AHC Reminds Owners:

It’s That Time of Year Again: Time to Vaccinate

The American Horse Council reminds all horse owners to vaccinate their horses to guard against serious diseases. With warmer months come mosquitos and other vectors that can spread viral diseases that seriously affect horses. Encephalitic diseases, such as Eastern Equine Encephalitis (EEE) and West Nile virus (WNV), are spread by mosquitoes and are often experienced during the summer months. Vaccinating now ensures horses have a strengthened immune system when the virus starts circulating in the mosquito population.

“Diseases like EEE and West Nile Virus can significantly affect horses. Fortunately, they can be prevented with vaccination,” says Jay Hickey, president of the American Horse Council. “Horse owners need to remain vigilant in their vaccination programs.”

EEE is a viral disease of horses that is very often fatal. Death (mortality) rates due to EEE are commonly reported above 90% in horses affected with EEE. Despite its name, Eastern Equine Encephalomyelitis also affects humans.

West Nile Virus is another encephalitic disease of importance to horse owners. It also can be fatal in horses but the mortality rate is significantly lower than what is seen with EEE, generally between 30 and 40%. Humans can also be infected with WNV.

Although humans can contract both diseases, horses play no role in the transmission of either virus to humans. Mosquitoes and birds are primarily responsible for the spread of both viruses. Mosquitoes feed on the blood of infected birds and spread the virus when they bite another host animal such as a horse or human. Although humans and horses can become ill from the infection, the level of virus in their blood is too low to infect mosquitoes so they are unable to spread the disease either directly human-to-human, horse-to-horse, horse-to-human or vice versa.

In 2005, Florida experienced a high number of cases of Eastern Equine Encephalitis in horses. On average each year, the state has approximately 60 cases of EEE annually in horses but in 2005, there were more than 140 confirmed cases of the disease. The year rivaled the two highest years: 1982, when 203 cases were confirmed and 2003 when 207 cases confirmed.

In 2005, the U.S. Department of Agriculture confirmed 1,075 equine cases of West Nile Virus nationwide. The largest number of cases was reported in California with 456 confirmed cases. Idaho had the next largest number of cases at 114.

“An effective vaccine for horses is available and horse owners are encouraged to vaccinate their horses regularly against these diseases,” says Dr. Michael Short, Equine Programs Manager for the Florida Department of Agriculture and Consumer Services, Division of Animal Industry.

The American Horse Council encourages all horse owners to ensure their horses are vaccinated for all the encephalitic diseases such as eastern encephalomyelitis and West Nile virus. “We often hear from horse owners asking why is it necessary to vaccinate our horses, as ‘they don’t get these diseases anyway’,” says Amy Mann, Director for Health and Regulatory Affairs at the AHC. “The truth is, little evidence of infection is seen when horses are vaccinated because their immune systems are protected and able to fight infection if exposed to these viruses. However, when horses are not vaccinated, their immune systems don’t have the necessary tools to fight the virus and subsequently the number of cases goes up.” The increased incidence of disease includes an increase in virus-related deaths in horses also.

For more information regarding vaccination programs for horses, horse owners should consult with their veterinary practitioners.