Equine Disease Quarterly Newsletter

KENTUCKY

Equine Tyzzer’s Disease Update: January 1993-April 2015

T

yzzer’s disease was originally described in micein 1917, and since then has been diagnosed in
multiple species of domestic animals and wildlife
worldwide. Tyzzer’s disease is highly fatal in young
foals, and is caused by the bacterium Clostridium
piliforme. The organism is an intracellular pathogen that primarily infects the lower intestinal tract

and can disseminate through the circulatory or
lymphatic systems to visceral organs.
C. piliforme can cause subclinical infections, but
infections are commonly acute and fatal in foals.
Foals are usually found comatose or dead, but clinical signs can include depression, anorexia, pyrexia,
jaundice, diarrhea, and recumbency. Affected foals

JULY 2015
Volume 24, Number 3

C O M M E N TA RY
IN THIS ISSUE
Commentary
International
First Quarter2015  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2Working Equids
in Low-Income
Countries .  .  .  .  .  .  .  .  .  .  .  . 3National
Atopic Dermatitis .  .  .  . 3Vesicular Stomatitis . . 5

12Kentucky

10

Tyzzer’s Disease
Update .  .  .  .  .  .  .  .  .  .  .  .  .  . 5

8
6
4
2

Year

with the breed distribution typically seen at thediagnostic lab. The ages of affected foals ranged
from 7 to 270 days with an average age of 26 days.
Fifteen foals were 30 days of age or older. Of the 92
cases, 89 died in the months of February throughJune. The other three cases occurred in January,
July, and October.
CONTACT
Dr. Jacqueline Smith(859) 257-8283
jsmit8@uky.edu
University of Kentucky
Veterinary Diagnostic Laboratory
Lexington, Kentucky

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20

11
20

09
20

07
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05
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03
20

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20

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are typically between one to six weeks of age, but
most cases occur between one and two weeks ofage. The disease primarily affects the liver, causing
necrotizing hepatitis.
Antemortem serology and fecal polymerase
chain reaction (PCR) assays can be used to test forC. piliforme, however results must be interpreted
in combination with appropriate clinical signs tomake a presumptive clinical diagnosis. A definitive
diagnosis is made upon postmortem examinationand is accomplished by associating the organismwith characteristic liver lesions; this association canbe made by microscopically visualizing the organism or by detecting the organism’s genetic material
by PCR. There is no known effective treatment forthe disease, and vaccines are not available.
Over the last 23 years, 92 cases of Tyzzer’s
disease have been diagnosed at the University of
Kentucky Veterinary Diagnostic Laboratory (Figure 1). The disease was identified in 44 colts, 36
fillies, and in 12 foals where the sex was not noted.
Of the 92 cases diagnosed, there were 82 Thoroughbreds, three Tennessee Walking Horses, one
Quarter Horse, one Standardbred, one Paint, one
Morgan, and three foals without breed notation.
The high number of Thoroughbreds is consistent

19

CONTACT
Dr. Angela Pelzel-McCluskey(970) 494-7391
Angela.M.Pelzel-McCluskey@aphis.usda.gov
USDA-APHIS-Veterinary Services
Fort Collins, Colorado

Address Service Requested

95

ally, extensive fly control was necessary to prevent
transmission and the development of additional
cases. Long quarantine periods, experienced while
affected animals healed for an average of 30 days or
more, caused additional strain and, in some cases,
prevented horses from being used for their intended purpose during the prime summer and fallshow season. Quarantines placed on large boarding
facilities were especially difficult to manage forowners, barn managers, veterinarians, and regulatory personnel. On another level, equine events in
VS-affected states also suffered serious impacts.
While most events were not cancelled, unless theevent facility itself had been quarantined, there
was still reduced attendance at events in affectedstates due to movement restrictions and difficultyin getting out-of-state and Canadian horses backhome after entering a VS-affected state. Finally,
international movement of horses from the U.S.
was impeded by destination countries imposing
strict VS testing requirements or not allowing
entrance of horses from certain states.
While it remains to be seen whether the 2015
VS outbreak will approach the size and scope of the2014 experience, it seems certain that the equine
industry will again have to contend with some
impacts this year, economic and otherwise.
For current information on the 2015 VS outbreak, see the VS situation reports on the APHIS
website at: http://www.aphis.usda.gov/wps/portal/
aphis/home/

19

esicular stomatitis (VS) is a viral disease that
can affect many livestock species, most often
in horses and cattle. The virus causes vesicles (blisters) that form primarily on the lips and tongue,
around the mouth or nose, along the udder or
sheath, or along the coronary bands. These viruscontaining vesicles later rupture, forming erosions
and ulcers. The disease is transmitted by biting flies,
mainly black flies and sandflies, or biting midges.
There is no specific treatment for the disease, only
supportive care until the lesions heal. The impact ofthe disease on the individual horse varies, depending on the location of the lesions. Severe mouth
and tongue lesions can interfere with the horseeating or drinking and severe coronary band lesions
can result in temporary lameness. VS is a reportable disease in the U.S. and affected premises areplaced under quarantine to prevent disease spread.
The recent identification of VS cases in Arizona, New Mexico, and Utah marked the start ofa 2015 outbreak in the U.S. This comes on theheels of a significant VS outbreak during 2014
in which a total of 435 premises in Arizona,
Colorado, Nebraska, and Texas were confirmed
infected; 408 of which involved affected equines.
The 2014 outbreak was the worst VS outbreak in
the U.S. since 2005, and the economic impacts ofthe disease were felt within the equine industry at
multiple levels. While the exact dollar amount for
the economic loss cannot be quantified, Colorado
was certainly the hardest hit and had a total of 370
VS-affected premises in 17 counties.
Beginning at the individual equine premiselevel, owners were first faced with veterinary bills
for confirmation of the disease and supportive carethat was needed for horses with lesions. Addition-

93

V

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

19

Economic Impacts of Vesicular Stomatitis Outbreaks

5

Presorted Standard
US Postage Paid
Permit 51
Lexington KY

Figure 1. Incidenceof Tyzzer’s Diseasediagnosed at the UK
Veterinary Diagnostic
Laboratory, 1993-2015.

Let’s just jump to the bottom line: If you hear
thunder you (and your horse) can be struckby lightning.
Summer is the long-awaited horseback riding,horse event, and trail riding season. Summer isalso peak season for lightning strikes in the US,
although lightning can occur year-round. According to the National Oceanic and Atmospheric
Administration (NOAA), an estimated 25 million
lightning strikes occur in the US every year.
Human deaths due to lightning are well documented. According to NOAA, from 2006-2014,
287 people were killed by lightning in the US.
Statistics on lightning-related deaths of horses are
not maintained. However after just one April 2015
thunderstorm in central Kentucky, three horses
from one farm and two cattle from another farm
were killed by lightning.
Organized trail rides, horse shows, race tracks,sales venues…how many have a responsible person
monitoring weather who has the knowledge andauthority to stop the event in case of an inboundthunderstorm? Guidelines are useless unless they
are up-to-date and followed, from county horseshows to international competitions.
An outdated guideline (but one still referenced)
is the 30/30 rule: If thunder is heard less than 30
seconds after seeing lightning, an outdoor event
should be stopped and not started until 30 minutes
after the severe weather has passed.
Don’t bother counting. If you can hear thunderor see lightning, you can be struck by lightning.
There is no safe place to be outdoors!
Horse event organizers have much to learn
from the United States Golf Association (USGA).
At USGA national championships—and at mostregional and local tournaments run under USGA
guidelines—an official monitors weather radar
when players are on the golf course. This person

is in contact with the official-in-charge of theevent who has the authority and the obligation tosuspend play in the event of threatening weather.
Comprehensive evacuation plans are drawn up
before a tournament. These plans typically designate several specific evacuation points around thegolf course, where players have access either tosafe areas or transportation to the clubhouse. Oncourse officials are required to know evacuation
locations and are responsible for getting players
and their caddies to safety when the horn sounds
and play is suspended. Players know this standardized procedure.
How many times have you seen horse shows
continuing with classes when thunder can beheard, or seen jockeys riding racehorses into a
metal starting gate during a thunderstorm? We
would challenge all organizers of equestrian events
to develop, implement, and communicate a severe
weather plan that is based on science and the safetyof humans and horses. Until then, individuals
need to have their own plan for safety by taking
weather spotter classes, having a NOAA weather
radio, getting a weather app for cell phones, andusing common sense. Sitting atop a horse withmetal horse shoes on is a bad place to be during athunderstorm. Remain weather-aware and ensure
people and horses are in safe places before severe
weather strikes!
CONTACT
Matt Dixon(859) 218-4363
matt.dixon@uky.edu
Meteorologist, Biosystems & Agricultural Engineering;
Dr. Roberta Dwyer(859) 218-1122
rmdwyer@uky.edu
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky

Working Equids in Low-Income Countries–
Impact of Infectious Disease

2

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

First Quarter 2015

T

Equine Disease Quarterly
Editors

Roberta Dwyer
Alan LoynachanPeter Timoney

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://www.ca.uky.edu/
gluck/index.htm
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 Center, Newmarket, United Kingdom, and other sources
reported the following disease outbreaks.
The final outbreak in the 2014/2015 occurrenceof vesicular stomatitis in the USA was reported
early in the first quarter of 2015. It involved two
horses on a premises in southern Arizona, both
infected with the New Jersey serotype of the virus.
One case of glanders was confirmed in Germany. There was no evidence of spread of infection
to other horses on the index premises. The sourceof infection remains undetermined.
Outbreaks of strangles were reported by Denmark, France, Germany, Ireland, and the USA.
Denmark confirmed an isolated case of the disease. A total of 14 outbreaks were diagnosed in
France, involving primarily Thoroughbreds andWarmbloods. Germany and the USA reported
that strangles was endemic. The disease was considered widespread in Germany. At least 16 statesin the USA recorded outbreaks of strangles, withmultiple cases confirmed on premises in Kentucky,
Maryland, and South Carolina.
Equine influenza was reported by France, theUK, and the USA. Three outbreaks were confirmed
in France and five in the UK. The USA reported
influenza as endemic, with outbreaks diagnosed
in Kentucky (two), Michigan (one), and South
Dakota (one).
Equine herpesvirus-1 and -4 (EHV-1 andEHV-4) related diseases were recorded in France,
Germany, Ireland, Japan, Switzerland, the UK,
and the USA. Respiratory disease was confirmed in
France (five outbreaks), Ireland (12 cases), Switzerland (undefined number on several premises), theUK (three cases, separate premises), and the USA(disease endemic, indeterminate number of cases).
Abortion due to EHV-1 was diagnosed in France(eight cases, all but two on individual farms),
Germany (five cases), Japan (28 cases together withdeaths in eight neonatal foals on 19 premises),
and the USA (five cases). EHV-1 associated neurologic disease was reported by France (one case),
Germany (two cases), Switzerland (cases on several
premises), and the USA (two cases). Respiratory
disease caused by EHV-4 was confirmed by France(15 outbreaks), Germany (one case), Switzerland(indeterminate number on several premises), andthe UK (four outbreaks on separate premises). The
UK reported one case of EHV-4 abortion.
Two cases of equine coital exanthema (EHV-3)
were confirmed in the USA (Kentucky).
Numerous cases of EHV-2 infection associatedwith signs of respiratory disease were reported in
the USA. A few were dual infections with EHV-5.
Cases of equine arteritis virus infection wererecorded by Germany (carrier stallion) and
Switzerland (one case). Canada and Germany
reported equine infectious anemia. Four cases
were confirmed on individual premises in twoWestern provinces in Canada; three outbreaks wererecorded in Germany.
Equine piroplasmosis was considered endemic
in France and the United Arab Emirates, withisolated clinical cases in non-Thoroughbreds inthe latter.
Germany reported contagious equine metritis
in two non-Thoroughbred stallions on one premises.
Infection with Leptospira spp. was confirmed
by France (one case of uveitis) and the USA (twocases of abortion). The USA diagnosed six cases ofnocardioform placentitis and abortion.
Cases of salmonellosis were reported by Ireland (three cases), Switzerland (two cases of S.
typhimurium), and the USA (eight outbreaks associated with Salmonella Group C3 strains).
Clostridial enteritis was recorded in the USA
including isolated cases of C. perfringens Type A
in foals, two cases of C. difficile, and one case of
C. sordellii. The USA also reported cases of equine
proliferative enteropathy in Thoroughbred foals in
two states.
Two outbreaks of rotavirus infection were recorded in France.
A fatal case of Eastern equine encephalomyelitis
was confirmed in a horse in Florida, USA.
Rhodococcal-related disease was reported as
endemic in the USA, with at least 22 cases diagnosed.
Infection with Corynebacterium pseudotuberculosis was reported as endemic in the USA.
Ireland reported three cases of atypical myopathy.

M

ost of the horses and donkeys in the world
live with and work for poor people. The
impact of these animals on the lives of poor people
is enormous and global. Working equids reducepoverty, provide food security, and help promote
gender equity for much of the “bottom billion” of
the world’s growing population.
Despite these critical roles, somehow the world
has largely forgotten these animals. We don’t evenproperly count them; the Food and Agriculture
Organization of the United Nations’ estimate of
the global equine population, at approximately
113 million, is widely regarded as a gross underestimate because of their routine omission fromcensus data. Despite the enormous positive impactof these horses and donkeys on people, humanity
frequently fails to prioritize their health.
An international Havemeyer Workshop reportpublished in the January 2015 Equine Veterinary
Journal described strategies to reduce the burdenof infectious diseases in working equids worldwide.
The task is daunting, and the solutions needed arediverse. Technical solutions such as new diagnostic
tests and vaccines represent only a part of the answer, as there are extensive social-behavioral andinstitutional barriers to overcome.
The workshop proposed three categories of
diseases. The first category includes diseases such
as African horse sickness, rabies, tetanus, andgastrointestinal parasites, for which most technical barriers have been overcome, but which need
improved surveillance, owner education, and advocacy at the governmental level in order to achieve
progress. A second category includes diseases forwhich significant gaps still exist in our technicalunderstanding and resources, such as epizootic

3

4

lymphangitis, piroplasmosis, and trypanosomiasis. A third category includes syndromic diseases,
where the role of infectious agents has not been
defined, including respiratory, neurologic, andanemia syndromes that are highly prevalent inthese populations.
The challenges that complicate addressing infectious diseases in working equids are captured by the
One Health paradigm. Both people and animals
face environmental factors such as water shortage,
climate change, and environmental pollution toname but a few that shape the infectious diseases
from which they suffer. Impoverished humans andanimals have limited access to pharmaceutical treatments that often are of questionable quality andfrequently are misused in ways that can exacerbate
problems such as antimicrobial resistance. For
investigators like me, who have spent our careers
pursuing technical advances in vaccine or diagnostic technologies, it is vital that we understand that
education and advocacy, at both the governmental
and local levels, are likely to be more importantin addressing the enormous impact of infectious
disease in working horses and donkeys. It is instructive to study the evolving behavior of majorcharities that operate in this area, such as SPANA,
the Brooke, and the Donkey Sanctuary. While theirclinical hospitals are still central pillars of activities,
efforts are currently focused on building sustainablelocal capacity and educational development.

USEF Drugs andMedications Rules
 The most common medica-

CONTACT
Dr. D. Paul Lunn(919) 513-6210
dplunn@ncsu.edu
College of Veterinary Medicine
North Carolina State University
Raleigh, North Carolina

N AT I O N A L

Atopic DermatitisA

topic dermatitis, defined as an allergic reaction to environmental allergens (pollens, barn
dust, molds, etc.), is probably more common inhorses than currently reported. It may be seasonalor, in climates such as California, year round. The
three most common presentations are urticaria(“hives”), urticaria with pruritus (itching), andpruritus alone. Pruritus most commonly affects

the face and trunk. Seasonal signs would be mostconsistent with allergy to pollens; year-round signs
would be more consistent with an allergy to molds
or barn dust. Urticaria, secondary to atopic dermatitis, may be a familial problem in some horses.
Diagnosis of atopic dermatitis is based on clinical signs and the exclusion of other diagnoses (especially Culicoides [“no-see ums”] allergy). Horses

may have a secondary bacterial skin infection(pyoderma), typified by excess scale, particularlyin the shape of a circle (epidermal collarettes).
Intradermal tests (IDT) or serum allergy tests
may be performed to identify allergens which
may be used for hyposensitization (allergy shots,
or more recently available, oral drops). Horses
with atopic dermatitis and recurrent hives generally have a higher incidence of positive reactions
than healthy horses, but the diagnosis (as in otherspecies) cannot solely be made on the basis of the
IDT or serologic testing alone. Any testing should
be interpreted in light of the history of the disease
and used to determine which allergens might beuseful to use in hyposensitization, should the owners elect that route of treatment.
Medical therapy may include corticosteroids;
prednisolone or dexamethasone are the mostcommonly used. Prednisolone seems to be better
absorbed orally in horses than prednisone. The
injectable dexamethasone solution may be usedorally, although the bioavailability is 60%-70% of
the injectable route. Antihistamines are sometimes
quite effective: hydroxyzine pamoate, cetirizine, or
doxepin (a tricyclic anti-depressant with antihistaminic effects). Antihistamines rarely cause either
drowsiness or excitability in horses, although theauthor has seen these adverse effects in less than 5%of horses receiving these drugs. The commonly usedantihistamine pyrilamine maleate has been shown

MATT BARTON, AGRICULTURAL COMMUNICATIONS, UNIVERSITY OF KENTUCKY

tions used for the treatment of
atopic dermatitis in horses are
considered forbidden under
the United States EquestrianFederation’s (USEF) Equine
Drugs and Medications Rules.
As identified by Dr. Stephen
D. White, these usually include
antihistamines and corticosteroids. In addition to limiting
the use of forbidden substances,the Equine Drugs and Medications Rules provide for legitimate use of these medications
with the proper withdrawal anddocumentation. Conditions fortherapeutic administrations offorbidden substances include
that the medication must be
for the diagnosis or treatment

to have poor bioavailability when given orally in thehorse, but detectable in the urine up to one week
after a single dose, which may present difficulties
with withdrawal times. Some clinicians have noted
improvement when an essential fatty-acid productis added to the feed as an adjunctive treatment.
Atopic dermatitis has been successfully managed with hyposensitization, with horses showing
improvement as early as two months into treatment. However, a full 12 months of hyposensitization should be given before fully evaluating its
effectiveness, and veterinarians should maintainconsistent communication with the client to monitor the progress of the treatment and to encourage
the owner to continue with the injections for thefull year. While in other domestic species it isthought that most patients will need to be maintained on the injections for life, in the horse, thismay not be true, as a small number of horses have
had the hyposensitization injections stopped anddid not relapse. In general, approximately 70% of
atopic horses improve with hyposensitization. (Seebelow.)CONTACT
Dr. Stephen D. White(530) 752-5908
sdwhite@ucdavis.edu
School of Veterinary Medicine
University of California
Davis, California

of an existing illness or injury,
and that the horse must bewithdrawn from competition
for a period of no less than 24hours following the administration. Additionally, a medication
report form must be filed in
the competition office withthe show Steward or Technical Delegate within one hour
following the administration.
Medication reports can also be
filed online at https://www.usef.
org/_IFrames/Drugs/MedicationReportForm/.
 One corticosteroid, dexamethasone, is quantitatively
restricted and no medication
report form is necessary. However, there are recommendations for its use that need to bestrictly followed to avoid an excessive level of drug in the horseat the time of competition.
These recommendations can befound at https://www.usef.org/
documents/drugsMeds/2015/
drugsmedsguidelines15_web.
pdf. The treatment of atopic
dermatitis using hyposensitization is permitted under USEF
rules as long as no injections
take place within the 12 hours
prior to competing; no medication report form is required. For
further information regarding
the use of medications whileremaining compliant with the
Equine Drugs and Medications rules, please visit https://www.usef.org/_IFrames/Drugs/
Default.aspx or call 1 (800)633-2472.
Dr. Stephen Schumacher, Chief
Administrator, USEF Equine Drugs
and Medications ProgramWorking Equids in Low-Income Countries–
Impact of Infectious Disease

2

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

First Quarter 2015

T

Equine Disease Quarterly
Editors

Roberta Dwyer
Alan LoynachanPeter Timoney

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://www.ca.uky.edu/
gluck/index.htm
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 Center, Newmarket, United Kingdom, and other sources
reported the following disease outbreaks.
The final outbreak in the 2014/2015 occurrenceof vesicular stomatitis in the USA was reported
early in the first quarter of 2015. It involved two
horses on a premises in southern Arizona, both
infected with the New Jersey serotype of the virus.
One case of glanders was confirmed in Germany. There was no evidence of spread of infection
to other horses on the index premises. The sourceof infection remains undetermined.
Outbreaks of strangles were reported by Denmark, France, Germany, Ireland, and the USA.
Denmark confirmed an isolated case of the disease. A total of 14 outbreaks were diagnosed in
France, involving primarily Thoroughbreds andWarmbloods. Germany and the USA reported
that strangles was endemic. The disease was considered widespread in Germany. At least 16 statesin the USA recorded outbreaks of strangles, withmultiple cases confirmed on premises in Kentucky,
Maryland, and South Carolina.
Equine influenza was reported by France, theUK, and the USA. Three outbreaks were confirmed
in France and five in the UK. The USA reported
influenza as endemic, with outbreaks diagnosed
in Kentucky (two), Michigan (one), and South
Dakota (one).
Equine herpesvirus-1 and -4 (EHV-1 andEHV-4) related diseases were recorded in France,
Germany, Ireland, Japan, Switzerland, the UK,
and the USA. Respiratory disease was confirmed in
France (five outbreaks), Ireland (12 cases), Switzerland (undefined number on several premises), theUK (three cases, separate premises), and the USA(disease endemic, indeterminate number of cases).
Abortion due to EHV-1 was diagnosed in France(eight cases, all but two on individual farms),
Germany (five cases), Japan (28 cases together withdeaths in eight neonatal foals on 19 premises),
and the USA (five cases). EHV-1 associated neurologic disease was reported by France (one case),
Germany (two cases), Switzerland (cases on several
premises), and the USA (two cases). Respiratory
disease caused by EHV-4 was confirmed by France(15 outbreaks), Germany (one case), Switzerland(indeterminate number on several premises), andthe UK (four outbreaks on separate premises). The
UK reported one case of EHV-4 abortion.
Two cases of equine coital exanthema (EHV-3)
were confirmed in the USA (Kentucky).
Numerous cases of EHV-2 infection associatedwith signs of respiratory disease were reported in
the USA. A few were dual infections with EHV-5.
Cases of equine arteritis virus infection wererecorded by Germany (carrier stallion) and
Switzerland (one case). Canada and Germany
reported equine infectious anemia. Four cases
were confirmed on individual premises in twoWestern provinces in Canada; three outbreaks wererecorded in Germany.
Equine piroplasmosis was considered endemic
in France and the United Arab Emirates, withisolated clinical cases in non-Thoroughbreds inthe latter.
Germany reported contagious equine metritis
in two non-Thoroughbred stallions on one premises.
Infection with Leptospira spp. was confirmed
by France (one case of uveitis) and the USA (twocases of abortion). The USA diagnosed six cases ofnocardioform placentitis and abortion.
Cases of salmonellosis were reported by Ireland (three cases), Switzerland (two cases of S.
typhimurium), and the USA (eight outbreaks associated with Salmonella Group C3 strains).
Clostridial enteritis was recorded in the USA
including isolated cases of C. perfringens Type A
in foals, two cases of C. difficile, and one case of
C. sordellii. The USA also reported cases of equine
proliferative enteropathy in Thoroughbred foals in
two states.
Two outbreaks of rotavirus infection were recorded in France.
A fatal case of Eastern equine encephalomyelitis
was confirmed in a horse in Florida, USA.
Rhodococcal-related disease was reported as
endemic in the USA, with at least 22 cases diagnosed.
Infection with Corynebacterium pseudotuberculosis was reported as endemic in the USA.
Ireland reported three cases of atypical myopathy.

M

ost of the horses and donkeys in the world
live with and work for poor people. The
impact of these animals on the lives of poor people
is enormous and global. Working equids reducepoverty, provide food security, and help promote
gender equity for much of the “bottom billion” of
the world’s growing population.
Despite these critical roles, somehow the world
has largely forgotten these animals. We don’t evenproperly count them; the Food and Agriculture
Organization of the United Nations’ estimate of
the global equine population, at approximately
113 million, is widely regarded as a gross underestimate because of their routine omission fromcensus data. Despite the enormous positive impactof these horses and donkeys on people, humanity
frequently fails to prioritize their health.
An international Havemeyer Workshop reportpublished in the January 2015 Equine Veterinary
Journal described strategies to reduce the burdenof infectious diseases in working equids worldwide.
The task is daunting, and the solutions needed arediverse. Technical solutions such as new diagnostic
tests and vaccines represent only a part of the answer, as there are extensive social-behavioral andinstitutional barriers to overcome.
The workshop proposed three categories of
diseases. The first category includes diseases such
as African horse sickness, rabies, tetanus, andgastrointestinal parasites, for which most technical barriers have been overcome, but which need
improved surveillance, owner education, and advocacy at the governmental level in order to achieve
progress. A second category includes diseases forwhich significant gaps still exist in our technicalunderstanding and resources, such as epizootic

3

4

lymphangitis, piroplasmosis, and trypanosomiasis. A third category includes syndromic diseases,
where the role of infectious agents has not been
defined, including respiratory, neurologic, andanemia syndromes that are highly prevalent inthese populations.
The challenges that complicate addressing infectious diseases in working equids are captured by the
One Health paradigm. Both people and animals
face environmental factors such as water shortage,
climate change, and environmental pollution toname but a few that shape the infectious diseases
from which they suffer. Impoverished humans andanimals have limited access to pharmaceutical treatments that often are of questionable quality andfrequently are misused in ways that can exacerbate
problems such as antimicrobial resistance. For
investigators like me, who have spent our careers
pursuing technical advances in vaccine or diagnostic technologies, it is vital that we understand that
education and advocacy, at both the governmental
and local levels, are likely to be more importantin addressing the enormous impact of infectious
disease in working horses and donkeys. It is instructive to study the evolving behavior of majorcharities that operate in this area, such as SPANA,
the Brooke, and the Donkey Sanctuary. While theirclinical hospitals are still central pillars of activities,
efforts are currently focused on building sustainablelocal capacity and educational development.

USEF Drugs andMedications Rules
 The most common medica-

CONTACT
Dr. D. Paul Lunn(919) 513-6210
dplunn@ncsu.edu
College of Veterinary Medicine
North Carolina State University
Raleigh, North Carolina

N AT I O N A L

Atopic DermatitisA

topic dermatitis, defined as an allergic reaction to environmental allergens (pollens, barn
dust, molds, etc.), is probably more common inhorses than currently reported. It may be seasonalor, in climates such as California, year round. The
three most common presentations are urticaria(“hives”), urticaria with pruritus (itching), andpruritus alone. Pruritus most commonly affects

the face and trunk. Seasonal signs would be mostconsistent with allergy to pollens; year-round signs
would be more consistent with an allergy to molds
or barn dust. Urticaria, secondary to atopic dermatitis, may be a familial problem in some horses.
Diagnosis of atopic dermatitis is based on clinical signs and the exclusion of other diagnoses (especially Culicoides [“no-see ums”] allergy). Horses

may have a secondary bacterial skin infection(pyoderma), typified by excess scale, particularlyin the shape of a circle (epidermal collarettes).
Intradermal tests (IDT) or serum allergy tests
may be performed to identify allergens which
may be used for hyposensitization (allergy shots,
or more recently available, oral drops). Horses
with atopic dermatitis and recurrent hives generally have a higher incidence of positive reactions
than healthy horses, but the diagnosis (as in otherspecies) cannot solely be made on the basis of the
IDT or serologic testing alone. Any testing should
be interpreted in light of the history of the disease
and used to determine which allergens might beuseful to use in hyposensitization, should the owners elect that route of treatment.
Medical therapy may include corticosteroids;
prednisolone or dexamethasone are the mostcommonly used. Prednisolone seems to be better
absorbed orally in horses than prednisone. The
injectable dexamethasone solution may be usedorally, although the bioavailability is 60%-70% of
the injectable route. Antihistamines are sometimes
quite effective: hydroxyzine pamoate, cetirizine, or
doxepin (a tricyclic anti-depressant with antihistaminic effects). Antihistamines rarely cause either
drowsiness or excitability in horses, although theauthor has seen these adverse effects in less than 5%of horses receiving these drugs. The commonly usedantihistamine pyrilamine maleate has been shown

MATT BARTON, AGRICULTURAL COMMUNICATIONS, UNIVERSITY OF KENTUCKY

tions used for the treatment of
atopic dermatitis in horses are
considered forbidden under
the United States EquestrianFederation’s (USEF) Equine
Drugs and Medications Rules.
As identified by Dr. Stephen
D. White, these usually include
antihistamines and corticosteroids. In addition to limiting
the use of forbidden substances,the Equine Drugs and Medications Rules provide for legitimate use of these medications
with the proper withdrawal anddocumentation. Conditions fortherapeutic administrations offorbidden substances include
that the medication must be
for the diagnosis or treatment

to have poor bioavailability when given orally in thehorse, but detectable in the urine up to one week
after a single dose, which may present difficulties
with withdrawal times. Some clinicians have noted
improvement when an essential fatty-acid productis added to the feed as an adjunctive treatment.
Atopic dermatitis has been successfully managed with hyposensitization, with horses showing
improvement as early as two months into treatment. However, a full 12 months of hyposensitization should be given before fully evaluating its
effectiveness, and veterinarians should maintainconsistent communication with the client to monitor the progress of the treatment and to encourage
the owner to continue with the injections for thefull year. While in other domestic species it isthought that most patients will need to be maintained on the injections for life, in the horse, thismay not be true, as a small number of horses have
had the hyposensitization injections stopped anddid not relapse. In general, approximately 70% of
atopic horses improve with hyposensitization. (Seebelow.)CONTACT
Dr. Stephen D. White(530) 752-5908
sdwhite@ucdavis.edu
School of Veterinary Medicine
University of California
Davis, California

of an existing illness or injury,
and that the horse must bewithdrawn from competition
for a period of no less than 24hours following the administration. Additionally, a medication
report form must be filed in
the competition office withthe show Steward or Technical Delegate within one hour
following the administration.
Medication reports can also be
filed online at https://www.usef.
org/_IFrames/Drugs/MedicationReportForm/.
 One corticosteroid, dexamethasone, is quantitatively
restricted and no medication
report form is necessary. However, there are recommendations for its use that need to bestrictly followed to avoid an excessive level of drug in the horseat the time of competition.
These recommendations can befound at https://www.usef.org/
documents/drugsMeds/2015/
drugsmedsguidelines15_web.
pdf. The treatment of atopic
dermatitis using hyposensitization is permitted under USEF
rules as long as no injections
take place within the 12 hours
prior to competing; no medication report form is required. For
further information regarding
the use of medications whileremaining compliant with the
Equine Drugs and Medications rules, please visit https://www.usef.org/_IFrames/Drugs/
Default.aspx or call 1 (800)633-2472.
Dr. Stephen Schumacher, Chief
Administrator, USEF Equine Drugs
and Medications ProgramWorking Equids in Low-Income Countries–
Impact of Infectious Disease

2

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

First Quarter 2015

T

Equine Disease Quarterly
Editors

Roberta Dwyer
Alan LoynachanPeter Timoney

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://www.ca.uky.edu/
gluck/index.htm
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 Center, Newmarket, United Kingdom, and other sources
reported the following disease outbreaks.
The final outbreak in the 2014/2015 occurrenceof vesicular stomatitis in the USA was reported
early in the first quarter of 2015. It involved two
horses on a premises in southern Arizona, both
infected with the New Jersey serotype of the virus.
One case of glanders was confirmed in Germany. There was no evidence of spread of infection
to other horses on the index premises. The sourceof infection remains undetermined.
Outbreaks of strangles were reported by Denmark, France, Germany, Ireland, and the USA.
Denmark confirmed an isolated case of the disease. A total of 14 outbreaks were diagnosed in
France, involving primarily Thoroughbreds andWarmbloods. Germany and the USA reported
that strangles was endemic. The disease was considered widespread in Germany. At least 16 statesin the USA recorded outbreaks of strangles, withmultiple cases confirmed on premises in Kentucky,
Maryland, and South Carolina.
Equine influenza was reported by France, theUK, and the USA. Three outbreaks were confirmed
in France and five in the UK. The USA reported
influenza as endemic, with outbreaks diagnosed
in Kentucky (two), Michigan (one), and South
Dakota (one).
Equine herpesvirus-1 and -4 (EHV-1 andEHV-4) related diseases were recorded in France,
Germany, Ireland, Japan, Switzerland, the UK,
and the USA. Respiratory disease was confirmed in
France (five outbreaks), Ireland (12 cases), Switzerland (undefined number on several premises), theUK (three cases, separate premises), and the USA(disease endemic, indeterminate number of cases).
Abortion due to EHV-1 was diagnosed in France(eight cases, all but two on individual farms),
Germany (five cases), Japan (28 cases together withdeaths in eight neonatal foals on 19 premises),
and the USA (five cases). EHV-1 associated neurologic disease was reported by France (one case),
Germany (two cases), Switzerland (cases on several
premises), and the USA (two cases). Respiratory
disease caused by EHV-4 was confirmed by France(15 outbreaks), Germany (one case), Switzerland(indeterminate number on several premises), andthe UK (four outbreaks on separate premises). The
UK reported one case of EHV-4 abortion.
Two cases of equine coital exanthema (EHV-3)
were confirmed in the USA (Kentucky).
Numerous cases of EHV-2 infection associatedwith signs of respiratory disease were reported in
the USA. A few were dual infections with EHV-5.
Cases of equine arteritis virus infection wererecorded by Germany (carrier stallion) and
Switzerland (one case). Canada and Germany
reported equine infectious anemia. Four cases
were confirmed on individual premises in twoWestern provinces in Canada; three outbreaks wererecorded in Germany.
Equine piroplasmosis was considered endemic
in France and the United Arab Emirates, withisolated clinical cases in non-Thoroughbreds inthe latter.
Germany reported contagious equine metritis
in two non-Thoroughbred stallions on one premises.
Infection with Leptospira spp. was confirmed
by France (one case of uveitis) and the USA (twocases of abortion). The USA diagnosed six cases ofnocardioform placentitis and abortion.
Cases of salmonellosis were reported by Ireland (three cases), Switzerland (two cases of S.
typhimurium), and the USA (eight outbreaks associated with Salmonella Group C3 strains).
Clostridial enteritis was recorded in the USA
including isolated cases of C. perfringens Type A
in foals, two cases of C. difficile, and one case of
C. sordellii. The USA also reported cases of equine
proliferative enteropathy in Thoroughbred foals in
two states.
Two outbreaks of rotavirus infection were recorded in France.
A fatal case of Eastern equine encephalomyelitis
was confirmed in a horse in Florida, USA.
Rhodococcal-related disease was reported as
endemic in the USA, with at least 22 cases diagnosed.
Infection with Corynebacterium pseudotuberculosis was reported as endemic in the USA.
Ireland reported three cases of atypical myopathy.

M

ost of the horses and donkeys in the world
live with and work for poor people. The
impact of these animals on the lives of poor people
is enormous and global. Working equids reducepoverty, provide food security, and help promote
gender equity for much of the “bottom billion” of
the world’s growing population.
Despite these critical roles, somehow the world
has largely forgotten these animals. We don’t evenproperly count them; the Food and Agriculture
Organization of the United Nations’ estimate of
the global equine population, at approximately
113 million, is widely regarded as a gross underestimate because of their routine omission fromcensus data. Despite the enormous positive impactof these horses and donkeys on people, humanity
frequently fails to prioritize their health.
An international Havemeyer Workshop reportpublished in the January 2015 Equine Veterinary
Journal described strategies to reduce the burdenof infectious diseases in working equids worldwide.
The task is daunting, and the solutions needed arediverse. Technical solutions such as new diagnostic
tests and vaccines represent only a part of the answer, as there are extensive social-behavioral andinstitutional barriers to overcome.
The workshop proposed three categories of
diseases. The first category includes diseases such
as African horse sickness, rabies, tetanus, andgastrointestinal parasites, for which most technical barriers have been overcome, but which need
improved surveillance, owner education, and advocacy at the governmental level in order to achieve
progress. A second category includes diseases forwhich significant gaps still exist in our technicalunderstanding and resources, such as epizootic

3

4

lymphangitis, piroplasmosis, and trypanosomiasis. A third category includes syndromic diseases,
where the role of infectious agents has not been
defined, including respiratory, neurologic, andanemia syndromes that are highly prevalent inthese populations.
The challenges that complicate addressing infectious diseases in working equids are captured by the
One Health paradigm. Both people and animals
face environmental factors such as water shortage,
climate change, and environmental pollution toname but a few that shape the infectious diseases
from which they suffer. Impoverished humans andanimals have limited access to pharmaceutical treatments that often are of questionable quality andfrequently are misused in ways that can exacerbate
problems such as antimicrobial resistance. For
investigators like me, who have spent our careers
pursuing technical advances in vaccine or diagnostic technologies, it is vital that we understand that
education and advocacy, at both the governmental
and local levels, are likely to be more importantin addressing the enormous impact of infectious
disease in working horses and donkeys. It is instructive to study the evolving behavior of majorcharities that operate in this area, such as SPANA,
the Brooke, and the Donkey Sanctuary. While theirclinical hospitals are still central pillars of activities,
efforts are currently focused on building sustainablelocal capacity and educational development.

USEF Drugs andMedications Rules
 The most common medica-

CONTACT
Dr. D. Paul Lunn(919) 513-6210
dplunn@ncsu.edu
College of Veterinary Medicine
North Carolina State University
Raleigh, North Carolina

N AT I O N A L

Atopic DermatitisA

topic dermatitis, defined as an allergic reaction to environmental allergens (pollens, barn
dust, molds, etc.), is probably more common inhorses than currently reported. It may be seasonalor, in climates such as California, year round. The
three most common presentations are urticaria(“hives”), urticaria with pruritus (itching), andpruritus alone. Pruritus most commonly affects

the face and trunk. Seasonal signs would be mostconsistent with allergy to pollens; year-round signs
would be more consistent with an allergy to molds
or barn dust. Urticaria, secondary to atopic dermatitis, may be a familial problem in some horses.
Diagnosis of atopic dermatitis is based on clinical signs and the exclusion of other diagnoses (especially Culicoides [“no-see ums”] allergy). Horses

may have a secondary bacterial skin infection(pyoderma), typified by excess scale, particularlyin the shape of a circle (epidermal collarettes).
Intradermal tests (IDT) or serum allergy tests
may be performed to identify allergens which
may be used for hyposensitization (allergy shots,
or more recently available, oral drops). Horses
with atopic dermatitis and recurrent hives generally have a higher incidence of positive reactions
than healthy horses, but the diagnosis (as in otherspecies) cannot solely be made on the basis of the
IDT or serologic testing alone. Any testing should
be interpreted in light of the history of the disease
and used to determine which allergens might beuseful to use in hyposensitization, should the owners elect that route of treatment.
Medical therapy may include corticosteroids;
prednisolone or dexamethasone are the mostcommonly used. Prednisolone seems to be better
absorbed orally in horses than prednisone. The
injectable dexamethasone solution may be usedorally, although the bioavailability is 60%-70% of
the injectable route. Antihistamines are sometimes
quite effective: hydroxyzine pamoate, cetirizine, or
doxepin (a tricyclic anti-depressant with antihistaminic effects). Antihistamines rarely cause either
drowsiness or excitability in horses, although theauthor has seen these adverse effects in less than 5%of horses receiving these drugs. The commonly usedantihistamine pyrilamine maleate has been shown

MATT BARTON, AGRICULTURAL COMMUNICATIONS, UNIVERSITY OF KENTUCKY

tions used for the treatment of
atopic dermatitis in horses are
considered forbidden under
the United States EquestrianFederation’s (USEF) Equine
Drugs and Medications Rules.
As identified by Dr. Stephen
D. White, these usually include
antihistamines and corticosteroids. In addition to limiting
the use of forbidden substances,the Equine Drugs and Medications Rules provide for legitimate use of these medications
with the proper withdrawal anddocumentation. Conditions fortherapeutic administrations offorbidden substances include
that the medication must be
for the diagnosis or treatment

to have poor bioavailability when given orally in thehorse, but detectable in the urine up to one week
after a single dose, which may present difficulties
with withdrawal times. Some clinicians have noted
improvement when an essential fatty-acid productis added to the feed as an adjunctive treatment.
Atopic dermatitis has been successfully managed with hyposensitization, with horses showing
improvement as early as two months into treatment. However, a full 12 months of hyposensitization should be given before fully evaluating its
effectiveness, and veterinarians should maintainconsistent communication with the client to monitor the progress of the treatment and to encourage
the owner to continue with the injections for thefull year. While in other domestic species it isthought that most patients will need to be maintained on the injections for life, in the horse, thismay not be true, as a small number of horses have
had the hyposensitization injections stopped anddid not relapse. In general, approximately 70% of
atopic horses improve with hyposensitization. (Seebelow.)CONTACT
Dr. Stephen D. White(530) 752-5908
sdwhite@ucdavis.edu
School of Veterinary Medicine
University of California
Davis, California

of an existing illness or injury,
and that the horse must bewithdrawn from competition
for a period of no less than 24hours following the administration. Additionally, a medication
report form must be filed in
the competition office withthe show Steward or Technical Delegate within one hour
following the administration.
Medication reports can also be
filed online at https://www.usef.
org/_IFrames/Drugs/MedicationReportForm/.
 One corticosteroid, dexamethasone, is quantitatively
restricted and no medication
report form is necessary. However, there are recommendations for its use that need to bestrictly followed to avoid an excessive level of drug in the horseat the time of competition.
These recommendations can befound at https://www.usef.org/
documents/drugsMeds/2015/
drugsmedsguidelines15_web.
pdf. The treatment of atopic
dermatitis using hyposensitization is permitted under USEF
rules as long as no injections
take place within the 12 hours
prior to competing; no medication report form is required. For
further information regarding
the use of medications whileremaining compliant with the
Equine Drugs and Medications rules, please visit https://www.usef.org/_IFrames/Drugs/
Default.aspx or call 1 (800)633-2472.
Dr. Stephen Schumacher, Chief
Administrator, USEF Equine Drugs
and Medications ProgramEquine Disease Quarterly Newsletter

KENTUCKY

Equine Tyzzer’s Disease Update: January 1993-April 2015

T

yzzer’s disease was originally described in micein 1917, and since then has been diagnosed in
multiple species of domestic animals and wildlife
worldwide. Tyzzer’s disease is highly fatal in young
foals, and is caused by the bacterium Clostridium
piliforme. The organism is an intracellular pathogen that primarily infects the lower intestinal tract

and can disseminate through the circulatory or
lymphatic systems to visceral organs.
C. piliforme can cause subclinical infections, but
infections are commonly acute and fatal in foals.
Foals are usually found comatose or dead, but clinical signs can include depression, anorexia, pyrexia,
jaundice, diarrhea, and recumbency. Affected foals

JULY 2015
Volume 24, Number 3

C O M M E N TA RY
IN THIS ISSUE
Commentary
International
First Quarter2015  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2Working Equids
in Low-Income
Countries .  .  .  .  .  .  .  .  .  .  .  . 3National
Atopic Dermatitis .  .  .  . 3Vesicular Stomatitis . . 5

12Kentucky

10

Tyzzer’s Disease
Update .  .  .  .  .  .  .  .  .  .  .  .  .  . 5

8
6
4
2

Year

with the breed distribution typically seen at thediagnostic lab. The ages of affected foals ranged
from 7 to 270 days with an average age of 26 days.
Fifteen foals were 30 days of age or older. Of the 92
cases, 89 died in the months of February throughJune. The other three cases occurred in January,
July, and October.
CONTACT
Dr. Jacqueline Smith(859) 257-8283
jsmit8@uky.edu
University of Kentucky
Veterinary Diagnostic Laboratory
Lexington, Kentucky

15
20

13
20

11
20

09
20

07
20

05
20

03
20

01
20

19

99

0

97

are typically between one to six weeks of age, but
most cases occur between one and two weeks ofage. The disease primarily affects the liver, causing
necrotizing hepatitis.
Antemortem serology and fecal polymerase
chain reaction (PCR) assays can be used to test forC. piliforme, however results must be interpreted
in combination with appropriate clinical signs tomake a presumptive clinical diagnosis. A definitive
diagnosis is made upon postmortem examinationand is accomplished by associating the organismwith characteristic liver lesions; this association canbe made by microscopically visualizing the organism or by detecting the organism’s genetic material
by PCR. There is no known effective treatment forthe disease, and vaccines are not available.
Over the last 23 years, 92 cases of Tyzzer’s
disease have been diagnosed at the University of
Kentucky Veterinary Diagnostic Laboratory (Figure 1). The disease was identified in 44 colts, 36
fillies, and in 12 foals where the sex was not noted.
Of the 92 cases diagnosed, there were 82 Thoroughbreds, three Tennessee Walking Horses, one
Quarter Horse, one Standardbred, one Paint, one
Morgan, and three foals without breed notation.
The high number of Thoroughbreds is consistent

19

CONTACT
Dr. Angela Pelzel-McCluskey(970) 494-7391
Angela.M.Pelzel-McCluskey@aphis.usda.gov
USDA-APHIS-Veterinary Services
Fort Collins, Colorado

Address Service Requested

95

ally, extensive fly control was necessary to prevent
transmission and the development of additional
cases. Long quarantine periods, experienced while
affected animals healed for an average of 30 days or
more, caused additional strain and, in some cases,
prevented horses from being used for their intended purpose during the prime summer and fallshow season. Quarantines placed on large boarding
facilities were especially difficult to manage forowners, barn managers, veterinarians, and regulatory personnel. On another level, equine events in
VS-affected states also suffered serious impacts.
While most events were not cancelled, unless theevent facility itself had been quarantined, there
was still reduced attendance at events in affectedstates due to movement restrictions and difficultyin getting out-of-state and Canadian horses backhome after entering a VS-affected state. Finally,
international movement of horses from the U.S.
was impeded by destination countries imposing
strict VS testing requirements or not allowing
entrance of horses from certain states.
While it remains to be seen whether the 2015
VS outbreak will approach the size and scope of the2014 experience, it seems certain that the equine
industry will again have to contend with some
impacts this year, economic and otherwise.
For current information on the 2015 VS outbreak, see the VS situation reports on the APHIS
website at: http://www.aphis.usda.gov/wps/portal/
aphis/home/

19

esicular stomatitis (VS) is a viral disease that
can affect many livestock species, most often
in horses and cattle. The virus causes vesicles (blisters) that form primarily on the lips and tongue,
around the mouth or nose, along the udder or
sheath, or along the coronary bands. These viruscontaining vesicles later rupture, forming erosions
and ulcers. The disease is transmitted by biting flies,
mainly black flies and sandflies, or biting midges.
There is no specific treatment for the disease, only
supportive care until the lesions heal. The impact ofthe disease on the individual horse varies, depending on the location of the lesions. Severe mouth
and tongue lesions can interfere with the horseeating or drinking and severe coronary band lesions
can result in temporary lameness. VS is a reportable disease in the U.S. and affected premises areplaced under quarantine to prevent disease spread.
The recent identification of VS cases in Arizona, New Mexico, and Utah marked the start ofa 2015 outbreak in the U.S. This comes on theheels of a significant VS outbreak during 2014
in which a total of 435 premises in Arizona,
Colorado, Nebraska, and Texas were confirmed
infected; 408 of which involved affected equines.
The 2014 outbreak was the worst VS outbreak in
the U.S. since 2005, and the economic impacts ofthe disease were felt within the equine industry at
multiple levels. While the exact dollar amount for
the economic loss cannot be quantified, Colorado
was certainly the hardest hit and had a total of 370
VS-affected premises in 17 counties.
Beginning at the individual equine premiselevel, owners were first faced with veterinary bills
for confirmation of the disease and supportive carethat was needed for horses with lesions. Addition-

93

V

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

19

Economic Impacts of Vesicular Stomatitis Outbreaks

5

Presorted Standard
US Postage Paid
Permit 51
Lexington KY

Figure 1. Incidenceof Tyzzer’s Diseasediagnosed at the UK
Veterinary Diagnostic
Laboratory, 1993-2015.

Let’s just jump to the bottom line: If you hear
thunder you (and your horse) can be struckby lightning.
Summer is the long-awaited horseback riding,horse event, and trail riding season. Summer isalso peak season for lightning strikes in the US,
although lightning can occur year-round. According to the National Oceanic and Atmospheric
Administration (NOAA), an estimated 25 million
lightning strikes occur in the US every year.
Human deaths due to lightning are well documented. According to NOAA, from 2006-2014,
287 people were killed by lightning in the US.
Statistics on lightning-related deaths of horses are
not maintained. However after just one April 2015
thunderstorm in central Kentucky, three horses
from one farm and two cattle from another farm
were killed by lightning.
Organized trail rides, horse shows, race tracks,sales venues…how many have a responsible person
monitoring weather who has the knowledge andauthority to stop the event in case of an inboundthunderstorm? Guidelines are useless unless they
are up-to-date and followed, from county horseshows to international competitions.
An outdated guideline (but one still referenced)
is the 30/30 rule: If thunder is heard less than 30
seconds after seeing lightning, an outdoor event
should be stopped and not started until 30 minutes
after the severe weather has passed.
Don’t bother counting. If you can hear thunderor see lightning, you can be struck by lightning.
There is no safe place to be outdoors!
Horse event organizers have much to learn
from the United States Golf Association (USGA).
At USGA national championships—and at mostregional and local tournaments run under USGA
guidelines—an official monitors weather radar
when players are on the golf course. This person

is in contact with the official-in-charge of theevent who has the authority and the obligation tosuspend play in the event of threatening weather.
Comprehensive evacuation plans are drawn up
before a tournament. These plans typically designate several specific evacuation points around thegolf course, where players have access either tosafe areas or transportation to the clubhouse. Oncourse officials are required to know evacuation
locations and are responsible for getting players
and their caddies to safety when the horn sounds
and play is suspended. Players know this standardized procedure.
How many times have you seen horse shows
continuing with classes when thunder can beheard, or seen jockeys riding racehorses into a
metal starting gate during a thunderstorm? We
would challenge all organizers of equestrian events
to develop, implement, and communicate a severe
weather plan that is based on science and the safetyof humans and horses. Until then, individuals
need to have their own plan for safety by taking
weather spotter classes, having a NOAA weather
radio, getting a weather app for cell phones, andusing common sense. Sitting atop a horse withmetal horse shoes on is a bad place to be during athunderstorm. Remain weather-aware and ensure
people and horses are in safe places before severe
weather strikes!
CONTACT
Matt Dixon(859) 218-4363
matt.dixon@uky.edu
Meteorologist, Biosystems & Agricultural Engineering;
Dr. Roberta Dwyer(859) 218-1122
rmdwyer@uky.edu
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky

Equine Disease Quarterly Newsletter

KENTUCKY

Equine Tyzzer’s Disease Update: January 1993-April 2015

T

yzzer’s disease was originally described in micein 1917, and since then has been diagnosed in
multiple species of domestic animals and wildlife
worldwide. Tyzzer’s disease is highly fatal in young
foals, and is caused by the bacterium Clostridium
piliforme. The organism is an intracellular pathogen that primarily infects the lower intestinal tract

and can disseminate through the circulatory or
lymphatic systems to visceral organs.
C. piliforme can cause subclinical infections, but
infections are commonly acute and fatal in foals.
Foals are usually found comatose or dead, but clinical signs can include depression, anorexia, pyrexia,
jaundice, diarrhea, and recumbency. Affected foals

JULY 2015
Volume 24, Number 3

C O M M E N TA RY
IN THIS ISSUE
Commentary
International
First Quarter2015  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2Working Equids
in Low-Income
Countries .  .  .  .  .  .  .  .  .  .  .  . 3National
Atopic Dermatitis .  .  .  . 3Vesicular Stomatitis . . 5

12Kentucky

10

Tyzzer’s Disease
Update .  .  .  .  .  .  .  .  .  .  .  .  .  . 5

8
6
4
2

Year

with the breed distribution typically seen at thediagnostic lab. The ages of affected foals ranged
from 7 to 270 days with an average age of 26 days.
Fifteen foals were 30 days of age or older. Of the 92
cases, 89 died in the months of February throughJune. The other three cases occurred in January,
July, and October.
CONTACT
Dr. Jacqueline Smith(859) 257-8283
jsmit8@uky.edu
University of Kentucky
Veterinary Diagnostic Laboratory
Lexington, Kentucky

15
20

13
20

11
20

09
20

07
20

05
20

03
20

01
20

19

99

0

97

are typically between one to six weeks of age, but
most cases occur between one and two weeks ofage. The disease primarily affects the liver, causing
necrotizing hepatitis.
Antemortem serology and fecal polymerase
chain reaction (PCR) assays can be used to test forC. piliforme, however results must be interpreted
in combination with appropriate clinical signs tomake a presumptive clinical diagnosis. A definitive
diagnosis is made upon postmortem examinationand is accomplished by associating the organismwith characteristic liver lesions; this association canbe made by microscopically visualizing the organism or by detecting the organism’s genetic material
by PCR. There is no known effective treatment forthe disease, and vaccines are not available.
Over the last 23 years, 92 cases of Tyzzer’s
disease have been diagnosed at the University of
Kentucky Veterinary Diagnostic Laboratory (Figure 1). The disease was identified in 44 colts, 36
fillies, and in 12 foals where the sex was not noted.
Of the 92 cases diagnosed, there were 82 Thoroughbreds, three Tennessee Walking Horses, one
Quarter Horse, one Standardbred, one Paint, one
Morgan, and three foals without breed notation.
The high number of Thoroughbreds is consistent

19

CONTACT
Dr. Angela Pelzel-McCluskey(970) 494-7391
Angela.M.Pelzel-McCluskey@aphis.usda.gov
USDA-APHIS-Veterinary Services
Fort Collins, Colorado

Address Service Requested

95

ally, extensive fly control was necessary to prevent
transmission and the development of additional
cases. Long quarantine periods, experienced while
affected animals healed for an average of 30 days or
more, caused additional strain and, in some cases,
prevented horses from being used for their intended purpose during the prime summer and fallshow season. Quarantines placed on large boarding
facilities were especially difficult to manage forowners, barn managers, veterinarians, and regulatory personnel. On another level, equine events in
VS-affected states also suffered serious impacts.
While most events were not cancelled, unless theevent facility itself had been quarantined, there
was still reduced attendance at events in affectedstates due to movement restrictions and difficultyin getting out-of-state and Canadian horses backhome after entering a VS-affected state. Finally,
international movement of horses from the U.S.
was impeded by destination countries imposing
strict VS testing requirements or not allowing
entrance of horses from certain states.
While it remains to be seen whether the 2015
VS outbreak will approach the size and scope of the2014 experience, it seems certain that the equine
industry will again have to contend with some
impacts this year, economic and otherwise.
For current information on the 2015 VS outbreak, see the VS situation reports on the APHIS
website at: http://www.aphis.usda.gov/wps/portal/
aphis/home/

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esicular stomatitis (VS) is a viral disease that
can affect many livestock species, most often
in horses and cattle. The virus causes vesicles (blisters) that form primarily on the lips and tongue,
around the mouth or nose, along the udder or
sheath, or along the coronary bands. These viruscontaining vesicles later rupture, forming erosions
and ulcers. The disease is transmitted by biting flies,
mainly black flies and sandflies, or biting midges.
There is no specific treatment for the disease, only
supportive care until the lesions heal. The impact ofthe disease on the individual horse varies, depending on the location of the lesions. Severe mouth
and tongue lesions can interfere with the horseeating or drinking and severe coronary band lesions
can result in temporary lameness. VS is a reportable disease in the U.S. and affected premises areplaced under quarantine to prevent disease spread.
The recent identification of VS cases in Arizona, New Mexico, and Utah marked the start ofa 2015 outbreak in the U.S. This comes on theheels of a significant VS outbreak during 2014
in which a total of 435 premises in Arizona,
Colorado, Nebraska, and Texas were confirmed
infected; 408 of which involved affected equines.
The 2014 outbreak was the worst VS outbreak in
the U.S. since 2005, and the economic impacts ofthe disease were felt within the equine industry at
multiple levels. While the exact dollar amount for
the economic loss cannot be quantified, Colorado
was certainly the hardest hit and had a total of 370
VS-affected premises in 17 counties.
Beginning at the individual equine premiselevel, owners were first faced with veterinary bills
for confirmation of the disease and supportive carethat was needed for horses with lesions. Addition-

93

V

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

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Economic Impacts of Vesicular Stomatitis Outbreaks

5

Presorted Standard
US Postage Paid
Permit 51
Lexington KY

Figure 1. Incidenceof Tyzzer’s Diseasediagnosed at the UK
Veterinary Diagnostic
Laboratory, 1993-2015.

Let’s just jump to the bottom line: If you hear
thunder you (and your horse) can be struckby lightning.
Summer is the long-awaited horseback riding,horse event, and trail riding season. Summer isalso peak season for lightning strikes in the US,
although lightning can occur year-round. According to the National Oceanic and Atmospheric
Administration (NOAA), an estimated 25 million
lightning strikes occur in the US every year.
Human deaths due to lightning are well documented. According to NOAA, from 2006-2014,
287 people were killed by lightning in the US.
Statistics on lightning-related deaths of horses are
not maintained. However after just one April 2015
thunderstorm in central Kentucky, three horses
from one farm and two cattle from another farm
were killed by lightning.
Organized trail rides, horse shows, race tracks,sales venues…how many have a responsible person
monitoring weather who has the knowledge andauthority to stop the event in case of an inboundthunderstorm? Guidelines are useless unless they
are up-to-date and followed, from county horseshows to international competitions.
An outdated guideline (but one still referenced)
is the 30/30 rule: If thunder is heard less than 30
seconds after seeing lightning, an outdoor event
should be stopped and not started until 30 minutes
after the severe weather has passed.
Don’t bother counting. If you can hear thunderor see lightning, you can be struck by lightning.
There is no safe place to be outdoors!
Horse event organizers have much to learn
from the United States Golf Association (USGA).
At USGA national championships—and at mostregional and local tournaments run under USGA
guidelines—an official monitors weather radar
when players are on the golf course. This person

is in contact with the official-in-charge of theevent who has the authority and the obligation tosuspend play in the event of threatening weather.
Comprehensive evacuation plans are drawn up
before a tournament. These plans typically designate several specific evacuation points around thegolf course, where players have access either tosafe areas or transportation to the clubhouse. Oncourse officials are required to know evacuation
locations and are responsible for getting players
and their caddies to safety when the horn sounds
and play is suspended. Players know this standardized procedure.
How many times have you seen horse shows
continuing with classes when thunder can beheard, or seen jockeys riding racehorses into a
metal starting gate during a thunderstorm? We
would challenge all organizers of equestrian events
to develop, implement, and communicate a severe
weather plan that is based on science and the safetyof humans and horses. Until then, individuals
need to have their own plan for safety by taking
weather spotter classes, having a NOAA weather
radio, getting a weather app for cell phones, andusing common sense. Sitting atop a horse withmetal horse shoes on is a bad place to be during athunderstorm. Remain weather-aware and ensure
people and horses are in safe places before severe
weather strikes!
CONTACT
Matt Dixon(859) 218-4363
matt.dixon@uky.edu
Meteorologist, Biosystems & Agricultural Engineering;
Dr. Roberta Dwyer(859) 218-1122
rmdwyer@uky.edu
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky