West Nile virus (WNV) is spreading. Horse owners are asking, “What can I do to protect my horses?” Thegood news is that a vaccine for horses has been developed and approved by the USDA. Experts say the WNV vaccine should work like other encephalitis vaccines, which are protective. However, responsible horse owners must take steps to prevent the disease by wisely managing property and horses.

At this time, WNV had been detected in eight states that had not been previously affected, plus Canada. After biting infected birds,mosquitoes spread the virus to horses, humans, and other birds. Horses and humans cannot spread the disease; they are dead-end hosts. Only mosquitoes infected from biting birds with the virus can spread the disease to horses and humans. Therefore, horse owners need to target mosquitoes for eradication.

“There are three steps: source reduction, larval control, and if that fails, adulticides,” explains Don Barnard, PhD, Research Leader of the Mosquito and Fly Research unit at USDA’s Center for Medical, Agricultural, and Veterinary Entomology. Reduce the source of mosquitoes by eliminating breeding sites. “Many mosquitoes develop in small bodies of water or containers,” explains Barnard. Drain or eliminate anything on your property that traps water, such as old buckets, tires, or birdbaths. Water troughs for horses that are used infrequently can be drained and cleaned weekly to discourage mosquito breeding.

Horse owners should also eliminate standing water in pastures. However, Barnard says it is not always environmentally acceptable or feasible to fix these wet spots. Some mosquito breeding sites are on adjacent property, such as tire dumps. According to Barnard, many states have statutes that control the disposal of tires. Your local government can tell you if cleanup of these areas is in order. Mosquitoes begin life as larvae in standing water (more on the life cycle at https://www.mosquito.org/mosquito.html). Microbial larvacides and insect growth regulators are acceptable and safe ways to eliminate larvae without endangering the horse. The products are more expensive than some adulticides