Detection of Rickettsial organisms in ticks collected from Ursus americanus (Carnivora: Ursidae) in Mississippi

Abstract

The black bear, Ursus americanus (Carnivora: Ursidae), is a large mammal listed as threatened in the state of Mississippi since 1992. After years of historical decline, black bear numbers and their range have been increasing in Mississippi, with bears returning to areas within their historic range. Little is known about ectoparasites and vector-borne microorganisms associated with black bears. During 2024, 83 ticks comprising 4 species were removed from 17 bears (one of which was a recapture) captured in 9 central and southern Mississippi counties. Upon molecular screening of the 83 ticks, 11 specimens contained DNA of the Rickettsia endosymbiont of Ixodes scapularis (also known as Rickettsia buchneri); 20 contained Rickettsia parkeri; 21 had “Candidatus Rickettsia andeanae;” 9 had R. tillamookensis; 4 had R. amblyommatis; 1 had R. bellii; and 4 had organisms in the family Anaplasmataceae; of these, 1 was identified as Ehrlichia chaffeensis. Four ticks had detectable levels of Rickettsia DNA that could not be identified to the species level.