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Tennessee : West Nile Virus and Equine Infectious Anemia cases confirmed

Horses in Davidson and Knox county have tested positive for West Nile Virus (WNV) and another tested positive for Equine Infectious Anemia (EIA) in Bedford county over the past few days. Awareness of disease signs and symptoms, along with preventative strategies and farm management are important to protect your horses.

 

 

West Nile Virus is transmitted from bird reservoir hosts by mosquitoes to horses. Mosquitoes must first feed from an infected bird before it is able to transmit WNV to a horse or human. Since horses and humans are dead end hosts for WNV, the disease cannot be directly transmitted from horse to horse, or horse to human. Dr. Lew Strickland, University of Tennessee Extension Veterinarian states “Horses with WNV do not need to be isolated from other horses, as the WNV is not present in high amounts within their blood to allow for mosquitoes to pass the disease from horse to horse.”
Horses affected with WNV may display depression, muscle tremors, convulsions, and/or have a decreased appetite. Also, horses may be easily startled by noise or touch, while others may seem drowsy and less reactive than normal. Other indications of WNV include continuous walking without purpose, lack of coordination, or paralysis especially in the hind legs.
The WNV vaccine is considered a core vaccination and is recommended for all horses, independent of location, travel and management practices. Additionally, most Veterinarians recommend horses in Tennessee receive Spring and Fall booster vaccinations after the initial two-dose series.
Equine Infectious Anemia, or Swamp Fever, is transmitted through blood-sucking insects, such has horse or deer flies. Residual blood from one horse is carried within the insect’s mouthparts, and then can be passed to other horses. Also, transmission can occur from blood-contamination when reusing needles, or other medical instruments, along with passage from mare to foal in-utero or through milk. Strickland says “EIA can be difficult to diagnose, as symptoms can vary from horse to horse, and many horses may not demonstrate obvious signs of illness.” Symptoms of EIA include fever, weakness/fatigue, depression, pale or yellow mucous membranes, and decreased appetite. Also, a complete blood count performed by a veterinarian may show decreased red blood cell count or anemia, along with low platelets, which are cells needed for blood clotting.
There is no vaccination available for EIA, but annual screening through a Coggins Test should be performed on all horses. Testing horses for EIA aids in eradicating the disease, as there is no treatment. Unfortunately, options for horses that test positive are minimal. The American Association of Equine Practitioners supports euthanasia of EIA-positive horses and other equids as the best option. An alternative option is lifelong quarantine in a screened stall, and sequestration from other horses to prevent transmission of the disease.
Using good management practices in combination with preventative health measures can greatly reduce the risk of both WNV and EIA. Dr. Jennie Ivey, University of Tennessee Equine Extension Specialist states “Reducing the ability for flies and mosquitoes to breed by managing waste and standing water is critical in preventing WNV and EIA transmission.” Regularly removing manure and other waste from stalls, pastures, and other areas where horses congregate will help to decrease breeding areas for many fly species. Move waste holding areas as far as possible away from where horses are housed.  “Composting is an ideal solution for horse owners, can be easily achieved through a bin system, and produces a usable product that eliminates internal and external parasite reproduction, along with weed seeds if done correctly” Ivey states.
Reducing standing water within your farm is important for preventing mosquitoes. Any object that can hold water can become a mosquito breeding ground. Check for buckets, wheelbarrows, plant pots, or other items around farms that can store water and eliminate these sources. Additionally, look for areas where water collects in pasture, and take measures to increase drainage and/or increase grass stands. “Bring horses inside during peak insect feeding times (early morning and dusk) to reduce exposure,” Ivey says “and use a topical insect repellent can to aid in decreasing mosquito and fly feeding.”
WNV or EIA can be devastating for your horse; however, prevention and management will decrease the risk at your facility. For more information on waste management, drainage, and equine health, contact your local county extension office, veterinarian, Dr. Lew Strickland at lstrick5@utk.edu or Dr. Jennie Ivey at jzivey@utk.edu. Also, for online information on equine diseases, management, and health, visit UTHorse.com.
University of Tennessee, By: Dr. Jennie Ivey
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Terry Simmons