Rhinopnuemonitis is more commonly known by its more descriptive name, Snots. This is because this virus, which is actually a form of the equine herpes virus, lives in the mucosal membranes of the nasal cavity and is most easily identified by the large amounts of mucous that are discharged from the nose as well as a dry, hacking cough.
Equine herpes virus is present in most adult horses, but the horse's immune system is able to keep the virus under control so it does not affect the horse under normal conditions. In young horses that don't have a fully developed immune system or that are being exposed to many different viruses at the same time the immune system may not be able to control the development of the virus, resulting in the symptoms. It appears that the rhinopneumonitis occurs in mild stages over a three to seven day cycle and then will clear up on its own. In actuality the virus is still present in the lymph nodes of the horse and will be for life. Horses that are stressed, are taking immunosuppressive medications such as steroids or have other viral infections may suddenly show signs of the condition when the immune system is no longer able to keep the virus in check.
In pregnant mares rhionpneumonitis usually results in the abortion of a perfectly formed but deceased foal at any stage of the pregnancy. More rarely the virus may not kill the foal but it will be born weak and with severe health conditions that will result in death within a few days. Mares can be vaccinated routinely during their pregnancy to control the virus and prevent any problems with abortion or possible health risks to the foal. Foals that develop rhinopneumonisits in the days immediately after birth are at the greatest risk of dying from this condition.
Very rarely the rhinopneumonitis virus will leave the respiratory system and attack the central nervous system. The signs of this atypical condition include paralysis, lack of coordination of the muscles and eventual collapse. The signs of rhinophneumonitis are fairly easy to recognize. They include red mucous membranes in the nose and tearing from the eyes, mucous discharge, dry coughing that is nonproductive, large lymph nodes in the jaw and neck and a temperature rise in the legs.
As it is a virus the only treatment is to keep the horse calm, in a dry and warm environment and provide lots of good quality food and fresh water. Isolation of the infected horse is important, as is routine vaccination of horses and foals throughout their life. Avoiding other stressers and keeping the horse in the best possible health is the best prevention for developing the condition.