New weapons against EPM

currently being conducted at NVSL.

WEST NILE VIRUS IN FLORIDA The Florida Department of Health (FDOH) has identified the first “presumptive” human case of West Nile virus (WNV) in Florida. The patient developed acute encephalitis in mid-July. Analysis of the patient’s serum showed a positive IgM antibody test to WNV. FDOH expects to have results of additional laboratory tests by the end of July. The patient lives in Madison County, Florida. Madison County has reported 4 birds which tested positive for WNV. Madison County is adjacent to Jefferson County, where WNV has been found in 5 birds and in 1 horse. Because of the increased activity of Eastern equine encephalitis and the WNV activity, a medical alert that was issued last month for Holmes, Washington and Jackson counties has been extended to include Bay, Calhoun, Gulf, Franklin, Liberty, Gadsden, Wakulla, Leon, Jefferson, Madison and Taylor counties. The confirmed equine case was in an adult male horse that was euthanized on or about July 12, 2001. Serum and brain samples were collected prior to death and sent to the Florida Department of Agriculture and Consumer Services’ laboratory in Kissimmee. A positive hemagglutination inhibition (HI) test result was obtained at that lab and serum and brain was forwarded to NVSL for WNV confirmation. NVSL confirmed the diagnosis by positive results on an IgMcapture enzyme-linked immunosorbent assay (ELISA) on serum and a positive reverse transcriptase nested polymerase chain reaction (RT-nPCR) on brain tissue. Serum from the other two horses with signs of WNV infection also tested positive on HI testing in Kissimmee, FL. Serum from these 2 horses was then forwarded to NVSL. Both horses had positive IgM-capture ELISA test results at NVSL. Onset of illness in one of the horses was late June and the other horse in early July. These probable cases may be reclassified as confirmed cases based on the results of additional serological testing 332

TESTING FOR EQUINE ENCEPHALO-MYELITIDES IN CALIFORNIA The California Department of Health Services and the California Department of Food and Agriculture provide free diagnostic testing for arboviral encephalomylitides. These include western equine encephalitis, eastern equine encephalitis, and West Nile Fever. These diseases may affect horses, ratites, humans, and other mammals. Therefore, veterinrians' continued support of the surveillance program in California is important to both human and animal health Veterinarians are often the first to detect the emergence of zoonotic diseases. It was an equine practitioner who last spring identified the first case of EEE in California. Veterinarians were the first to detect the presence of West Nile Virus in New York during the fall of 1999. In 2000, 60 equine cases of WNF were reported in seven eastern states. Twenty- three (38%) of the infected horses died. To date, this disease has not been found in California. However, the potential exists for its introduction via infected mosquitoes, birds, or mammals. Therefore, continued vigilance on the part of veterinarians, public health officials, and animal keepers is critical. Arbovirus surveillance in recent past years has revealed high levels of WEE activity in mosquitoes and sentinel chickens. Therefore, clients should be encouraged to vaccinate their horses. A commercial vaccine for WNF may be available this summer. It is important to emphasize that once a horse has developed encephalitis, vaccination provides no benefit. Furthermore, due to the possibility that vaccination will interfere with diagnostic tests, combination equine encephalitis vaccines should not be used in suspect cases. NEW WEAPONS AGAINST EPM New weapons are available for the fight against Equine Protozoal Myeloencephalitis (EPM). The USDA has renewed Fort Dodge Animal Health’s conditional

license for their Sarcocystis neurona, killed protozoa, vaccine for one full year. The vaccine is intended to aid in the prevention of disease due to new infections by Sarcocystis neurona, the organism identified as the cause of EPM. Bayer has received approval from the FDA for Marquis (15% w/w ponazuril) Antiprotozoal Oral Paste for the treatment of EPM. The new product offers equine veterinarians and their clients the first approved tratment for EPM, combining safety, efficacy and convenience. Fort Dodge Animal Health’s vaccine renewal was given as a result of the USDA’s review of information supplied by Fort Dodge Animal Health describing their progress toward fulfilling the requirements for full licensure. The data submitted by Fort Dodge included: 1. A report describing challenge model development experiments conducted and in progress. 2. A preliminary report describing studies of the vaccine’s ability to induce cell mediated immune responses. 3. A progress update concerning the planned multi-center field performance study of the vaccine. 4. A report updating the long-term safety of the vaccine in which field trial horses were followed-up and monitored following an annual booster administration. No adverse events were noted in the 392 horses. 5. The record of reports of adverse events. On the basis of review of this information, USDA concluded the materials comprising the submission demonstrated progress toward full licensure of the product. In December 2000, the original conditional license period was set at six months by the USDA in order to require an early review of the field adverse events reporting history. Based on the first six months’ field experience data, the renewal period for the vaccine conditional license was set at 12 months, which is the most common conditional license renewal interval used by USDA. The EPM vaccine is distributed through licensed, practicing veterinarians only. Individual states may have their own restrictions for this conditionally licensed product. For more information, veterinarians can call Fort Dodge Animal Health Professional Services at 800-533-8536, or

JOURNAL OF EQUINE VETERINARY SCIENCE

contact their Fort Dodge representative. “EPM has caused more concern among veterinarians and horse owners than perhaps any other equine disease in recent memory,” said John Payne, Senior Vice President with Bayer. “Because exposure to the disease is so widespread among the equine population and because the resulting neurological problems are so devastating, Bayer committed extensive research and development efforts over the past three years toward finding a treatment for EPM that is safe, effective and convenient. We are proud to say Marquis offers exactly those benefits.” The active ingredient in Marquis is ponazuril, an anticoccidial compound with cidal activity against Sarcocytis neurona. It acts against the parasite at several stages of the life cycle. Ponazuril crosses the blood/brain barrier to reach the central nervous system where damage from EPM occurs. With Marquis, equine veterinarians can offer their clients a tratment with a once-daily dosage of just 5 mg/kg, which is administered for 28 days. The product is packaged with a reusable plunger and a calibrated dosing syringe that assures dosing accuracy. According to Dr. Kenton Morgan, Senior Technical Services Veterinarian with Bayer, “EPM is a debilitating and often fatal disease. Accurate diagnosis can be challenging even for the most experienced clinicians. Until now, current therapies were not approved for the treatment of EPM and some of these treatments have legitimate safety issues. Marquis will offer the veterinarian and horse owner a product that is safe, efficacious and convenient.” In clinical efficacy trials1 conducted at equine referral clinics across the country, Marquis was proven effective at the recommended dose level. Efficacy was defined as clinical improvement of a least one grade (0-5 scale) within 3 months post treatment, regardless of whether the CSF Western Blot was positive or negative. It is important to note that Maquis should effectively clear the horse of S. neurona, but may have no effect on the irreparable, pre-existing CNS damage caused by the protozoal parasite rior to treatment. Early and accurate diagnosis followed by immediate treatment are critical for best clinical response. Marquis offers a wide margin of Volume 21, Number 7, 2001

safety. In a recent safety study2 dosing Marguis 2x the label dose (10mg/kg) and 6x the label dose (30 mg/kg) for two periods of treatment (28 and 56 days), few adverse effects were seen as a result of treatment. There were several instances of loose feces in all animals in the study irrespective of treatment, sporadic inappetence, and one horse at 2x the label dose lost weight while on test. At 6x the label dose, moderate edema in the lamina propria of the uterine epithelium was seen in 3 of the 4 mares. The safety of this product in horses used for breeding purposes, during pregnancy or in lactating mares has not been evaluated. This product is not for use in animals intended for food. “We believe that education plays a key role in the diagnosis and treatment of this disease,” says Allyn Mann, Bayer Equine Products Manager. “In addition to offering Marquis, Bayer will be providing educational tools to equine veterinarians that provide crucial information on EPM including prevention, accurate diagnosis, proper treatment and therapy. We also have websites for veterinarians (www.Epmnews.com) and clients (www.EPMinfo.com) that will offer upto-date findings, research, and information on Marquis and the disease itself.” EPM is considered the leading cause of neurologic disease in horses in the United States. Almost every region of the country now has reported cases of EPM.3 The clinical signs of EPM can be quite varied from horse to horse, because actual signs are related to the location and severity of the lesions that randomly develop in the animal’s central nervous system. References 1. Furr, M. et al. Treatment of equine protozoal myeloencephalitis (EPM) with various doses of ponazuril. Study Report 150-664 Bayer Corporation. 2. Campbell, J. Study to evaluate the general safety of 15% toltrazuril sulfone (Bay Vi 9143) oral past formulation in the target species, the adult horse. February, 1999. 3. Reed, S. and Saville, W. Equine protozoal encephalomelitis. 1999 Proceedings TNAVC.

Continued from page 308 I’ve also noted some breed predisposition to laminitis, particularly in stocky breeds such as Morgans. Many horses suffer a mild laminitis, recover without a diagnosis or treatment, and go through life classified by farrier, owner, and veterinarian as a “tenderfooted” horse. I can never forget the Grey national champion Arabian stallion which foundered badly in Kentucky and spent the next two years there undergoing every known therapy including acrylic reconstruction of his feet. Finally, his wealthy owner had him shipped home to California. The suffering animal spent most of his time lying down. I telephoned the Kentucky colleague and asked how, in good conscience, he could continue to allow an animal in such agony to live. He said, “doctor, when you get to know that horse as I know him, you’ll find that he wants to live.” In time, I learned what my Kentucky colleague meant. I took the stallion off of grain forever, and had them feed him only mixed hay and a cup of corn oil daily. I did a very primitive thing. I had his farrier put shoes on his forefeet backwards, a very old treatment. That courageous stallion not only survived but had a successful career as a stud. I’d choke up in later years when I saw him running in pasture (a bit awkwardly, but he cound run) with his mane and tail flying, the very picture of the classical Arabian stallion. Over the years I’ve watched varied and often radical therapies for laminitis come and go. Inevitably, some “work” and none do so all the time despite the claims of its advocates. Obviously early and maximum intervention is still our best insurance against a catastrophic conclusion. I don’t really expect to learn a reliable answer to the enigma in my lifetime. There is a product in use in New Zealand and Australia that colleagues there have told me is very efficacious as a preventative. It is called “Founder-Guard” but, as far as I know, it has not been available in the U.S. As I understand it, it contains an antibiotic effective against the intestinal microflora responsible for laminitis following carbohydrate overload. Robert M. Miller, DVM Thousand Oaks, California

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