Maine Government News
Maine Has No Ties to Equine Disease in Western States
May 19, 2011
Agriculture
AUGUSTA—A devastating and fatal neurologic disease that has caused the deaths of horses in several western states does not appear to have any ties to Maine at this time. Equine herpes virus type 1 (EHV-1) is a contagious viral disease which can cause progressive neurologic disease and abortion in affected animals, often resulting in death. State veterinarians were informed earlier this week that EHV-1 had been confirmed in a number of horses which had competed in the National Cutting Horse Association (NCHA) Western Horse Championships in Ogden, Utah, during the first week of May.
Dr. Don Hoenig, State Veterinarian for Maine, reports, “From information that we’ve received from the NCHA, it appears that 29 states and Canada sent horses to this show, but Maine was not one of these states.” Currently, the states of California, Colorado, and Utah have horses under quarantine, and several other states have imposed movement restrictions on horses that attended the event.
Equine Herpes Virus is a common virus in equine populations worldwide. There are several strains of the virus, with EHV-1 and EHV-4 being most often involved in clinical disease. EHV-1 can cause respiratory disease (also known as “rhinopneumonitis”), abortion and neurologic disease. The neurologic disease is sometimes referred to as Equine Herpes Myeloencephalopathy. Although EHV-1 is highly contagious among horses, it does not pose a threat to human health.
EHV-1 is transmitted primarily by aerosol when infectious droplets are inhaled. The source of infectious droplets is most often respiratory secretions. Direct horse-to-horse contact is a common transmission route for the virus, but indirect transmission is also possible. Indirect transmission occurs when infectious materials (nasal secretions, fluids from abortions, etc.) are carried between infected and non-infected horses by people or fomites (inanimate objects, such as buckets, etc.).
Fever is one of the most common clinical signs and often precedes the development of other signs. Respiratory signs include coughing and nasal discharge. Horses with neurologic symptoms may appear weak and uncoordinated. Urine dribbling and loss of tail tone may also be seen. Severely affected horses may be unable to rise. None of those signs are specific to EHV-1, and diagnostic testing is required to confirm EHV-1 infection. Many horses exposed to EHV-1 never develop clinical signs.
Depending on the weather (viruses survive well in the cold, the damp, and the dark, and don’t survive long under hot, dry, sunny conditions), the virus may persist in the environment for several weeks. Inanimate objects, such as grooming tools, water and feed buckets, and contaminated clothing or footwear can also be potential sources of spread. Therefore, all horse owners and people who conduct business on horse farms (feed trucks, farriers, veterinarians, sales people, etc.) should practice strict biosecurity.
Over the past several years there have been numerous outbreaks of EHV-1 at farms, stables, and racetracks throughout the country. Maine’s last experience with EHV-1 occurred in 2007 when three horses died at a Rome stable.
Vaccines effective in preventing respiratory and reproductive EHV-1 are widely available and should be administered as directed by the owner’s veterinarian. Often that means at least twice every year, and horses that travel to events should get booster vaccines as often as every three months. The vaccine does not appear to protect horses from neurologic herpes. However, vaccination will reduce the amount of circulating EHV-1 in equine populations, thereby lowering exposure risks. Horse owners are encouraged to visit with their veterinarians to determine the vaccination program best suited to their individual needs.
Dr. Hoenig also states, “Since 2005, the Department has recommended that racetracks, agricultural fairs, and equine training facilities in Maine require that all horses entering their facilities be vaccinated for EHV-1 (rhinopneumonitis) and equine influenza, not more than six months or less than 14 days before entry.” Dr. Hoenig also strongly encourages organizers and planners of equine events to seek the advice of veterinary professionals for guidance on disease prevention.
For more information, contact Don Hoenig at 207-287-3701, donald.e.hoenig@maine.gov.
