Friday, May 20, 2011

EHV1 - thinking about the risks

So, if you're not a horse person, or if I am somehow your only source of horse news, you may be unaware that there's an outbreak of EHV-1 in western North America right now. If you read this blog, you probably already know that.

I've been looking for numbers on this outbreak since it started, but it's only today that I started to find firm ones. I wanted to try to quantify the actual risk. News sources only talk in vague terms - the disease is highly contagious and fatal. They tell you how many have died, but not how many were exposed. How highly contagious? How fatal? That gap in the information really pisses me off.

To be fair, part of the problem is that the vets just don't know. Tbe equine herpesviruses are, they think, largely asymptomatic. Most horses have antibodies to them without ever showing signs of being infected. And when they do show symptoms, they only shed the virus for a short period of time - apparently it's hard to "prove" a horse has EHV.

My first questions are how virulent and how fatal is this outbreak? Any googling at all will tell you running totals on how many horses are confirmed to have EHV-1 / are confirmed dead of EHV-1, but that's kind of useless. How many were exposed? You have to have both numbers to get a percentage. Here's (pdf) yesterday's USDA situation report. It's the only document I've seen so far with numbers of horses exposed. It's also really fascinating! Look at Texas - 26 exposed at the Ogden event, 323 exposed secondarily, ONE death. Versus California - 54 exposed in Ogden, a totally unknown number exposed secondarily, five deaths.

As of yesterday, there were 997 horses exposed (primarily and secondarily, not including California). 21 were confirmed to have EHV-1, and 13 of the 21 had neurological symptoms. Personally, I'm rounding that up a bit and calling it a 1.5% chance of Dixie dying if she's exposed to a sick horse.

(There's a new article on with slightly increased totals, but it doesn't have corresponding increases in exposed horses. Ffffff so frustrating! The new cases in WA are secondaries, exposed at the vet hospital. There are 8 new cases in CA, but they're all fever-only, not neuro. I'm not changing my 1.5% based on that.)

You might think that's all you need to know. Maybe it is. It's not enough for me, though. I've read a lot of hysterical content online about how any risk at all to our precious ponies is too much. They do so much for us and how could we possibly be so selfish as to risk their needless deaths! Just stay home and don't be an asshole.

Here's my problem with that: we're killing them every time we ride. We're killing them every time we feed. We're killing them by ignoring them. You cannot win. There's no way to Do It Right and make sure your horse lives forever. If everything you do carries a risk, you should at least know those risks and try to decide if it's worth it.

The main cost to keeping Dixie at home for two more weeks is that I'll be bored. (Poor me!) I'm also missing out on opportunities to train her - we can go slog on through training rides in our backyard, but they're not the same mentally as organized endurance-type events. That's it though. The "don't risk your pony" people are right about that - there's not much cost to me keeping her at home.

But, regardless, I'm going to a NEDA ride tomorrow. The actual risk is much much lower than 1.5%. There are no cases in Nevada. At the ride, there are no vet checks and it's only 20 miles, so I can insist that she drink our water from the trailer. This is a really great opportunity for a good training ride, in all senses of "training" - trailer somewhere, deal with race environment, stand tied at the trailer for a while. Since I've seen the data and worked through the risk, I'm ok with it.

Longer term plans: Wild West has been rescheduled for the end of June. If NASTR doesn't cancel/reschedule, I might do NASTR then Wild West three weeks later. G's coming home for Memorial weekend, then I'm going to SF for our anniversary in mid-June.


  1. I'm with two of my horses at a 3-day clinic right now in Wisconsin - none of the horses at the farm or attending the clinic has been in contact with an exposed (or secondarily exposed) horse, and that's good enough for me.

  2. I love it when my friends spend some time thinking about shit like this. We can all be epidemiologists.

  3. Kate - WI is almost far enough east that I wouldn't worry at all. Still, you've got western horses at the clinic too, I'm sure. But yeah, not much risk, and you're definitely missing an opportunity if you stay home...

    DP - I thought about you when I wrote this! And I didn't knee-jerk say "western US," just for youuuu :)

  4. Another advantage to living in Alaska!!

    I practice biosecurity for my whole place as a matter of course. This outbreak underscores how little most people think about that kind of security. I agree with you about the risk factor and will be riding my horse in a Poker Ride next week.

    The one statement I read that does concern me is that this virus can be in a horse's system for years and only become symptomatic under conditions of stress. I don't know if they shed the virus before those symptoms appear though.

    I say.......Ride ON!!

  5. I think you have more incentive to ride in Alaska - if you choose to stay home for three weeks, you've lost a substantial part of your riding season!

    The spontaneous disease thing doesn't really worry me. I've got it mentally classified as "Act of God", like colic or shredding a tendon in the pasture. Nothing you can do about that; it's just the shitty horse luck lottery.

  6. Fund,
    I'm with you..but since I board, I'm screwed...had to cancel my plans of horse camping next weekend. I could go, but my barn owner said, I could not come back. And listen to this...I can borrow my friends saddle-but she's doesn't want me to ride near any other horses...the saddle may become infected!

    I'm bummed.
    I have permission to trailer off still, and ride elsewhere..just not organized horsey events for 14 days.
    I'm happy you are still going on you're trips...I'll ride through you.

  7. I think you just have to look at what is going on in your area. In Nevada I would probably go on the ride too, why not? (Have fun!) Here in the Denver area there are now 10 confirmed cases, possibly 22 more and 2 dead. Totally different amount of risk. I wish people here would just stay put (most are) for a couple of weeks so this thing could be isolated and we could get back to our regularly scheduled.... schedule.

  8. Funder,
    I left a comment on your FaceBook post, but your discussion here is much more complete. I liked the letter that Aarene posted at Haiku from the ride vet for the ride she's gone to this weekend. I think the endurance community is far enough removed from the western performance group, and your events are not set in potentially contaminated equine centers/show grounds, that is probably safe.
    I'm in cowboy country, with horses that were in Ogden less than 4 miles away (that barn has closed it's doors to any movement in or out). Friends who do team penning, hang out with cutters (similar skill sets, so therefore common trainers and training barns). Do they ride with the trail club? Sometimes! So I guess I'm feeling the need to be more careful.
    Right now, careful is what will keep things from being worse. I'm not saying that you're being less than careful--in fact, you've looked at the risks and decided it's okay for you and Dixie. That's fine--Have fun and let us know how it goes.

  9. KK - oh that sucks! But i understand the barn owner's POV. I might do the same thing if I were her... she could lose her whole business if she let a positive horse come on the property.

    And that kind of ties in with Barbara and ES - risk analysis is really individual, based on your own circumstances! If I were in WA or CA, I might not go anywhere.

    Interestingly, if you look at that pdf, CA and WA seem to have bad luck / a more virulent strain. They're running well above the 1-2% mortality rate the other states are showing. Even CO has only had 2 dead out of 98 exposed.

    I am not really tracking horses that got sick but displayed no neurological symptoms, because I wouldn't feel too bad if Dixie spiked a fever and had a snotty nose for a couple of days. The neurological aspect is the only thing that makes this scary.

  10. I canceled going to a CTR this weekend because earlier this week, we just didn't know. Plus there were thunderstorms predicted. Plus it was a 500+ mile round trip drive. Combined with diesel prices, riding in the mud and the unknown at that point about EHV, I decided I could spend $300 somewhere else and have more fun.

    I have also been calculating my risk & saw that table from the APHIS today. No horses have been diagnosed with EHV in Nebr although 5 barns are quarantined because of attending the Ogden show. A majority of the people I ride with stable at home. We do not show or participate in large rides. Our horses can get West Niles, they can get strangles and are at risk for a handful of other diseases, vaccinated or not, it would seem, and now they can get this. There is always a risk. We just need to determine how much risk to take.

    I am not staying home. Oh, I'm not planning on any cross country travel. But I am riding with friends. I may not go on any big group rides because I can't deal with the "what ifs" from others or the hysteria that might follow should a horse show symptoms. And it's not that important for me to go on these rides.

    I probably won't use community pens or water if I camp.

    I respect those who make the decision to stay home. They will stay safe. Using your percentages, I am only slightly more at risk than they are. I hope we all stay safe and there is an end to this ugly disease. And if things roll out differently, I may change my mind. It's not necessarily business as usual for me, but close to it.

  11. Hey Tammy - great post on your blog and comment here!

  12. The endurance community is so level-headed. It's good to hear good discussion about the situation, not panic. You really do need to think on an individual basis: what's going on near you and who you will be in contact with. Good luck to all of you who are getting to ride right now.

  13. I'm glad work sucks right now and I couldn't show even if I wanted to. I'm in NC and we don't have any confirmed cases here but I would really be torn about going vs not going. I'm not sure if I'd have an issue with my BO if I did go...

    Sounds like you've made a really informed decision and I hope you and Dixie have a great time!

  14. If the people with exposed horses would just stay the fuck home, there'd be no problem. I've seen a lot of different types of outbreaks and it's almost always some asshole who thinks they can't possibly skip this show even though their horse has a snotty nose, a high temp, and a listless attitude. That's how the strangles outbreak in NJ started last year. It's why I take intake quarantine VERY seriously at my farm. My guess is you're LEAST likely to get something at an endurance event... y'know?

  15. Well said. I'm watching it, thinking about it, leaning against taking Consolation to a clinic at a public arena of which I have little knowledge...but hardly think this is worth a panic. I'd certainly go to Fandango next weekend, if Consolation wasn't NQR. By the way, I finally got off my lazy butt and added you to my blogroll. :D

  16. i2p - Seriously, I wouldn't worry about Lilly catching the western outbreak of EHV-1 any more than I'd worry about her getting strangles or pigeon fever. Vanishingly unlikely in NC!

    Dom - I worry about horses that are just starting to shed the virus but aren't showing any signs yet. I don't think any e-riders would knowingly take a sick horse, but it's the silent shedders and horses that are juuuust starting to get sick that worry me.

    But that's why I did the numbers. If there's a silent shedder at today's ride, Dixie's only got a 1.5% chance of dying from it.

    inthenight - ahahah, no worries. I am also a shockingly slow blog updater. Speaking of, I've got some new readers I need to add... later. ;)

  17. Much that we do in life involves some level of risk. If I were in EvenSong's shoes my decisions would be much different than if I were in your shoes. I remember when there was an outbreak in florida a few years ago. WEF (Winter Equestrian Festival h/j circuit in Wellington) went on and there were no new cases reported because of the circuit. The cases has been traced and barns quarantined at that point.

  18. It's a no-go for me, which is easy for me to say, because I wasn't really planning on going anywhere anyway! Here in Colorado the risk is higher We were officially notified yesterday that a horse came home infected from a RMDS (Rocky Mountain Dressage Society) show, so it's not restricted to the cutting horses here any more. I've seen the photos of a dying horse in a sling at the vet clinic, so I'm completely scared straight.

  19. We are just a few miles down the road from a barn that had 10 horses at the show and the trainer at my barn works there during the day. The BO where I am is not taking any precautions and is continuing twice weekly roping, saying it's ok because they are people they know. I'm horribly upset that they can't even take a couple weeks off roping to ensure our horses safety. But nothing stands in the way of their roping. I could go on... Anyway, to add to complications, we are planning to move at the end of this month (the lack of precautions in the face of obvious risk just adds to the reasons) but the barn we are headed to is being much more cautious about this thing and we may get blocked due to my current barn's risk situation. Very upsetting!

  20. Hi Funder! Thought I`d drop this in, seems we are`nt immune here in the Uk. Its a peice from Horse and Hounds magazine:

    An outbreak of a rare strain of the equine herpes virus has resulted in the deaths of at least eight horses in the south of England during the past month

    Vets and horse owners have been put on the alert after more cases of equine herpes virus (EHV) paralytic disease have been identified in the south of England.
    This is the rarest form of EHV, which usually results in respiratory disease in young horses, and abortion in pregnant mares. The recent outbreaks are unusual, as they involve mostly non-breeding and performance animals of both sexes.

    The first two cases were at racehorsetrainer Nigel Twiston-Davies's Gloucestershire yard and both horses were destroyed. The third, in a point-to-pointer in Sussex, was confirmed on 13 March, and this horse was also put down.

    Probable cases in two Kent yards were reported around the same date. Two horses on a show jumping yard suffered relatively mild neurological signs, from which they are recovering, and, approximately 40 miles away, a large livery yard has tragically lost at least five horses to the infection.

    "We are all very concerned," says Jackie Cardwell, vet and epidemiologist at the Animal Health Trust's Centre for Preventive Medicine. "But fortunately, this is not the kind of infection that will spread rapidly across the country like foot-and-mouth."

    Respiratory disease or a high temperature can preceed paralytic disease and horse owners are advised to keep their horse at home and call their vet signs of these illness are shown.

    However, neurological signs can also appear out of the blue. Signs to look out for include a high temperature, dribbling urine and weakness or paralysis of the hindlimbs and tail.

    The disease may progress rapidly, usually peaking by 48hr after onset, and the horse may go down and be unable to get up: if this happens, in many cases it is more humane to put the horse to sleep.

    However, the outlook for an infected horse is not always bleak - many horses on an affected yard will become infected but not develop neurological disease. Others will show some signs but recover fully - and there is no evidence to suggest that once a horse has recovered, it is likely to spread the disease to others.

    Unlike foot-and-mouth, this virus does not tend to travel long distances through the air. Infection is spread mainly by contact with infected horses. People can carry infection between horses by handling an infected animal and touching other horses, tack, equipment and so on.

  21. Terry & Story - scary stuff!

    Cheyenne - Interesting news piece! Slightly different from the basic EHV-1 news here. I don't think US horse owners ever consider foot & mouth as a threat. :o

  22. A good friend of mine asked to borrow my rig this weekend so she could pick up a horse to try out. Since I don't know the trial horse, or where he's been recently, or where his buddies have been... I chose to play it safe and say no.

    I feel bad for saying no, but I'd rather play it safe for a week or two than worry. I'm probably being really over-cautious... but, my boys, my choice I guess.

  23. Our main barn vet, had this to say about the situation: for our barn, he recommended a 10-day lockdown, re-check with him on state of virus (he's tracking it) in CA. We have an at-risk population for a number of reasons.

    He said that sadly, except to those he is positive are savvy, he's recommending lockdown even to backyard horse owners, whose risk is virtually non-existent, because so many folks do not practice basic horse husbandry (or if we want to get fancy, bio-security). People for whom it would be almost no risk to trailer out for a nice trail ride.

    He put it simply: do not use ANYONE'S stuff: halters, leads, brushes, buckets feed bags/nets etc, and keep your horses away from other horses. Bring your own water, and always use your own bucket. Wash your hands, don't let people not with you touch your horses or feed them.

    He said the recommended quarantine distance from horses actively shedding the virus is 60 feet. (I'm not including the possibility of people carrying it that 60 feet on clothing/manure forks here.)

    He said, yes, it's highly contagious, but doesn't come close to the dire speed of infection that Strangles is capable of. Unfortunately, the consequences, since there is no vaccine, have the potential to be more severe than Strangles.

    I agree, everyone has to stay calm and evaluate their own situation as realistically as possible. The more info the better. Good for you, looking for actual NUMBERS in all the areas, instead of panicking.

  24. I'm not too worried, as I'm so far away from ya'll to have to worry about it. However, my LL has my horses at his place, about 8 miles away. They're over there to help keep the county from putting a road in, right through the middle of where his barn is. Long story, but in the mean time, my horses are fat on pasture and I get a reduced feed bill!

    My LL was thinking of taking on some new boarders who wanted to come in from out West. I made it clear that if he did, my horses were to come home first, just to be safe. He was unaware of the EHV outbreak out West. So, once he educated himself, he turned the new boarders down. (Really, I think he didn't want the work of boarders- it's easier to borrow my horses for the decoy work). There is plenty of open boarding situations here, so the new horses coming into the state will probably have a great place to land anyways.

  25. I've been studying the risks mostly because my mind loves teh challenge, not because I have plans of going anywhere. However, that said, the powers that be here cancelled a lots of horse shows the first two weeks but now they are recommending that horses be checked by a vet including temperature before going to an event and then their temps must be checked twice a day and posted on the stall door. Any horse getting a temp during the show must leave immediately or it will be removed.

    Also it is my understanding that the secondary cases here are not from exposure at the hospital but at the farms the horses from Ogden returned to when they came home. The horses that did go to the hospitals (two of them, one on each side of the state) were never in the general population. Both went immediately into quarantine.

    When I was doing my research on the web, I believe what I read from UCDavis said the shedding happens only when the affected horse's immune system is compromised. As long as an affected horse's immune system stays strong, no shedding occurs.

    That's pretty much the way that EPM functions too.


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