ITHACA, N.Y. — Following a 2005 deadly outbreak of equine herpes virus at Churchill Downs in Kentucky, a Cornell University virologist says his preliminary research indicates that vaccines containing weakened live viruses, called modified live vaccines (MLV), appear to be more effective in preventing horse herpes than other more widely used vaccines.

“It’s important that people know that the MLV has been in use for decades, has proven to be reasonably safe, and–in my opinion–it should be the vaccine of choice, at least in non-pregnant animals,” said Klaus Osterrieder, associate professor of virology in the College of Veterinary Medicine at Cornell.

Osterrieder’s preliminary study compared the effectiveness of MLV vaccines to another more widely used vaccine for equine herpes. Owners and veterinarians have been wary of live vaccines because of past incidences in which a previous MLV that was incompletely weakened caused neurological disease symptoms after it was administered. The more widely used type of vaccine, called an inactivated vaccine, employs a killed virus to activate the horse’s immune response.

Osterrieder vaccinated five horses with an MLV and five with an inactivated virus; five received no vaccination. None of the 15 horses was pregnant. The horses were then exposed to the herpes virus.

The study found that the horses with MLV vaccinations consistently had lower fevers, no neurological disorders and less virus in nasal fluids. One horse vaccinated with the inactivated virus and one from the control group showed mild neurological symptoms. All the horses, however, have fully recovered.

Read the full story at www.vet.cornell.edu/news/articles/horseHerpes.htm.