Brucella placentitis and seroprevalence in northern fur seals (Callorhinus ursinus) of the Pribilof Islands, Alaska

Abstract

Brucella species infect a wide range of hosts with a broad spectrum of clinical manifestations. In mammals, one of the most significant consequences of Brucella infection is reproductive failure. There is evidence of Brucella exposure in many species of marine mammals, but the outcome of infection is often challenging to determine. The eastern Pacific stock of northern fur seals (NFSs, Callorhinus ursinus) has declined significantly, spawning research into potential causes for this trend, including investigation into reproductive health. The objective of the current study was to determine if NFSs on St. Paul Island, Alaska have evidence of Brucella exposure or infection. Archived DNA extracted from placentas (n = 119) and serum (n = 40) samples were available for testing by insertion sequence (IS) 711 polymerase chain reaction (PCR) and the Brucella microagglutination test (BMAT), respectively. As well, placental tissue was available for histologic examination. Six (5%) placentas were positive by PCR, and a single animal had severe placentitis. Multilocus variable number tandem repeat analysis profiles were highly clustered and closely related to other Brucella pinnipedialis isolates. A single animal was positive on BMAT, and 12 animals had titers within the borderline range; 1 borderline animal was positive by PCR on serum. The findings suggest that NFSs on the Pribilof Islands are exposed to Brucella and that the organism has the ability to cause severe placental disease. Given the population trend of the NFS, and the zoonotic nature of this pathogen, further investigation into the epidemiology of this disease is recommended.

Pathological findings and survey for pathogens associated with reproductive failure in perinatal Steller sea lions Eumetopias jubatus

“…Thus far, detection of Brucella spp. in otariid seals inhabiting Alaska waters has only been in northern fur seals, and 1 case exhibited severe placentitis (Duncan et al 2014). In our study, the 3 SSL cases that were PCR positive for Brucella spp.…”

“…DNA was detected by real-time PCR as described by Hinić et al (2008) targeting a region of the IS711 gene and by a Brucella assay targeting 3 genomic regions (BRU 1, BRU 2 and BRU 3) developed by the Centers for Disease Control and Prevention (CDC). A sample was considered to be positive if the cycle threshold (C t ) value was below or equal to 40 (Duncan et al 2014). Suspect samples were positive on 1 of 3 targets on the CDC Brucella assay and a high C t value on the IS711 protocol.…”

“…In one study in harbor seals, Brucella was detected in lung lesions; however, these animals also demonstrated lungworm infections, and lungworms are thought to play a possible role in Brucella transmission (Lambourn et al 2013). In contrast, placentitis and multifocal acute necrosis associated with Brucella has been reported in a limited number of eared seal species including California sea lions Zalophus californianus and northern fur seals, indicating that transplacental transmission occurs and that morbidity and mortality may be associated with Brucella infection in eared seals (Goldstein et al 2009b, Duncan et al 2014.…”

Pinnipediae

“…The majority of B. pinnipedialis infections in pinnipeds are subclinical. However, suppurative and necrotizing placentitis in a northern fur seal was confirmed to be due to Brucella spp infection by immunohistochemistry and PCR (Duncan et al, 2014).…”

Brucellosis associated with stillbirth in a bottlenose dolphin in Australia

“…This may reflect differences in virulence or host susceptibility, though there is at least one report of isolation associated with placentitis in seals. The mode of transmission of both organisms has not been established. Suggested routes of transmission include horizontal transmission (including venereal or via aborted foetuses), vertical transmission, infected fish prey and carriage on parasites such as lungworm .…”