Horses Deadly Equine Virus

Northern Virginia's first-ever confirmed case of a rare mosquito-borne disease that is fatal to most horses is spreading concern among health officials who worry that the virus is somehow moving beyond its normal stamping grounds.

Eastern equine encephalitis, a noncontagious virus spread by mosquitoes, not unlike West Nile Virus, was diagnosed last month in a 28-year-old mare from Middleburg in eastern Loudoun County's vaunted horse country. The mare -- which had been riddled with health problems, including kidney disease -- was euthanized Aug. 6. Brain tissue samples sent to the National Veterinary Services Laboratories in Ames, Iowa, were examined, and three weeks later the lab confirmed the encephalitis diagnosis.

"Frankly, no one expected for the test to come back positive. This is a very unusual case, and a lot of us have been saying to ourselves, 'Gee, what does this mean?' " said Elaine Lidholm, a spokeswoman for the Virginia Department of Agriculture and Consumer Services. "We don't know if it's an isolated case or there's more out there in the environment."

What makes the case so unusual is that the horse had not traveled outside Loudoun County, its owners told state officials. The disease -- which more commonly goes by the name "triple E" -- largely has been concentrated in southwestern Virginia, especially the Tidewater region, where mosquitoes are plentiful.

"Up here, we certainly have mosquitoes, but not the same as the marshy areas," said Martin O. Furr, a professor of equine medicine at Virginia Tech's Marion duPont Scott Equine Medical Center in Leesburg. "I suspect it's a random outlier case. But I suppose it could be the tip of the iceberg ready to hit us."

Sandy Vine, a Middleburg horse trainer and show-jumping judge who owns three horses, said her animals receive annual encephalitis shots. Vine said the Loudoun case is worrisome, especially because most horse owners in the area have little knowledge of the disease and its symptoms. "You don't know if the horse was by itself or with others or if the owners traveled a lot," she said.

Virginia's agriculture department began tracking equine encephalitis cases in 2000. Since then, it has found 50 cases in horses, goats, emus and alpacas, none north of Madison, a small community between Culpeper and Shenandoah National Park, about 75 miles from Loudoun.

Although there are effective vaccines for the disease, there is no cure. And although many horse owners vaccinate their animals every six to 12 months, with recommended booster shots in the interim, others have forgone the $10 shots. In horses, the Eastern strain of the disease is 75 percent fatal, health officials say.

About 240 cases have been reported in humans in the United States since 1964, according to the federal Centers for Disease Control and Prevention, with fewer since 1984 because of the decreasing number of people living near marshland. Since 2003, there have been five human cases in Virginia. The fatality rate for humans is lower than that for horses, but those who survive the disease can be left with mild to severe brain damage. Transmission of the virus is most common in and around freshwater hardwood swamps in the Atlantic and Gulf Coast states.

The report of triple E so far from its home base caught many Loudoun veterinarians by surprise.

James Joyce, a veterinarian at Blue Ridge Veterinary Associates in Purcellville, said the case is "concerning because it's a reminder that it's now here." But Joyce cautioned that the disease is not contagious and is "very uncommon to this region."

William H. McCormick, a Middleburg veterinarian who has been practicing in Loudoun since 1974, said that he had never seen a case of triple E in Loudoun but that an older horse with a weakened immune system could be more prone to the virus. He added that the diagnosis, taken by itself, was no cause for concern.

"I've seen West Nile over the years, but never triple E. You certainly don't want to vaccinate horses for something they aren't going to get, but I would do it if they're traveling to Florida or the Eastern Shore," McCormick said.

Furr agreed, saying the horse, due to its age, could have become more susceptible to viruses because of cortisol-secreting tumors. "Still, in the years I've been here, this is the first case I've heard about," he said.

Horse Strangles Disease

Strangles is a highly contagious disease that affects a horse’s lymph nodes in its upper respiratory tract. It is caused by a bacterium called streptococcus equi. The name, strangles, was coined due to the strangling breathing sounds made by affected horses, caused by the enlarged lymph nodes of the jawbone.

The first signs of strangles are a high fever, poor appetite, and depression. Owners will also notice a thin, watery discharge from the horse’s nostrils. This discharge quickly turns thick and yellow. The horse’s upper respiratory lymph nodes become enlarged, most noticeably the ones between the jawbones. These can even abscess.

Strangles is not usually fatal to horses, but it can be.

Strangles can affect horses of any age, but most commonly infects those between one and five years of age. The disease is usually acquired after exposure to another horse that is shedding the streptococcus equi bacteria, either during or after its own bout of the illness. This commonly occurs when new horses are introduced to an established herd. Although the infectious horse may no longer show signs of strangles, it can still spread the bacteria. Around twenty percent of horses remain contagious for a month after all symptoms vanish.

While direct contact between horses is the most common way that strangles is spread, it can also be spread by contaminated equipment. Improperly cleaned and shared buckets, stalls, and tack can spread the disease between horses. Fortunately, the bacteria die fairly quickly in the environment.

Once a horse is exposed to the bacteria, it will begin to show symptoms in two to six days. If left untreated, it will develop abscessed lymph nodes within one to two weeks after the onset of illness. These lymph nodes will rupture and drain, and the drainage is highly contagious. Most horses will recover, but around ten percent of untreated horses die, usually from a secondary infection which causes pneumonia.

Rarely, the abscesses will spread to other parts of the horse’s body, such as the lungs, internal organs, or even the horse’s brain. This condition is called “bastard strangles.” It is uncommon and is usually fatal.

The treatment of strangles is dependent on the stage of the disease.

To control the spread of the strangles bacteria, any new horse with a vague or unknown health history should be isolated for four to six weeks before being added to the general population of the stable or paddock. Nasal swabs can ascertain whether the horse is shedding the streptococcus equi bacteria, but because affected horses shed the bacteria sporadically, one swab test is not enough. Three nasal swabs over a period of seven days are required before it can be assumed that the horse is negative for strangles.

Strangles can also be controlled by vaccinations. Although modern vaccines are more effective than those of the past, providing better protection with fewer side effects, they are not a complete guarantee against the disease. Still, vaccinated horses tend to have a less severe illness if they do contract strangles. Horses cannot contract strangles from the vaccine itself, since it is made from only parts of the pulverized bacterium.

If you suspect that your horse has strangles, notify your veterinarian to confirm the presence of the disease. The sooner a positive diagnosis is reached, the less “down time” the stable will have to tolerate. Also, if a horse begins antibiotic treatment in the early stages of the disease, lymph node abscesses can be prevented.

Old veterinary practices warned against using antibiotics for strangles because of the suspicion that it could cause bastard strangles. However, there is no evidence that this is the case. Usually, when horses are treated with antibiotics in the early stages of strangles, they will recover unless the antibiotics are not given in the correct amounts or are stopped too soon. Even if the horse is on antibiotic therapy, it must be isolated from the rest of the stable and herd to prevent the spread of the illness.

However, once lymph nodes have enlarged and become abscessed, antibiotic treatment will only prolong the horse’s illness. It is better to allow the abscess to open, or have the veterinarian lance it, so that it may drain. The best treatment at this point is to flush the drainage site, keep the area as clean as possible, and to maintain strict isolation of the ill horse.

If your horse was stabled near one who had strangles at a show or rodeo, it is reasonable to treat it with antibiotics for at least six days after exposure. This is because horses usually don’t show the first signs of the disease for two to six days. However, if your horse is kept in a barn where other horses have strangles, antibiotics will do little to prevent it from getting the disease.