West Nile Virus (WNV) strikes again in Gila County. Dr. Jeff Eubank of Samaritan Veterinary Clinic in Globe has confirmed the first case in a local horse this year. Horse owners and humans beware.
“With all these mosquitoes due to our weather, we want to stay ahead of this,” says Jeff.
West Nile Virus (WNV) is a mosquito-borne virus that affects humans and other animals, primarily horses (96.9%). The virus is only transmitted through mosquitoes; humans and horses cannot give it to each other. When the host is bitten by an infected mosquito, the virus enters the bloodstream and multiplies. If it crosses the blood-brain barrier, WNV can cause inflammation of the brain and possibly death.
SYMPTOMS & PROGNOSIS
The signs of WNV range from flu-like symptoms to lack of strength and coordination, sensitivity to sound and touch, muscle twitching, head drooping, grinding teeth and falling down.
“It can be hard to pick up,” says Dr. Mary Eubank. “It becomes more obvious once they develop more serious clinical symptoms — dragging feet, stumbling, really weak to where you can pull a horse over.”
A white horse from San Carlos was losing weight and acting sick. During examination, Mary noticed the horse was stumbling about. They took a blood sample to rule out neurological conditions. Results came back positive for West Nile Virus. The case was reported to the EDCC on September 16th.
There is no specific treatment for WNV in horses. Only supportive care is available for the diagnosis.
“Anti-inflammatories can help with swelling around the nerves,” explains Dr. Mary Eubank. “It serves as a pain reliever — can alleviate some symptoms.”
It was not enough to save the horse that had lived its whole life here.
“It was progressing really rapidly,” says Mary. “It was humanely euthanized.
The case fatality rate for WVN is approximately 33%. The prognosis is poorer for older horses and those more severely affected.
“A lot of cases can be asymptomatic,” says Mary, “They get a little bit sick. About 10% get sick enough to be neurological.”
Many horses with milder symptoms recover without intervention, Jeff adds, though some experience “long-hauler” effects, including gait and behavioral abnormalities.
“We encourage horse owners to contact your veterinarian and vaccinate your horses,” says Jeff, “and exercise mosquito control.”
Only 10-15% of their business in his horse care, but the intensity of mosquitoes and the local case are motivating horse owners into action.
“We have had people calling and wanting to get their horses vaccinated,” says Jeff. “We’ve ordered a bunch more vaccines.”
Native horses get two shots spaced weeks apart to get the most benefit, and annual boosters.
The WNV vaccine takes about a month to be fully effective and is recommended annually by the American Association of Equine Practitioners (AAEP).
Vaccine recommendations vary by region. Typical in the southwest United States, horses cared for at Samaritan Veterinary Clinic get vaccinated annually in the spring for sleeping sickness, tetanus, influenza and WVN. They get a separate shot for rabies.
“I am concerned because of all the mosquitoes this year,” says Jeff.
He recommends that owners further protect horses (and themselves) by using repellents and eliminating mosquito breeding sites by removing standing water.
“Tires and junk,” says Jeff, “anything that puddles water.”
In addition, AAEP recommends that owners and facilities stock water troughs with fish that feed on mosquito larvae and bring horses in at peak mosquito feeding periods (dawn and dusk).
Gila County investigates complaints and sometimes fogs mosquito breeding grounds.
“It’s in the larger area,” stresses Jeff. “People are affected. People can die.”
There’s no WVN vaccine for humans. Centers for Disease Control and Prevention (CDC) reports 49 cases and two deaths in Arizona this year. In the 20 years since WNV emerged in the U.S., it has caused just under 2400 human deaths.
This is fewer than the number of U.S. Covid-19 deaths confirmed in a single day in mid-September.
A traveler, Patti Daley came to Globe in 2016 to face the heat, follow love, and find desert treasure. She writes in many formats and records travel scraps and other musings at daleywriting.com.