The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.
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32 TheHorse.com THE HORSE October 2015 there was a trend toward PPID when three of the remaining clinical signs from the list of 11 were present (polydip- sia, polyuria, and laminitis). Cushing's prevalence was actually less when four of the remaining signs were absent (cresty neck and fat pads, potbelly, weight gain, and recurrent infections). Delayed hair coat shedding and weight loss were also significant PPID predictors. More studies are planned with this group of horses, with the goal of linking particular PPID clinical signs in specific age groups. "So if you're looking at a 12-year-old horse, you're thinking about this (set of clinical signs)," Grubbs said, "and when you're looking at a 20-year- old horse, you're thinking about this. It may be that one clinical sign doesn't fit (certain) ages for PPID." Better characterizing differences will help veterinarians assess horses whose owners might not be able to pay for test- ing but want to treat symptomatically. "Watching for improvement (after treatment), it gives you more confidence if you've got those clinical signs and you're looking at (those in) a 14-year-old horse versus a 24-year-old horse." Mycotoxin Causes Bone Marrow Suppression, Hair Loss Researchers recently documented a case in which feedstuffs contaminated with trichothecene mycotoxins caused hair loss and potentially lethal bone mar- row cell proliferation suppression in four Quarter Horses. Rachel Liepman, DVM, a resident in internal medicine at The Ohio State University Veterinary Medical Center, shared what she and colleagues learned about trichothecene ingestion's impact on those horses. She said the index case—an 11-year-old mare—presented to a clinic with lethargy, acute perineal edema (fluid swelling beneath the tail), hematochezia (bloody stools), fever, patchy alopecia (hair loss), and petechiation (small purple spots on mucous membranes). The mare's bloodwork showed severe panleukope- nia (a decreased white blood cell count), thrombocytopenia (decreased numbers of circulating blood platelets), and a prolonged prothrombin time (how long it takes blood to clot). Additionally, when veterinarians evaluated her bone marrow, they found profound myeloid hypoplasia (decreased white blood cell production) and megakaryocytic hypoplasia (de- creased production of megakaryocytes, which produce platelets), she said. In collecting the mare's history, Liep- man said the veterinarians learned that she, along with other horses, had recently begun eating a new batch of hay. This ini- tially caused feed aversion and later some drooling, she said, and the team further learned that the hay had been improperly cured (dried) during production. On initial presentation the mare also had septic peritonitis (inflammation of the membrane lining the abdomen), Liep- man said, most likely secondary to severe immunosuppression and gut irritation from the toxins. The team treated her aggressively with anti-inflammatories, antibiotics, and blood transfusions. After eight days, however, her condition dete- riorated, and she was euthanized. Subsequently, veterinarians ran blood tests on the other horses that had shared the contaminated hay. One 19-year-old gelding exhibited only mild petechia- tion and patchy alopecia and had similar bloodwork and bone marrow findings as the mare and was referred to the clinic. He recovered following treatment with a blood transfusion, anti-inflammatories, and antibiotics—a result Liepman said was notable in itself. The remaining horses both recovered with conservative management, including removal of the hay from their diet and supplementation with antioxidants. Liepman said toxicology testing showed high levels of mycotoxins in the hay, including T-2 toxin at 1,627 parts per billion and vomitoxin at 1.1 parts per million, both substances that fall in the trichothecene mycotoxin group. ACVIMForum Firocoxib, Acetaminophen as Laminitis Treatments A University of Illinois research team recently compared the efficacy of alternative pain killers to traditional non-steroidal anti- inflammatory drugs (NSAIDs) for managing acute foot pain, such as that seen in laminitic horses. Jonathan H. Foreman, DVM, MS, Dipl. ACVIM, pro- fessor of veterinary clinical medicine at the school's College of Veterinary Medicine Veterinary Teaching Hospital, presented results. He said traditional NSAIDs such as phenylbutazone (Bute or PBZ) and flunixin meglumine (Banamine, or FM) are pan-cyclooxygenase (COX) inhibitors known to have potentially harm- ful side effects, such as gastrointestinal ulceration and kidney disease. So he and colleagues compared them to two alternatives— firocoxib and acetaminophen, both non-pan-COX inhibitors—along with a saline control. They induced reversible lameness in eight healthy horses. Following drug administration, a blinded investigator monitored horses for 12 or 24 hours. The researchers determined that: ■ Firocoxib administered intravenously (IV) at a label dose of 0.09 mg/kg proved no more effective than the control, and both treatments were less effective than PBZ administered IV at 4.4 mg/kg; ■ When administered at loading dose levels (0.27 mg/kg, a higher dose given at the begin- ning of treatment), firocoxib had a similar efficacy to PBZ administered at 4.4 mg/kg; ■ Acetaminophen (administered orally at 20 mg/kg) and FM (orally at 20 mg/kg) were simi- larly effective, and both drugs were more effective than the control; and ■ Administered concurrently, acetaminophen (orally at 20 mg/kg every 12 hours) and firocoxib (IV at 0.27 mg/kg every 24 hours) were similar in efficacy to PBZ administered IV every 12 hours at 4.4 mg/kg. "Intravenous firocoxib and oral acetaminophen showed promise in alleviating acute equine foot pain," he concluded, warning that both medications have caused drug testing positives, so take care when administering them to show horses.—Erica Larson Feed contaminated with trichothecene mycotox- ins can cause hair loss in horses. COURTESY DR. RACHEL LIEPMAN