There have been 21 horses that have tested positive for West Nile in Utah since the virus was first confirmed in the state on Aug. 15.
Six of the infected horse cases occurred in Emery County. Twelve cases were identified in Uintah, one of the animals was in Duchesne, one was in Sanpete and one was in Wayne County.
One human case of the West Nile virus has been detected in Uintah County.
The virus is not transmissible from horses to humans.
Of the nine most recently confirmed cases, one of the horses was reported to have been vaccinated prior to being purchased at auction, but the administration of the second shot was not verified, indicated the Utah Department of Food and Agriculture.
One of the horses received a single dose in late August. None of the other horses was vaccinated.
At least two of the animals infected with the virus were euthanized when the horses could no longer get up, indicated the state agriculture agency.
Five of the animals infected with the West Nile virus were younger than 10 years of age, while three of the horses were older than 20.
The age of the other animals was not reported.
Utah has not had a West Nile virus positive animal reported from the 10 to 20 age range, according to the state agency.
The Utah Department of Agriculture and Food advises horse owners throughout the state to continue to protect animals by vaccinating for West Nile virus.
The UDAF also advises all Utahns to take necessary precautions to protect families and individuals from the virus.
The agriculture department has been encouraging horse owners to administer two vaccination shots since last spring.
It is now advisable to administer a booster shot for added protection, added the state agency.
The WNV vaccine is available from local veterinarians.
The most common sign of West Nile virus in horses is weakness, usually in the hindquarters.
Weakness may be indicated by a widened stance in the horse, stumbling, leaning to one side and toe dragging.
In extreme cases of the virus, paralysis may follow.
Fever is sometimes evident in infected horses, as are depression and fearfulness.
WNV causes encephalitis and affects the central nervous system.
Carbon County horse owners who suspect West Nile viral infection in animals should contact a veterinarian immediately.
Approximately one-third of horses that show signs of the illness will die, pointed out the state agriculture department.
Eighty percent of WNV in horses occurs in the months of August and September.
Horse owners in Carbon County should contact local veterinarians and have the animals vaccinated, emphasized the state agriculture department.
However, vaccination after exposure may not protect the horses against the disease.
The equine vaccine requires two doses and takes approximately five weeks to offer horses protection from the disease.
Once vaccinated, yearly booster shots are necessary.
Horse owners can protect animals by applying approved repellants to animals and controlling mosquitoes and mosquito breeding areas.
Owners may also protect horses by putting the animals in barns or enclosed structures.
Carbon County residents who are concerned about their health or believe they may have contracted West Nile virus should contact physicians.