Kentucky Horse Owners Should Seriously Consider West Nile Virus Vaccination


By: Megan Crenshaw, Staff Member

With the fall season approaching, several horse owners are beginning to seriously consider West Nile virus (WNV) vaccinations.[i] The number of WNV cases confirmed in U.S. horses continues to rise slowly.[ii] As of September 5, 2013, the United States Department of Agriculture Animal Health Monitoring and Surveillance confirmed 64 cases of WNV in 23 states.[iii] The United States Department of Agriculture Animal and Plant Health reported 627 cases of WNV in U.S. horses in 2012.[iv] Thirteen of those cases were reported in Kentucky.[v] Since 1999, over 25,000 cases of WNV have been reported in U.S. horses.[vi]

The viral disease is transmitted to horses by infected mosquitoes.[vii] A mosquito that bites a bird carrying WNV becomes infected.[viii] The infected mosquito can then feed on horses thereby spreading WNV to the horse.[ix] WNV can cause encephalitis, which is characterized by inflammation of the spinal chord and brain.[x] Signs of WNV in horses includes, changes in mentality, flulike signs, hypersensitivity to touch and sound, twitching, when horses look like they are daydreaming or “just not with it,” drowsiness, propulsive walking (driving or pushing forward, often without control), and spinal signs (including asymmetrical weakness).[xi] It is important to remember WNV does not always result in signs of illness. Some horses that become infected can suffer a loss of appetite and depression.[xii]

As of September 12, 2013, three horses tested positive for WNV in Kentucky.[xiii] Most recently, a 6-year old Standardbred gelding from Todd County tested positive for WNV on September 11.[xiv] None of the three horses affected by the virus in Kentucky were reportedly not properly immunized.[xv] The amount of horses affected by the virus could continue to rise, specifically in Kentucky, if more horses do not receive the WNV vaccination.

WNV remains a concern but with the right vaccine and preventative measures, horse owners can help protect their horses against this life threatening disease.[xvi] Vaccination is the most effective way to protect horses against WNV. In conjunction with the vaccination, good techniques for managing mosquitoes should be used, such as, destroying any mosquito breeding habitats by removing all potential sources of stagnant water and cleaning and emptying any water-holding containers, including buckets, water troughs, and plastic containers, on a weekly basis.[xvii]

It would be very beneficial for Kentucky horse owners to obtain the vaccine for their horses as well as adhere to preventative measures in order to protect their equine. 
[i] West Nile Virus Reported in Horses Nationwide, FARMS.COM (Sept. 6, 2013)
[ii] Id.
[iii] Id.
[iv] Erica Larson, Kentucky Confirms Second Equine WNV, THEHORSE.COM (Sept. 3, 2013),
[v] Id.
[vi] West Nile Virus, AAEP.ORG, (last visited Sept. 13, 2013).
[vii] Larson, supra note 4.
[viii] West Nile Vaccine: What is West Nile virus?, Allivet (Feb. 21, 2013),
[ix] Id.
[x] Id.
[xi] Larson, supra note 4.
[xii] West Nile: First Equine Cases Reported In 2013, THEHORSE.COM (July 17, 2013),
[xiii] Erica Larson, Virginia, Kentucky Confirm New Equine WNV Cases (Sept. 12, 2013),
[xiv] Id.
[xv] Id.
[xvi] West Nile: First Equine Cases Reported In 2013, supra note 11.
[xvii] Id.