North American Arboviruses and White-Tailed Deer (Odocoileus virginianus): Associated Diseases and Role in Transmission

Causes of mortality in farmed white-tailed deer in the midwestern United States, 2004-2023

Farmed cervids are of growing economic importance in the midwestern United States. Although diseases of wild and captive cervids have been examined in more northerly climates, little information exists on the health challenges of deer in the Midwest. We characterized and summarized the causes of mortality in farmed white-tailed deer (Odocoileus virginianus) submitted to the University of Missouri Veterinary Medical Diagnostic Laboratory (Columbia, MO, USA) over a 19-y period (2004-2023). Of 388 cases examined, 253 (65%) were carcasses submitted for autopsy, and 135 (35%) cases were tissue samples harvested by field veterinarians. Infectious disease was the most common cause of mortality (n = 335; 86.3%). Of infectious causes, primary pneumonia was most common (n = 140; 41.7%), followed by septicemia (n = 68; 20.1%), and primary enteritis (n = 64; 19.1%). Viruses were detected in 18% of pneumonia cases. The most common non-infectious diagnoses were emaciation and trauma (both 4 each; 1%). Thirteen animals (3.4%) died of unknown causes. Forty-nine percent of cases were juvenile deer <1-y-old. Most cases were received in the summer (212; 54.6%). Infectious diseases, particularly bacteria and viruses, pose a significant health challenge to farmed deer in the midwestern United States.

Evidence of Active Orbivirus Transmission in 2016 in Kansas and Nebraska

Retrospective serological and case diagnostic data of endemic bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) provide evidence of viral transmission among livestock and wildlife from 2016 in Kansas and Nebraska. Serological testing of mature cattle in nine distinct regional zones of Kansas revealed 76% to 100% had detectable antibodies to BTV and/or EHDV. Specimens tested in the Kansas Veterinary Diagnostic Laboratory (55 submissions) were 51% test positive for antibodies to BTV and/or EHDV. Specimens tested in the Nebraska Veterinary Diagnostic Center (283 submissions) were 25% test positive for antibodies to BTV and/or EHDV. Low disease incidence in white-tailed deer and other susceptible wild ungulates was observed during 2016. However, there were no confirmed reports of disease in livestock in either state. The reasons for emergence of significant clinical disease in livestock and wildlife populations remain undefined.

Cache Valley virus: an emerging arbovirus of public and veterinary health importance

Cache Valley virus (CVV) is a mosquito-borne virus in the genus Orthobunyavirus (Bunyavirales: Peribunyaviridae) that has been identified as a teratogen in ruminants causing fetal death and severe malformations during epizootics in the U.S. CVV has recently emerged as a viral pathogen causing severe disease in humans. Despite its emergence as a public health and agricultural concern, CVV has yet to be significantly studied by the scientific community. Limited information exists on CVV's geographic distribution, ecological cycle, seroprevalence in humans and animals, and spectrum of disease, including its potential as a human teratogen. Here, we present what is known of CVV's virology, ecology, and clinical disease in ruminants and humans. We discuss the current diagnostic techniques available and highlight gaps in our current knowledge and considerations for future research.