July 5, 2018
The Equine Herpes Virus (EHV) aka Rhinopneumonitis is at its height again. There are three different types: the flu-like type, the abortion type and the neurological type. Outbreaks of this last type have recently been reported from the Netherlands, Germany, France, Belgium, Denmark and America.
Rhinopneumonitis is constantly present at all locations with horses. It often stays dormant in the body but at times of fatigue or stress it can suddenly emerge. As a consequence the virus can hide in the horse´s body and under normal circumstances causes hardly any problems. However in times of stress, intense competition or other situations that have an impact on the horse’s defence system they can suddenly release many virus particles and contaminate other horses. A period particularly at risk is the foaling season.
A horse infected with Rhinopneumonitis usually develops a fever and shows signs of a cold or flu. Most of the times the owner doesn´t even notice the symptoms. The horse develops anti-bodies and recovers. The virus also has a preference for white blood cells. Via the white blood cells the virus can migrate into the pregnant uterus where it harms the foal and induces an abortion or premature birth. There are no long-term effects for the mare. Alternatively, the virus can migrate into the central nervous system via the white blood cells. The result will be damage to the spinal cord which causes paralysis of the limbs or muscles of the bladder, rectum and tail.
How can Rhino be detected?
There are two types of the herpes virus: EHV-1 and EHV-4. Clinical symptoms triggered by EHV- 4 are usually very mild and seldom lead to abortion. EHV-1 infections can lead to outbreaks of abortion or signs of paralysis. Diagnosis of the illness is done by identifying symptoms, checking the horse´s nose or blood for the presence of the virus (PCR) or by the detection of anti-bodies in the blood.
The initial stage of both types starts with multiplying of the virus in the airways. The veterinarian takes a swab of the nose for a quantitative PCR. This is a highly sensitive test that can differentiate between EHV-1 and EHV-4.After multiplication in the respiratory tract the EHV-1can permeate the surface lining of the respiratory system, invade the white blood cells and migrate to the blood stream. When the virus has entered the blood stream this is called viraemia. From that moment onwards the virus can be transported through the entire body. When the vet has taken blood from the horse during this viraemic stage it can be used to carry out another PCR at the laboratory.
How should owners act?
For horse owners a lot can be won by sensible management and vaccination. Newly-purchased horses must be kept isolated for a period of three to four weeks. Keep pregnant mares away from newly-weaned foals, yearlings and competition horses. Avoid nasal contact with strange horses. Use your own drinking buckets, clean all transport items and don´t go from horse to horse giving them all a pat on the nose. Via the air the contamination radius of the virus is no more than a few yards.
Current vaccinations don’t offer 100% protection but in places where vaccinations are carried out in compliance with the rules the outbreaks make fewer victims and the symptoms of the disease are milder. The message to get across is vaccination, especially when stable companions regularly go out competing.
As posted in the July 2018 KFPS Newsletter