Have you ever wondered why it’s so important to vaccinate your mare’s at their 5th, 7th and 9th months of pregnancy? Have you been tempted to skip one sequence of the vaccine – or the whole thing altogether – figuring that “it can’t make that much of a difference?” If you’re of this school of thought, I have one word for you: Rhinopneumonitis.
Rhinopneumonitis is also known as two distinct viruses: Equine Herpes Virus Type 1 (EHV-1) and Equine Herpes Virus Type 4 (EHV-4). Each of these types cause two different diseases, both of which are known as Rhinopneumonitis and both of which cause respiratory tract problems. However, where they differ is in the fact that EHV-1 may also cause abortion in pregnant mares – making the economic and emotional losses of this disease immeasurable. It is a very contagious viral disease that can creep up suddenly and affect large numbers of mares in what is known as an “abortion storm”. Rhinopneumonitis is transmitted by direct contact or airborne respiratory secretions and the initial source of the infection is often unknown.
Symptoms of the EHV-1 disease can be tricky. Mares may show signs of respiratory disease 3-4 months prior to the actual abortion taking place. Symptoms include a horse that is feverish, lethargic and has a loss of appetite, plus a possible nasal discharge and cough. At the time of abortion, the mare will often display no other sign of illness. Most often, the abortion takes place in the last 1/3 of pregnancy as the virus attacks the lung tissue of the fetus. The fetus then dies in the uterus and the mare aborts it due to the fact that it is no longer alive. And the saddest thing of all, if the fetus has been exposed to the disease but does not die in utero it can be carried full term – only to be born in a weakened condition and die within 24 hours.
There is no known treatment against Rhinopneumonitis and once a mare has contracted the disease, the result is tragic for the foal. However, Rhinopneumonitis can be prevented and a vaccination protocol of pregnant mares at 5,7 and 9 months of pregnancy is the only way to guard against it. Commonly, the killed vaccine Pneumabort K is given to mares at these specific times in their pregnancies and may offer some cross over protection against the flu variety. Young horses can also suffer from respiratory tract infections as a result of EHV-1 and may secondarily also develop pneumonia. Therefore, weanlings, yearlings and young horses under stress should also be vaccinated – speak to your veterinarian for vaccine and protocol advice for these animals.