Canine distemper virus was recently detected in free-ranging bears in Maryland (see abstract below). Scientific studies to determine if ticks on bears could contract the virus and transmit it to humans has not been explored.
J Wildl Dis. 2014 Jul 30. [Epub ahead of print]
Serosurvey For Selected Pathogens In Free-Ranging American Black Bears (Ursus americanus) In Maryland, USA.
11 Maryland Zoo in Baltimore, 1876 Mansion House Drive, Baltimore, Maryland 21217, USA.
Abstract American black bears (Ursus americanus) in Maryland, USA, live in forested areas in close proximity to humans and their domestic pets. From 1999 to 2011, we collected 84 serum samples from 63 black bears (18 males; 45 females) in five Marylandcounties and tested them for exposure to infectious, including zoonotic, pathogens.
A large portion of the bears had antibody to canine distemper virus and Toxoplasma gondii, many at high titers. Prevalences of antibodies to zoonotic agents such as rabies virus and to infectious agents of carnivores including canine adenovirus and canine parvovirus were lower.
Bears also had antibodies to vector-borne pathogens common to bears and humans such as West Nile virus, Borrelia burgdorferi, Rickettsia rickettsiae, and Anaplasma phagocytophilum. Antibodies were detected to Leptospira interrogans serovars Pomona, Icterohaemorrhagiae, Canicola, Grippotyphosa, and Bratislava. We did not detect antibodies to Brucella canis or Ehrlichia canis.
Although this population of Maryland black bears demonstrated exposure to multiple pathogens of concern for humans and domesticated animals, the low levels of clinical disease in this and other free-ranging black bear populations indicate the black bear is likely a spillover host for the majority of pathogens studied.
Nevertheless, bear populations living at the human-domestic-wildlife interface with increasing human and domestic animal exposure should continue to be monitored because this population likely serves as a useful sentinel of ecosystem health.