Neurotropic Equine Herpes Virus Update

 

 

           Currently there are numerous reports of equine herpesvirus myeloencephalopathy (EHM) affecting a few horses in western North America.  This outbreak appears related to initial cases at a cutting horse show in Ogden, Utah, which was held from April 29-May 8.  Horses at that event may have been exposed to this virus and subsequently spread the infection to other horses.  While the true extent of this disease outbreak is uncertain, there is clearly a very significant elevated risk of EHM cases at this time in horses that have been exposed to other horses involved in this outbreak.  At this time control of the outbreak is critically dependent on biosecurity.   

     Equine Herpes  Virus-1 is a contagious disease of horses that has been around for a long time.  The classical form of the disease causes respiratory disease, abortions in mares and rarely neurological (brain and spinal cord) disease.  In the past few years a new strain of the virus has emerged that causes more severe disease.  It is called neuropathogenic or neurotropic EHV-1.  It poses no human health risk. 

       Affected horses may develop fevers, runny noses, wobbly gait, hind end weakness and may become recumbent.

     The vast majority of horses become infected with herpes virus as foals and either get a very mild illness or may show no visible signs at all.  This would be similar to children getting exposed to human respiratory viruses as babies from contact with other humans.  This is a normal part of life.  We believe that most foals are exposed at a very young age and may carry the virus for life with absolutely no consequences, however, rarely, the virus may become active in a particular horse and may mutate to form the strain of herpes virus that becomes responsible for the neurological disease now being seen in the Ogden outbreak.

     Should you be worried about your horses?  This disease is spread by horse to horse contact but can also be spread by the virus being carried on peoples hands, tack, buckets, etc.  It does NOT affect humans.  In our area, the only way your horse could be at risk is if they come in contact with other horses that were somehow associated with the Ogden show and outbreak.  Humans who attended that show would be very unlikely to be transporting the virus on their clothes or hands as changing clothes and washing would get rid of it.  Trailers and tack used with sick horses shedding the virus could remain contaminated for up to 21 days.

    So how should you best avoid exposing your horse to this disease?  Obviously you would avoid contact with horses associated with the Ogden show.  Certainly anyone who had horses at the Ogden show would know what is going on and should be keeping their horses at home until this outbreak passes.

     Many manufacturers produce herpes virus vaccines (commonly called Rhino vaccine) however, none have been proven to be useful in preventing the neurological form of this disease.

 

     This in not the first such outbreak, nor will it be the last.  Similar outbreaks of this disease occur all over the world.  They start up with out warning, create havoc during the outbreak and then fade away.  This one will also pass, but during it's active time, DILIGENT BIO SECURITY IS THE ONLY KNOWN WAY TO CONTROL IT'S SPREAD.  Put simply, this means avoiding contact with horses that may have been in Ogden or horses secondarily exposed to Ogden horses.

 

     As always in these sort of situations, rumors run rampant.  Do make yourself informed and do keep abreast of what is going on in this outbreak, but there is no reason for panic.  Over the coming days here will be lots of information online about the Ogden outbreak, but scrutinize your sources carefully.  Not all you see online will be true.

 

     We will keep this page updated, so check our web site for updates.

 

 

 

May 18, 2011

 

     To date,  only horses from the Ogden Utah cutting show have come down with this disease.  In the Okanagan, there is one barn with three cases all of which were in Ogden. These cases have not been confirmed in the laboratory, but considering their attendance at the Ogden show and the clinical signs presented, there is a good level of confidence that these horses have neurological herpes infection. This barn is completely quarantined and there have been no new cases within that barn. 

 

     We contacted the BC. provincial veterinary laboratory this morning and they have NO confirmed cases.  Alberta has reported one case confirmed in one of their laboratories.

 

      We participate in two online discussion groups for equine veterinarians which include thousands of  veterinarians and yesterday the question was asked if any cases had been seen in horses except for those who had been to Ogden.  As of today no one has reported any cases other than horses that had been to the Ogden show.

 

 

May 19, 2011

 

     There are no new reports to indicate that this disease is spreading in any sort of epidemic fashion.  The cases being dealt with are still only those that were somehow directly or secondarily exposed  in Ogden, Utah. 

 

May 23, 2011

 

     As of the 22nd of May, officials monitoring this disease report a total of 33 confirmed cases in nine US states and 1 in southern Alberta. Only 7 deaths have been reported.  British Columbia has three suspect, but unconfirmed cases.  These are quarantined in a private stable in Vernon. Of the 33 confirmed cases, 32 were at the Ogden show.  All owners of horses that attended the show or had horses secondarily exposed have been contacted and all horses are quarantined.  Officials continue to monitor the situation daily and we will try to keep you up to date on this web site.  

     The case numbers provided would indicate that the situation is well in hand and the spread of the virus is being controlled by good quarantine protocols.  We all need to remember that the virus does not move long distances through the air, and as long as the infected horses are properly quarantined, this whole situation should be expected to resolve over the next few weeks. 

     The paranoia surrounding this situation is being fueled mostly by  internet communication among misinformed or uninformed equestrians, but the facts would show it is completely unfounded.    A few shows and events have been postponed, but there is now less talk of postponements as it becomes more clear that the disease is not spreading in any significant way and control measures are working well.

 

 

 

May 25, 2011

 

     Nothing new to report.  So far this small outbreak seems to be better contained than some earlier outbreaks.  Equine Canada has a good information page at their web site which is

www.equinecanada.ca

 

 

 

 

May 28, 2011

 

 

      USDA is doing an excellent job of monitoring this situation and providing objective data.  You can access their updates online.  If you do, read the information very, very carefully.  Do not confuse the number of quarantined horses with the small number of actual cases.  USDA has identified all the primary exposed horses (from the Ogden show), secondary exposed horses (horses that subsequently came into direct contact with horses that attended the Ogden show) and tertiary exposed horses (horses with three degrees or more separation from direct contact with a horse that attended the Ogden show).  Once those horses were  all identified,   the number of quarantined premises increased, but now that most of the data collecting is done,  the number of quarantined farms should become more stable.

     Organizers and officials of equestrian events are using the objective data provided by USDA to help them make informed and sensible decisions  regarding their events. 

     Alberta and BC are the only places in Canada reporting any cases and there is no indication that the virus has spread from the quarantined premises.

 

 

June 24, 2011

 

     There are no new cases reported in relation to this outbreak.  USDA has issued the following statement:

 

"There are no new cases and no new premises affected. Disease spread in connection with this incident has been contained and no further situation reports will be generated."  The situation in Canada is the same.

 

We will not be posting any more updates on our website regarding this outbreak.  We hope you have found our updates useful.  Incidents such as this one do arise from time to time, and when they do we will do our best to keep you appraised of the facts.

 

 

December 6, 2011

 

 

     The scare we had with EHV-1 this summer passed with a very good outcome.  Through the diligent work of horses owners, veterinarians and regulatory people, the disease outbreak was quickly and completely contained.   It did, however, serve as a reminder to us all to be careful about trying to avoid the spread of infectious equine diseases. 

     Over the last few months, Dr. Alex Wales attended two different educational conferences where equine herpes virus was discussed at length by some of the world experts. 

     All agree that the virus is everywhere  in our horse population, and only occasionally does it cause an outbreak such as we saw this spring in the Utah outbreak.  

     There is also good agreement among the experts that currently available vaccines do not protect against the disease, but MAY reduce shedding of the virus between horses in the face of an outbreak.  The following statement was made by one of the experts:

 

"There is no clear relationship between protection from EHV1 infection and the concentrations of circulating antibody induced by vaccination or infection.  However, the duration and amount of virus shedding from the nasopharynx are reduced in horses with high levels of circulating neutralizing antibody and this may decrease spread of virus between horses in EHV1 outbreaks in vaccinated populations."