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Texas entomologist cautions on virus: Guard livestock against West Nile

While you're taking precautions against West Nile virus and other mosquito-borne diseases for yourself, take them for your horses and pets as well.

“Animals are susceptible and, in some cases, can be severely affected by the West Nile virus,” said Jim Olson, entomologist with the Texas Agricultural Experiment Station.

If horses have not been vaccinated, owners should do this immediately. Since the vaccination is not always effective, protect horses from bites by covering them with blankets in the early-morning and evening hours; placing them in mosquito-proofed buildings, or treating with approved repellents. Repellents are available at local feed stores and other outlets, he said.

“The reason people need to be even more cautious of West Nile virus and other such viruses from now on is because these bird-reservoired, mosquito-borne viruses tend to build up during the early to mid-part of the summer,” Olson said.

“The chances that your animal can come into contact with an infected mosquito are currently quite high from late summer until the first cold weather of fall,” he added.

The symptoms of West Nile are listlessness and high fever, followed by a drop-off in eating. Dogs become unstable while walking, then become comatose, Olson said.

West Nile virus, or encephalitis, is an infection of the brain, Olson said. The most serious manifestation of West Nile virus is fatal encephalitis in humans and horses, as well as certain domestic and wild birds and animals.

The West Nile virus was first isolated in the 1930s in the blood of a woman in the West Nile Province of Uganda. Officials do not know how the virus migrated from Central Africa to the United States, where it first caused problems in the New York area in the summer of 1999. A total of 753 human cases and 17 deaths have been reported since it entered the U.S.

Humans and horses are usually infected by the bite of a mosquito that has fed on an infected bird.

According to the Centers for Disease Control, West Nile virus is primarily transmitted by infectious mosquitoes, but there are other ways this can occasionally happen, such as transfusions with contaminated blood, organ transplants and through mother's milk, and bird-to-bird transmissions have been proven in lab settings. There is no documented evidence of person-to-person transmission of West Nile virus by contact.

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