Brucellosis in Marine Mammals

Brucella infections have recently been recognized in seals, sea lions, walruses, dolphins, porpoises, whales and an otter. This organism appears to be widespread in marine mammals, and has probably been endemic in these populations for a long time. The clinical significance is uncertain. A few infections have been associated with placentitis/abortions, neonatal mortality, meningoencephalitis, abscesses or other syndromes, but Brucella has also been isolated from normal tissues and asymptomatic animals. There are concerns that brucellosis might affect reproduction or echolocation, particularly in threatened species or naive populations. These concerns are highlighted by the recent isolation of Brucella from a newborn Maui’s dolphin that died shortly after birth. Maui’s dolphins are a highly endangered species, with a population consisting of approximately 100 animals. Marine mammal isolates of Brucella can infect terrestrial mammals, but the frequency of this event is unknown. Some polar bears, which feed on marine mammals, are seropositive for Brucella, and there are concerns about possible impacts on this species. Experimental infections in cattle and sheep have been described. Rare human infections have also been documented. One marine mammal isolate caused acute brucellosis in a researcher. Three other infected people had no occupational exposure to marine mammals; two individuals had neurological signs, and the third developed spinal osteomyelitis.