Equine Health Issues
Three EIA-Positives Found in Indiana; Horse Owners Advised to Test Animals Regularly
 
INDIANAPOLIS (27 May 2008)­—Horse owners and veterinarians should watch their horses, mules, donkeys and other equine closely for any unusual disease symptoms, in light of a cluster of recent positive cases of equine infectious anemia (EIA).
            According to Dr. Tim Bartlett, a veterinarian and director of Equine for the Indiana State Board of Animal Health, three horses on a south-central Indiana farm have tested positive for the disease in the last few weeks.
            State and federal veterinarians have been working with the owner to identify the source of infection and determine if any other animals are at risk. All three positives have been euthanized; two herd mates have tested negative and remain under quarantine until further testing is complete.
            EIA, also known as swamp fever, mountain fever or malarial fever, is an untreatable and incurable viral disease that infects horses, ponies, donkeys, mules and other equine. An estimated 30 percent to 50 percent of infected equine die within two weeks to four weeks of the onset of EIA.
            Depending on an individual horse's immune system and the severity of its reaction, EIA symptoms can range from virtually none at all (except a positive blood test) to weakness, weight loss and swelling to fever, rejection of feed and sudden death. A blood test (often called Coggins' test), conducted by a veterinarian, can detect the infection. However, equine owners should remember that test results can produce a false negative up to 42 days after exposure to the disease, before a detectable level of antibodies develops.
            What can horse owners do to prevent EIA? Dr. Bartlett explains the disease is spread via blood-to-blood transmission, not close proximity or casual contact. "Blood transfusions, unsterilized or contaminated needles and medial instruments can transmit the virus," he says. "But horse owners should be most concerned about biting insects­—especially horseflies—which can spread the disease.
            "Research shows that as few as three horseflies can carry enough virus from one animal to another to cause an infection. That's why pest control is critical to the control of this disease," adds Dr. Bartlett.
            He also advises equine owners to minimize the chances of EIA entering their herds through newly purchased animals. "All equine should be tested for EIA before being brought onto a farm," Dr. Bartlett says. "Then, the animal should be isolated and observed for 45 days to 60 days, then retested before it is introduced to the herd."
            State law requires all equine entering Indiana have a health certificate indicating a negative EIA test within the previous 12 months. Suckling foals, accompanied by an EIA-negative dam, are exempt from testing.
            Once a horse (or other equine) tests positive for the disease, the animal must be permanently identified with "32A" freeze-branded on the left side of the neck to comply with state law. Permanent identification is designed to protect Indiana's healthy equine population, by eliminating confusion about health status.
            The owner then has two options for handling the horse:  1. Permanently quarantine the animal to the owner's premises, at least 200 yards from the nearest equine; or 2. Euthanasia (at the owner's expense) after notifying the State Veterinarian. All other animals in the herd must also be tested for EIA.
            Anyone wanting more information about EIA may contact his/her local veterinarian. Information about EIA is available online at:  www.boah.in.gov.

Fatal horse infection making comeback in Florida

More than 50 horses have died statewide this year [2008] from the worst outbreak in recent summers of an infection caught from mosquito
bites. No people have gotten the illness, but the state confirmed 56 cases of Eastern equine encephalitis (EEE) in horses as of early July
2008. Animals from Orange, Volusia, Lake, Osceola and Polk counties were among the victims. For comparison, there were 18 cases in horses during all of 2007, and 17 in 2006.

"This infection is almost always fatal," said Dr. Michael Short, a veterinarian and equine program manager with the Florida Department
of Agriculture and Consumer Services. "These horses get very sick, very fast. It's horrible to see."

The condition is caused by the Eastern equine encephalitis virus, which can be carried by mosquitoes and passed to people or animals
through bites. EEE always exists at some level in Florida's abundant insect population, but it tends to peak in July and August.

At its worst, the virus can lead to a brain infection called encephalitis. Florida hasn't had a human case of Eastern equine
encephalitis since 2005, and it has been pretty infrequent for horses, too. In a bad year, more than 200 horses have gotten sick.
But the animals have an advantage over people: They can be vaccinated.


In normal circumstances, horses should be immunized for Eastern equine every 6 months, said Dr. Erin Denney-Jones, a Lake County
veterinarian. But during an outbreak such as Florida is experiencing, vets recommend a shot every 4 months.

The vaccine doesn't give complete protection -- some horses still get sick. But it cuts the chances significantly. Short said the "vast
majority" of this year's cases have occurred in animals that were not up-to-date on their immunizations.

The economy may be contributing to the outbreak. Eastern equine vaccines are relatively inexpensive, running about USD 7 a shot if
ordered directly from a supplier, Short said. But it's illegal in Florida for anyone other than a veterinarian to give the shots, and
people may not have the cash to pay for a veterinarian visit.

"We send out reminders when it's time for vaccinations," Denney-Jones said, "and we're definitely not getting as many people responding" this year.
 

Mosquitoes may be early and numerous due to floods

 

WEST LAFAYETTE, Ind. - Hoosiers should be extra vigilant this year to avoid mosquito bites because itching and scratching season likely will begin early due to June's massive flooding, according to Purdue University experts.
 

The heavy rains that hit Indiana the first 10 days of June will leave numerous areas of standing water, the breeding ground for mosquitoes, said Ralph Williams, a public health entomologist in the Department of Entomology. Initially, this will result in an influx of nuisance mosquitoes that don't transmit disease to people, but can carry canine heartworm to dogs.

"As floodwaters recede, pockets of water may linger where mosquitoes can lay their eggs," Williams said. "With the earlier chance for the mosquitoes to breed, it's especially important to take precautions that will help keep the mosquitoes from spreading a disease to you."
As the water stands longer and becomes stagnant, it will become a harbor for other mosquitoes, including the type that carries West Nile virus, which potentially can be fatal to humans and horses.
 

The high probability of an early emergence of the Culex mosquitoes that carry West Nile virus means horse owners should ensure their animals are vaccinated against the disease and other mosquito-borne encephalitic illnesses, said William Hope of the Purdue community equine clinic.

"It looks like it will be a big mosquito season, so horses will have more of a chance to contract these diseases," he said. "Horses should be vaccinated now, if they haven't been already, and then receive a second shot in the fall."

The vaccine is effective for horses, but no vaccine has been developed to protect people or other animals against West Nile virus and related diseases. Other animals, including dogs and cats, can be infected, but it's rare for them to develop the disease, according to the Centers for Disease Control and Prevention.

Culex mosquitoes usually are most active in Indiana from mid-August through the fall. However, the Indiana State Department of Health already this year has found the virus in some mosquitoes.

Among diseases that mosquitoes spread are West Nile virus, malaria, yellow fever, dengue fever, and Eastern and Western encephalitis. West Nile virus, and occasionally Eastern and Western equine encephalitis, St. Louis encephalitis, and La Crosse fever, appear in Indiana. People and some other mammals can contract all of these diseases, but horses don't contract St. Louis encephalitis or La Crosse fever.

Mosquitoes spread West Nile virus when they bite an infected bird and then bite a person, horse or some other mammal. Although a mosquito may bite an infected mammal, no evidence exists that the diseases can be spread to another mammal, or directly between mammals. This is because, unlike birds, there is not a high enough concentration of the virus in other animals to allow for transmission.
Of the more than 3,000 known mosquito species, Indiana is home to more than 50. Their life cycle is seven to 10 days, and they all breed in standing water.

Williams and Hope recommend that people and animals avoid mosquito-infested areas as much as possible, especially during dusk and dawn, which are prime biting times for the insects. People should use insect repellents containing DEET and picaradin, Williams said.

Insecticides are available to spray on horses and around horse areas.
In addition, the experts recommend these precautions:
  • Dispose of, empty and/or clean livestock watering troughs, ditches, puddles, birdbaths, rain gutters, buckets, old tires, ponds and swimming pools so mosquitoes can't breed.
  • Make sure the mosquito repellent you use is registered with the U.S. Environmental Protection Agency and check that the concentration is approved for use on children.
  • Don't use human anti-insect products on animals; those repellents could sicken an animal. Special repellents are available for horses, but not for dogs and cats.
  • Wear light-colored clothing, long-sleeve shirts, long pants, socks and hats when outside.
  • Cover horses with light-colored, lightweight or netted sheets to help keep insects away.