Horse Health Concerns: Equine Rhinitis Virus and Coronavirus

Horse Health Concerns: Equine Rhinitis Virus and Coronavirus

Many horses affected by coronavirus go off their feed, and are lethargic and febrile.

Photo: Erica Larson, News Editor

By C.J. (Kate) Savage, BVSc(Hons), MS, PhD, Dipl. ACVIM, WEVA Junior Vice President

Veterinarians and horse owners should remain vigilant for two relatively new horse health challenges: equine rhinitis A (ERAV) and B (ERBV) viruses and coronavirus.

In the past, these viruses have been rarely specifically implicated as the cause of disease because, until recently, veterinarians have not typically requested them on a panel; instead, they concentrated on the more common and clinically important diseases, such as equine herpesvirus types 1 and 4 and influenza virus.

Previously, ERAV and ERBV were rarely implicated as causes of equine disease. Equine rhinitis A appears to cause mild to moderate respiratory disease, with or without nasal discharge, pharyngitis (inflammation of the pharynx), and coughing. Horses shed ERAV in urine, feces, and respiratory secretions, whereas veterinarians have not recognized urine and fecal shedding of ERBV. In 2012 a conditionally licensed ERAV vaccine became available in the United States. Equine rhinitis viruses also have some zoonotic potential, meaning they are communicable to people, but the risk of human infection appears low.

Coronavirus was thought to be a pathogen (agent causing disease) 30 years ago, but it is only recently that it's been shown to be important and in immunologically competent horses. In 1983 and 1990 veterinarians reported isolating a corona-type virus from adult horses and a foal with combined immunodeficiency, respectively. And since 2000 there have been various reports of coronavirus isolation in foals (without any known immune deficiencies) with diarrhea and other reports of adult horses with fevers and bowel disease. In 2011 and 2012 veterinarians reported a number of coronavirus cases in adult horses in the United States. In these cases, 34 of 44 sick adult horses were positive for coronavirus using fecal (manure) polymerase chain reaction testing. Most of the horses were off their feed, lethargic, and febrile, and some had changes in their manure consistency (ranging from soft to watery). Most horses' condition improved rapidly (within 4 days), but approximately 7% of affected animals were euthanized. Also in recent years, there was a large coronavirus outbreak in adult horses in Japan with more than 200 horses becoming ill. Most horses in that outbreak had fevers, but only 13% had diarrhea and/or colic signs.

To avoid disease infection, farms and stables should adequately isolate newly introduced horses and, of course, any horses with clinical signs including respiratory disease and/or diarrhea. Your veterinarian can help you make rational decisions regarding testing and quarantine measures.

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