A horse from the HITS Ocala show grounds that was confirmed positive for equine herpesvirus myeloencephalopathy (EHV-1 neurologic disease) on February 22, 2013 is responding well to aggressive treatment. The horse has been quarantined in the equine isolation facility since admission.
Aggressive treatment of horse diseases
A horse from the HITS Ocala show grounds that was confirmed positive for equine herpesvirus myeloencephalopathy continues to respond well to aggressive treatment and no other cases have been reported.
According to attending veterinarians, no new cases of equine herpesvirus myeloencephalopathy (EHM) have presented among exposed horses in the area.
The Large Animal Medicine Service at the University of Florida provides the following information for horse owners concerned about EHV and EHM:
How does EHV cause EHM?
EHV can cause inflammation of the blood vessels surrounding the brain and spinal cord. The neurologic signs (EHM) result from that inflammation and small blood clots that affect the neural tissue. During an outbreak of EHM, usually only 10% of infected horses develop neurologic signs. At this time, we still don’t fully understand why some horses get EHM and others don’t, but it is likely a combination of factors specific to that individual horse and to the virus infecting it.
What does “wild type” strain mean?
There are two strains of EHV-1, known as D752 and N752. D752 is more frequently associated with EHM, and is therefore sometimes called the “neurotropic strain” while N752 is called the “wild type” strain, implying that it is the “normal” variant. This is misleading, however, as either strain can cause neurologic disease. D752 is more likely to cause neurologic disease, but the same control methods are indicated for either strain.
What are the signs of EHM?
Clinical signs typically begin with a fever, usually 1-3 days after infection although it can be up to 10 days. Neurologic signs usually appear around 7 days post-infection, and progress rapidly over 24 to 48 hours. Signs may include incoordination, weakness, loss of tail tone, urine dribbling, head tilt, and inability to rise.
How is EHV spread?
Herpesvirus is primarily spread by direct horse to horse contact via the respiratory tract. It is unknown how far the virus can spread in the air surrounding an infected horse. Virus can also be spread by contaminated hands, clothing, buckets, tack, grooming equipment, and trailers. The virus can live for about 7 days in the environment, but it is easily killed by most disinfectants.
How is EHM diagnosed?
Horses with a fever and neurologic signs should be tested by your veterinarian. Currently recommended testing consists of a nasal swab and blood collection to detect virus by PCR (polymerase chain reaction) which detects the DNA of the virus. Doing both nasal swab and blood testing increases the likelihood of making a correct diagnosis. Any horse that dies or is euthanized due to neurologic disease should also be submitted for a necropsy examination.
Who decides how an outbreak is managed?
EHM is a reportable disease. That means that when a veterinarian confirms that a horse is positive for EHV and showing neurologic signs, the state animal health officials are notified. The state veterinarians are specially trained to deal with animal disease prevention, surveillance, and control programs. They determine the necessity for quarantine or restricted movement of animals.
Is there a treatment for EHM?
Treatment is primarily supportive. This includes anti-inflammatory drugs. Intravenous fluids may be necessary if the horse is having trouble drinking. Nursing care is also extremely important if the horse is unable to rise. Antibiotics are not effective against EHV, but can be used if there is a secondary bacterial infection. Antiviral drugs such as valacyclovir may prevent infection in exposed horses.
My horse is vaccinated, so he is safe, right?
Unfortunately, no. While there are several vaccines available that provide protection against respiratory disease and abortion, none are labeled for protection against the neurologic form.