TEXAS VET NEWS By Dr. Bob Judd, DVM and the Texas Farm Bureau Texas Farm Bureau Radio Network

Last program I talked about the fact that not all vaccines are 100% and that equine influenza vaccine is a prime example of that fact.  Although hopefully equine influenza vaccine will prevent the disease, sometimes the best you can hope for is to reduce clinical signs and decrease the amount of the virus shed to other horses.  Today I am going to talk about another equine disease that is difficult to control with vaccine and that is herpes virus.  Equine herpes virus 1 can cause respiratory disease, abortion in pregnant mares, and nervous system disease.  Killed vaccines are commonly used to control equine herpes virus abortion and several studies have revealed these vaccines are effective at least at reducing the number of abortions.  To prevent abortions it is recommended on the label to vaccinate pregnant mares at five, seven, and nine months.  Unfortunately, there are no published studies to indicate how the manufacturers came up with this schedule.  In fact, many vets are now recommending also vaccinating at 3 months of pregnancy. 

A recent paper in Veterinary Clinics of North America indicated these killed herpes virus vaccines also have been shown to decrease the severity and the duration of both herpes virus 1 and herpes virus 4 respiratory diseases.  Again, these vaccines only claim to reduce the incidence and not to prevent the disease 100 percent.  Over the last couple of years, there has been renewed interest in using a modified live herpes virus vaccine to prevent abortion and possibly prevent the nervous system form of the disease.  However, there are no published studies indicating the effectiveness of any vaccine in preventing the very serious nervous system form of the disease. 

Date Published: 6/29/2009 9:36:00 AM