Equine Health Alert

State veterinarian Ehlenfeldt: Horse Owners Take Note; Dangerous Strain of EHV-1 on the Rise

Contact: Donna Gilson  608-224-5130

MADISON – A soon-to-be published study reports that a common virus that infects horses is increasingly taking a more dangerous form, prompting Wisconsin State Veterinarian Dr. Robert Ehlenfeldt to remind owners to protect their stock with basic biosecurity.

Equine herpes virus type 1, or EHV-1, usually causes a respiratory infection called rhino-pneumonitis. It also has a more serious, often fatal, neurologic form that strikes the horse’s central nervous system. A recent study by researchers at the University of Kentucky found that the neurologic form is increasingly prevalent.  Results of that study are to be published in the journal Veterinary Microbiology. The researchers found that only about 3 percent of EHV-1 cases were neurologic in the 1960s.  In the 1990s, over 14 percent were neurologic, and by 2006, more than 19 percent of EHV-1 cases were the more dangerous strain, they found.

In 2006 an outbreak of this strain of the disease arrived in the United States with a shipment of horses from Germany that scattered to eight states.  Two unrelated cases were also found in a Wisconsin stable that year.

“Like a lot of viruses, this one thrives in cooler conditions, so we’re coming into EHV season,” Ehlenfeldt said.  “There’s no vaccine for this form of the disease, so biosecurity is even more important.”

EHV-1 spreads when horses in close contact cough or sneeze, and on contaminated hands, water and feed. It can cause abortion in pregnant mares and death in foals.  The neurologic strain may cause horses to be uncoordinated, unable to stand, and unable to eliminate urine and manure.  They may also have swollen, inflamed legs and hemorrhages on their gums. EHV-1 vaccines are not effective against the neurologic form.

Ehlenfeldt recommends these biosecurity precautions:

· Day-to-day practices

• Require barn personnel and riders to wear rubber or plastic boots that can be disinfected, and keep a disinfectant tub with a 1:10 bleach-water solution at the barn entrance.
• Ask all visitors, including blacksmiths and veterinarians, to step in the disinfectant wash before entering the barn, and change the solution daily.
• Wash hands before handling horses.
• Don’t share water buckets, feed tubs or stalls among horses.
• Segregate horses into the smallest possible groups to limit the number of animals exposed if one is infected.

· When bringing new horses onto the premises or returning from places where they’ve mingled with other horses, isolate them for seven days and take rectal temperatures every day during that time

· When horses have been exposed to EHV-1, isolate them for 21 days.

· When a horse has a temperature over 101 degrees or any other symptom of EHV-1, isolate it and call a veterinarian. Disinfect all areas of the barn where it has been housed or worked.

For more information about EHV-1, visit the U.S. Department of Agriculture website: http://www.aphis.usda.gov/vs/nahss/equine/ehv/index.htm.