Posted by Dr. Cory Reng on June 15 2009 15:57
Equine Newsletter 4th Quarter 2004
Most mare owners know that they should vaccinate their pregnant mares with Pneumoabort K at 5, 7,and 9 months of pregnancy. But it takes a thorough understanding of Herpes virus to take all the steps necessary to prevent abortion storms in your mares.
Equine Herpesvirus, also known as Rhinopneumoninitis or "Snots" is caused by a tight familiy of viruses. There are 2 strains that are most important (EHV-1 and EHV-4). As a rule EHV-4 mostly causes the respiratory form of the disease and EHV-1 causes abortions. The EHV-2 strain is becoming more important in very young foals but is still uncommon.
The respiratory form causes fever, lack of appetite, cough, and a nasal discharge. The horses that are most affected are weanlings, yearlings, and young horses in training. Most intections resolve without treatment in a few weeks. Rest is the most important part of a good recovery. Horses in training should be rested until cough and nasal discharge have completely resolved.
In some cases, the respiratory infection progresses to pneumonia or persistent lower airway inflammation. These will need antibiotics, anti-inflammitories, and extended rest. This is the exception to the rule however and most will be sick only a few weeks. Though all infections cannot be prevented by vaccination, a good vaccination program, with foals getting inoculated every 3 months starting at 3 months of age, can dramatically reduce incidence and severityof symptoms.
The reproductive form of the Herpes virus is the form that can cause severe financial problems. Herpes virus will cause abortion at 4+ months of pregnancy. It can be individual animals affected or more than 50% of the brood herd can abort. Mares may or my not have any symptoms before aborting.
There is sometimes a history if respiratory disease in young horses on the farm 2-5 months before abortions start. This piece of history isn't necessary however.