DILLON COUNTY, S.C. (WBTW) — A 13-year-old gelding in Dillon County died from the first confirmed West Nile Virus case of the year, according to State Veterinarian Michael J. Neault, who is the Director of Clemson Livestock Poultry Health.

The diagnosis was made Wednesday during necropsy and was confirmed by the National Veterinary Services Laboratories. The horse’s vaccination status is unknown. The announcement was made in a news release by Clemson University.

A total of six horses have died from preventable mosquito borne diseases in 2023. In addition to the most recent death from West Nile Virus, horses in Sumter, Lee, Berkeley, Kershaw and Dillion counties have died from Eastern Equine Encephalitis, according to the release.

Horse owners can take measures by turning them in at dawn and dusk, using spray repellents, but vaccination is the only surefire way to protect their horses from Eastern Equine Encephalitis, West Nile Virus and rabies, the release stated. “Horse owners must stay on top of equine vaccination schedules in order to protect their horses from these diseases,” Neault said.

Borne by mosquitoes, these diseases have a very high mortality rate in infected, unvaccinated horses — between 30 and 40 percent for WNV and 90 percent for EEE. However, widespread vaccination has kept the number of cases comparatively low in South Carolina compared to nearby states, according to the release.

Likewise, mosquito control is an important precaution. Both EEE and WNV are maintained in nature through a cycle involving the freshwater swamp mosquito, Culiseta melanura, commonly known as the black-tailed mosquito.

The EEE and WNV viruses are fast-acting. Symptoms of both diseases usually develop from two to five days after exposure and include neurologic difficulties such as stumbling, circling, head pressing, depression or apprehension, weakness of legs, partial paralysis, the inability to stand, muscle twitching or death, according to the release.

In addition to EEE and WNV, other neurologic diseases, including rabies and EHV-1, can infect horses. Any livestock that display neurologic symptoms such as stumbling, circling, head pressing, depression, or apprehension must be reported to the state veterinarian at 803-788-2260 within 48 hours, according to state law.