Equine Infectious Anemia: Horse in Michigan Tests Positive for Fly-Borne Disease

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Officials with the Michigan Department of Agriculture and Rural Development (MDARD) today confirmed Equine Infectious Anemia (EIA) in a 17-year old grade mare from Mecosta County.

EIA is an infectious virus spread between equidae (horses, asses, jacks, jennies, hinnies, mules, donkeys, burros, ponies, and zebras) by deer and horse flies. EIA can cause severe illness, including fever, anemia, swelling, lethargy, and death. EIA can also be spread through repeat use of needles or through other acts where blood is exchanged from one equine to another.

“This is the first case of EIA in Michigan since 2008,” said State Veterinarian Dr. Steven Halstead. “MDARD is investigating the case to identify other horses that may have been exposed to the positive horse or may have caused the exposure. Any such horses will be quarantined on their farms and tested for EIA by a regulatory veterinarian.”

expecting to fly

Every horse needs its own Coggins Test for EIA done annually or more frequently, according to the state regulations of the state where it lives--or might visit. (Thomas Levinson photo)

To protect all Michigan equidae, MDARD requires a negative test for EIA within the last 12 months prior to movement, in order to travel to a public event (fairs, expositions, exhibitions), auction markets, or traveling as part of sale to a new owner.
“Because there are no effective and safe vaccines, nor can infection be treated, Michigan law established a control program requiring owners of equines attending commingling events, or changing ownership and housing location, to have proof of a negative EIA test,” said Halstead.

Additionally, to import equidae into Michigan, the equidae must:

1. Test negative to an official test for equine infectious anemia (EIA) within 12 months prior to importation, except equidae that are both 6 months or younger and nursing.
2. Be accompanied by an official interstate health certificate or certificate of veterinary inspection documenting the date, laboratory, accession number, and results of the latest equine infectious anemia test, signed by an accredited veterinarian.

Act No. 466, Public Acts of 1988, as amended, the Animal Industry Act, Section 19 (9) (MCL 287.719) gives the director of the department of agriculture the authority to institute this requirement.

Complete importation requirements for equidae and other animals can be found at www.michigan.gov/mda, by selecting “Bringing Animals into Michigan.”

To learn more:

Twin Pines Equine background article on Coggins Test and EIA

Central Georgia Veterinary Services article on photos for Coggins Test

2011 EIA-infected herd of horses in Arkansas

2011 EIA in Missouri

Three EIA-positive horses in Indiana in 2008

This article was provided as a press release, which was edited for The Jurga Report

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Arkansas: Horse Herd Tests Positive for Equine Infectious Anemia (EIA)

horse fly by     Davis Kwan

Another reason to hate horse flies: they transmit EIA from horse to horse. But they are only one mode of transmission. Horse fly photo by Davis Kwan.

Here’s a press release from the government agriculture officials in the state of Arkansas. It is providing for public information in its entirety.



LITTLE ROCK, AR, AUGUST 24, 2011–The State of Arkansas has had multiple positives for Equine Infectious Anemia (EIA) in the Clarksville, AR., area (Johnson County). Arkansas Livestock and Poultry Commission (ALPC) along with a local veterinarian are investigating the positive herd.

At present the infection seems to be isolated to the single herd. The owner of the herd does not show horses nor do they sell any horses to any extent. The index herd has only one adjacent herd and that herd is in the process of being tested today.

The source of the infection has not been found. The most recent addition to the index herd was traced back to its origin. Those horses had all negative EIA tests but were retested by Arkansas Livestock Poultry Commission personnel and all their horses were negative.

The number of positives horses in the index herd is substantial and alarming. Arkansas Livestock Poultry Commission is investigating all leads to make sure that this does not spread from the index herd.

Since the index herd has added horses over the years some of those horses may have been the source of infection.
The herd has been quarantined from the time of the first positive and Arkansas Livestock Poultry Commission has a livestock inspector on the premises daily. There has not been any information that warrants canceling horse shows, etc., in Arkansas at the present time.


State of Arkansas contact: Dr. Pat Badley Phone: (501) 907-2400

About EIA, courtesy of USDA: EIA is an infectious and potentially fatal viral disease of horses. No vaccine or treatment exists for the disease. Clinical signs of EIA include fever, weight loss, icterus (yellowing of body tissues), anemia, swelling in the limbs, and weakness. However, not all equids infected with the equine infectious anemia virus (EIAV) show signs of illness, and these animals serve as inapparent carriers.

EIAV is usually transmitted from horse to horse by large biting insects such as horseflies and deerflies. The bites from these flies stimulate defensive movement by the horse, which often results in an interruption of the flies’ blood feeding. When interrupted, flies are motivated to complete feeding as soon as possible. They then attack the same or a second host and feed to complete their meal. In this manner, any infective material from the blood of the first host that is present on the mouthparts of the flies can be mechanically transmitted to the second host.

Needles and equipment contaminated with blood from an infected horse can also spread the virus when used on unexposed horses. Horses demonstrating clinical signs of EIA pose the greatest risk of spreading the virus because they have the greatest concentrations of circulating virus. However, even inapparent carriers pose a risk to other horses.

For more information, please download the complete EIA information sheet from the USDA website.

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