The Disease WEST NILE VIRUS (horses)
West Nile Virus (WNV) is one of several viruses in the Arboviral Encephalitis family. This family of viruses can cause inflammation of the brain and spinal cord and death in humans, birds and animals (horses). Within the Arboviral Encephalitis family are Alphaviruses and Flavaviruses. Alphaviruses include Eastern Equine Encephalomyelitis and Western Equine Encephalomyelitis. Which are commonly known as "Sleeping Sickness". Flavaviruses include St. Louis encephalitis and West Nile Virus.
WNV was first discovered in 1937 in a woman in the West Nile province of Uganda in Central Africa. Since then it has been reported in Egypt, Israel, Africa, India, Pakistan, Borneo, Cypress, France, Romania, Thailand, the Philippines, Malaysia, Turkey, Albania, Canada and the United States.
In the United States, it was first identified in the summer of 1999 in New York City, NY. There, flamingos and pheasants exhibited WNV. In 2001, the virus spread to the District of Columbia, Indiana, Georgia, Florida, Louisiana, Maryland, Massachusetts, Michigan, New Jersey, Pennsylvania, New York, Ohio and Canada, hitting Florida particularly hard. In 2002, the virus has spread to horses across the United States.
To illustrate how the virus mutates over time, twenty-three strains of WNV were isolated from children in Egypt during the early 1950s. However, in the United States only a single genetic strain of WNV has been found suggesting that it has not resided here very long.
Statistics on Equine WNV Cases
In 2001 there were 738 cases of equine WNV in 20 states. Of the 738 reported, 651 were verified through blood tests. Of those, 640 were confirmed and 11 were probable. For the 470 horses for which an outcome was reported, 156 (33.2%) died or were euthanized. The peak months for illness were late August — mid October. The Florida Department of Agriculture opined that for every one case that was confirmed there were probably 200 more horses that had contracted the disease, however a local veterinarian in North Florida opined that for every one case confirmed there were probably 400 cases that were not. Also in 2001, 20 horses were confirmed with Eastern Equine Encephalitis, which is normal for any given year in Florida.
In 2002 between January 1 and October 13 there were 10,172 reported cases of equine WNV in 38 states. Canada has not been included with this report as this time as to number of cases confirmed.
WNV is a mosquito borne illness. It travels from mosquito to bird to mosquito and then to humans, horses, and in rare cases other mammals and reptiles. Until a few months ago it was thought that there was no human-to-human or animal-to-human transmission, as humans and horses are dead end hosts. However, there is now evidence that the disease can be transmitted between humans through blood transfusions, organ transplants, and breast milk. You might assume the same would be true for horses.
In horses, symptoms observed, included drooling, runny nose or eyes, loss of appetite, colic-like symptoms, lameness-like symptoms, depression, fever (both elevated and subnormal), swelling of the limbs, twitching of muzzle or other muscles, staggering in front, inability to stand on three legs, weakness in rear, falling or lying down, blank stare, temporary blindness, swelling of the tongue, lips and throat with inability to swallow, introspection, lethargy, and dehydration.
RATHER THAN DEVELOPING A "LETS WAIT AND SEE ATTITUDE", CONTACT YOUR NEAREST VET IMEDIATELY SHOULD YOUR HORSES EXHIBIT ANY OF THESE SIGNS AND SYMPTOMS OR A COMBINATION OF THESE SIGNS AND SYMPTOMS. During Mosquito season for your area!