Dr. Stephen reed on EPM

DR. STEPHEN REED ON EPM Speaking at the recent Veterinary Medical Forum, Dr. Stephen Reed described the latest finding on equine protozoal encephalomyelitis (EPM). After describing the history of what we have learned in the past about this disease, he talked about more recent findings: "The recent information published by Fenger et al. strongly suggests the causative organism may actually be Sarcocystis falcatula, a well known Sarcocystis for which the definitive host is the opossum. Many species of birds serve as intermediate hosts for S. falcatula: Budgerigars, canaries, cowbirds, pigeons, some finches, ducks, and grackles. These birds have a wide geographic distribution in North America. The life cycle of S. falcatula is typical of sarcocystis parasites. Infective sarcocysts are found in skeletal, and some smooth muscles of birds. The muscle and infective sarcocysts are ingested by the opossum, the definitive host. In the intestinal tract of the opossum, bradyzoites are released from the infective sarcocyst and sexual reproductive forms of the parasite develop. Sporulation occurs and infective sporocysts (oocysts) are formed and released in the fecal material. The organ:isms survive for up to one year in feces in the environment. Although hot and dry weather tend to inactivate them, the oocysts are quite sensitive to freezing and may not survive well. Roaches, bugs and birds may act as fomites. The intermediate host (birds) or the horse ingests the infective sporocyst in c o n -

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mediate host, releasing sporozoites. Asexual reproduction of the parasite ensues in the vascular endothelium throughout the body. In the horse, schizogony (asexual reproduction) occurs in the spinal cord and CNS tissue. Schizonts, the product of asexual reproduction of the parasite, are not infective, and sarcocysts apparently do not develop in equine CNS tissue, making the horse a dead-end host. S.falcatula develops infective sarcocysts in the muscle of intermediate hosts and i s sometimes pathogenic for infested birds. "It is thought that the organism may reside in the horse for some time (possibly a year or more) before discernible disease develops. Stress may precipitate clinical signs. The severity of the disease is proportional to the dose of organisms. Prevention of the disease should involve protection of the horse from exposure to contaminated feed or water. It is likely that the definitive and intermediate hosts are prevalent in the environment of the horse. Proof that S. faleatula is the offending organism will require the reproduction of the disease by feeding the organism and developing characteristic clinical signs and then re-isolating the organism."

SYMPOSIUM ON RACING Regulating soundness and safety The following is an edited transcript of an address by Dr. George D. Mundy, chief veterinarian for the Kentucky Racing Commission, made at the recently concluded Symposium on Racing, held annually in Tucson, Ariz.,

was a panelist for a session entitled, "Regulating Animal Soundness and Safety." "I would like to say at the beginning that I am coming at this from the point of view of the commission, in trying to promulgate rules and implement things that will improve the health and safety of horses .... " I ' m going to focus on an area that is very important to me and the indusi try, and that is the prevention or reduction of racing injuries. "There's a couple of things about racing injuries that are unique. One is, that it is a very rare event, thankfully. But that makes it extremely difficult for us to scientifically approach that .... Another thing about racing injuries is that they are definitely multifactorial. If we were to poll everyone in this room as to their personal opinion as to why horses sustain injuries, we'd get, I ' m sure, a lot of different opinions .... "For instance, if we find out that horses have a higher risk of injury on rainy days, what can we do about that? Because we know it rains a whole lot and we race a whole lot in the rain. So, n o t only can you identify something, you need to identify something that can be implemented practically. If we can identify something in which we can implement a change, then we somehow need to monitor that change. "First of all, if our desired effect was to reduce the incidence of injuries, and we implement something and no corrective change occurs, then that wasn't our desired effect. So before we start, we have to find a way to monitor what we're doing and to continue to monitor it as we implement change .... "And... is the change enforceable? Do we have an effective means of pro-

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