Sleeping Sickness Description

In horses, sleeping sickness has three major strains. The Venezuelan strain originated from Central America and is the most deadly of all the strains. It is however the rarest strain in the U.S. with southern states more at risk than northern states. The eastern and western strains are named after the U.S. regions in which they are most common in.

Transmission of Disease

Sleeping sickness is transmitted to horses by mosquitoes. Hence the risk of the disease is highest during the spring and summer months when mosquitoes are likely to be more in number. Carrier mosquitoes are not the original sources of the virus that causes the disease. They get the virus from birds, rodents and reptiles that carry it. Aside from horses, the virus can also affect humans.

Horses that have been infected with the western and eastern strains are generally considered dead end hosts. This means that except for a very short period of time during their illness, horses are unable to transmit the virus to mosquitoes that bite them. It is a different story though for the more deadly Venezuelan sleeping sickness. Mosquitoes that bite horses that are sick with this strain are able to carry off the virus to other hosts.

Common Symptoms

The disease ultimately affects the central nervous system. Hence, its symptoms are quite linked to the nervous system. Strangely enough, this dangerous disease does not immediately lead to a show of symptoms. Indications of the ailment often surfaces only after seven to twenty-one days after a mosquito bite. Without prompt medical attention, an infected horse can die in less than two weeks.

Initial symptoms include fever. This is followed by an apparent disorientation and lack of coordination. A horse with an infection will inexplicably begin to crash into objects. This is an indication that the virus is already beginning to affect the nervous system. In its final stages, the disease will cause severe depression in a horse. At this point, the term sleeping sickness becomes most appropriate. A horse will seem like it is asleep because of its lack of interest in anything and its low head carriage.

Treatment Options
Unlike bacterial infections, there is hardly any good treatment option for a severe viral infection. The most that can be done for an ailing horse is to provide it with comforting care. It may be given medication to lower its fever. Some horses may survive sleeping sickness. Often though, these survivors suffer permanent brain damage.

Disease Prevention

This deadly disease can be prevented through vaccination. This is the best option for horse owners since mosquito eradication is virtually impossible. There are vaccines for all three strains but since the Venezuelan strain is rare, some horse owners do not opt to have their horses vaccinated for this strain.

Robert L. is the creator and writer of Horsemanship a website created for those looking to learn more about the horse human bond. To learn more about Horsemanship visit his site at

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