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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YOUR GUIDE TO THE 2017 AAEP CONVENTION SPONSORED BY A40 TheHorse.com/AAEP2017 AAEP Wrap-Up THE HORSE March 2018 contagious disease, which is transmit- ted via the fecal-oral route, often occur at boarding facilities. But mortality rates are low. To better determine prevalence of and risk factors for coronavirus seropositivity, Pusterla tested blood serum samples from 5,247 healthy adult horses in 18 states us- ing an ELISA test. He found that: ■ The overall seroprevalence of coronavi- rus was 9.4%; ■ The highest seroprevalence was among horses from the Midwest; ■ Seroprevalence among draft horses was higher than in other breeds; ■ Seroprevalence was lowest among Thoroughbreds; ■ As far as horse use, seroprevalence was highest in ranch/farm and breeding horses; and ■ There were no differences between ages and sexes. "Coronavirus seroprevalence is associ- ated with region, herd size, animal den- sity, and biosecurity measures (or a lack thereof)," he said. And that makes sense, given the breed and horse use findings: "Breeding and ranch/farm operations generally have large numbers of horses," he added. "And the Midwest has the high- est percentage of drafts (30%) used as farm or breeding animals." Pusterla noted, however, that he had no information on farm management practices, how long horses had lived in a region, or the number of horses on each premises. Still, he said he could confidently report that coronavirus sero- positivity is significantly associated with horses from the Midwest, draft horses, and ranch/farm and breeding uses. Potential R. equi Vaccine Tested Rhodococcus equi (R. equi) is the most serious cause of pneumonia in 1- to 4-month-old foals. It is expensive to treat and sometimes fatal, yet no vaccine to protect against the pathogen exists. Researchers from Texas A&M;'s College of Veterinary Medicine and Biomedical Sciences considered if a newly developed vaccine given to pregnant mares could protect their foals from R. equi pneumo- nia. Noah Cohen, VMD, MPH, PhD, Dipl. ACVIM, professor of large animal internal medicine, presented their findings. R. equi is a Gram-positive bacterium found in soil. Grazing animals can ingest spores and become infected, but foals gen- erally get it after they inhale R. equi-laden particles. Treatment is prolonged and, so, in addition to risks of mortality, the dis- ease has serious economic consequences. Like many other bacterial pathogens, R. equi expresses the polysaccharide poly- N-acetyl glucosamine (PNAG) on its sur- face. Study collaborators from Harvard Medical School created a candidate vac- cine containing a fragment of synthetic PNAG attached to tetanus toxoid—a protein veterinarians already administer to protect horses against tetanus—to de- termine its effectiveness against R. equi. They gave the intramuscular vaccine to 12 pregnant mares six and three weeks be- fore foaling, and saline to seven pregnant control mares at the same time points. When foals were approximately 28 days old, the team infected them intrabronchi- ally (i.e., via an endoscope through the trachea into each of the large tubes that carry air to the lungs) with live, virulent R. equi. They confirmed an R. equi pneu- monia diagnosis if they found ultrasono- graphic evidence of abscesses in the lungs, microscopic evidence of bacterial infec- tion in tracheal lavage fluid consistent with bacterial pneumonia, and a positive culture for R. equi in the fluid. Also, foals had to display three or more of the follow- ing clinical signs: coughing, depression, a temperature >103°F, and a respiratory rate ≥60 breaths per minute. Vaccinated mares showed significantly higher anti-PNAG IgG (antibody) levels at three weeks pre-foaling and on foaling day than on the day of first vaccination. The foals born to vaccinated mares had signifi- cantly higher anti-PNAG IgG from birth though Day 56 after birth, confirming the antibodies were transferred to the foal via passive transfer and colostrum ingestion. When vets challenged the foals with R. equi, only one of the 12 born to vac- cinated mares developed pneumonia as compared to six out of the seven born to the unvaccinated mares. That foal did not require treatment, whereas the infected foals from the control mares did. Cohen said this research suggests that vaccinating mares against PNAG effectively protects foals against R. equi pneumonia. He added that it's unknown if and when this vaccine will come on the market. h ISTOCK.COM Draft horses, horses from the Midwest, and those used for farming and ranching or breeding are most at risk of contracting coronavirus. e Visit TheHorse.com/AAEP2017 ■ Japanese Vets Transferred MRSA to Racehorses, TheHorse.com/40209 ■ Quick Response Key in Equine Antimicrobial Cases, TheHorse.com/40210