In addition to vaccination, mosquito control is critical in protecting your horses against WNV. Here’s quick review on controlling mosquito populations in your barn:

• Eliminate areas of standing water through improved drainage, or treat them with larvacides.
  
• Get rid of scrap tires that collect water or drill holes in them; turn over birdbaths, buckets, tarps, plastic wading pools, wheelbarrows, or anything that could collect water. Mosquitoes can lay eggs in just a tablespoon of water or any puddle that lasts for more than four days.
  
• Aerate ornamental pools or stock them with fish.
  
• Clean and chlorinate swimming pools not in use.
  
• Clean gutters.
  
• Trim weeds (adults hide in shady areas).

Turnout recommendations for your horses are less finite. Michael Turell, PhD, of the Virology Division’s Department of Vector Assessment at the U.S. Army’s research laboratory at Ft. Detrick, Md., says, “A great place to catch mosquitoes is in the barn. The problem with having your horses in the barn at dusk to avoid the really bad mosquitoes is that some mosquito species have learned to go in the barn at dusk. But if you leave horses out in the field, they get chewed alive. “We’re not sure which mosquitoes are going in the barn vs. which are feeding out in the field,” he adds. Those species will depend on your geographic area, time of year, temperature, and the kind of barn you have. Is it open on one side? Do you have an air curtain set up (a screen that covers the doorways of your barn to reduce bug entry into the barn)? “Some of those work fairly well,” he says. Sprays and pour-on repellents are available from many companies, as are sheets, covers, masks, and leg wraps that can cut down on the number of mosquitoes that have access to your horse.