According to EDCC Health Watch infectious diseases continue to appear in many areas of the country as summer time heads toward autumn.
Horse isolated in stall.
EDCC Health Watch is a program provided by Boehringer Ingelheim and hosted by the Equine Network which distributes current disease information affecting horses throughout the industry.
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In New York, a 4-year-old gelding in St. Lawrence County, was euthanized on August 17 due to severe clinical signs caused by Eastern equine encephalitis (EEE). The horse, who was unvaccinated, developed clinical signs on August 16, including trouble eating, dull mentation, fever, head hanging, possible loss of vision and camped under appearance of front and hind legs. He fell over when asked to move, and the vet deemed his prognosis poor.
On August 24, a yearling Trakhener colt in Suwannee County, Florida, was confirmed positive for Eastern equine encephalitis (EEE). The horse, who was vaccinated, developed clinical signs on August 21, including depression, elevated temperature, muscle twitching, incoordination, weakness in the hind limbs and head pression. He was euthanized. This is the 11th confirmed case of EEE in Florida in 2023.
About Eastern equine encephalitis
Eastern equine encephalomyelitis is caused by the Eastern equine encephalitis virus, for which wild birds are a natural reservoir. Mosquitoes that feed on EEE-infected birds can transmit the virus to humans, horses, and other birds. Horses do not develop high enough levels of these viruses in their blood to be contagious to other animals or humans. Because of the high mortality rate in horses and humans, EEE is regarded as one of the most serious mosquito-borne diseases in the United States.
Tips for preventing mosquito-borne diseases include:
• Avoid mosquito bites: Use insect repellent when outdoors, especially from dusk to dawn.
• Look for EPA-labeled products containing active ingredients such as DEET, picaridin (KBR3023), or oil of lemon eucalyptus (p-menthane 3,8-diol).
• Apply more repellent, according to label instructions, if mosquitoes start to bite.
• Mosquito-proof homes: Fix or install window and door screens, and cover or eliminate empty containers with standing water where mosquitoes can lay eggs.
• Protect your horses: Veterinarians recommend commercially available licensed vaccines against EEE for all horses in the U.S. Horses should be vaccinated at least annually (recommendations vary in high-risk areas). It’s not too late this year to vaccinate your horses.
• Use approved insect repellents to protect horses.
• If possible, put horses in stables, stalls, or barns during the prime mosquito exposure hours of dusk and dawn.
• Eliminate standing water, drain water troughs, and empty buckets at least weekly.
• Stock water tanks with fish that consume mosquito larvae (contact your local mosquito control for assistance), or use mosquito “dunks” (solid “donuts” of Bacillus thuringiensis israelensis, which are nontoxic to horses) available at hardware stores.
In Florida, on August 22, a 13-year-old Andalusian gelding in Alachua County, was confirmed positive for strangles. The horse developed clinical signs on August 18, including fever, ventral edema and sheath edema. Four additional horses are exposed, and the horse is under official quarantine. This is the 24th confirmed case of strangles in Florida in 2023.
On August 17, a 17-year-old Thoroughbred mare in Brown County, Wisconsin, was confirmed positive for strangles. The mare developed clinical signs on August 9, including fever and nasal discharge. She is under voluntary quarantine.
About Strangles
Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.
Infected horses can exhibit a variety of clinical signs:
• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing
Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.
A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.
Six new cases of West Nile virus (WNV) have been confirmed in Colorado. The cases are located in Conejos, Larimer, Weld, Saguache, Fremont and Elbert counties (there is one new case in each county).
About West Nile virus
West Nile virus is transmitted to horses via bites from infected mosquitoes. Not all infected horses show clinical signs, but those that do can exhibit:
• Flulike signs, where the horse seems mildly anorexic and depressed;
• Fine and coarse muscle and skin fasciculation (involuntary twitching);
• Hyperesthesia (hypersensitivity to touch and sound);
• Changes in mentation (mental activity), when horses look like they’re daydreaming or “just not with it”;
• Occasional drowsiness;
• Propulsive walking (driving or pushing forward, often without control); and
• Spinal signs, including asymmetrical weakness; and
• Asymmetrical or symmetrical ataxia.
West Nile virus has no cure. However, some horses can recover with supportive care. Equine mortality rates can reach 30-40%.
Studies have shown that vaccines can be effective WNV prevention tools. Horses vaccinated in past years need an annual booster shot, but veterinarians might recommend two boosters annually—one in the spring and another in the fall—in areas with prolonged mosquito seasons. In contrast, previously unvaccinated horses require a two-shot vaccination series in a three- to six-week period. It takes several weeks for horses to develop protection against the disease following complete vaccination or booster administration.
In addition to vaccinations, owners should work to reduce mosquito population and breeding areas and limit horses’ mosquito exposure by:
• Removing stagnant water sources;
• Dumping, cleaning, and refilling water buckets and troughs regularly;
• Keeping animals inside during insect feeding times (typically early in the morning and evening); and
• Applying mosquito repellents approved for equine use.
EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.
EDCC Health Watch is a new program brought to you by Boehringer Ingelheim and hosted by the Equine Network. This program distributes the most current disease information from the EDCC throughout the industry.
Press release by EDCC