SEROSURVEY FOR SELECTED PATHOGENS IN FREE-RANGING AMERICAN BLACK BEARS (URSUS AMERICANUS) IN MARYLAND, USA

Abstract

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 Maryland counties 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 rickettsii, 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.

Listeria monocytogenes at the human–wildlife interface: black bears (Ursus americanus) as potential vehicles for Listeria

“…While the prevalence of several zoonotic pathogens in black bears has been investigated, the focus has been primarily on viruses and vector-borne pathogens (Binninger et al, 1980;Ruppanner et al, 1982;Gage et al, 1995;Bronson et al, 2014;Stephenson et al, 2015). A substantial knowledge gap currently exists regarding the incidence of other human pathogens in bear populations, especially in urban and suburban regions of the United States.…”

Zoonoses and potential zoonoses of bears

“…The presence of the bacteria was theorized to be due to bears cohabitating with rodents. Antibodies to the bacteria have also been found in bears throughout the United States, including in 14/61 black bears in Maryland from 1999 to 2011 (Bronson, Spiker, & Driscoll, ) and in 7% of 104 brown bears blood and serum samples collected from 2013 to 2016 in five locations in Alaska (Ramey et al, ). Seropositive bears were mainly (5/7) from Lake Clark National Park and Preserve in south‐west Alaska.…”

“…Borrelia burgdorferi antibodies have been detected in black bears where Lyme disease is prevalent in North America and could potentially be spread via tick vectors (Bronson et al, ; Stephenson et al, ). Prevalence of B. burgdorferi DNA in 321 black bears from Humboldt County, California was 26%.…”

“…Ticks collected from black bears and the bears themselves have tested positive for antibodies to the spotted fever group of Rickettsia spp., Anaplasma phagocytophilum and Ehrlichia spp. across the United States (Binninger et al, ; Bronson et al, ; Chern, Bird, Frey, & Huffman, ; Leydet & Liang, ; Ruppanner et al, ; Skinner et al, ; Stephenson et al, ; Yabsley, Nims, Savage, & Durden, ). Anaplasma phagocytophilum has also been detected in brown bears in Slovakia (Víchová, Majláthová, Nováková, Straka, & Pet’ko, B., ).…”

“…Studies in Maryland have shown a low prevalence of rabies antibody titres in black bears (4/77), suggesting past exposure and an adequate immune response. Only four cases of clinical/neurologic rabies in bears were documented in the United States between 1992 and 2011, with all cases occurring in the eastern USA and involving the raccoon variant of the virus (Bronson et al, ). A few cases (seven black bears) were reported in Ontario, Canada (Walroth, Brown, Wandeler, Casey, & MacInnes, ), and on 1 November 1989, the first confirmed case of rabies in a polar bear ( U. maritimus ) was encountered by Inuit hunters in the vicinity of Cape Kendall, Southampton Island, Northwest Territories, Canada (Taylor, Elkin, Maier, & Bradley, ).…”