West Nile virus infects two Lemitar horses
West Nile virus has been confirmed in two Lemitar horses — one last week and the previous one in mid-September, according to local veterinarian David Baker. Both horses have now fully recovered.
The Lemitar horses are the first equine cases of West Nile this year in Socorro County, Baker said. The horses had not been vaccinated. Other vaccinated horses in the same herd were not affected, which shows the current equine West Nile vaccine is still effective, he said.
Mosquitoes transmit the disease, Baker said. September and October are the prime months for West Nile infections. Although humans and horses are the most common victims, West Nile can also affect cats, dogs, sheep and goats.
Thirty-six human cases of West Nile virus have been reported in New Mexico as of Oct. 2, and one person has died, according to the Centers for Disease Control. The CDC maps show concentrations of human cases in both the Las Cruces and Albuquerque areas, but no human cases in central New Mexico as of Oct. 2. Mosquitoes transmit the disease by feeding on infected birds and then pass it on to humans and other animals.
Only one out of 150 human West Nile cases progresses to a serious neurological illness that may cause coma, disorientation, blindness and paralysis.
In humans, about 20 percent of infected people have mild symptoms: fever, nausea, vomiting and possibly a rash or swollen lymph glands. Most people infected with West Nile develop no signs at all of the disease, according to the CDC.
Similarly, most un-vaccinated horses infected with West Nile disease show no symptoms at all and develop a natural immunity to the disease, Baker said.
Horses that do become infected can develop severe symptoms similar to tetanus and equine encephalitis, he said. The affected horses will at first seem weak. They may act as if they are dizzy, and their legs, especially the rear ones, can wobble noticeably. After that, the muscles in their faces may begin to twitch and sometimes their eyes will dart back and forth uncontrollably. Owners need to be cautious, he said, because the virus tends to enhance the animals' "flight or fight" mechanism, so a previously quiet and compliant horse may now react violently to minor disturbances.
Baker said there is no treatment for the disease except to medicate the symptoms. Anti-inflammatories will reduce the swelling in the brain and spine, and sedatives will calm the horse. Affected horses should be kept in darkened, quiet enclosures until they have recovered. Baker said most horses recover fully although some may have some lingering neurological impairments.