F U N D E D B Y U N D E R W R I T E R S AT L LOY D ' S , LO N D O N

OCTOBER 2017
Volume 26, Number 4

C O M M E N TA RY

IN THIS ISSUE
Commentary
International
Second Quarter2017  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2Equine Colic Update . 3
Equine Influenza
Beyond Equines .  .  .  .  . 3National
EquineIdentification .  .  .  .  .  .  .  . 4Kentucky
Clostridium Perfringens and Necrotizing
Enterocolitis .  .  .  .  .  .  .  .  . 5

College of Agriculture,
Food and Environment
Department of
Veterinary ScienceW

ith the growing occurrence and unpredictable nature of natural disasters, many
horse owners are looking for ways to protect theiranimals. In addition to disasters, horse theft also
is giving horse owners cause to look for guaranteed
methods of identifying their horses. Microchip
identification is an excellent tool for improving thetraceability of horses in disease outbreak scenarios
and allows for the rapid and efficient managementof investigations to minimize spread of contagious
diseases in horses. Diseases such as equine herpesviral myeloencephalopathy, strangles, influenza,salmonellosis, and others can spread rapidly andthe ability to quickly identify animals aids veterinarians, farm managers, and other animal healthprofessionals in developing the most appropriate
action plan to protect them.
Microchip implantation is safe, simple, andinexpensive and usually will last a horse’s entire
life. The cost is generally about $50 to $75 and thechips currently being manufactured are functioning for 25 years or longer. The tiny, non-migratory
chip is the size of a grain of rice and takes only
seconds to implant with a small syringe by aveterinarian or other trained person. The chip is
implanted halfway between the horse’s poll andwithers, just below the mane in the nuchal ligament on the horse’s near (left) side. The injection
site is cleaned and disinfected prior to injection andsometimes shaved, ensuring little to no occurrenceof an adverse reaction.
The microchip is encapsulated in glass and isetched with a unique one-of-a-kind number. The
accredited veterinarian will use the unique microchip number to record on official health papers

and medical records. It is up to the owner to havethat unique code maintained in personal medical
records or registered with a commercially available and searchable database. A special handheld
scanner is used to read the microchip through theskin of the animal. The scanner reads the number
on the chip through radio frequency identification
technology. Although there are several different
companies manufacturing these microchips, mostscanners are now considered universal as they areengineered to read a common frequency.
In the 1990s, Louisiana became the first state
to require mandatory unique identification for all
horses and annual Coggins testing. Microchips area unique identifier superior to lip tattoos or brands
since brands are not unique per horse and both
tattoos and brands can be altered and/or difficult
to read. Many breed organizations are now requiring microchipping for registration. Microchipping
became especially important in the aftermath of
hurricanes Katrina, Rita, Gustave, Ike, and Isaac inLouisiana when many horses were separated fromtheir owners and needed to be identified in order
to be reunited. Veterinarians working with affectedhorses in the recent aftermath and recovery efforts
in Texas and Florida from hurricanes Harvey andIrma are finding microchipping invaluable withthe massive ongoing sheltering operations. Thereis really no down-side and no reason that a horseshould not have microchip identification.
Contact:
Rebecca S. McConnico, DVM, PhD, Dipl. ACVIM (LA)Professor of Agricultural Sciences
Rmcconn@latech.edu(318) 257-2418
Louisiana Tech University
Ruston, LA

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I N T E R N AT I O N A L

Second Quarter 2017

T

Equine Disease Quarterly
Editors

Peter Timoney
Alan Loynachan
Cynthia Gaskill

Staff

Diane Furry
Tawana Brown
Dennis Duross

Correspondence should be
addressed to the editors,
Department of Veterinary
Science, Maxwell H. Gluck
Equine Research Center,
University of Kentucky,
Lexington, Kentucky USA,40546-0099
Telephone (859) 257-4757
Fax (859) 257-8542
Internet address:
http://gluck.ca.uky.edu/
equine-disease-quarterly
Material published in the
Quarterly is not subject tocopyright. Permission istherefore granted toreproduce articles, althoughacknowledgment of thesource and author is requested.
The University of Kentucky
is an Equal Opportunity
Organization.

Printed on recycled paper

he International Collating Centre, Newmarket, United Kingdom, and other sources
reported the following disease outbreaks.
Outbreaks of African horse sickness were reported in all provinces in South Africa except theWestern Cape. Occurrence was as expected for thistime of the year.
Equine influenza was reported by the UK and
the USA. The UK confirmed two outbreaks. Influenza was recorded in 14 states in the USA, where
it is considered endemic.
France, Germany, South Africa, Switzerland,
and the USA recorded outbreaks of strangles. The
number of confirmed outbreaks includes three in
Switzerland, four in Germany, and 16 in France.
Whereas the disease was reported as sporadic in
South Africa, it is considered endemic in the USA.
High clinical attack rates were seen in ponies andhorses on a premises in one western state and incorralled wild horses in two states.
Equine herpesvirus 1 (EHV-1) related diseases
were reported by France, Germany, Ireland, Japan,
Switzerland, the UK, and the USA. Fever withor without respiratory disease was confirmed on
two premises in France. Ireland reported fourcases of infection. Germany, Switzerland, and the
UK recorded one or two outbreaks and the USA
reported that the disease was present in various
states. Cases of abortion were diagnosed in France(two outbreaks), Germany (three outbreaks), Japan(10 outbreaks), the UK (two outbreaks), and theUSA (one outbreak). EHV-1 related neurologic
disease was recorded in France (one case), the UK(isolated cases on two premises), and the USA (fouroutbreaks on facilities in California, Colorado,
Maryland, and New Jersey, each involving a single
case of the disease).
Equine herpesvirus 4 was reported by France,
Germany, Ireland, and the UK. The number ofoutbreaks varied from one in Ireland, three inGermany, four in the UK, and 14 in France.
The USA recorded multiple cases of equine
herpesvirus 2 and/or 5 infection, some associatedwith respiratory disease, in several states.
Equine infectious anemia was confirmed inGermany, Switzerland, and the USA. The disease
was identified on three premises in Germany,
one in Switzerland, and two in the USA, both
epidemiologically linked, with three cases on eachpremises.
France and Switzerland reported the presenceof equine piroplasmosis. France considered theinfection endemic and Switzerland recorded asingle case of the disease.
Contagious equine metritis was diagnosed inGermany. Ten Icelandic stallions and five mares
were confirmed positive on a total of 13 premises.
France diagnosed a case of equine coital exanthema (equine herpesvirus 3) on two premises aswell as one case of leptospiral abortion.
Nocardioform placentitis was confirmed in
Kentucky, USA, with five cases caused by Amycolatopsis spp and two by Crossiella equi.
Twenty-three cases of salmonellosis were reported by the USA during the second quarter of
2017; reported serogroups included B (15), C1(2), and C2 (6).
The USA confirmed three cases of Clostridium
perfringens Type A genotype in foals in Kentucky,
one case of Tyzzer’s disease (C. piliforme), andisolated cases of C. novyi and C. sordelli infection.
Three outbreaks of rotaviral diarrhea wererecorded in France. The USA reported a case of
proliferative enteropathy (Lawsonia intracellularis)in a foal.
Rhodococcal related disease was reported as
endemic in the USA, with 22 cases recorded during
the review period.
Switzerland diagnosed two cases of atypicalmyopathy and four cases of ehrlichiosis, the latter
involving three premises.
West Nile encephalitis was reported by South
Africa (44 cases, lineage 2 virus) and the USA (onecase). Five of the cases in South Africa represented
co-infection with equine encephalosis virus andthree others with Middleburg virus.
Equine encephalosis was reported by South
Africa and confirmed mostly in Gauteng Province.
Encephalitis due to Middleburg virus was reported
across South Africa with 41 confirmed cases, two of
which were co-infections with equine encephalosis
virus.

Equine Colic UpdateThere is a prophecy about equine colic: As longas there are horses, they will have colic. Basedon reports in the literature over the last 50 years,
the incidence of all colic cases has not changed overtime and the incidence in a normal horse population ranges from 1 to 10 episodes of colic per 100
horses each year. However, horses that have had
one or more previous episodes of colic have an
incidence rate up to 5 times higher. Survival varies with the severity of the disease, but the overallmortality rate for all types of colic in horses isapproximately 7%-10%, second only to fatalities
due to musculoskeletal injuries. Incidence varies
from farm to farm based on management, with ahigher frequency expected in specific populationsof horses such as broodmares near term, horses
with small strongyle infection, or those exposed
to abrupt changes in management. Horses being
treated for eye disease and those hospitalized aftergeneral anesthesia for elective procedures also havean increased incidence of colic.
The causes of these acute intestinal diseases
remain elusive. Simple colic, commonly diagnosed
as “gas colic,” “spasmodic colic,” or “ileus,” makes
up approximately 85% of all colic episodes, yet
the cause or mechanism for these gastrointestinal
abnormalities remains unknown. Similarly, thecause of diseases with a higher morbidity andmortality such as intestinal strangulations haveno known cause. Epidemiological research overthe past three decades has identified risk factors
appearing to have a causal relationship, yet specificmechanisms such as why intestine twists and strangulates on its mesentery is unknown. Alteration
in intestinal function is most likely multifactorial,with combined event and environmental factors
increasing risk.

Numerous factors are reported to increase colicrisk including some basic husbandry and feedingpractices (see Table 1). Some of these factors are
non-specific, but still are significantly related toincreased colic risk.
Over the last four to five decades, survival has
improved for the most life-threatening types ofcolic. During the 1960s to 70s, the survival rate
for severe obstructions and strangulations was reported at less than 50%. Although improvements
in surgical expertise, anesthesia, and postoperative
medical care are associated with improved survival,
rapid recognition of the need for surgery or criticalcare by veterinarians is a major reason for the improvement. With a rapid assessment and decision
for specialty care, survival of 80%-90% can now
be expected.
Multiple aspects of the pathophysiology of colic
have been investigated. Research on intestinal motility, systemic inflammatory response syndrome(also known as endotoxic shock), intestinal injury
and inflammation, parasite control, gastric ulcers,
surgical techniques, and response to therapy haveall improved the understanding of events that
occur during colic. There is no question the additional information has changed the veterinarian’s
ability to improve colic treatment and survival.
Still, how intestinal dysfunction and systemic
responses are initiated remain to be discovered.
More research is needed if we are to change thecolic prophecy.
Contact:
Nathaniel A. White, DVM, MS, DACVS
nawhite2@vt.edu(703) 771-6800
Marion duPont Scott Equine Medical Center
Virginia-Maryland College of Veterinary Medicine
Leesburg, Virginia

Equine Influenza Beyond EquinesThe human “influenza season” in North America is now about to begin again, while in SouthAmerica spring is approaching and their influenza
season is almost over. The influenza season happens
every year during autumn, winter, and early springmonths, and the influenza viruses that circulate
each season tend to be the usual suspects: influenza
A/H1N1, A/H3N2, and influenza B viruses.
However, there are many other influenza virusesin the world. The ‘H’ and ‘N’ varieties (called“subtypes”) of influenza A viruses now go up to
H18 and N11 with the recent discovery of new

subtypes in bats. Most of these subtypes are rarein mammals but common in wild waterfowl. The
only influenza subtypes that have been confirmed
to infect horses naturally are H3N8 and H7N7,
and the horse-adapted H7N7 viruses appear tohave disappeared from horses nearly 40 years ago.
Does this mean that horses cannot be infectedby influenza viruses from other species of animals?
The answer is no, possibly they can be. Transmission of influenza viruses between different species
definitely occurs. Humans, swine, dogs, cats,
whales, seals, and sometimes other mammals

Table 1.
Factors predisposing to colic• Breed• Older age• Increased time in a stall• Cribbing/crib-biting• Recent transport• Inactivity following injury• Change in weather• Diet change• Round bale hay• High concentrate feeds• Decreased potable water• History of colic• Absence of deworming• Absence of dental exams• Tapeworm infection
Source: Cohen ND, Epidemiologyof risk factors, in The Equine Acute
Abdomen, Wiley, 2017 in press.

such as mink have occasionally been infected byinfluenza viruses from birds. This was long thought
to happen only rarely, but since 1997 in southeast
Asia there have been annual occurrences of humans
contracting bird flu subtypes such as H5N1 or
H7N9 and these cases are often lethal. Almost allof these cases have been dead-end transmissions,meaning that each case appears to be a separate
event with very little sign that they are capable of
spreading from human to human.
Can bird flu viruses infect horses? The answer
is most likely yes. One piece of evidence is thatthe H3N8 subtype was not always circulating inhorses; it first appeared in 1963, and its genetic ancestors seem to have been bird flu viruses. In 1989
in northern China a strain of bird flu was positively
confirmed to cause a large-scale disease outbreakin horses. Its subtype was also H3N8. Was thatcoincidence or is there some unique characteristicof the H3N8 subtype that makes it more apt toinfect horses? Those questions remain unanswered.
It is known that the molecular receptors present
on the surface of horse tracheal respiratory cells area little different from other species, which could
be a contributing factor to the specificity of theinfluenza viruses that infect horses. Work in theauthor’s laboratory suggests that this not the entire
explanation and other factors must be involved.
A related question is whether influenza viruses
can be transmitted from horses to other mammals.
That answer is definitely yes. About 15-20 years

ago, H3N8 horse flu infected dogs in the USA andhas persisted in dogs ever since. Can it jump fromdogs back into horses?—maybe, although once thevirus adapted to dogs, it became much less adapted
to horses.
Are humans at risk of infection from equine
influenza viruses? Experimental infection of human volunteers conducted 50 years ago suggeststhat infection can happen but the result is mild oreven sub-clinical. Humans with horse exposure dosometimes develop antibodies against equine influenza virus. The only report of a suspected naturally
occurring clinical disease from equine influenza
virus in a human never actually demonstrated thepresence of equine influenza virus in that patient.
The message for readers is: Transmission of
influenza viruses from one species to anothercan happen and sometimes does happen. If yourhorse is sick with the flu, take elementary biosafety
precautions such as washing hands and clothes or
equipment that came in contact with that horse,
as soap will kill influenza viruses. And if you aresick with the flu, it is probably best not to cuddle
your pets.
Contact:
Thomas M. Chambers, PhD
tmcham1@uky.edu(859) 218-1126
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, KY

N AT I O N A L

Equine Identification in the United StatesT

he need for horse identification spans back to
the 1800s, when branding cattle and horses
was commonplace for tracing these animals to
specific ranches or owners. Historically, horses wereidentified by physical description. With many solid
horses without unique identifying markings, thisidentification modality had limited usefulness. For
example, it would be challenging to individuallydescribe a group of yearling Friesian fillies in a field.
The transition to utilization of individual animalbrands and lip tattoos aided in the identificationof equine in the United States. Unfortunately, therecognized disadvantages of these identification
modalities include inducing pain and stress in the
animal, potential transmission of disease agents,

and inherent safety issues associated with theprocedures. Additionally, brands can be considered unsightly, difficult to read, and altered.Over
the years, the industry has researched innovative
ways to uniquely identify horses. Iris scanning wasdeveloped by Japanese researchers in 2000, but theexpense of this process and limited access to reading equipment made this a non-viable option. The
recent advances in microchip technology has madethis procedure the desired identification modalityof the future. Today, the international standards
for acceptable microchips are:• ISO 11784/11785 compliant and ICAR certified• 15-digit numeric, no letters format• 134.2 kHz frequency

Equine Disease Quarterly Newsletter
Concerns have been raised regarding impactof the invasive procedure and longevity of the
microchip. However, subsequent microchip implantation studies have proven that microchip
administration yields minor transient pain andinflammation at the injection site and minimal
microchip migration following the correct implantation in a horse.
Recently, improved microchip temperaturesensing technology has enabled accurate bodytemperature recording. Not only does this type ofchip provide a unique individual identification, but
it also provides a value added health monitoring
benefit. For example, should an equine herpesvirus
myeloencephalopathy incident occur at a large
boarding facility, management could easily andrapidly monitor temperatures via the biothermal
microchip and move horses with elevated temperatures to isolation before the horses start shedding
virus.
In the last five years, the equine industry in the
United States has embraced the use of microchips
for equine identification. In 2008, the Jockey
Club began offering microchips for sale to its
members. The Jockey Club began mandating thatthoroughbred foals have an ISO 11784/11785
compliant microchip implanted starting with the2017 foal crop. Impressively, Jockey Club members embraced microchipping technology andtwo-thirds of the 2016 foal crop were voluntarily
microchipped. Recognizing the need and benefit of
microchipping, the United States Hunter Jumper
Association (USHJA) passed a regulation 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 microchip will be required for
all horses competing in USHJA competitions. At
the recent Equine Identification Forum in January
2017, the industry recognized the great strides thathave been taken related to equine identification
but agreed that additional efforts are necessary forindustry wide acceptance of microchipping. For
more information on the Forum discussions visit
http://www.animalagriculture.org/proceedings/
equineidforum.
Contact:
Dr. Katie Flynn
kflynn@cdfa.ca.gov(916) 900-5039
Equine Staff Veterinarian
California Department of Food and Agriculture
Animal Health Branch
Sacramento, CA

KENTUCKY

Clostridium Perfringens andNecrotizing Enterocolitis in Neonatal Foals

N

ecrotizing enterocolitis (damage and death ofcells in small intestine and colon) is a serious
disease of sudden onset in foals less than 4-6 daysof age associated with a high death rate, despite
therapeutic interventions. Clinical manifestationsof enterocolitis in foals vary from being founddead to a spectrum of clinical manifestations.
The most common of these include failure tosuck, fever, depression, severe colic, and diarrhea.
Although the association of Clostridium difficile,
Neorickettsia risticii (Potomac horse fever) andSalmonella infection with enterocolitis in adulthorses 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 acquisitionof this bacterium by the foal from the mare’s teatsor the environment, the organism multiplies rapidly in the stomach and intestines. C. perfringens
numbers are reduced fairly quickly, so that by thetime foals are several months of age, the organism is found in relatively low numbers within thelarge intestine. The almost universal presence of C.
perfringens, belonging to the type A group, in theintestine of healthy young animals has complicatedthe 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 wellestablished but relatively uncommon cause of necrotizing enteritis. The other is C. perfringens typeA, which includes a small subset that produces anovel pore-forming toxin called NetF (Necrotizing
enteritis toxin, Foal). This novel toxin is related

Department of Veterinary Science
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky 40546-0099
Address Service Requested

Equine Disease Quarterly Newsletter
Department of Veterinary Science
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky 40546-0099
Address Service Requested

to the beta toxin of type C strains that causes
severe enteric disease in foals, other species, andin humans. We found netF-positive C. perfringens
in 74% (11/15) of foals with necrotizing enteritis
but not in 11 foals with undifferentiated diarrheal
illness. In another study, netF-positive C. perfringens was identified in 6 of 23 isolates from foals
in Kentucky with severe enteritis. In adult horses
with undifferentiated diarrhea, the detection rateof netF among C. perfringens isolates was low(4/58). This would suggest this toxin is primarily
associated with severe enteritis in neonatal foals.
One explanation why type C and netF-positive
type A C. perfringens cause necrotizing enteritis invery young foals is because of the trypsin inhibiting
effect of colostrum. Trypsin is a protein-degrading
enzyme secreted by the pancreas during digestion, and its inhibition by colostrum prevents thebreakdown of protein toxins, such as NetF. The
reservoir for NetF-producing C. perfringens is not
yet known.
Real-time PCR can be used to rapidly diagnose
necrotizing enteritis caused by netF-positive C.
perfringens. An alternative but slower approach is
to culture C. perfringens and confirm the presenceof toxin genes (cpb for type C and netF for type A)
by PCR.
In terms of prevention, an autogenous bacterintoxoid vaccine has been used for mare immunization in Kentucky in an attempt to prevent type A
C. perfringens enteritis in foals. This vaccine likely
includes NetF toxin since mares immunized withthe vaccine have antibodies to NetF. Hyperimmune plasma is commercially available for theprevention or treatment of necrotizing enteritis in
foals caused by C. perfringens types A (includingNetF), C, and D.
Although the discovery of NetF has furthered
our understanding of C. perfringens enterocolitis in
foals, further work is required to fully understandhow NetF-producing type A C. perfringens causes
disease. Research studies are slowly chipping away
at C. perfringens enterocolitis, and the discovery of
NetF has been another important step forward.
Contact:
Iman Mehdizadeh Gohari
imehdiza@uoguelph.ca
John F. Prescottprescott@uoguelph.ca(519) 824-4120 ext. 54716
Department of Pathobiology
Ontario Veterinary College
University of Guelph, Canada