Equine rhinitis viruses produce clinical signs similar to other viral respiratory infections, including nasal discharge. | Photo: Photos.com

Respiratory viral infections are present in horses worldwide, with two of the most recognized viruses being equine influenza virus and equine herpesviruses. Although identified in the past mid-century, equine rhinitis viruses (ERVs) have emerged as significant contributors to equine respiratory infections. In the last decade, particularly, researchers have demonstrated that ERVs are highly prevalent in the horse population and are associated with clinical disease that can’t be differentiated from that caused by other viral respiratory infections. 

Until recently, researchers’ and veterinarians’ lack of knowledge about ERVs was largely due to their belief that these viruses were insignificant contributors to respiratory viral outbreaks and clinical disease. It is clear now that ERVs have circulated for decades within the global horse population. 

From a recent systematic respiratory outbreak study in Canada, along with an experimental infection study, we have established that the disease is characterized by increased body temperature, serous (clear, runny) to purulent (pus-containing) nasal discharges, submandibular lymphadenopathy (lymph node enlargement beneath the lower jaw), abnormal lung sounds, and excess airway secretions. In the challenge model, we detected mucus secretions up to 21 days post-infection