West Nile Virus Update: An Ounce of Prevention
Horse Tales
by Candice C. Dunnigan

Whoever said, “An ounce of prevention is worth a pound of cure,” is right, especially when it comes to the West Nile Virus and horses. The latest update that I have on the disease is that the problem is being kept under some control by preventative measures. West Nile Virus, however, continues to be a real threat to horses, even those in Mackinac County.

Statistics tell us that the most effective way to combat West Nile in horses is by vaccination.

The latest West Nile updates came to me from the United States Pony Club, which has more than 12,000 members, and they strongly advocate that all horse owners should vaccinate their stock each year. So does the Michigan Horse Council and the American Quarter Horse Association. Nowadays, many perspective horse owners will not purchase a horse unless they have proof of West Nile vaccination. Most horses on the racetrack have been inoculated.

It is true that West Nile has spread, but it seems that this year it can be curtailed because more and more people are doing what they can to stop it. We have our horses vaccinated every April.

West Nile is a virus, and just about the fastest growing one to threaten the health of horses across the United States. It was first seen in New York State in 1999, and has expanded westward since, carried by migratory birds. The real culprit of the whole matter is the mosquito. Infected mosquitoes transmit the virus to the birds by biting them. Then, migratory birds, such as geese and ducks, carry the disease with them to other areas. Mammals bitten by the infected mosquito are considered “dead-end hosts.” While their blood level is not sufficient to be transmitted back to the mosquito, they can fall victim. Mammals, especially horses, can get the disease.

West Nile is considered to be of real concern because it can cause a disease called encephalitis (which is a swelling of the brain), muscle weakness, convulsions, fever, partial paralysis, coma, and death in horses. As of January 2003, 40 percent of the horses that contracted West Nile died.

Many horse owners vaccinate annually with a 4-in-1 vaccine that protects against Eastern and Western encephalitis, tetanus, and equine influenza. Now, West Nile should be included.

The United States Department of Agriculture has approved the West Nile vaccine for horses. It has shown to be effective and safe; not foolproof, but safe at least 90 percent of the time. That vaccine is only available through a licensed veterinarian. The manufacturer of West Nile vaccine is a company called Fort Dodge Animal Health. For more information on West Nile Virus, you can go to a dedicated Web site entitled www.equinewestnile.com. The initial vaccine costs an average of $50 per horse, followed by a booster four to six weeks later. After the first year, an annual booster is a must, and costs run about half.

There are, however, safe and practical things that any horse owner on Mackinac Island can do to help keep mosquitoes at bay. These do not have to be administered by a veterinarian. Use a mosquito repellent on your horse in the late spring, summer, and fall. There are several now on the market. Three of these recommended to me are Endure (by Farnum), Bug Block (by Absorbine), and Pre-Strike (by Zodiac). Another safety must is to empty water that collects in buckets or tarps. Clean your water troughs at least twice a week. If you have a barn, keep screens in your windows, and turn off lights at night so as not to attract insects. Mosquitoes are most active during dawn and dusk, so, if possible, try to keep your horses in, or at least sprayed. There are also flying insect and fogger sprays on the market.

A company called Cheval International offers a feed product called Inside Out that it claims will detract biting insects, which include mosquitoes and flies. The product contains cider vinegar, garlic, and brewer’s yeast. People have known for a long time that flies and mosquitoes can make horses sick and in Ireland and Great Britain, horse owners have been feeding garlic, cider, and brewer’s yeast to their equines each season for those very causes. That makes me smile and think perhaps there is some reason my horses have always liked to eat treats from my garlicky hands, as well as have a bit of beer. Maybe they were trying to tell me this is as a connection to keep the bugs at bay. Then again, maybe they thought my Celtic ways, and my Guinness, were appealing.

Candice Dunnigan is an active member of the American Equestrian Association, the Waterloo Hunt, and the Mackinac Island Horsemen’s Association. Seasonally she resides at Donnybrook and Easterly Cottage.