02/16/2018
Good information for the horse community
Dear IEH clients:
The Idaho State Department of Agriculture released today that a farm in Bannock County is now under quarantine. 3 horses showing signs of fever, ataxia and neurological signs were confirmed positive for EHV-1. Two of the affected horses were euthanized.
We have been publishing information about the EHV-1 cases in Idaho because we want you all to be well informed about the situation. These cases offer us an opportunity to reflect on our horseās health, our biosecurity protocols, and our overall strategy for trying to prevent the spread of infectious disease, but in no way do we feel like these cases represent the need for panic.
By its very nature, EHV-1 is always present in our horse community. It is a Herpes virus that most horses will be exposed to by the time they reach adulthood. Once exposed, horses become latent carriers of the virus for life. In this way it acts much like cold sores in people which are also caused by a Herpes virus. Just like cold sores, when horses are stressed, the virus can become active again leading to shedding by the horse. This can happen with associated clinical signs, or in many cases without any outward clinical signs in the horse that is shedding. This is why we see sporadic outbreaks of disease from EHV.
There are currently 4 farms under quarantine in Idaho. One in Gem county had documented cases of abortion due to EHV-1 but no neurological manifestations of the disease. A farm in Jerome county, one in Gooding county, and one in Bannock county have all been quarantined due to horses developing EHM or equine herpesvirus myeloencephalopathy-the neurological form of herpes. Any connection between the current cases is actively being investigated, but at this point an epidemiological connection has not been made. This is in contrast to the outbreak that many of us remember following the Ogden show in 2011 where multiple horses were exposed at a single event. Ogden was an unusually severe outbreak and probably reflected a āperfect stormā of simultaneous occurrences that led to so many horses being exposed and as a result, carrying the virus back to their home farms.
At this point there are not any travel restrictions in place for the general horse population in Idaho. Many people are choosing not to attend events right now until the full scope of the cases is understood and a complete epidemiological evaluation can be done. This is a conservative choice, but certainly a reasonable one at this time, and will help diminish the chances of coming in contact with a horse that might be actively shedding the virus.
People who do continue to transport their horses can help minimize the risk to their horses by practicing good biosecurity practices that includes things like:
-Disinfect your stall before placing your horse in it or keep your horses at your trailer
-Avoid having your horse in common areas (like tie rails) where they will have close contact with other horses
-Avoid touching other peopleās horses. Wash your hands before and after handling horses
-Donāt use common water sources if it can be avoided. Bring your own water buckets and make sure you donāt dip the end of the hose in buckets when filling. Alternately you can bring your own water
-Bring your own equipment for cleaning stalls-donāt share equipment
-Never share bits, bridles, grooming equipment, tack, etc between horses
-Take your horseās temperature twice a day on the day before you leave for a show and while you are at the show to monitor for signs of illness. Any horses with a fever (over 101.5 degrees F) should not taken to the show. If a horse develops a fever at a show, that horse should be isolated as quickly as possible.
Separating horses that travel from resident horses at the home farm is very important to minimize the negative impacts should a horse come home from a show with an infection. Similarly, trying to separate groups of horses with different disease susceptibility on a farm can also help limit the impact of infectious. Try to physically separate pregnant mares, mares and foals, resident horses, and traveling horses into separate areas on a farm.
EHV-1 is spread through aerosol particles from nasal discharge, in aborted tissues (placenta, fetus, etc) and on fomites (peopleās hands, clothes, equipment). Any aborted tissues should be considered infectious until a definitive diagnosis can be made. Do not allow other horses to come into contact with them. If you travel to another horse facility, change your clothes and wash your hands before you handle your own horses. Be aware that equipment, trailers, and tack can spread the disease. Have designated stall cleaning equipment for different groups of horses (eg traveling horses vs mare and foals) or disinfect equipment between groups. Make sure trailers are cleaned and disinfected after hauling to events.
In an abundance of caution, our hospital has instituted more stringent biosecurity practices including taking horseās temperatures before they enter the hospital. If we receive any calls about horses that are showing clinical signs of disease that may be consistent with EHV-1, we will be evaluating them at their home farms to minimize spread of the disease. Thankfully, at this time all of the reported cases have been outside of the treasure valley, and all affected farms have been quarantined.
While it is true that none of the vaccines are labeled to prevent the neurological form of herpes, that does NOT mean that vaccination is not worthwhile. There are good studies that show that the vaccines can help decrease the amount of virus shedding by infected horses, which helps lessen disease transmission between horses. So keeping your horses current on their vaccinations against EHV-1 is still an important step in preventing outbreaks. How often horses need to be vaccinated depends some on whether or not they travel and if they are used for breeding, so it is important to talk to your vet about what schedule is most appropriate for your horse.
EHV-1 outbreaks can be very scary. If Ogden taught us anything, it is that rapid diagnosis and quarantine can do wonders in minimizing the scope of an outbreak. We know that EHV-1 is present latently in most adult horses and thus will continue to cause sporadic disease outbreaks. The impact of these outbreaks can be lessened by horse owners being responsible about monitoring their horses for fevers or signs of illness and making sure that any horses that are sick stay home. Farms that have sick horses should work with their veterinarian to get an accurate diagnosis since many different infectious diseases can cause similar clinical signs. Horses should be kept current on vaccines to limit shedding of the virus. We will continue to keep you updated on our local situation as development occur.
If you have more questions regarding EHV-1 and EHM, here are some good references:
General Biosecurity Information-http://www.equineguelph.ca/pdf/facts/bio_security_info_FINAL.pdf
Biosecurity Poster-http://equineguelph.ca/pdf/infosheets/Beat%20the%20Bugs%20Poster%20Inside.pdf
General EHV informationhttps://aaep.org/sites/default/files/Documents/DiseaseFactsheetEHV.pdf
EHM information-https://aaep.org/sites/default/files/Documents/DiseaseFactsheetEHM.pdf
PowerPoint presentation from AAEP about EHV-What Every Horse Owner Should Know- https://aaep.org/sites/default/files/Powerpoint%20Presentations/EHV_2017F.pptx
