interpopulation disease transmission, thus we hypothesize that the seroprevalence of marine Brucella will vary significantly between these populations. Additionally, while antibodies to Brucella have previously been detected in Alaskan and southern sea otters2, we propose that our new assay, developed specifically for marine Brucella, will improve our ability to detect exposure to this pathogen.
Serum samples collected and archived by multiple institutions were assayed by cELISA. Russian sea otter seroprevalence was significantly greater than that of Alaskan and southern sea otters by Chi-squared test. Seroprevalence differences may reflect spatial or temporal variability in sampling or exposure status. These data demonstrate exposure to marine Brucella in all sea otter subspecies, and combined with a previously reported study and the isolation of marine Brucella from a European otter (Lutra lutra)1, suggest that this pathogen may pose a health risk to otter species.
We are very grateful to Erin Dodd for her assistance in sample preparation, and to Inga Sidor for her review and comments. This Brucella research project is funded by NOAA Oceans and Human Health Initiative Grant #NA04OAR4600209.
1. Foster G, Jahans KL, Reid RJ, Ross HM. 1996. Isolation of Brucella species from cetaceans, seals and an otter. Vet Record 138:583-586
2. Hanni KD, Mazet JAK, Gulland FMD, Estes J, Staedler M, Murray MJ, Miller M, Jessup DA. (2003) Clinical pathology and assessment of pathogen exposure in southern and Alaskan sea otters. J Wildlife Diseases 39(4):837-850
3. Meegan J, Romano T, Mazzaro L, Sidor I, Dunn JL. 2006. Serosurveillance of wild bottlenose dolphins (Tursiops truncatus) and evaluation of both newly developed marine-specific and commercially available Brucella abortus serologic tests for the detection of antibodies to marine-origin Brucella. Proceedings of the 37th Annual International Association of Aquatic Animal Medicine Meeting--Abstract. Pp 65-67