Cross-Species Transmission of Lentivirus between Bobcats and Pumas in Fragmented Habitats of Southern California
1Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA; 2U.S. Geological Survey, Carlsbad, CA, USA; 3Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, CO, USA
Species-specific lentiviruses are prevalent in many nondomestic species of the family Felidae. Seroprevalence can approach 100% in some populations. However, previous serosurveys in bobcats (Lynx rufus) have found that lentiviral prevalence is usually less than 10%. Blood from 17 wild bobcats captured in Orange County, CA was screened to assess lentiviral seroreactivity using a standard immunoblot assay to detect antibodies to feline (Felis catus) immunodeficiency virus (FIV), lion (Panthera leo) lentivirus (LLV), and puma (Felis concolor) lentivirus (PLV) antigens. DNA was isolated from blood cells of all animals with positive or inconclusive immunoblot results and subjected to PCR amplification using degenerate feline lentivirus pol primers. Additionally, we screened a subset of positive individuals with a commercial FIV antibody diagnostic test (SNAP™ test, IDEXX Laboratories, Westbrook, ME, USA) to compare assay sensitivity.
Ten of 17 individuals (59%) had antibodies that bound strongly to the PLV gag protein on the immunoblot with weaker affinity for LLV and FIV antigens. Two individuals had inconclusive immunoblot results with weak binding to PLV only. PCR product was amplified from all 10 individuals positive by immunoblot. The SNAP™ test had a relative sensitivity of approximately 80% compared to PCR or immunoblot.
Phylogenetic analysis of the 10 amplified proviral sequences revealed that the lentivirus infecting these individuals is closely related to PLV isolated from a puma captured in Orange County in the late 1980s. Interestingly, genetic distances between the Orange County PLV and bobcat pol regions were less than distances between the Orange County puma sequence and PLVs from pumas in nonoverlapping geographic locations. We conclude that lentiviral infection in bobcats may be more common than previously believed, and that immunoblot, or PCR has higher sensitivity of detection than a commercially available FIV ELISA. Further, the homology between bobcat and puma lentivirus suggests that cross-species transmission of feline lentivirus has occurred in southern California. We speculate that shrinking habitat and scarcity of resources in urban regions may lead to greater contact rates between large carnivore species, thus prompting interspecies transmission of this virus.