Equine Health Update EHU Vol 19 Issue 4 - Page 17

EQUINE | Equine Disease Update tion change requiring microchips starting in the 2018 competition year. During that competition year, any horse wishing to participate in the USHJA points program will require a microchip and for the 2019 competition year, a mi- crochip will be required for all horses competing in USHJA competitions. At the recent Equine Identifica- tion Forum in January 2017, the industry recognized the great strides that have been taken related to equine identification but agreed that additional efforts are necessary for industry wide acceptance of microchip- ping. Contact: Dr. Katie Flynn kflynn@cdfa.ca.gov (916) 900-5039 Equine Staff Veterinarian Department of Food and Ag- riculture Animal Health Branch, Sacramento, CA KENTUCKY Clostridium Perfringens and Necrotizing En- terocolitis in Neonatal Foals Necrotizing enterocolitis (damage and death of cells in small intestine and colon) is a serious disease of sud- den onset in foals less than 4-6 days of age associated with a high death rate, despite therapeutic interven- tions. Clinical manifestations of enterocolitis in foals vary from being found dead to a spectrum of clinical manifestations. The most common of these include failure to suck, fever, depression, severe colic, and diarrhea. Although the association of Clostridium dif- ficile, Neorickettsia risticii (Potomac horse fever) and Salmonella infection with enterocolitis in adult horses is clearly established, many cases of fatal necrotizing enterocolitis in foals have no known risk factors. Clostridium perfringens is the most commonly isolated clostridial species worldwide and is part of the normal intestinal flora. Following acquisition of this bacterium by the foal from the mare’s teats or the environment, the organism multiplies rapidly in the stomach and intestines. C. perfringens numbers are reduced fairly quickly, so that by the time foals are several months of age, the organism is found in relatively low numbers within the large intestine. The almost universal pres- ence of C. perfringens, belonging to the type A group, in the intestine of healthy young animals has compli- cated the understanding of its role in enterocolitis. Although most strains don’t cause intestinal disease, there are two types that do so in foals. One of these, C. perfringens type C, is a wellestab- lished but relatively uncommon cause of necrotizing enteritis. The other is C. perfringens type A, which includes a small subset that produces a novel pore- forming toxin called NetF (Necrotizing enteritis toxin, Foal). This novel toxin is related to the beta toxin of type C strains that causes severe enteric disease in foals, other species, and in humans. We found netF- positive C. perfringens in 74% (11/15) of foals with necrotizing enteritis but not in 11 foals with undiffer- entiated diarrheal illness. In another study, netF-pos- itive C. perfringens was identified in 6 of 23 isolates from foals in Kentucky with severe enteritis. In adult horses with undifferentiated diarrhea, the detection rate of netF among C. perfringens isolates was low (4/58). This would suggest this toxin is primarily as- sociated with severe enteritis in neonatal foals. One explanation why type C and netF-positive type A C. perfringens cause necrotizing enteritis in very young foals is because of the trypsin inhibiting effect of co- lostrum. Trypsin is a protein-degrading enzyme secret- ed by the pancreas during digestion, and its inhibition by colostrum prevents the breakdown of protein tox- ins, such as NetF. The reservoir for NetF-producing C. perfringens is not yet known. Real-time PCR can be used to rapidly diagnose necro- tizing enteritis caused by netF-positive C. perfringens. • Volume 19 no 4 • December 2017 • 17