New Jersey Reports First West Nile Case of Year

An 11-year-old mare from Monmouth County, N.J., has tested positive for West Nile virus (WNV), New Jersey Secretary of Agriculture Douglas H. Fisher said Oct. 12. The mare was not vaccinated against the disease.

The affected horse first showed symptoms of WNV on October 10 and is being treated for the disease. This is the state's first reported case this year.

"We urge horse owners to vaccinate their animals from serious mosquito-borne illnesses such as West Nile virus and Eastern equine encephalitis," said Fisher. "We have found that animals that are vaccinated are less likely to contract these deadly diseases."

The New Jersey Department of Environmental Protection reports that the exceedingly high levels of precipitation experienced statewide due to Hurricane Irene and subsequent rainstorms have resulted in much higher than normal mosquito populations. They said the immense amount of floodwater throughout the state created habitat for those species of mosquitoes which utilize semi-permanent, standing water for larval development.

Horses contract WNV, a viral disease that affects horses' neurological systems, when infected mosquitoes bite them. The disease cannot be spread from horse to horse or from an infected horse to humans or domestic pets.

Clinical signs of WNV include flulike conditions where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia, or hypersensitivity to touch and sound; changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia (incoordination on one or both sides, respectively). Equine mortality rate can be as high as 30-40%.

Currently, no cases of EEE have been reported in New Jersey horses in 2011. A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. The fatality rate for EEE in horses is 75-95%. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care. Horses that survive might have long-lasting impairments and neurologic problems. Clinical signs of EEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures.

In 2010, New Jersey had two cases of equine WNV and one case of EEE. All three animals were euthanized.

Effective equine vaccines for WNV and EEE have been available for several years. Horse owners should contact their veterinarians now if their horses are not already up-to-date on their vaccinations against both EEE and West Nile virus.

In Jew Jersey, WNV and EEE, like other viral diseases affecting horses' neurological systems, must be reported to the state veterinarian at 609/292-3965 within 48 hours of diagnosis.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More