I doubt there’s one among us that’s not aware of West Nile virus (WNV). Since the disease was first reported on in the United States in 1999, more than 30,000 people have been reported as getting sick with West Nile virus. As we all know, it’s the dreaded mosquito that spreads this serious, life altering disease.


The very safest method of mosquito control for you, your horses and the environment includes reducing the breeding ground for mosquitoes: mud and stagnant water. This wet situation is not ideal.

This year incidences of the disease have been on the rise. As of September 4, 2012, 48 states have reported WNV infections in people, birds, or mosquitoes--1,993 cases in people, including 87 deaths. Over 70 percent of the cases have been reported primarily in six states: Texas, South Dakota, Mississippi, Oklahoma, Louisiana, and Michigan, however some type of WNV activity has hit the entire continental United States. Since the disease was first detected, this is the highest amount of cases reported for this time period.

As you may recall, most people who become infected with WNV don’t get sick. Some develop mild flu-like symptoms. In rare cases, WNV may cause encephalitis or inflammation of the brain. The majority of humans who die from WNV are older and may had a weakened immune system. 

It appears to be different for horses; horses of all ages have succumbed to the disease. Symptoms of WNV are similar to other neurological conditions including rear limb buckling, knuckling over and ataxia. As of the first part of this month 33 states had reported 186 equine cases of WNV. Horses doing poorly rarely recover--the fatality rate for horses with WNV is about 33%--but fortunately there are steps that we can take that can help reduce our risk and the risk of our horses for exposure.

The number one thing is to vaccinate them. Talk with your veterinarian and get their recommendations. While no vaccine is 100% effective, the WNV vaccine is performing well with a very high rate of effectivity and few side effects.

Reducing Mosquito Habitat on Horse Properties, Ranches and Farms

The very safest method of mosquito control for you, your horses and the environment includes reducing the breeding ground for mosquitoes: mud and stagnant water. The mosquito larva eats organic material and lives in stagnate water -- stagnant usually means water that has not been moving or added to (such as from rain) for four days. For farms, this means muddy pastures and paddocks are prime mosquito habitat.

Here is a checklist of horse farm management techniques for reducing mosquito habitat:

  • Pick up manure in your paddocks and sacrifice area every 1 to 3 days. This is important because it will greatly decrease the build-up of mud. While you’re at it, pick up stray clumps of bedding or leftover hay. All organic material eventually decomposes and leads to mud.
  • Install gutters and downspouts on all buildings and divert the rainwater away from confinement areas. In most parts of the Midwest, the amount of rainwater that runs off a two-stall run-in shed per year can be anywhere from 7,000 gallons to 14,000 gallons--or much more! Diverting 14,000 gallons of water away from your horse’s paddock will greatly reduce the amount of mud, standing water and mosquito habitat around your farm. Divert clean rainwater to areas on your property such as a dry well, rain barrel, stock watering tanks, a well-vegetated woods or unused portion of your pasture.
  • Use footing in paddocks and high-traffic areas to reduce mud. Popular choices include hogfuel (chipped wood products), gravel (crushed rock) or sand. Use 3 to 6 inches of footing throughout your paddock.
  • If surface water flows run into your barn or paddocks look at other means for diverting this water away. Possibilities for dealing with surface water drainage include French drain lines, water bars (like a speed bump for water runoff), grassy swales, and dry wells.
  • Tarp your manure pile. This will keep your manure pile looking like a pile of compost and not a pile of mush.
  • Practice good pasture management techniques. In the summer the golden rule for pasture management is don't graze below 3 to 4 inches. Cross fencing and controlled grazing are important components of good pasture management.
  • Winter pasture management techniques include creating a sacrifice area (a paddock) to keep your horses in when soils are saturated or frozen and pasture plants are dormant. Keeping horses off dormant grass plants and soggy soils is critical for maintaining a healthy pasture next summer and avoiding a muddy mess in between which can harbor mosquitoes.
  • Plant and maintain native trees and shrubs. Plants use a lot of water and can potentially reduce the amount of standing water around your horse place. A mature Douglas fir can drink 100-250 gallons of water per day. Evergreens have an added advantage in that they keep on using water in the winter when deciduous trees are dormant. Use water-loving native shrubs along the outside of paddocks may help keep the area dryer and reduce runoff.
  • Dump scrub and refill all stock watering tanks at least once each week.
  • Check for clogged rain gutters and clean them out.
  • Check for containers and places where water may collect. At least once a week empty water from flowerpots, pet food and water bowls, birdbaths, swimming pool covers, buckets, barrels, wheelbarrows, and tarps.
  • Remove old tires and other items that collect water. Be sure to check for containers or trash in places that may be hard to see, such as under bushes or around your home.

For more information:

CDC map of WNV activity since the first part of September 2012:  http://www.cdc.gov/ncidod/dvbid/westnile/Mapsactivity/surv&control12MapsAnybyState.htm

For WNV information in Canada:  http://www.phac-aspc.gc.ca/wnv-vwn/index-eng.php

Also, check out: West Nile Virus Still a Threat on TheHorse.com