Disease Update: Colorado, Maryland, Michigan, New Jersey and South Carolina Report Horses with EEE or WNV


States all over the nation have reported new cases of mosquito-borne diseases in the past week. To update the tally, The Jurga Report has collected several notifications from states, listed in alphabetical order.


The first reported equine case of West Nile Virus (WNV) was diagnosed in Colorado?last week. Colorado State University’s Veterinary Diagnostic Laboratory diagnosed the WNV positive horse, a 3-month-old colt from Montezuma County.


“The majority of horses, like people, that become infected with West Nile Virus do not show any signs of illness,” said Hana Van Campen, a professor of Microbiology, Immunology and Pathology at CSU?who also works at the Veterinary Diagnostic Laboratory. “In a small percentage of infected horses, the virus reaches the brain and spinal cord. These horses may have a fever, be lethargic, stop eating, and have muscle fasciculation (twitching), tremors, incoordination and weakness progressing to recumbency.”


According to the Maryland Department of Agriculture (MDA), a case of Eastern equine encephalitis (EEE) has been confirmed in a horse in Worcester County. The last confirmed case in a horse in Maryland was in 2009 in Wicomico County.

The horse in Worcester County had not been vaccinated. Infected horses show a range of clinical signs that often progress over two to three days, including depression, altered mental status, circling, problems with balance, weakness, aimless wandering, impaired vision, walking (gait) abnormalities, head pressing, paralysis, convulsions and death. Horses that survive serious disease often have permanent nervous system deficits.

As a result of the EEE discovery, MDA will increase ground spraying activities to approximately every 5 to 7 days over the next two weeks. Spraying will take place between dusk and dawn.


Michigan Department of Agriculture and Rural Development (MDARD) State Veterinarian Dr. James Averill confirmed the first case in his state of Eastern Equine Encephalitis (EEE) in a horse for 2013: a 12-year-old grade mare from Van Buren County.


“This horse was never vaccinated against EEE and died after she developed severe swelling of the brain, her clinical signs were stumbling, depression, and blindness,” said Dr. James Averill.

“In 2010, statewide there were 56 cases of EEE, and since then the cases have steadily declined – more than likely because Michigan veterinarians encourage EEE vaccinations as part of the spring horse vaccination protocol,” Averill said.? “Vaccinating at any time against the virus is encouraged, even this late in the year.”

The highest concentration of the disease has historically been in Southwestern Michigan.?The only Michigan case of EEE last year was in an eight-week-old puppy from the same county.


Today the New Jersey Department of Agriculture reported that a?seven-year-old horse from Cape May County was humanely euthanized on August 3, one day after showing neurologic symptoms for Eastern Equine Encephalitis (EEE). Tests on the gelding concluded the animal was positive for EEE.


The Cape May horse was obtained from a horse rescue two weeks prior to the onset of illness and the animal’s vaccination history was unknown.

In 2012, New Jersey had six cases of EEE and four cases of West Nile Virus (WNV) between June and October.


The South Carolina State Veterinarian’s Office has confirmed a total of 30 cases of Eastern Equine Encephalitis (EEE) for 2013 as of Friday, August 16th at 4:00 PM. On Friday they also confirmed South Carolina’s first 2013 case of West Nile Virus (WNV) in a horse from Lancaster County.


During 2012, there were 14 confirmed cases of EEE and seven of WNV in South Carolina.




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