Ogden, Utah - 25th street, sans horses
OK, I will admit to occasionally being impatient. But this EHV-1 stuff has pretty much pushed me over the edge. Assuming that you haven’t been living in a cave, or haven’t been enjoying some wonderful vacation in a remote location without internet access (they exist), by now, you’ve probably heard of the [horrible, deadly, awful, terrible] outbreak of EHV-1 that occurred at a cutting horse show in Ogden, Utah, starting about April 30, 2011.
And you may be very worried. Very, very worried.
I get it. So let’s discuss this and see if we can’t get you to calm down.
EHV-1 stands for “Equine Herpes Virus-1.” It’s given the “1″ because there are several herpes viruses that affect horses (and I’m not going to talk about the other ones right now), and this one was apparently first in line when it came to giving out names. Other than that, the “1″ has no significance.
A wombat (which, as far as I know, does not carry a herpes virus)
Herpes viruses are arguably the most successful of all the viruses, if you measure success in terms of how many of them there are, and how many mammalian species are affected. There are herpes viruses of horses, and people, and dogs, and cats, and pigs, and cattle, and, for all I know, kangaroo, camels, and wombats, too. They are successful for two primary reasons.
REASON ONE FOR THE SUCCESS OF HERPES VIRUSES – They usually don’t hurt the host very much. That’s right, most of the time, herpes viruses are unnoticed by the host. It doesn’t do a virus much good to go killing off its host – that’s one reason why you don’t see Ebola virus spreading rapidly around the world. If the host doesn’t live, the virus can’t spread. Mostly, herpes viruses don’t cause much fuss. They are sort of like the quiet family that lives in the dark house down the street, or in the apartment down the hall. If you didn’t know that they were there, you wouldn’t know that they were there.
REASON TWO FOR THE SUCCESS OF HERPES VIRUSES – They have (very cleverly) figured out how to evade the body’s immune system. Once a horse (or wombat, etc.), gets infected with a herpes virus, the virus finds a nice home, usually in and around nerves. There, they stay nice and quiet (medical folk say latent), until some stress causes the virus to activate and start causing trouble. And the fact that they can evade the body’s immune system also means that, so far, nobody has been able to develop an really effective vaccine against them.
Do you get cold sores? Something like 70% of the human population does. Most of the time, people with cold sores have perfectly normal looking lips. But add some stress – say, illness, tax returns, school (for kids) – and, BOOM,
Ideal conditions for starting a disease outbreak
you end up with a big, painful knot on your lip. Then, the body fights it off, and the virus goes latent, waiting for another stressful opportunity.
In horses, depending on the study you read, it’s estimated that as many as 50% (or more) carry the latent EHV-1 virus in some form. Sending 700-some horses to Ogden, Utah to compete in a horse show was the equine equivalent of sending the kids to school. (So was sending horses to the veterinary hospital at Cornell University earlier this year, but that’s another story.) Panicked, excited, stressed, and packed together, it was an absolutely perfect scenario for the herpes viruses to come out and play. So, some poor horse – one of hundreds that were probably carrying the virus – stressed, and far away from home, broke with the virus, which reproduced, and then spread to other horses. Think kids in school with a cold: one of them gets sick, and before you know it, everyone gets sick.
Remember when I said that herpes viruses usually don’t hurt the host very much? Well, that’s usually true. Unfortunately, in some cases, the EHV-1 virus gets into the horse’s nervous system and causes a great deal of mischief. It can even cause horses to die. This is unfortunate, and also not uncommon with viruses.
If you read about the EHV-1 virus, you’ll hear about the problems it causes. You’ll hear stuff like, “Symptoms include fever, decreased coordination, nasal discharge, urine dribbling, loss of tail tone, hind limb weakness, leaning against a wall of fence to maintain balance, lethargy, and the inability to rise.” I guess that’s strictly true, but that’s kind of like saying that side effects of taking a bath include drowning.
Or, it’s like this clip, from the old movie, “Kindergarten Cop.”
[youtube]OaTO8_KNcuo[/youtube]
Most horses that get exposed to the EHV-1 virus DON’T get neurologic disease. Take these stats, from California horses, as of May eq, 2011. In California, exposure has been confirmed in 20 horses. Of those:
- 2 were euthanized
- just less than half showed neurologic signs
- half only had a fever
- 1 didn’t show any signs of disease at all
The bottom line? Most of the horses that were exposed to the EHV-1 virus are going to be OK.
Of course, no one wants any horse to get sick, ever, so, understanding that, your reasonable question would be, “What can/should we do?”
And my response would be, “Go out and enjoy your horse.”
Arguably worse than EHV-1 for most horses
Are you going to stop driving because people die in auto accidents? Going to stop flying because occasionally airplanes crash? (Well, actually, some people do, but that’s a psychiatric discussion.) One of the many uncomfortable facts of horse life (besides, say, having to dress up in costumes, or wear brightly colored blankets, boots, etc.), is that the EHV-1 virus is pretty much everywhere. Your horse has probably already been exposed at some point in his life. The virus has been identified in 5 week old foals, who pass it back and forth with their mums (at least in England).
Vaccination won’t help. Vaccination simply is not effective. This isn’t just a horse thing; there’s no really good herpes virus vaccination against any 
disease of any species. In fact, the best things that you can do involve good hygiene measures, that is, the types of things that people should do with their horses anyway (but often don’t).
So, for example, new arrivals to farms should be quarantined for a few weeks before being introduced to new horses. People working around horses should wash their hands often so that they don’t carry disease. If you’re working around a sick horse, change your clothes before moving on to the next horse. Don’t crowd horses together. Feed them well. Get them fresh air and exercise. All common sense and mundane. And important, too.
I don’t want to seem unsympathetic. EHV-1 can be a bad deal for individual horses. Quarantining sick horses, or horses that were exposed at the show in Utah was absolutely the right thing. But for most horses, EHV-1 is no no big deal at all. It’s one thing to be prudent and cautious, but it’s quite another thing to be paranoid; cancelling or avoiding horse shows in southern California because there was an EHV-1 outbreak in Utah is akin to closing the Los Angeles Unified School District because some kids in Missouri got chicken pox (which, by the way, is another herpes virus).
I feel better now.
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