Colorado hit by three serious horse diseases

A horse suffering from Strangles, a very contagious disease.

Three serious horse diseases have affected Colorado this month, with the state veterinarian assuring the public that appropriate efforts are being made to contain them.

The American state has had confirmed cases of equine infectious anemia, the neurological form of equine herpesvirus-1 (EHV), and the bacterial disease strangles.

State veterinarian Keith Roehr said the Colorado Department of Agriculture was working with the equine industry and veterinarians to contain the spread of the diseases.

“An important reminder is that owners should always practice proper disease prevention practices for their horses. Proper sanitation and biosecurity is often the first step in protecting your horse,” he said.

On May 4, the state agriculture department and Dr Roehr’s office were told by the US Department of Agriculture’s National Veterinary Services Laboratory that a horse in Weld County horse had tested positive for equine infectious anemia (EIA).

The disease, also known as swamp fever, is a persistent and incurable viral disease of equines which is found nearly worldwide. It is transmitted almost exclusively through blood or blood products, most commonly through biting insects.

Although most affected equines appear to have few clinical consequences, perhaps a low-grade fever or lethargy, some forms of the disease can cause extreme sickness and even death. The disease can be diagnosed easily using the Coggins blood test, but there is no available vaccine or treatment.

Cross section of the equine infectious anemia virus.
Cross section of the equine infectious anemia virus. © APHIS

Roehr said that two additional cases of EIA had since been confirmed at the same location. All three belonged to the same owner. All were euthanized.

The Weld County facility remains under a quarantine order that restricts movement of horses until further testing is completed by authorities.

The state agriculture department is also investigating a confirmed case of Equine Herpesvirus Myeloencephalitis – a disease in which a form of EHV-1 cause neurological problems.

A property in Mesa County has been quarantined. The horse is showing neurological signs associated with the disease and subsequently testing positive for EHV-1. The animal is under private veterinary care and seems to be making a good recovery.

The horse had been to events over the previous two weeks, and all of those events have been notified.

Event organizers are communicating with participants to monitor their horses for signs of the disease, especially for fever.

EHV-1 most commonly causes mild respiratory illness and fever, but in more serious cases it can causing neurological problems, with decreased coordination, urine dribbling, loss of tail tone, and hind limb weakness. Horses with the disease might lean against a wall or fence to maintain balance. Once they lay down, they may be unable to rise, which will often result in euthanasia..

While there is no cure, the clinical signs of the disease may be treatable.

Roehr said his office has recently received a high volume of calls with questions about strangles.

In Colorado, it is not a reportable disease. Therefore, it is not a disease that the State Veterinarian’s Office will issue State quarantines for affected facilities or horses. It is recommended that affected barns limit movement, but such restrictions are managed by the barn and the attending veterinarian.

Strangles is a contagious disease of horses of all ages but it is more commonly seen in young horses, usually less than two years of age.

Foals are usually not susceptible until the antibodies that they receive from the mare decline which is usually around four months of age but it can be very variable. Commonly, once a horse has gone through the infection, they become immune to developing clinical signs again or the disease is not as severe the next time it develops in their system.

Using common sources of water, feed bunks, and housing will allow transmission of the bacteria from horse to horse. Horses that are spread out in pastures or large exercise areas in which they can move and graze will not share the infection as readily.

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