The Horse

JAN 2019

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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TheHorse.com | The Horse January 2019 37 not all navicular bone pathology involves bone loss or resorption." Therefore, he said, only cases with bone lesions should theoretically benefit from bisphosphonates. However, as research continues, scientists might find that horses with other podotrochlear appara- tus issues might also benefit from their anti-inflammatory and analgesic effects. Ultimately, he said, these drugs might be a fairly short-term adjunctive therapy (in addition to orthopedic shoeing, intrabursal and IA injections, and non- steroidal anti- inflammatories) for horses with navicular-associated lameness. Controlling EHV-1 Outbreaks When a vet suspects a horse has the neurologic form of equine herpesvirus-1 (EHV-1), it's imperative he or she take the appropriate diagnostic and control mea- sures to prevent an outbreak of this often- fatal infectious disease. This is because EHV-1 can spread before horses show any signs of infection, creating a "potential perfect storm," said Richard Newton, BVSc, MSc, PhD, FRCVS, director of epi- demiology and disease surveillance at the Animal Health Trust, in Newmarket, U.K. Neurologic EHV-1 is a contagious viral disease that can cause signs of ataxia (incoordination), weakness, paralysis, difficulty urinating and defecating, and recumbency (inability to rise). It spreads via horse-to-horse contact, contaminated hands/equipment, and possibly through aerosolization (coughing), said Newton. Infected horses might not show clinical signs (subclinical infection). "Clinical neurological signs often occur about 10 days after infection, as antibody levels (against the pathogen) are rising," he said. With these challenges in mind, Newton listed his general principles for controlling disease spread: ■ Act on suspicion, making a diagnosis as soon as possible. The AHT uses blood testing, qPCR tests on nasopharyngeal swabs, the complement fixation test (CFT) to measure blood antibodies, and/or histopathology on affected tis- sues collected post-mortem; ■ Isolate affected horses. Newton sug- gests categorizing groups of horses by their risk of circulating virus; ■ Stop all mixing of horses and move- ment on and off the property, and implement increased biosecurity measures, such as use of dedicated equipment, foot baths, and hand disin- fection when moving between horses; ■ Monitor horses more closely (e.g., take temps twice daily) for signs of early viral infection, such as nasal discharge, coughing, or not finishing meals; ■ Perform extensive, repeated lab testing to evaluate subclinical infection; and ■ Establish freedom from active infec- tion, and return horses to normal activ- ity. Newton said he considers horses to be EHV-1-free when both their CFT and qPCR are negative. "There's no quick, easy fix for getting through outbreaks," he said, "The basic premise is to segregate, sample, test, and observe for at least three to four weeks." While an EHV-1 vaccine exists, it's not licensed to prevent the neurologic form. Newton advises against vaccinating horses in the face of an outbreak because the vaccine can interfere with blood screening and might create a false sense of security among horse owners. "Appropriate management of index cases can prevent major outbreaks," he said. "But disaster can happen even with good management." Managing Salmonella on the Farm Salmonella enterica can spread quickly between horses, causing significant finan- cial and even equine losses. So Nathan Slovis, DVM, Dipl. ACVIM, CHT, of Hag- yard Equine Medical Institute, in Lexing- ton, Kentucky, described how to manage these cases for the best outcomes. The hallmark sign of this infectious and zoonotic (can transfer between humans and animals) disease is profuse diarrhea. It typically spreads via the fecal- oral route but can also be shed by sub- clinical horses after stressful situations, such as trailering or showing. At most risk are neonates, horses on antibiotics, and stressed animals, Slovis said. Slovis and his colleagues routinely test any horse admitted to Hagyard for Sal- monella. This allows for early detection of clinical and subclinical horses, he said. If you do detect a subclinically affected horse, however, "it's not the end of the world," he said. In fact, with a few practi- cal biosecurity steps, the horse can return to its farm during treatment. Before sending an affected horse home, Slovis said he instructs the owner or care- taker to adhere to the following protocols: ■ Isolate the affected animal, particularly from susceptible groups such as young and pregnant horses; ■ Clean and disinfect the trailer after bringing the horse home; ■ Practice good hand hygiene (sanitizer); ■ Disinfect hand-traffic areas, such as light switches and stall latches, daily; ■ Wear protective gear, such as gloves and booties, when handling the horse; ■ Place boot baths in the barn aisle, and clean them multiple times a day; ■ Clean the infected horse's stall last, us- ing designated muck boots and tools; ■ Don't spread his manure. If possible, compost it to kill the pathogens; and ■ Clean common areas, such as feed rooms, and surfaces, such as sinks. Slovis believes educating owners about containing Salmonella can help prevent outbreaks and horse owner panic. H Biosecurity measures such as boot baths or mats are crucial for managing infectious diseases. STEPHANIE L. CHURCH/THE HORSE Salmonella Facts ■ 7-15% of normal horses shed it. ■ 1,000 colonies can grow to more than 1 billion in six to eight hours at 100 degrees F. ■ A fly can carry 6,000 colonies. ■ Maggots found in Salmonella- positive manure are carriers for life. ■ Mice, dogs, and cats can potentially spread the disease to horses. ■ Asymptomatic horses can shed 100 to 200 colonies per gram of feces.

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