Questions and answers on equine herpesvirus-1 (EHV-1)
The University of Minnesota Equine Center provided an onsite information session with a hundred people in attendance on March 26th 2014. Dr. Carrie Finno, Dr. Christie Ward and Dr. Jeff Bender answered horse owner’s questions.
1. Where is the information published on the new neurologic cases of EHV-1? An outbreak of the neurologic strain of equine herpesvirus-1 began in early March 2014 in Minnesota. Unfortunately, the strain of herpesvirus that caused the neurologic disease is not reportable to the Board of Animal Health. There are 2 strains of equine herpesvirus-1, the D strain or neuropathic form, and the N strain or nonneuropathic form (poorly named since both strains can cause neurologic disease). Currently, only the D strain is a reportable disease which means that the Minnesota Board of Animal Health would oversee and report on the outbreak. The N strain is responsible for the current outbreak of neurologic disease in Minnesota and Wisconsin is unfortunately not a reportable disease. There is not one source authorized to collect and disseminate information about the spread of infection in the horse community. Veterinary clinics within the state have information posted on their websites and Facebook pages to update their clients. There is no formal requirement to report cases to the Board of Animal Health but they are monitoring the situation and they do have some information on their website. 2. Do you have detailed information of movement of sick horses? No, this is not being tracked. Initial transmission likely occurred at one or more barrel events but since then horses have dispersed and travelled to other events. There is no entity that is charged with tracking horses and there have been numerous events so it is impossible to know where it may have started. If your horse was at a barrel event in March, or is in contact with horses that did there is a possibility it could have been exposed. It is important to note that this type of problem can arise among horses of any discipline, and it this particular case seems to have started in barrel horses or those in contact with them. Next time it could be another performance type. Lists of all horses at all events are not available, so there is no way to contact everyone who has been at every show or event. Spreading the word is important and anyone that has horses that have been in contact with any horses that have been at shows or other venues should be keeping an eye on their horses – taking temperatures twice per day and looking for any signs of the disease. 3. Since we do not have the central website, how do we know when the last case is and when the 2 weeks has run? We and other equine veterinary practices, such as Anoka Equine and Stillwater Veterinary Clinic, are tracking confirmed and suspect cases and maintaining lists of confirmed cases that are posted to Facebook pages. Tracking would be easier if the disease were reportable. The state Board of Animal Health should be encouraged to require reporting of any case of neurologic disease caused by EHV-1, whether it is caused by the D or the N strain of EHV-1.
4. What is the single most effective thing you can do to limit the spread of the virus? Limit the movement of horses and limit the exposure of horses to unknown horses. There should be a 28 day quarantine for any farm where virus has been confirmed beginning from last day of possible shedding of disease. 5. How long do you keep a recovered horse in quarantine? 28 days following resolution of fever and/or resolution of shedding from nose, which is tested from nasal swabs. Usually the recommendation is to take swabs until 2 swabs in a row are negative for herpes on a PCR test.
6. Why is the University of Minnesota using UC Davis for herpes testing? California has been the hotbed of EHV-1 for many years. They created the quantitative PCR test and patented it. UC Davis has done the most work on creating the most reliable test results.
7. What about quarantine for farms where no affected horses have been housed? There is not one universally accepted recommendation for farms where no infection or exposure has occurred but you are in a region of an outbreak. Err on the side of caution by minimizing movement and mixing of horses. Do not go to shows, clinics, or other events at which horses from different farms and locations gather. If transmission can be prevented until all infected horses stop shedding virus, the outbreak will die out. There is no standard recommendation in this scenario but we encourage you keep your horses at home for at least 2 weeks from the most recent case to minimize risk of exposure. If you have new horses moving onto your property, we recommend that it be quarantined for 3 weeks. 8. When does this virus outbreak usually happen and how long does it usually last? We see it most often in spring and fall when it is wetter out. The virus does not survive long in the environment and most disinfectants kill it immediately. We encourage more use of biosecurity measures on all farms and at shows to reduce the spread of the virus. 9. What should horse show managers do if a sick horse is at their event? The sick horse should receive immediate veterinary attention, and show organizers should consult with the veterinarian about how to minimize the risk of contagious spread. As situations like this become more common, horse people and show organizers will need to become more educated and proactive about biosecurity at horse events. This will help to decrease future EHV-1 outbreaks, but also reduce the spread of other contagious diseases such as strangles and viral respiratory disease. Examples of steps show organizers can take to reduce the spread of contagious disease, including EHV-1, include vet checks on arrival at the show; no-fever policies (horses on the show grounds must have temperatures taken and any horse with a fever must be taken home); requiring attendees to have a health certificate; and a veterinarian’s supplementary statement on the health certificate that the horse has not been on any property with a confirmed or suspect case of EHV-1. 10. Should we go to out of state shows? Owners have to make own decisions but, we think you should keep your horses at home for at least 2 weeks following the most recent confirmed case to help minimize further spread.
11. As a show manager, what should we ask of facility for cleaning? As show manager, you should ask what is being done by facility between shows. Use your common sense, if things look clean and dry and smell clean then you can feel pretty comfortable they are doing a good job. Remember that surfaces are different and some are easier to clean than others. Is organic material visible or is there no sign of it? The website given on our fact sheet has a long and detailed document on how to clean effectively between shows.
12. Are health certificates helpful? Health certificates are most useful when they have been issued a short time prior to a show (within 7 days or less), and the veterinarian should verify that horse has not been exposed to any sick horse.
13. When can a closed farm feel safe that they are not going to have horses affected during this outbreak? The incubation period is 7-10 days and fever should be monitored for 14 days to start feeling confident that your horse is ok. Closed farms where no horses have come and gone for 2 weeks can feel pretty safe. 14. If we have not done temperatures for 2 weeks but horses may have been exposed are we also safe? No, because symptoms do not appear until after 7-10 days from onset of fever.
15. Is it possible that horses can be carriers and not show symptoms? Yes it is possible. The virus can be latent just like human herpes. It stays dormant in the body and is shed under periods of stress. Exposed horses may develop fevers and be shedding virus, yet show no obvious symptoms like runny noses or neurologic abnormalities. That’s why take temps! In your barns now during the outbreak take temps twice a day for the next 2 weeks if horses have been off the property and come back.
16. Are carrier horses shedding? They can but are less likely than the ones who are showing neurologic signs. The one with neurologic signs is the big shedder. Horses with neurologic signs can shed for 7-10 days.
17. What is the length of the latent period of the virus? For the life of the horse possibly and many adult horses are latent carriers. It is impossible to know when a carrier may reactivate and shed virus. They can look completely normal but in times of stress they may start to shed.
18. Can you test your horse to see if it’s a carrier? It is not possible to test a live horse to see if it is a latent carrier, as this requires samples of lymph nodes and brain. You can test horses to see if they are shedding virus by taking nasal swabs, but most of the time a latent carrier is not shedding virus.
19. Are there any other animals that can carry and shed the virus? Mules, donkeys, and zebras can be infected by EHV-1 and shed the virus, and can also develop neurological disease as a result of infection. This is also the case for camelids such as llamas and alpacas. 20. Is this a new disease? EHV-1 has been around a long time but the EHM (neurologic form) development is considered an emerging disease because outbreaks are becoming more common We are not sure why other than it is possible that there is an increase in stress from horses traveling more.
21. Is the virus in the environment and a horse can get it without exposure to a shedding horse? No, not unless the environment has been contaminated by a shedding horse.
22. How long does virus survive? It depends. On a smooth dry surface, especially if it is exposed to UV light (sunshine), the virus dies within hours. In a moist and dark protected environment it could possibly survive for as long as a month Luckily it is not hardy virus! On dry hands and clothing it probably lives no longer than 4 – 6 hours It can be killed by washing hands and using hand sanitizer. It is susceptible to a wide range of disinfectants so if in doubt it is better to wash and disinfect than to rely on an estimate of how long the virus might live.
23. How long on boots? Again depends on moisture levels and the amount of organic material on your boots (manure) it could live longer on boots. If you think you could have come into contact with the virus it is best to clean off the manure and dip your boots in disinfectant.
24. Can leather gloves be disinfected with aerosol Lysol? Spraying is not the best way to ensure adequate coverage of an entire surface. The recommendation is to dip or if smooth gloves wipe with a disinfectant wip. Most disinfectants are effective against this virus, but it is important that organic material be removed or cleaned off.
25. Do natural products work as disinfectants? If not tested or proven, do not trust it. If you’re concerned about using disinfectants, soap and water is fine. 26. What do you recommend about farriers and trainers going from barn to barn? Increase the awareness and consider holding off on farrier or trainer. If farrier/trainer services are necessary or if this voluntary quarantine period lasts longer, talk to your farrier and trainer about hygienic precautions they can take to avoid bringing the virus in. Consider a change clothes between barns, create biosecurity baths for boots. Use common sense. Consider cleaning surfaces that a horse’s nose touches. This is how it moves from one horse to another. 27. Are there any supplements or additives that can help protect against the virus becoming neurologic? No, there is no research to indicate that specific supplements are likely to be helpful. 28. Are there extra precautions for a pregnant mare? Abortion caused by equine herpes virus can be decreased by using the vaccine Pneumabort K. We recommend to vaccinate pregnant mares 3 times during pregnancy to increase their immunity to EHV-1. Again, vaccination does not protect horses from the neurologic form of herpes virus. 29. Can stallion semen carry the virus? Highly unlikely and it has never been shown that semen carries the virus.
30. Is the herpes vaccine effective against neurologic disease? No vaccine protects against the neurologic form of this disease!
31. Can you over- vaccinate for equine herpes? Yes. Stick with your regular schedule of vaccinating. There is a lot of chatter that the EHV vaccination could bring on the disease but there is no proof of this. More vaccination is not better. 32. If horse gets disease and recovers, will they get it again or relapse? This has not been shown to be the case.