BOISE -- The Idaho State Department of Agriculture is warning horse owners to take precautions and vaccinate their animals to protect against the West Nile virus.

There have been confirmed cases of the virus in humans and horses in 10 southern Idaho counties. Three horse cases have been detected this past week. The virus in contracted through mosquitoes.

State officials recommend taking precautions to protect equines (horses, mules, asses and zebras) and small camelids (llamas, alpacas, vicunas, guanacos) against the West Nile virus.

The most common sign of West Nile virus in horses is weakness, usually in the hindquarters. Weakness may be indicated by a widened stance, stumbling, leaning to one side and toe dragging. In extreme cases, paralysis and inability to stand may follow. Fever sometimes is evident, as are depression and fearfulness. Additionally, lip-smacking, chewing movements and fine muscle tremors may be noticed.

West Nile virus vaccines have dramatically reduced the number of horses with infections over the past decade. About one-third of all horses that tested positive for West Nile virus died or were euthanized.

Although the vaccines are not a 100 percent guarantee, they are the best way to help prevent West Nile infection in horses, said Dr. Marilyn Simunich, a veterinarian with ISDA. More vaccine choices are available now; horse owners should have their veterinarian determine which is best for each horse. Llamas and similar small camelids can be affected by West Nile Virus, too, so speak to your veterinarian about preventative measures for your llamas and alpacas.

Horses that have never been vaccinated for the virus will initially need two doses. The booster is typically administered a minimum of three weeks after the first dose. Maximum immunity from the vaccine typically is achieved six weeks after the first dose. An annual booster vaccination is recommended in subsequent years.

For more information about West Nile virus go to:

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