|www.SpeakingEquine.com||Volume 2, Issue 7|
Speaking Equine is
brought to you by:
Dr. John Canning, DVM (970) 963-4573 www.drcanning.com
Equine Herpesvirus Type 1 (EHV-1)
is an, ongoing concern for horse owners! The quarantine at Pimlico in February raised our awareness of the threat of EHV-1. On October 31, 2006 the virus raised its ugly head in Colorado.
Colorado Veterinary Teaching Hospital Lifts Equine Quarantine
"Colorado State University today lifted the voluntary quarantine of horses hospitalized at the James L. Voss Veterinary Teaching Hospital, initiated on Oct. 31. Close monitoring and repeated testing of quarantined horses for equine herpesvirus type 1 (EHV-1) has allowed university officials to lift the quarantine today. The hospital will resume all normal activities on Saturday, Nov. 18.
Viral infections were initially discovered in two horses being treated for unrelated illnesses. Hospital officials immediately elected to quarantine all hospitalized horses, to protect other horses in the community. In total, five hospitalized horses admitted for other reasons were found to be infected with EHV-1. Four horses had mild fevers, and one developed mild neurological signs that are improving.
"No horses from the hospitalized population have shown new signs of infection for two weeks, and all quarantined horses have tested negative on four consecutive tests for the virus," said Paul Morley, DVM, PhD, director of biosecurity for the hospital. "Because of these findings, combined with our understanding of disease caused by this virus, we are confident that all quarantined horses can leave the hospital without posing an increased risk to other horses."
Hospital officials at Colorado State worked closely with the Colorado state veterinarian's office to develop a monitoring and testing plan to determine when to lift the quarantine. The equine hospital has also been thoroughly cleaned and disinfected to eliminate any potential contamination.
"Colorado State University's Veterinary Medical Center has one of the best teams of veterinary specialists in the world. This includes experts with extensive knowledge of EHV-1 and strategies to prevent and contain the spread of this disease," said Martin Fettman, DVM, MS, PhD, director of the Veterinary Teaching Hospital. "We take exceptional measures to provide the best care possible, and those measures include maintaining one of the most rigorous biosecurity programs of any veterinary hospital in the world. While this voluntary quarantine was a precautionary move, we felt it was prudent and in the best interest of our clients and their horses."
All equine inpatient and outpatient care will be resumed on Saturday. No other veterinary activities at the hospital were affected by the quarantine, and no other equine services or facilities at the university were affected.
Horse owners with questions about EHV-1 should contact their veterinarian."
Equine herpesvirus is a highly contagious virus that causes upper respiratory infection in young horses, abortion in pregnant mares, and other damaging problems. Researchers believe that only one or two strains of EHV-1 (equine herpesvirus) have the potential to cause neurological problems, but when one of these strains does strike a herd, the results can be devastating. A severe case can cause a neurological disease that affects the horse's brain and spinal cord resulting in paralysis and death.
There is currently no known method to reliably prevent the neurologic form of EHV-1 infection. Neurological symptoms include incoordination that can progress to the inability to stand, lower leg swelling, the inability to urinate or pass manure, urine dribbling, and reduced tail tone. Some of these symptoms also occur in other neurological diseases such as rabies, EPM, and West Nile Virus infections, so it is important that the animals be examined by a veterinarian as soon as possible.
First exposure to herpesviruses typically happens very early in life, and then horses are constantly re-exposed throughout life as they encounter different strains. Young horses may become sick and then recover uneventfully. Some of those strains are more harmful than others and are more likely to cause disease. So far, researchers have identified nine herpesviruses in equines, but only five are common in domestic horses; the others are found chiefly in other equids, such as zebras, onagers (wild asses) and donkeys. These five viral species fall into two categories, depending on how seriously they affect the horse. The viruses are constantly spreading, and most of the time the infections are mild enough to go unnoticed, but on occasion they will find the right population and the right circumstances to cause serious disease.
How Equine Herpesvirus Starts
When a horse is first infected with a new strain of the herpesviruses, the organisms penetrate the cells that line his respiratory system, sparking an inflammatory response. It can take anywhere from a day to more than a week for that response to cause outward signs, such as nasal discharge and fever. Just as often, however, the horse never becomes ill. Either way, he is capable of spreading the virus, by nose-to-nose contact as well as by expelling airborne droplets during coughs or snorts.
Once the virus enters a horse's body, it's there to stay. All herpesviruses have a unique characteristic; they can "hide" from the immune system so that it is impossible for the body to clear them entirely away. Instead, the viruses change their outward forms and go "latent" in some part of the body, such as lymph glands. While latent, the viruses cause no harm. However when the horse is stressed by such things as weaning, transportation, or fatigue, these viruses sometimes revert to a more active state and revive the infection. The biggest problem with EHV-1 (herpesvirus) is that once horses have been infected, they can become latent carriers of the virus for the rest of their life. Although infected horses are no longer sick or shedding the virus (nasal discharge and fever), they carry the virus and can spontaneously begin shedding it during periods of stress.
The Spreading of Equine Herpesvirus
EHV-1 is spread primarily through coughing or sneezing, but can also be carried in fetal tissues, the placenta and uterine fluids from mares that have aborted. Studies have shown that the virus doesn't live long in the environment, but transmission via coughing or sneezing can occur over a distance of up to 35 feet. Direct contact with infected horses as well as contaminated feed, equipment, clothing, and tack can also spread the disease. The intermittent shedding of the virus by carrier horses is thought to be the source of sporadic outbreaks of the disease, including closed herds where no new horses have been introduced.
EHV-1 is a virus and does not respond to antibiotics. Therefore, supportive treatment is the only option and is tailored to the individual horse depending on the severity and range of symptoms. It usually includes anti-inflammatory drugs, fluids to maintain hydration, and slinging of horses that are unable to stand. In most cases, horses that remain standing have a good prognosis, although recovery may take weeks or months. Horses that go down and are unable to stand have a poor prognosis.
To Reduce the Incidence of Equine Herpesvirus
Establishing a wellness program will save you time, money and headaches. Following a well thought out program will help assure that you are giving your horses the care they need when they need it.
|Call Dr. John Canning, DVM to establish an equine wellness program for your horse. (970) 963-4573|
We strongly encourage horse owners to seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy. After all, it is your horse's life.