Persistent Bovine viral diarrhea virus infection in wild cervids of Colorado

Bovine viral diarrhea virus (BVDV) is a significant viral pathogen of domestic cattle. Worldwide, there is evidence of BVDV exposure and infection in wild ungulates; however, the frequency and significance of such events are unknown. To determine the prevalence and distribution of Colorado deer, elk, and moose persistently infected (PI) with BVDV, a cross-sectional study was conducted using full-thickness ear tissue samples collected from animals presented to the Colorado Division of Wildlife for chronic wasting disease surveillance in the 2005-2006 hunting season. Tissue from 5,597 harvested animals (2,934 mule deer, 2,516 elk, 141 white-tailed deer, and 6 moose) was paraffin-embedded and stained for BVDV using immunohistochemistry. A single adult male mule deer had BVDV antigen in the skin; staining distribution was consistent with that seen in PI cattle. Skin and lymph node were also positive for viral RNA by polymerase chain reaction, and the virus was determined to be a type 1. The prevalence of BVDV PI cervids in Colorado is very low. However, the identification of a naturally infected adult PI animal in the wild suggests that the virus infects free-ranging populations. The source of the BVDV is unknown and is assumed to be spillover from cattle or maintenance within wildlife populations. Consideration of a potential wild animal reservoir is important in the design and implementation of BVDV management practices in cattle.