For the past few weeks we’ve been serializing a chapter entitled “Piaff” from the new book Equine ER: Stories from a Year in the Life of an Equine Veterinary Hospital by Leslie Guttman (Eclipse Press, 2009). Piaff, a Dutch warmblood gelding, had a devastating case of equine protozoal myeloencephalitis (EPM), an infection of a horse’s central nervous system, from which he did not survive. (See previous posts for installments.) As a final follow-up, here is a Q&A with Dr. Stephen Reed, one of the world’s experts on equine neurology and the lead veterinarian on Piaff’s case:
EQUINE ER: Was Piaff one of the most difficult EPM cases you’ve ever had?
DR. STEPHEN REED: Certainly it was one of the most challenging … the case had already been through so many excellent veterinarians prior to coming here [to Rood & Riddle Equine Hospital]. The case was also difficult in that there were periods of time when it looked like there was going to be some turnaround, and it made you think, “Oh my gosh, this is going to be OK.” But in the end, we became so distraught. No matter how hard we tried, we couldn’t make the turnaround. It reiterates again all the difficult things about EPM: the difficulty with accurate diagnosis, the difficulty with effective therapies, the understanding of how the organism hides, so there are so many aspects of the case that were in fact problematic and difficult in that regard. Couldn’t have had a better owner. She was so thoughtful and compassionate.
EQER: Is there anything Piaff’s owner could have done differently?
REED: If anything could be taken away from it, and I think even if you ask [the owner] she would say the same thing: I wish we had started aggressive treatment earlier. One of the things we know is the best likelihood and probability of saving the horse is to do really good effective treatment early on in the course of the disease. The case did bring up some ideas for me that maybe we need to supplement medications with things that will enhance the immune system … it’s probably a reasonable adjunct to therapy. I’ve been thinking about it for a while, but Piaff made me think even more that maybe we need to be more aggressive [with the immune system] early on. Since there are less than 1% of EPM cases, yet exposure rates are high, that must mean in most instances, the horse gets exposed and the immune system clears it. So perhaps in that 1 percent, there’s something unique. The uniqueness we don’t know: Is it the organism? Is it the horse’s [individual] immune system? Is it the lack of effective treatment? What is it that is different about those horses?
EQER: What were your first thoughts when the owner said she wanted to use the human drug interferon as a last resort?
REED: She had already investigated it to her satisfaction. I had to investigate it. I contacted the person I consider one of the best veterinary immunologists around, Dr. Dave Horohov at the [University of Kentucky’s] Gluck Equine Research Center, and I ran all the ideas by Dave. And he shared with me why he thought it would not be very helpful, but he also said having stated that … he didn’t see a big downside to administering it. [See Editor’s Notes at the end of this Q&A for more on Reed’s conversation with Horohov.]
The owner’s not an intimidating person. Even though she challenged you with difficult questions, she didn’t try to push her agenda. Because of that, it made it easier to go along with her, to say, “OK, Let’s try this.”
EQER: Also, because you’re a person of medicine who deals with percentages and odds, there wasn’t a 100 percent chance that it would not work, right?
REED: That’s correct …
EQER: What’s the No. 1 thing that horse owners can do to prevent EPM?
REED: Be aware of your environment. If you see a lot of the intermediate hosts around, if you see a lot of opossums on your premises, you need to be totally aware of what those opossums are doing, to be alert to where they’re eating. Owners need to be aware of what all the intermediate hosts are [which include skunks, cats, raccoons, armadillos, and sea otters], and if they see the intermediate hosts in the area dead, they need to dispose of them because they will infect the opossums. [Editor’s Note: The opossum, a definitive host for EPM, spreads the parasite that causes the disease by eating one of the intermediate hosts and passing the infection through stool, contaminating feed and water sources.]
If they see opossums, they need to live-trap them and dispense of them elsewhere (or send them to heaven if that’s their goal). They need to keep their feed covered. And then beyond that, they need to be very aware of their horse so they can identify when their horse starts to do unusual things. Difficulty with eating, difficulty with backing, maybe some subtle nuance with the way it moves or the way it eats or the way it whinnies. If there’s something different about what it does, they need to think: “Geez, that’s not normal, we need to keep an eye on it.” Because again, we definitely know early treatment has the best success.
EQER: What’s some of the most exciting research being done on EPM right now?
REED: I think some of the most exciting work is being done by Dan Howe at the Gluck Center [See Editor’s Notes at the end of this Q&A]. He’s looking really aggressively at some new diagnostic testing. … Beyond that I would say that what’s right around the corner is more and more effort devoted toward prevention. You know, the vaccine trials that were done at Ohio State, they didn’t show success, and I believe people are going to back away from that for a while now. People didn’t give up on malaria, so I don’t think that’s a totally dead deal, but I think it’s going to take some more thought. (And I don’t know who is doing that work right now.) I think what’s coming is the development of other ways to prevent EPM, such as feeding low-dose medications on a daily basis. That’s not out there yet, but I think it’s about to start.
EQER: What would be an analogy to that?
REED: The daily dewormer.
EQER: So in terms of an EPM vaccine, what you’re saying is … ?
REED: It’s not out of the picture, but it’s not imminent.
EQER: You’ve been a vet for 33 years. Does it ever get any easier to put a horse down?
REED: Not for me. It’s very difficult to put a horse down. But you have to always remind yourself that by definition, euthanasia is humane. In this instance, it was an opportunity to do the right thing, to prevent suffering. It’s always difficult at the time, but particularly in a case like Piaff, when you see the post-mortem showing that there were irreversible lesions, you know you did the right thing. And the other thing is when you have an owner like Piaff’s, she came to that realization on her own.
EQER: What’s your best advice for someone who wants to be an equine veterinarian?
REED: Study hard. Get lots of experience. Be interested in working hard. I think it’s a great profession. I would say an awful lot of equine veterinarians, not only here, but around the nation that I know, many of them don’t consider their jobs like going to work. You just have such satisfaction doing what you do.
EQER: What specifically makes it so enjoyable for you: the work, the camaraderie, the research?
REED: Well, for me, all of those things: the opportunity to be with people you really like and trust, the opportunity to help the horses and the owners – that really means a lot to me. Even though I’ve come here [to Rood & Riddle from Ohio State], I’ve had the opportunity to stay connected to some of what I think is the best research going on. About two weeks ago, I organized a special interest group on EPM of all the internists in Central Kentucky. … some of the top researchers came and we all discussed and talked about this disease. It was like, “You know, we’re going somewhere.”
Editor's Notes:
1) Equine ER talked to Dr. Dave Horohov who said the reason he didn't think the interferon would be effective in Piaff’s case was because what the horse needed for his illness was equine-specific interferon gamma, which was not available; only interferon alpha designed for humans was. However, Horohov said he did not think the interferon alpha would harm Piaff because studies have been done using it in horses that have shown some immune-boosting activity. Although Horohov did not think the drug would likely work in Piaff's case, he said he thought, like Reed, it was worth a try.
2) Dr. Dan Howe at the University of Kentucky's Gluck Equine Research Center said he believes the new (ELISA) test for EPM, developed in his lab (and tested and validated with the help of Dr. Martin Furr of Virginia Tech, Reed, and others), measures with much more accuracy than other EPM tests the amount of antibodies against the parasite that causes EPM, Sarcocystis neurona, in serum and cerebrospinal fluid, allowing for more accurate predictions about whether a horse has an active infection in the central nervous system. The test is still in development, but Howe said he hopes it will be commercially available fairly soon.
In her advance praise, Susan Richards, author of the New York Times best-seller “Chosen by a Horse,” calls the new book Equine ER “as thrilling and drama-filled as any of the popular hospital shows on television today.” To order, click here. Thanks for visiting this blog.
