In past years most of the U.S. could take some comfort in the prevalence of these diseases flourishing elsewhere such as Africa, Asia, Eastern Europe and Central and South America. In 1999, though, West Nile encephalitis, resident in Africa, Asia and Europe, struck in the U.S., all in New York CIty.
Spread by mosquitoes who feast on infected birds, West Nile encephalitis, caused by a virus, now proliferates nationwide, a horror especially for horses and humans.
The U.S. Center for Disease Control (CDC) reports 1,338 human cases of West Nile with 43 fatalities in the U.S. in 2008. It is not limited to the U.S. Canada saw its first case of West Nile virus infection in 2002.
West Nile Virus Symptoms
West Nile attacks the central nervous system. The clinical symptoms in horses may appear in various combinations of fever, listlessness, paralysis or weakness in the hind legs, hyper excitability, aimless walking, drooping lower lip, circling, head pressing, inability to swallow, convulsions and coma.
In people the symptoms are similar: e.g., fever, paralysis, neck stiffness, stupor, numbness, skin rash, swollen lymph glands, muscle weakness and convulsions.
The CDC estimates that one in 150 people who become infected will manifest serious symptoms. For those who do, the prognosis is not encouraging.
Neither is it for horses. So far there is no cure for an infected horse. Except for supportive treatment of the symptoms, the horse will either survive or not on its own. Treatment for serious cases in humans is not much better.
West Nile Virus Inoculations for Horses
Although symptoms could be mild or missed in some cases, West Nile encephalitis is often fatal. Annual equine inoculations against the disease are not 100 percent effective, but they are better than nothing, so long as the shots themselves do not adversely affect the horse in some way.
Currently West Nile inoculations are contraindicated for pregnant mares according to some expert opinions. Others feel the risk is worth the protection afforded by inoculations.
There is only a 35 percent survival rate for infected noninoculated horses.
Mosquito Control a Key to Preventing West Nile Virus
Preventing the West Nile virus means primarily combating mosquitoes. Many communities undertake wholesale spraying of high risk areas, such as swamps where standing water invites mosquito populations to flourish.
Battling the mosquito in this fashion while maintaining broader ecological integrity is no easy balancing act. Poisons that kill mosquitoes are not necessarily discriminating about what or whom else they affect, such as the water supply, animals, and benign or even desirable insects. Then there are the unknown future effects to humans and the environment such poisons bring as carcinogens, immune suppressors and allergens.
Less “poisonous” measures are regular removal of standing water sources, cleaning gutters, and keeping animal water troughs emptied, cleaned and refilled with fresh water. Mosquitoes also like to make their home in discarded tires. Physical mosquito control practices require vigilance and habit.
Another safety precaution is to not touch a dead bird and remove it safely for disposal. Dead birds should be presumed infected by West Nile virus. The local health department or state environmental protection agency may want dead birds reported for collection and testing.
Birds are also mosquito predators, though. Natural combaters of mosquitoes are resident bird and bat populations. Preserving their habitat is a smart practice.
Mosquito Repellants Aid Humans and Horses in Preventing West Nile Virus Infection
To ward off mosquitoes, the CDC recommends using a mosquito repellant containing DEET or Picaridin. Oil of Lemon Eucalyptus PMD and IR3535, called biopesticide repellants, are also effective.
A Vermont company called Insect Control Systems, Inc. has developed an effective natural insect killer derived from chyrsanthemums for spraying in barns.
Mosquitos are most active from twilight to dawn. Carefully burning smudge pots that give off repellant vapors can be helpful in outdoor areas where people will be congregating.
Staying inside is the most fool-proof method of protection. Many stables keep horses in at night during the height of summer seasonal mosquito activity, or if turned out, treated with repellant.
For More Information About West Nile Virus:
Ohio State University West Nile Virus Fact Sheet Index
Health Canada, Healthy Living, "West Nile Virus" Fact Sheet
Washington Dept. of Fish and Wildlife, "West Nile Virus" Fact Sheet
Washoe County, Nevada, "West Nile Virus" Fact Sheet
U.S. EPA Region 5 West Nile Virus Facts
Linda Ashar - Linda C. Ashar is a lawyer, educator, horse breeder, freelance writer, and artist. Her 25-year law practice in Avon, Ohio, focuses on ...
