Antibodies against rangiferine brucellosis, Brucella suis type 4, are commonly found in the serum of various domestic and wild Alaskan carnivores which feed on caribou, Rangifer tarandus granti, in arctic Alaska. Sled dogs from five native villages on the range of the Arctic caribou herd, but not from two villages on the range of the Porcupine caribou herd, are commonly infected. Wolves (Canis lupus) and red foxes (Vulpes fulva) are less commonly infected.

About 90% of the grizzly bears (Ursus arctos horribilis) associated with the Arctic caribou herd and 30% of those associated with the Porcupine caribou herd show serologic signs of exposure to Brucella, presumably the enzootic strain present in Alaska caribou. This is the first evidence of natural Brucella infection in bears.

It is concluded that infection of predators by enzootic strains of Brucella present in prey species (e.g., ruminants) is common to many areas of the world. Evidence from the literature and unpublished experimental data suggest that such infections may interfere with reproduction in wild species, but additional study is needed to clearly resolve this question.