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
[email protected] (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 •
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