Coinfection of Canine Distemper Virus and Rabies Virus in Wildlife Samples Submitted for Routine Rabies Testing

Canine distemper virus (also known as Canine morbillivirus), the etiologic agent of canine distemper, is a highly contagious pathogen causing a multisystemic infection in carnivores globally. Canine distemper may be clinically indistinguishable from rabies, and outbreaks of either disease are major concerns. In the US, both diseases are endemic and managed by parenteral vaccination in domestic animals. In wildlife, oral vaccination and trap-vaccinate-release programs are available for rabies prevention, but no such strategies exist for canine distemper. We evaluated the prevalence at which canine distemper virus occurred concurrently in animals infected with rabies virus. Real-time quantitative reverse transcriptase PCR (qRT-PCR) was performed on specimens previously diagnosed with rabies during 2017-19 by the New York State Rabies Laboratory. Real-time qRT-PCR detected concurrent canine distemper virus infection in 73 of 1,302 animals with rabies virus. Coinfection rates were approximately 9% in Procyon lotor, 2% in Vulpes vulpes, and 0.4% in Mephitis mephitis, with an overall prevalence of 5.6%. As comorbidities in wildlife occur, laboratory-based surveillance and confirmatory testing are critical to rapid decision making for disease prevention. Rabies virus incursions are expensive and difficult to manage, and spillover events create health risks to humans and domestic animals as well as to free-roaming wildlife.