Updates on Neurotropic EHV-1 in the Bay Area
SMCHA & Bayhill Equine held a community forum on March 21, 2007.
Read their write up here.
A perspective from veterinarians in Santa Cruz:
There have been 6 horses diagnosed positive with EHV-1 (neurogenic form of herpes) at ranches in Half Moon Bay. 3 have died and 3 are being treated and are in recovery. This makes 15 horses in California and Florida that we know have died from this disease in the past 4 months (For comparison, there were hundreds of deaths from West Nile virus in a similar time frame). Also, EHV-1 is present in our environment, we do think that there is a mutation in the virus, but that is no different than for influenza in people as viruses mutate, which is their job to get around treatment and survive.
So far it is not known where the horses in Half Moon Bay got the virus from. We do believe that it is horse to horse contact. That does not mean that people are not involved in this contact if they go from sick horse to healthy horse. Common sense about interaction between horses is good. When you are about to go to a show you can monitor your horse's temp to monitor any change in status or flare up. You can use your own buckets and equipment, do not use community water. You can get immune stimulants (see below).
There is NO vaccine for the neurogenic form of EHV. We do HOPE, but are not convinced that there is some cross over of resistance in the horses that are current on the Rhinopneumonitis (EHV) vaccines and we as a community are recommending that horses that are out showing were vaccinated within the last 3 months. There are some vaccines that are better than others because they have a higher antigenic load (like pneumabort), but there are no vaccines specific for EHV-1. Dr. Dave Wilson at UC Davis is not recommending that horses be vaccinated with vaccines that have a high antigenic load. It is hard on horses and it is not given for this purpose. They are trying to develop a vaccine....
Some vets are giving immune stimulants such as Eqstim and Zylexis. Zylexis is $55.00 per shot and it is in the muscle. EqStim is IV and is less (about $40 a shot), but you will have an easier time giving the Zylexis because it is IM. No one is recommending that people stop showing, but we can not guarantee that there will not be exposure.
From a conversation with Dr. Madigan (UC Davis):
- There is no need to cancel events or gatherings outside the three-barn quarantine. He said people outside those three barns should follow normal biohazard precautions and they'll be fine.
- Horses are infectious when they are highly febrile and very sick. He said that the quick response & voluntary quarantine by Dr. Browning, barn managers and owners means that the whole thing will probably begin and end within 21 days and be over. The absolute best thing to do is isolate the sick horse immediately. He commended their work. (Interesting: He said he's seen instances where horses have been dragged out of barns, too sick to walk, and still have not sickened a single other animal in the barn).
- If you are handling a very sick highly viremic horse, you should take a shower and wash your clothes before handling another horse, as a precaution. If you've been in the stall with the horse, in contact with its bodily fluids, you could transmit it for the next couple of hours. But if you are NOT handling a sick horse, you do not pose a risk. He said it is not spread like a cold or flu but like any other herpes virus (like nuzzling/kissing, sexual contact, etc.) Nor is it spread through casual exposure on clothing, shoes, tack etc. as has been rumored.
- Scientists have exposed healthy horses to a virulent virus from sick horse (i.e. rubbed their noses with mucus) -- and nobody got sick. So there is some natural resistance in the population.
- It is a newly recognized strain but not a new strain. It has been found in 35-year-old stored specimens.
- There is some data showing that it is endemic and can be found in low levels of 25% of the general population, not infectious and with no symptomology. Many horses have been exposed and have not sickened. The mystery is why it flares up and turns fatal.
- Fatality is not related to immune system compromise of horses with long-harbored virus. (None of the immune-deficient horses in Davis's ICU have ever gotten it.) They don't know why it sometimes is such a quick killer.
- Where did it come from? That's the mystery. It was at GGFields in January -- but where has it been for the past two months? No one knows. He said the two leading theories are: non-horse carrier (burro, llama, alpaca or wild animal) or an asymptomatic "typhoid mary".
- The recent clusters in FL, CT, VA, S. CA and N. CA (and HMB) are probably all linked to sick horses brought from Germany last November. But they haven't traced it precisely. On the other hand, there is a history of sporadic outbreaks that are never explained, such as the one at Golden Gate Fields in '00 that killed 5 horses and another one in '98 that killed 3 horses.
PENINSULA EQUINE MEDICAL CENTER Update on neurotropic EHV-1
These cases have been confirmed and their vaccination status is still under investigation. The State Veterinarians have been advised and will be meeting with UCD staff and others consulting on the implementation of more specific guidelines for handling quarantines, etc. as these are voluntary at this time.
Restriction of movement of horses between affected areas and surrounding horse populations is critical to prevent spread, as contagious horses may not be showing clinical signs of illness. Until more specifics are available regarding the scope and source of this EHV-1 hotspot, we recommend strict movement restrictions to-and-from the affected area, vigilant monitoring of healthy horses for fever or other signs, preventive immunization and measures specific to the population at risk, and SPECIAL consideration to potential spread of the virus via owners, handlers, service staff (farriers, trainers, etc.) by utilizing recommended biohazard transmission prevention measures.
An overview of these management measures, EHV-1 information from previous outbreaks, and links to informative web sites can be obtained on our website. Feel free to contact our staff or your individual DVMs for updates which we will strive to keep current as developments and info becomes available.
Russ Peterson, DVM, MS
(650) 854-3162
BAYHILL EQUINE Update on neurotropic EHV-1 (March 15, 2007)
As most of you already know there has been a recent outbreak of the neurotropic form of Equine Herpes Virus (EHV-1) in Montara. This was the first confirmed case in San Mateo County. To date, Bayhill Equine is the only veterinary practice that has seen, or treated any horse involved in this outbreak. Therefore, as many questions have arisen, I [Dr. Browning] felt I should respond to a previous post to let people know the current status and avoid any misinformation:
I [Dr. Browning] originally saw a 4-year old filly on Monday morning, March 11, that was unable to stand and had a history of fever 5 days earlier. Another horse in the same paddock was also showing signs of ataxia (incoordination). Based on clinical signs, history, and multiple horses affected, a tentative dagnosis of EHV-1 was made and the horses referred to UC-Davis. By 5:15 that afternoon, a positive diagnosis was confirmed by laboratory tests. I called at area veterinarians on Tuesday morning, which is where they got their information. Both horses were started on Valcyclovir, but were euthanized yesterday after failing to respond to treatment.
Two other horses on this ranch were febrile and were thus tested. One was positive and one was negative. One of these horses had gone on a ride with members of a neighboring ranch one day prior to breaking with a fever. Additionally, a 29 year-old mare was euthanized on a second neighboring ranch after being unable to stand. She and one additional horse tested positive today, March 15th. Therefore, these three ranches are currently on a voluntary quarantine based on recommendations from our practice and those of UC Davis.
No new horse had been introduced on the primary ranch for 6 weeks, and the last horse to do so was from Pescadero. Dr. Magdesian at UC Davis felt that a fomite, such as clothing or shoes, could have been the introduction method. He did not believe it was a spontaneous mutation. Additionally, Drs. Madigan and Dr. Ferraro are planning a site visit after they obtain ranch owner approval both to study and to make further recommendations to contain the outbreak.
I have attached a copy of the letter I wrote today, which is an updated version of the one posted on the 12th. Also, we have additional pages covering prevention, treatment, and management that are available. You may contact our office for these or with any addtional questions regarding the status of this outbreak.
Please excuse the length of this post. However, I wanted everyone to have the absolute latest information.
Sincerely,
Wayne Browning, DVM
Bayhill Equine, Inc.
123 Belmont Avenue
Redwood City, CA 94061
(650) 851-2300
PS
1) Obviously contact your regular veterinarian for information regarding treatment, prevention, etc. I simply said that we have those papers already available which include links to appropriate web sites for the latest information, etc.
2) Bayhill Equine is working with UC-Davis to contact the ranch owners to obtain permission to visit the properties. We will be there as well to ask questions of them, etc.
3) We are holding a community forum for all boarders on the coast so we can update them with the latest information as well in hopes of limiting this outbreak. There is a further community forum at the Mounted Patrol on Wednesday, March 21, 2007 at 7:00 PM, by Dr. Wayne Browning of Bayhill Equine. Write Up.
BAYHILL EQUINE Update EHV-1 (March 13, 2007)
A case of the neurotropic form of EHV-1 (equine herpes virus) was confirmed at a boarding facility in Montara, north of Half Moon Bay on March 12. A 4-yr old pleasure horse became febrile on March 6th. She began showing slight signs of ataxia on the evening of March 11th, and was unable to stand the next morning. At that time, one other horse in the paddock was also ataxic. Based on history, clinical signs and the number of horses affected, a presumptive diagnosis of Equine Herpes Virus was made and the horse was referred to the UC Davis Large Animal Clinic. The diagnosis was confirmed the afternoon of March 12; based on a positive nasal swab, blood, and spinal tap. Two other horses at the boarding facility have become febrile. Nasal swab PCRS are pending on 5 additional horses at this facility.
The neurotropic form of EHV-1 was first found in a horse imported from Europe and sent down to Florida for the winter shows in Wellington. A total of 6 horses died or were euthanized in Florida. One horse that was part of the initial quarantine with the horse from Europe died in Rancho Santa Fe, CA. Two horses at Los Alamitos Racetrack were euthanized recently. The three Bay Area racetracks were recently under quarantine when one horse at Golden Gate Fields was diagnosed with the neurotropic form.
To date, there is NO vaccine labeled effective against the neurotropic form of EHV-1. One small study of 5 horses demonstrated that a modified live virus vaccine reduced the amount and duration of shedding of the virus, and horses vaccinated did not exhibit neurologic signs. However, this vaccine has not been challenged against this current viral strain.
Treatment is generally supportive; with the exception ofvaltrex (Valcyclovir). This is an anti-viral drug with is given twice a day for 7 days. However, it is very expensive, with a cost of approximately $3.000 for the course of treatment.
Immunomodulators such as Zylexis or Eqstim may be beneficial in boosting your horse's immune system against a viral challenge. Please refer to our previous handouts for additional information on the vaccine, immunodulators, and web sites about this disease.
BAYHILL EQUINE UPDATE EHV-1 (January 5, 2007)
What we know: Each year there are small “pockets” of EHV-1 outbreaks. It is usually the respiratory form, as opposed to the abortive or neurologic strain. Traditionally, it has been very contagious and therefore, quickly self-limiting. This particular neurological strain is probably a mutation of a “normal” strain and appears to be a bit more virulent than past strains. It seems to affect horses more severely and can spread to other horses possibly up to 41 feet away. The incubation period is 1-12 days. However, it has not spread like West Nile Virus, for example, nor is it as contagious as infuluenza; we hope that it will run a very short course as it has historically.
Prevention:
- There is NO vaccine labeled to be effective against the neurotropic form of EHV-1.
- A modified live vaccine MAY help decrease the amount and duration of viral shedding.
- An immunomodulator, such as Zylexis or EqStim, MAY boost the immune system to provide a greater response.
What we [Bayhill Equine] recommend:
For those horses going to a show, at least one modified live virus vaccination and an injection series with an immunomodulator, such as Zylexis or EqStim. While there are no studies demonstrating their effectiveness against an EHV-1 challenge, we have had success in preventing or minimizing “shipping fever” in horses with these products. One to two of the immunomodulator injections should occur prior to shipping and the EHV-1 vaccine should not be given within 7 days of any immunomodulator injection.
Horses not going to a horse show can also be vaccinated with the modified live vaccine at the owner’s request. Remember that your horses have been vaccinated with the attenuated (killed) virus already. (If you follow their recommendation and vaccinating schedules.)
Please be aware that there is a higher incident of vaccine reaction with the modified live vaccine including localized swelling, fever and limb edema. It may be recommended to administer an anti-inflammatory such as Bute at the time of vaccination. Additionally, the protection from this vaccine is short-lived, lasting only about 60 days. So re-vaccination of this vaccine only may be necessary if this outbreak has not yet subsided at that time.
Other management practices:
- Prevent all contact between horses.
- Do not allow horses to share water sources; clean buckets daily. Do not submerge water hoses in water buckets.
- Take your horses temperature twice a day.
- Do not share equipment. Any shared equipment should be scrubbed and disinfected between uses.
- Do not share medications between horses. Each horse should have separate equipment for oral medications.
- ALWAYS use new needles and syringes for injectables. Wash hands after treating each horse.
