Seven Colorado horses infected with West Nile Virus

Sep 4, 2009
by WLJ
Seven Colorado horses infected with West Nile Virus

Seven equine cases of West Nile Virus (WNV) have been diagnosed in Colorado as of Aug. 28, 2009. The cases that have been recently diagnosed represent the first reported cases of WNV this year. The WNV positive tests were submitted from horses examined in the north central, northeast, and southeast regions of the state.

WNV is a disease that threatens the health of humans, horses, and other animals. The greatest implication of this disease is the capability of the virus to cause encephalitis (inflammation of the brain) in humans and horses which may result in death.

“Late summer and early fall have traditionally been the time of year when we are most likely to see WNV cases reported in horses,” said Colorado State Veterinarian Dr. Keith Roehr. “In 2008, there was only one reported equine case of WNV in Colorado; it is difficult to project how many WNV cases we may see in the coming months.”

The transmission of the disease varies from year to year and depends on a number of factors, including mosquito numbers. WNV can be carried by infected birds and then spread locally by mosquitoes that bite those birds.

The mosquitoes can then pass the virus to humans and animals. In 2006, more than 1,000 cases of WNV were reported in horses nationwide. WNV can cause an inflammation of the brain and spinal cord. Mosquitoes transmit the disease and infected horses may display symptoms including head tilt, muscle tremors, stumbling, lack of coordination, weakness of the limbs, or partial paralysis.

If horses exhibit clinical signs consistent with WNV, it is very important for horse owners to contact their veterinarian in order to confirm the diagnosis through laboratory testing. Horse owners should consult their private practicing veterinarian to determine an appropriate prevention strategy for their horses.

Horses that have been vaccinated in past years will need an annual booster shot. However, if an owner did not vaccinate their animal in previous years, the horse will need the two-shot vaccination series within a three- to six-week period.

In addition to vaccinations, horse owners also need to reduce the mosquito populations and their possible breeding areas. Recommendations include removing stagnant water sources, keeping animals inside during the bugs’ feeding times, which are typically early in the morning and evening, and using repellents.

“Even though the number of infected horses has dramatically reduced since 2006, it is still important to protect your horse through vaccination and good management practices,” said Roehr. — WLJ