Due to the possible threat of West Nile encephalitis many horse owners on the East Coast may choose to use a lot of fly spray this summer. In Rumania 55 people were killed by an outbreak in 1996. Six out of fourteen Italian horses died from this disease just two years later.
Last year alone twenty-two horses in Long Island contracted the virus and of them thirteen died. In New Jersey just across the river there were three thousand people who were exposed to the virus that causes the disease and nine people died from the infection.
In people, horses, birds and occasionally cats and dogs West Nile encephalitis is a type of viral disease that causes inflammation of the brain. The virus can infect sheep and pigs but the virus hasn’t yet caused disease in these species. The virus is present in birds and is transmitted mainly by mosquitoes.
The virus replicates when a female mosquito feeds on a bird and there is sufficient virus in the saliva of the mosquito after ten to fourteen days in order for an infectious dose to be transferred to any horse, dog, cat, bird or human that the mosquito bites. The possibility of infected horses transmitting the disease to people has no been confirmed yet and the disease also cannot spread from human to human.
For this type of encephalitis there is not treatment available. The best preventative measure is to avoid being bitten by mosquitoes. At dawn and dusk when mosquitoes are most active you should wear long-sleeved garments and long pants. As an insect repellent the use of DEET is particularly effective.
In the morning and evening horses should be sprayed with an insect repellent. Against mosquitoes the electric bug-zappers are often ineffective and give no protection against the disease. This disease has signs similar to that of Eastern equine encephalitis.
The signs include rapid loss of hind end coordination and balance which leads to recumbency in the most serious of cases. Horses may recover fully if they show milder signs of the disease. Horses will usually die if they become recumbent. This disease will also progress faster than the Equine Protozoal Myeloencephalitis.
There is no vaccine at present that can help protect a horse against West Nile encephalitis, although if you live near the Eastern Shore, it is still advisable that you vaccinate your horses against Eastern encephalitis.
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