Gotten a few questions about my last post, so here's the quick and dirty skinny:
EHV is Equine Herpes Virus. There are four ways it can hit but the main two are usually a version that causes spontaneous abortion in mares and a respiratory version.
Unfortunately one of the other versions creeps into the spinal fluid and brain and causes a severe infection, a myeloencephalopathy. They call this version EHM.
No one knows why any one horse gets EHM or why one strain of the virus is more likely to hit as EHM. All they know is when it does, you're pretty much screwed. Your horse's brain and spine will become inflamed, blood vessels swell, and it can just flat out lose the ability to stand. Once that point is reached there's really not a lot to do other than to put the horse down: chances are the damage is done and it'll never stand again.
To top off this big birthday cake of suck, the mutation in the virus's DNA that allows it to enter the nervous system (and they've only found one in comparative DNA analysis) also causes more shedding of the virus: the version that creeps into the brain is the version that is the MOST contagious.
This outbreak started at a cutting competition in Ogden Utah. So far Colorado, Idaho, New Mexico and Utah are tied for fatalities with two each, and Arizona, California, and Oregon following with one each. Confirmed cases numbers are far wider spread, and the associated deaths are higher as well, as not everyone reporting a case has a vet run the test before they euthanize.
So far the stats I found (read, the first place I pulled up, which is tagged as of 5/25/11) are reporting 35 horses from the Ogden event with EHV:1, 25 with EHM, and 9 total deaths related, suspect or confirmed.
That's primary exposure. All those horses left that event and went other places. Secondary and tertiary exposure stats stand so:
14 EHV:1, 3 EHM, 2 deaths related, suspect or confirmed.
The stats I quoted earlier on the state by state death count were slightly more recent, as of 5/27.
The scary part of this is, even if they manage to quarantine all of the effected horses, this virus is a lot like Parvo in dogs: the virus can live on surfaces for a period of time and in fabrics and woods for a longer period of time. Contaminated tack, buckets, clothes, blankets, stalls, all of those can infect another horse. I'm not sure about the time period but I sure as hell wouldn't put any of that stuff near another horse without a good disinfecting.
The current on-the-market vaccinations for EHV:1 may or may not protect a horse against EHM. They just don't know. None of the current vaccines claim any efficacy against the neurologic strain, but even the "normal" virus is nasty enough to be worth vaccinating against.
Events have been postponed or canceled in order to try to control the outbreak and minimize exposure, horse owners are being advised to keep their horses home and isolated, monitor temperature and nasal discharge if they may have been exposed, and generally just use caution until the outbreak is contained.
Some reports I've gotten from friends, who got them from friends, say that it takes about eight hours from a horse showing neurological symptoms for it to lose the ability to walk and or just fall over dead.
If ya'll have more questions by all means ask and I'll dig up answers if I can, but right now it's late and I'm tired and going to bed.