Equine Disease Quarterly Newsletter

5

lesion in the placenta is distinct from ascending
bacterial placentitis with lesions of nocardioform
placentitis commonly distributed in the cranial,
ventral portion of the placenta near the junctionof the uterine horns and body. The lesion is often
sharply demarcated from the surrounding normal
placenta, and the affected placenta is frequently
covered with thick, tan mucoid material.
Nocardioform placentitis is associated with
Gram-positive, branching actinomycetes including multiple Amycolatopsis spp., Crossiella equi,and, more recently, Streptomyces atriruber andStreptomyces silaceus. Characterization of actinomycetes associated with abortions during the 2011
outbreak of nocardioform placentitis in central
Kentucky revealed that Amycolatopsis spp. (49%of cases) were most commonly identified followedby Crossiella equi (29% of cases). Nocardioform
placentitis results in episodic abortions. A major
epizootic of nocardioform placentitis was recorded
in 2010-11, consisting of 390 confirmed cases ofplacentitis with 76 confirmed abortions. These
abortions occurred primarily between December
2010 and April 2011 and were diagnosed almost
exclusively during the last trimester of pregnancy.
Nocardioform placentitis is primarily characterized as a mucoid placentitis in which the bacterial
infection is limited to the chorionic surface of theventral placenta without infection of the fetus. To
date, the pathogenesis remains poorly understood.
Attempts to induce infection in mares by intrauterine inoculation of Crossiella equi at breeding
and in pregnant mares via oral, intravenous, andintranasal routes with this organism have been

350

350

300

300

250

250

200

200

150

100

50

50

1

2

3

4

5

6

Mean Aug-Sept rainfall

Mean Aug-Sept rainfall

7

8

Nocardioform placentitis abortions occur from
November to June, with a peak incidence in January and February. The majority of aborted fetuses
are in the last trimester of pregnancy, and the identification of nocardioform lesions on the placentaof term pregnancies is a common presentation. A
retrospective epidemiologic study of on-farm risk
factors associated with the 2010-11 epizootic ofnocardioform placentitis identified a number ofassociations with nocardioform placentitis. Larger
farms, higher mare numbers and higher animal
density on farms was positively associated with
the incidence of nocardioform placentitis. Longer grazing times during late winter, prebreedingadministration of progesterone to mares, humanchorionic gonadotropin (hCG) administration
post-breeding and nonsteroidal anti-inflammatory
drugs (NSAIDs) were negatively associated with
the incidence of nocardioform placentitis. Retrospective evaluation of monthly climate data(precipitation and average temperature) for central
Kentucky and the number of nocardioform placentitis cases seen by the University of Kentucky
Veterinary Diagnostic Laboratory for the period of
1990-2018 was conducted to evaluate climatologic
associations with nocardioform placentitis (Figures
1 and 2). This analysis demonstrated a moderately
strong negative association (ρ = -0.57; P = 0.001)

150

100

0

Epidemiology

Figure 2. Relationship between the number of nocardioform
placentitis cases seen by the UKVDL and average temperature(°F) in August and September preceding that foaling season.

NP cases

NP cases

Figure 1. Relationship between the number of nocardioform
placentitis cases seen by the UKVDL and average rainfall(inches) in August and September preceding that foaling
season.

unsuccessful. Likewise, the ecology and biologyof the causative agents, Crossiella equi and Amycolatopsis spp. remains unknown as these causative
organisms have only been isolated from affected
placentae in mares.

9

0

67

68

69

70

71

72

73

Mean Mean
Aug-Sept
temperature
Aug-Sept

74

75

76

Presorted Standard
US Postage Paid
Permit 51
Lexington KY

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

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

APRIL 2020
Volume 29, Number 2

C O M M E N TA RY
IN THIS ISSUE
Commentary
International
Fourth Quarter2019  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2Epiglottic
Entrapment  .  .  .  .  .  .  .  .  . 3National
Equine Abortion .  .  .  .  . 4Kentucky

between August and September rainfall and thenumber of nocardioform placentitis cases submitted for the subsequent foaling season. Likewise,
there was a moderately strong positive association(ρ = 0.47; P = 0.001) between mean temperaturesin August and September and the number of nocardioform placentitis cases submitted the next
foaling season. Because average temperatures inAugust and September 2019 were 5.3% above
the long-term average and average rainfall was
only 52% of long-term average, the 2020 foaling
season seems likely to have a higher incidence of
nocardioform placentitis. Although there does
seem to be an association between a hot and dry
August and September preceding an increase innocardioform cases, the causal relationship is lessclear. Other members of the actinomycetes, such as
Rhodococcus equi, are soil-dwelling pathogens thatare associated with hot, dry, dusty environments.
It is worth considering that the actinomycetes
responsible for nocardioform placentitis may also
originate as soil-borne organisms, despite thefailure thus far to isolate these pathogens fromenvironmental sources. Related members of Amycolatopsis and Streptomyces are well characterized
as soil-associated microorganisms, and a likely
environmental association (hot, dry periods in latesummer) may be associated with the disease.
It appears likely that the pathogenesis of nocardioform placentitis is multifactorial and may
involve environmental conditions (hot, dry periods in late summer) and possibly effects related
to host susceptibility. Pregnancy in many species,
including the mare, involves some degree of immunosuppression, and many actinomycetes are more
pathogenic in immunocompromised hosts. Moreresearch is needed to better unravel this complex
disease process in the mare.
CONTACT:
Barry A. Ball, DVM, PhD, DACT
b.a.ball@uky.edu(859) 218-1141
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky

Nocardioform
Placentitis .  .  .  .  .  .  .  .  .  .  . 4

College of Agriculture,
Food and Environment
Department of
Veterinary Science

Lloyd’s—An international
insurance market forbloodstock and otherspecialist insurance.

One benefit of being older is the ability toreflect on many equine medical crises. Contagious equine metritis was the first notable crisisof my career, but I have unfortunately witnessed
numerous others including: equine viral arteritis,
leptospirosis, mare reproductive loss syndrome,
track breakdowns, and more recently nocardioform placentitis. With each of these crises, scientists have stepped up to search for solutions, andI have seen first-hand the positive results that takeplace when practitioners work with scientists on
the medical issues facing our horses.
This year central Kentucky has again been confronted with a substantial increase in the numberof nocardioform placentitis cases. As with any caseof placentitis, and certainly with nocardioform
placentitis, the first clinical sign that the mare’s
pregnancy may be compromised is evident with“bagging up” early, which is horseman’s lingo forpremature lactation or increased udder size. Unlike
ascending placentitis, there is usually no vulvar
discharge in mares with nocardioform placentitis.
For the most part, it is relatively easy to diagnose nocardioform placentitis after the mare has
either aborted or foaled, as the placenta is usually
covered by a very characteristic brown mucoid
discharge—many people think it looks like peanutbutter. A diagnosis of nocardioform placentitis
is more challenging before the mare delivers her
foal (or fetus) and is made based on clinical signs

and abdominal ultrasound scans. Nocardioform
placentitis frequently forms lesions on the ventral
aspect of the placenta. This unique location negates
the usefulness of the standard placentitis ultrasound measurement of the combined thickness of
the uterus and placenta (CTUP), which is taken byrectal ultrasound of the uterus and placenta near
the cervix.
With suspect nocardioform placentitis cases,
one may see a range of abnormalities on transabdominal ultrasound scans. These include pockets
of separation with apparent exudate between theuterus and placenta and signs of placental inflammation. It is important to note that not all lesions
will be apparent by this method, and placental
examination for lesions should still be done after
abortion or parturition.
The greatest incidence of nocardioform placentitis occurs in December, January, and February.
As we enter March, the number of cases should
soon decrease. While we have unfortunately seen
an increased incidence of nocardioform placentitis
this year, one positive is that more cases have been
examined and increased samples have been collected to better understand this unique condition.
CONTACT:Tom Riddle, DVM
triddle@roodandriddle.com(859) 233-0371
Rood and Riddle Equine Hospital
Lexington, Kentucky

2

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

The fourth quarter saw an additional 35
outbreaks of vesicular stomatitis reported by the
USA on premises in eight states. No new affected
premises have been identified since late November.

Fourth Quarter 2019T

Equine Disease Quarterly
Editors

Peter Timoney
Alan Loynachan
Rebecca Ruby

Staff

Diane Furry
Tawana Brown
Dennis Duross
Anita HatchettCorrespondence 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 equine disease outbreaks.
The Republic of South Africa (RSA) reported
sporadic cases of African Horse Sickness inFree State, Gauteng, and North West Province.
These represented the first cases recorded in the
2019/2020 season.
Three separate outbreaks of glanders were confirmed in Turkey. These were associated with illegal
movement of horses without identification orveterinary certification. Of 1,375 horses tested, 63
were positive and 18 suspect; all were euthanized.
Equine influenza was confirmed in France,
Germany, the Netherlands, the UK, and the USA.
With the exception of the USA, the number ofoutbreaks ranged from 1-3, the majority in unvaccinated horses. The disease is endemic in theUSA, with outbreaks diagnosed in seven states andmultiple outbreaks in one state.
Belgium, France, Germany, the Netherlands,
Switzerland, and the USA recorded strangles. The
number of outbreaks varied from four (Belgium),
21 (France), three (Germany), 12 (the Netherlands), one (Switzerland) to 40 in the USA, where
the disease is endemic.
Equine herpesvirus 1 (EHV-1) related diseases
were recorded by Belgium, Canada, France, Germany, the Netherlands, RSA, UK, and the USA.
Respiratory disease outbreaks were diagnosed in
France (two), the Netherlands (one), RSA (one),
UK (four), and in several states in the USA. EHV-1
abortion was reported by France (one case) and theNetherlands (one case). EHV-1 neurologic disease
was confirmed in Belgium (one outbreak involving five horses), Canada (two cases), France (twooutbreaks), Germany (one case), the Netherlands(three outbreaks, one involving 11 affected horses
and the other two, single cases), and the USA (17outbreaks in 10 states, one involving eight cases
and the remainder, single cases).
Equine herpesvirus 4 (EHV-4) respiratory disease outbreaks were reported by France (41, themajority involving single cases), Germany (three,
all single cases), Japan (one outbreak involving
two horses), the Netherlands (five, involving one
to five animals apiece), and the UK (11). While
the majority were represented by single cases, one

outbreak involved 32 weanlings and another eight
yearlings. France (two outbreaks) and the USA(three outbreaks) reported single cases of EHV-4
abortion. Numerous cases of EHV-2 and EHV-5
infection were confirmed by the USA, a percentageof which were associated with clinical respiratory
disease.
France and the USA reported two outbreaks ofequine infectious anemia apiece. Each involved asingle case.
Only a single report of equine piroplasmosis wasreceived in the fourth quarter of 2019. The RSA
reported that the disease was endemic throughout
the country.
A total of 19 cases of nocardioform placentitis
and abortion were diagnosed in Kentucky, USA
during the period under review. A range of bacterial organisms were identified with cases of the disease. Contagious equine metritis was reported byseveral countries. Denmark, France and Germany
each detected Taylorella equigenitalis in a stallion.
South Korea recorded three positive animals outof 2,269 samples tested, the gender of the animals
was not identified.
Other causes of abortion reported by Kentucky,
USA included Neorickettsia risticii (two cases).
The USA recorded one case of Salmonella
infection in Kentucky; several cases of rotavirus
infection in three states, two involving strainsof the G3 genotype and four the G14 genotype;nine cases of Lawsonia enteropathy; and 10 casesof infection with Clostridium perfringens Toxin A
genotype.
Eastern equine encephalomyelitis (EEE) was
reported by the USA, with 30 cases diagnosed in
the fourth quarter, 10 in Michigan and nine in
Indiana. The majority were in unvaccinated horsesthat died or were euthanized.
France, Germany, Portugal, and the USA
confirmed cases of West Nile (WN) encephalitis.
Outbreaks in France (seven), Germany (three), andPortugal (one) involved one or two cases. A totalof 25 cases were recorded in the USA, of which
10 were in Colorado and six in Florida. One casewas positive for both EEE virus and WN virus.
The RSA confirmed one case of equine encephalosis, and the USA diagnosed three cases of equine
protozoal myelitis during the period under review.

The USA confirmed two outbreaks of Rhodococcus equi infection, but this significantly underrepresents the incidence of this endemic disease in
the country.

3

4

N AT I O N A L

Equine Abortion:
The 2016-2019 Breeding Seasons in Central Kentucky

Epiglottic EntrapmentThe epiglottis is a triangular shaped cartilage
located in the throat at the base of the entrance
to the airways. During normal breathing, it is situated above the soft palate and facilitates air movement. When eating, the epiglottis moves upwards
and backwards to allow swallowing and to prevent
food from entering the airways. To allow for such
movement, the lower surface of the epiglottis has
a loosely attached, elastic mucosa (subepiglottic
mucosa). Epiglottic entrapment occurs when the
subepiglottic mucosa becomes positioned above
the epiglottis, restricting movement.
The most common presenting sign in casesof epiglottic entrapment is abnormal respiratory
noise. The abnormally positioned subepiglottic
mucosa creates a slightly narrowed airway, as
well as increased air turbulence, which creates aharsh respiratory noise. Horses in a higher planeof work, racehorses for example, can also present
with exercise intolerance. In horses performing athigh speeds, even mild narrowing of the airway can
result in decreased athletic performance, and, asa result, decreased earnings. Coughing and nasal
discharge occur in some cases, as an abnormallyfunctional epiglottis can contribute to disruptionof airflow and slightly interfere with the swallowing process. As none of these changes indicate a
specific cause of disease, transnasal endoscopy isoften used to further investigate horses exhibitingthese clinical signs. This procedure is commonly
done in many cases with suspected upper airway
disease and involves the passage of a small, flexible
camera up the horse’s nose to visualize the airway.
Most horses tolerate this intervention well withminimal restraint or sedation.
The majority of cases have persistent epiglottic
entrapment; however, a small number of horses
experience intermittent epiglottic entrapment,
which is relieved when the horse swallows. The
membrane entrapping the epiglottis can vary inthickness, width, and can become ulcerated. In
addition to endoscopic evaluation, a radiograph ofthe laryngeal region can also be obtained to assess
the patient for epiglottic hypoplasia (a smaller thannormal epiglottis) as this can be an uncommon
cause of epiglottic entrapment.
Surgery is the most common treatment option
for this condition. An incision is made throughthe abnormally positioned subepiglottic mucosa
to release the entrapped epiglottis. The procedurecan be performed either under sedation and local anesthesia or under general anesthesia andtypically takes less than 30 minutes. There areseveral surgical methods available, namely use ofa transnasal endoscopically guided laser, transendoscopic electrosurgical instrument, or transnasal
or transoral curved surgical knife. Surgical excision
can also be performed via incision into the airway
via the pharynx or larynx, however, these methods
will result in an external scar and can contributeto surgical site complications. These procedures
are therefore typically reserved for cases with additional complications.
The potential complications of surgical intervention include thermal trauma to the epiglottis, adhesions, and cicatrix (scar) formation. To
reduce the risk of these occurring, horses should
receive systemic and topical anti-inflammatory
medications. Dorsal displacement of the soft palate can occur regardless of the treatment method
employed, particularly when epiglottic hypoplasia
is present.
Local inflammation is common following surgical correction of epiglottic entrapment. Horses
should therefore receive transnasal endoscopic
evaluation each week following surgery until thelarynx has a normal appearance. Throat sprays containing anti-inflammatory agents are also strongly
recommended. In order to reduce inflammationin the laryngeal region; horses require a period ofrest following surgery. Depending on the severity of the condition and the treatment method
employed, horses can return to work 3-8 weeks
post-operatively, providing transnasal endoscopic
evaluation is normal. Reoccurrence is not uncommon and can be treated by surgical excision of theexcess subepiglottic mucosa. The majority of horses
with epiglottic entrapment without epiglottic
hypoplasia are able to return to their original levelof activity.
CONTACT:
Alex Gillen, MA, MS, VetMB, CertAVP,
DipACVS, DipECVS, MRCVS
alexandra.gillen@liverpool.ac.uk
Phillip Leverhulme Equine Hospital
University of Liverpool
United Kingdom

causesFigure 1. Infectious Infectious
causes of abortion.
Infectious
causes ofof abortion
abortion
14.00%
14.00%
12.00%
12.00%
10.00%
10.00%
8.00%
8.00%
6.00%
6.00%
4.00%
4.00%
2.00%
2.00%
0.00%
0.00%

MucoidMucoidplacentitis
placentitis

E

FungalUnidentified Leptospirosis
Fetal
FungalUnidentified Leptospirosis
Fetal
placentitis
bacterial
bacteremia
placentitis
bacterial
bacteremia
placentitis
placentitis
2016
2016

2017
2017

2018
2018

EHV‐1
EHV‐1

2019
2019

Noninfectious
Figure 2. Non-infectious
causes of causes
abortion.of
Noninfectious
causesof abortion
abortion
10.00%
10.00%
9.00%
9.00%
8.00%
8.00%
7.00%
7.00%
6.00%
6.00%
5.00%
5.00%
4.00%
4.00%
3.00%
3.00%
2.00%
2.00%
1.00%
1.00%
0.00%
0.00%

Umbilical cord
Umbilical cord
torsiontorsionFetal stress
Fetal stress
2016
2016

Cervical pole
Cervical pole
necrosis
necrosis
2017
2017

2018
2018

Twinning
Twinning
2019
2019

Miscellaneous
Miscellaneousquine abortion is a common and frustrating
condition with a variety of infectious andnoninfectious causes. Evaluation of the fetoplacental unit can aid in understanding the cause ofindividual foal loss, allow early detection of infectious causes of abortion, and identify trends overmultiple years that can help predict future causesof fetal loss. Following changes in the causes ofabortion over multiple years may help to elucidate
environmental risk factors or changes in diseaseprevalence over time.
Causes of abortion over the last four breeding
seasons from 2016 to 2019 are presented in Figure
1 (infectious causes) and Figure 2 (non-infectious
causes). A review of the 2016 and 2017 seasons canbe found in the January 2018 issue of the Equine
Disease Quarterly. Total submission numbers were570, 328, 408, and 304 for 2016, 2017, 2018,and 2019, respectively. The overall submission
numbers vary based on numbers of mares bredthat year and incidence of diseases which create
noticeable placental lesions (such as nocardioform placentitis). General trends in abortion haveremained consistent over time, with placentitis
being the most commonly diagnosed cause ofabortion in all years. Placentitis cases represented
24.6%, 20.2%, 34.5%, and 25% for 2016, 2017,2018, and 2019. Typically, non-infectious causesof abortion (umbilical cord torsion, twins, fetal
and maternal stress, and abortions of unknown
etiology) are more common than infectious causes(viral, bacterial, and fungal infections) with the
exception of 2016, which had 145 cases of mucoid(nocardioform) placentitis, increasing the total

percentage of infectious abortions to 55%.
Evaluation of the last four breeding seasonsshows that cases of mucoid placentitis and abortionof undetermined cause have the most variation
between years. Abortions due to fungal infection,
fetal bacteremia, umbilical cord torsion, and fetal
stress have remained fairly stable. An increase in
miscellaneous causes of abortion and undetermined causes occurred in 2018 and 2019. Miscellaneous causes include a variety of conditions
including congenital malformations, fetal andmaternal stress, cervical pole necrosis, fetal organ
necrosis or inflammation, hydrops and Potomac
horse fever. This increase may reflect normal variation between years. Alternatively, monitoring andintervention for early placentitis and vaccination
for infectious cases of abortion such as leptospirosis and EHV-1 may be decreasing the incidenceof these recognized diseases and result in a corresponding increase in the percentage of cases ofabortion without an identified cause. Abortions of
undetermined cause increased each year at 14.9%
in 2016, 27.5% and 38.2% in 2017 and 2018 andpeaking at 44% in 2019. Continued monitoringof trends will help to determine the significanceof these variations.
CONTACT:
Alan Loynachan, DVM, PhD, DACVP
alan.loynachan@uky.edu
Rebecca Ruby, MSc, BVSc, DAVCP
rebecca.ruby@uky.edu(859) 257-8283
University of Kentucky Veterinary Diagnostic Laboratory,
Lexington, Kentucky

KENTUCKY

Nocardioform Placentitis: A Continuing Enigma

Nocardioform placentitis was first diagnosed incentral Kentucky in 1986 with subsequent
increased case incidences occurring in 1998, 1999,
and 2011. Cases of nocardioform placentitis havealso been reported sporadically in Florida, South
Africa, Italy, and most recently in New Zealand.

Nocardioform placentitis is characterized by lateterm abortions, premature foals, neonatal deaths,
and weak foals born at term. Nocardioform placentitis may involve large regions of the chorion
that can result in fetal growth retardation due toplacental insufficiency. The distribution of the

2

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

The fourth quarter saw an additional 35
outbreaks of vesicular stomatitis reported by the
USA on premises in eight states. No new affected
premises have been identified since late November.

Fourth Quarter 2019T

Equine Disease Quarterly
Editors

Peter Timoney
Alan Loynachan
Rebecca Ruby

Staff

Diane Furry
Tawana Brown
Dennis Duross
Anita HatchettCorrespondence 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 equine disease outbreaks.
The Republic of South Africa (RSA) reported
sporadic cases of African Horse Sickness inFree State, Gauteng, and North West Province.
These represented the first cases recorded in the
2019/2020 season.
Three separate outbreaks of glanders were confirmed in Turkey. These were associated with illegal
movement of horses without identification orveterinary certification. Of 1,375 horses tested, 63
were positive and 18 suspect; all were euthanized.
Equine influenza was confirmed in France,
Germany, the Netherlands, the UK, and the USA.
With the exception of the USA, the number ofoutbreaks ranged from 1-3, the majority in unvaccinated horses. The disease is endemic in theUSA, with outbreaks diagnosed in seven states andmultiple outbreaks in one state.
Belgium, France, Germany, the Netherlands,
Switzerland, and the USA recorded strangles. The
number of outbreaks varied from four (Belgium),
21 (France), three (Germany), 12 (the Netherlands), one (Switzerland) to 40 in the USA, where
the disease is endemic.
Equine herpesvirus 1 (EHV-1) related diseases
were recorded by Belgium, Canada, France, Germany, the Netherlands, RSA, UK, and the USA.
Respiratory disease outbreaks were diagnosed in
France (two), the Netherlands (one), RSA (one),
UK (four), and in several states in the USA. EHV-1
abortion was reported by France (one case) and theNetherlands (one case). EHV-1 neurologic disease
was confirmed in Belgium (one outbreak involving five horses), Canada (two cases), France (twooutbreaks), Germany (one case), the Netherlands(three outbreaks, one involving 11 affected horses
and the other two, single cases), and the USA (17outbreaks in 10 states, one involving eight cases
and the remainder, single cases).
Equine herpesvirus 4 (EHV-4) respiratory disease outbreaks were reported by France (41, themajority involving single cases), Germany (three,
all single cases), Japan (one outbreak involving
two horses), the Netherlands (five, involving one
to five animals apiece), and the UK (11). While
the majority were represented by single cases, one

outbreak involved 32 weanlings and another eight
yearlings. France (two outbreaks) and the USA(three outbreaks) reported single cases of EHV-4
abortion. Numerous cases of EHV-2 and EHV-5
infection were confirmed by the USA, a percentageof which were associated with clinical respiratory
disease.
France and the USA reported two outbreaks ofequine infectious anemia apiece. Each involved asingle case.
Only a single report of equine piroplasmosis wasreceived in the fourth quarter of 2019. The RSA
reported that the disease was endemic throughout
the country.
A total of 19 cases of nocardioform placentitis
and abortion were diagnosed in Kentucky, USA
during the period under review. A range of bacterial organisms were identified with cases of the disease. Contagious equine metritis was reported byseveral countries. Denmark, France and Germany
each detected Taylorella equigenitalis in a stallion.
South Korea recorded three positive animals outof 2,269 samples tested, the gender of the animals
was not identified.
Other causes of abortion reported by Kentucky,
USA included Neorickettsia risticii (two cases).
The USA recorded one case of Salmonella
infection in Kentucky; several cases of rotavirus
infection in three states, two involving strainsof the G3 genotype and four the G14 genotype;nine cases of Lawsonia enteropathy; and 10 casesof infection with Clostridium perfringens Toxin A
genotype.
Eastern equine encephalomyelitis (EEE) was
reported by the USA, with 30 cases diagnosed in
the fourth quarter, 10 in Michigan and nine in
Indiana. The majority were in unvaccinated horsesthat died or were euthanized.
France, Germany, Portugal, and the USA
confirmed cases of West Nile (WN) encephalitis.
Outbreaks in France (seven), Germany (three), andPortugal (one) involved one or two cases. A totalof 25 cases were recorded in the USA, of which
10 were in Colorado and six in Florida. One casewas positive for both EEE virus and WN virus.
The RSA confirmed one case of equine encephalosis, and the USA diagnosed three cases of equine
protozoal myelitis during the period under review.

The USA confirmed two outbreaks of Rhodococcus equi infection, but this significantly underrepresents the incidence of this endemic disease in
the country.

3

4

N AT I O N A L

Equine Abortion:
The 2016-2019 Breeding Seasons in Central Kentucky

Epiglottic EntrapmentThe epiglottis is a triangular shaped cartilage
located in the throat at the base of the entrance
to the airways. During normal breathing, it is situated above the soft palate and facilitates air movement. When eating, the epiglottis moves upwards
and backwards to allow swallowing and to prevent
food from entering the airways. To allow for such
movement, the lower surface of the epiglottis has
a loosely attached, elastic mucosa (subepiglottic
mucosa). Epiglottic entrapment occurs when the
subepiglottic mucosa becomes positioned above
the epiglottis, restricting movement.
The most common presenting sign in casesof epiglottic entrapment is abnormal respiratory
noise. The abnormally positioned subepiglottic
mucosa creates a slightly narrowed airway, as
well as increased air turbulence, which creates aharsh respiratory noise. Horses in a higher planeof work, racehorses for example, can also present
with exercise intolerance. In horses performing athigh speeds, even mild narrowing of the airway can
result in decreased athletic performance, and, asa result, decreased earnings. Coughing and nasal
discharge occur in some cases, as an abnormallyfunctional epiglottis can contribute to disruptionof airflow and slightly interfere with the swallowing process. As none of these changes indicate a
specific cause of disease, transnasal endoscopy isoften used to further investigate horses exhibitingthese clinical signs. This procedure is commonly
done in many cases with suspected upper airway
disease and involves the passage of a small, flexible
camera up the horse’s nose to visualize the airway.
Most horses tolerate this intervention well withminimal restraint or sedation.
The majority of cases have persistent epiglottic
entrapment; however, a small number of horses
experience intermittent epiglottic entrapment,
which is relieved when the horse swallows. The
membrane entrapping the epiglottis can vary inthickness, width, and can become ulcerated. In
addition to endoscopic evaluation, a radiograph ofthe laryngeal region can also be obtained to assess
the patient for epiglottic hypoplasia (a smaller thannormal epiglottis) as this can be an uncommon
cause of epiglottic entrapment.
Surgery is the most common treatment option
for this condition. An incision is made throughthe abnormally positioned subepiglottic mucosa
to release the entrapped epiglottis. The procedurecan be performed either under sedation and local anesthesia or under general anesthesia andtypically takes less than 30 minutes. There areseveral surgical methods available, namely use ofa transnasal endoscopically guided laser, transendoscopic electrosurgical instrument, or transnasal
or transoral curved surgical knife. Surgical excision
can also be performed via incision into the airway
via the pharynx or larynx, however, these methods
will result in an external scar and can contributeto surgical site complications. These procedures
are therefore typically reserved for cases with additional complications.
The potential complications of surgical intervention include thermal trauma to the epiglottis, adhesions, and cicatrix (scar) formation. To
reduce the risk of these occurring, horses should
receive systemic and topical anti-inflammatory
medications. Dorsal displacement of the soft palate can occur regardless of the treatment method
employed, particularly when epiglottic hypoplasia
is present.
Local inflammation is common following surgical correction of epiglottic entrapment. Horses
should therefore receive transnasal endoscopic
evaluation each week following surgery until thelarynx has a normal appearance. Throat sprays containing anti-inflammatory agents are also strongly
recommended. In order to reduce inflammationin the laryngeal region; horses require a period ofrest following surgery. Depending on the severity of the condition and the treatment method
employed, horses can return to work 3-8 weeks
post-operatively, providing transnasal endoscopic
evaluation is normal. Reoccurrence is not uncommon and can be treated by surgical excision of theexcess subepiglottic mucosa. The majority of horses
with epiglottic entrapment without epiglottic
hypoplasia are able to return to their original levelof activity.
CONTACT:
Alex Gillen, MA, MS, VetMB, CertAVP,
DipACVS, DipECVS, MRCVS
alexandra.gillen@liverpool.ac.uk
Phillip Leverhulme Equine Hospital
University of Liverpool
United Kingdom

causesFigure 1. Infectious Infectious
causes of abortion.
Infectious
causes ofof abortion
abortion
14.00%
14.00%
12.00%
12.00%
10.00%
10.00%
8.00%
8.00%
6.00%
6.00%
4.00%
4.00%
2.00%
2.00%
0.00%
0.00%

MucoidMucoidplacentitis
placentitis

E

FungalUnidentified Leptospirosis
Fetal
FungalUnidentified Leptospirosis
Fetal
placentitis
bacterial
bacteremia
placentitis
bacterial
bacteremia
placentitis
placentitis
2016
2016

2017
2017

2018
2018

EHV‐1
EHV‐1

2019
2019

Noninfectious
Figure 2. Non-infectious
causes of causes
abortion.of
Noninfectious
causesof abortion
abortion
10.00%
10.00%
9.00%
9.00%
8.00%
8.00%
7.00%
7.00%
6.00%
6.00%
5.00%
5.00%
4.00%
4.00%
3.00%
3.00%
2.00%
2.00%
1.00%
1.00%
0.00%
0.00%

Umbilical cord
Umbilical cord
torsiontorsionFetal stress
Fetal stress
2016
2016

Cervical pole
Cervical pole
necrosis
necrosis
2017
2017

2018
2018

Twinning
Twinning
2019
2019

Miscellaneous
Miscellaneousquine abortion is a common and frustrating
condition with a variety of infectious andnoninfectious causes. Evaluation of the fetoplacental unit can aid in understanding the cause ofindividual foal loss, allow early detection of infectious causes of abortion, and identify trends overmultiple years that can help predict future causesof fetal loss. Following changes in the causes ofabortion over multiple years may help to elucidate
environmental risk factors or changes in diseaseprevalence over time.
Causes of abortion over the last four breeding
seasons from 2016 to 2019 are presented in Figure
1 (infectious causes) and Figure 2 (non-infectious
causes). A review of the 2016 and 2017 seasons canbe found in the January 2018 issue of the Equine
Disease Quarterly. Total submission numbers were570, 328, 408, and 304 for 2016, 2017, 2018,and 2019, respectively. The overall submission
numbers vary based on numbers of mares bredthat year and incidence of diseases which create
noticeable placental lesions (such as nocardioform placentitis). General trends in abortion haveremained consistent over time, with placentitis
being the most commonly diagnosed cause ofabortion in all years. Placentitis cases represented
24.6%, 20.2%, 34.5%, and 25% for 2016, 2017,2018, and 2019. Typically, non-infectious causesof abortion (umbilical cord torsion, twins, fetal
and maternal stress, and abortions of unknown
etiology) are more common than infectious causes(viral, bacterial, and fungal infections) with the
exception of 2016, which had 145 cases of mucoid(nocardioform) placentitis, increasing the total

percentage of infectious abortions to 55%.
Evaluation of the last four breeding seasonsshows that cases of mucoid placentitis and abortionof undetermined cause have the most variation
between years. Abortions due to fungal infection,
fetal bacteremia, umbilical cord torsion, and fetal
stress have remained fairly stable. An increase in
miscellaneous causes of abortion and undetermined causes occurred in 2018 and 2019. Miscellaneous causes include a variety of conditions
including congenital malformations, fetal andmaternal stress, cervical pole necrosis, fetal organ
necrosis or inflammation, hydrops and Potomac
horse fever. This increase may reflect normal variation between years. Alternatively, monitoring andintervention for early placentitis and vaccination
for infectious cases of abortion such as leptospirosis and EHV-1 may be decreasing the incidenceof these recognized diseases and result in a corresponding increase in the percentage of cases ofabortion without an identified cause. Abortions of
undetermined cause increased each year at 14.9%
in 2016, 27.5% and 38.2% in 2017 and 2018 andpeaking at 44% in 2019. Continued monitoringof trends will help to determine the significanceof these variations.
CONTACT:
Alan Loynachan, DVM, PhD, DACVP
alan.loynachan@uky.edu
Rebecca Ruby, MSc, BVSc, DAVCP
rebecca.ruby@uky.edu(859) 257-8283
University of Kentucky Veterinary Diagnostic Laboratory,
Lexington, Kentucky

KENTUCKY

Nocardioform Placentitis: A Continuing Enigma

Nocardioform placentitis was first diagnosed incentral Kentucky in 1986 with subsequent
increased case incidences occurring in 1998, 1999,
and 2011. Cases of nocardioform placentitis havealso been reported sporadically in Florida, South
Africa, Italy, and most recently in New Zealand.

Nocardioform placentitis is characterized by lateterm abortions, premature foals, neonatal deaths,
and weak foals born at term. Nocardioform placentitis may involve large regions of the chorion
that can result in fetal growth retardation due toplacental insufficiency. The distribution of the

2

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

The fourth quarter saw an additional 35
outbreaks of vesicular stomatitis reported by the
USA on premises in eight states. No new affected
premises have been identified since late November.

Fourth Quarter 2019T

Equine Disease Quarterly
Editors

Peter Timoney
Alan Loynachan
Rebecca Ruby

Staff

Diane Furry
Tawana Brown
Dennis Duross
Anita HatchettCorrespondence 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 equine disease outbreaks.
The Republic of South Africa (RSA) reported
sporadic cases of African Horse Sickness inFree State, Gauteng, and North West Province.
These represented the first cases recorded in the
2019/2020 season.
Three separate outbreaks of glanders were confirmed in Turkey. These were associated with illegal
movement of horses without identification orveterinary certification. Of 1,375 horses tested, 63
were positive and 18 suspect; all were euthanized.
Equine influenza was confirmed in France,
Germany, the Netherlands, the UK, and the USA.
With the exception of the USA, the number ofoutbreaks ranged from 1-3, the majority in unvaccinated horses. The disease is endemic in theUSA, with outbreaks diagnosed in seven states andmultiple outbreaks in one state.
Belgium, France, Germany, the Netherlands,
Switzerland, and the USA recorded strangles. The
number of outbreaks varied from four (Belgium),
21 (France), three (Germany), 12 (the Netherlands), one (Switzerland) to 40 in the USA, where
the disease is endemic.
Equine herpesvirus 1 (EHV-1) related diseases
were recorded by Belgium, Canada, France, Germany, the Netherlands, RSA, UK, and the USA.
Respiratory disease outbreaks were diagnosed in
France (two), the Netherlands (one), RSA (one),
UK (four), and in several states in the USA. EHV-1
abortion was reported by France (one case) and theNetherlands (one case). EHV-1 neurologic disease
was confirmed in Belgium (one outbreak involving five horses), Canada (two cases), France (twooutbreaks), Germany (one case), the Netherlands(three outbreaks, one involving 11 affected horses
and the other two, single cases), and the USA (17outbreaks in 10 states, one involving eight cases
and the remainder, single cases).
Equine herpesvirus 4 (EHV-4) respiratory disease outbreaks were reported by France (41, themajority involving single cases), Germany (three,
all single cases), Japan (one outbreak involving
two horses), the Netherlands (five, involving one
to five animals apiece), and the UK (11). While
the majority were represented by single cases, one

outbreak involved 32 weanlings and another eight
yearlings. France (two outbreaks) and the USA(three outbreaks) reported single cases of EHV-4
abortion. Numerous cases of EHV-2 and EHV-5
infection were confirmed by the USA, a percentageof which were associated with clinical respiratory
disease.
France and the USA reported two outbreaks ofequine infectious anemia apiece. Each involved asingle case.
Only a single report of equine piroplasmosis wasreceived in the fourth quarter of 2019. The RSA
reported that the disease was endemic throughout
the country.
A total of 19 cases of nocardioform placentitis
and abortion were diagnosed in Kentucky, USA
during the period under review. A range of bacterial organisms were identified with cases of the disease. Contagious equine metritis was reported byseveral countries. Denmark, France and Germany
each detected Taylorella equigenitalis in a stallion.
South Korea recorded three positive animals outof 2,269 samples tested, the gender of the animals
was not identified.
Other causes of abortion reported by Kentucky,
USA included Neorickettsia risticii (two cases).
The USA recorded one case of Salmonella
infection in Kentucky; several cases of rotavirus
infection in three states, two involving strainsof the G3 genotype and four the G14 genotype;nine cases of Lawsonia enteropathy; and 10 casesof infection with Clostridium perfringens Toxin A
genotype.
Eastern equine encephalomyelitis (EEE) was
reported by the USA, with 30 cases diagnosed in
the fourth quarter, 10 in Michigan and nine in
Indiana. The majority were in unvaccinated horsesthat died or were euthanized.
France, Germany, Portugal, and the USA
confirmed cases of West Nile (WN) encephalitis.
Outbreaks in France (seven), Germany (three), andPortugal (one) involved one or two cases. A totalof 25 cases were recorded in the USA, of which
10 were in Colorado and six in Florida. One casewas positive for both EEE virus and WN virus.
The RSA confirmed one case of equine encephalosis, and the USA diagnosed three cases of equine
protozoal myelitis during the period under review.

The USA confirmed two outbreaks of Rhodococcus equi infection, but this significantly underrepresents the incidence of this endemic disease in
the country.

3

4

N AT I O N A L

Equine Abortion:
The 2016-2019 Breeding Seasons in Central Kentucky

Epiglottic EntrapmentThe epiglottis is a triangular shaped cartilage
located in the throat at the base of the entrance
to the airways. During normal breathing, it is situated above the soft palate and facilitates air movement. When eating, the epiglottis moves upwards
and backwards to allow swallowing and to prevent
food from entering the airways. To allow for such
movement, the lower surface of the epiglottis has
a loosely attached, elastic mucosa (subepiglottic
mucosa). Epiglottic entrapment occurs when the
subepiglottic mucosa becomes positioned above
the epiglottis, restricting movement.
The most common presenting sign in casesof epiglottic entrapment is abnormal respiratory
noise. The abnormally positioned subepiglottic
mucosa creates a slightly narrowed airway, as
well as increased air turbulence, which creates aharsh respiratory noise. Horses in a higher planeof work, racehorses for example, can also present
with exercise intolerance. In horses performing athigh speeds, even mild narrowing of the airway can
result in decreased athletic performance, and, asa result, decreased earnings. Coughing and nasal
discharge occur in some cases, as an abnormallyfunctional epiglottis can contribute to disruptionof airflow and slightly interfere with the swallowing process. As none of these changes indicate a
specific cause of disease, transnasal endoscopy isoften used to further investigate horses exhibitingthese clinical signs. This procedure is commonly
done in many cases with suspected upper airway
disease and involves the passage of a small, flexible
camera up the horse’s nose to visualize the airway.
Most horses tolerate this intervention well withminimal restraint or sedation.
The majority of cases have persistent epiglottic
entrapment; however, a small number of horses
experience intermittent epiglottic entrapment,
which is relieved when the horse swallows. The
membrane entrapping the epiglottis can vary inthickness, width, and can become ulcerated. In
addition to endoscopic evaluation, a radiograph ofthe laryngeal region can also be obtained to assess
the patient for epiglottic hypoplasia (a smaller thannormal epiglottis) as this can be an uncommon
cause of epiglottic entrapment.
Surgery is the most common treatment option
for this condition. An incision is made throughthe abnormally positioned subepiglottic mucosa
to release the entrapped epiglottis. The procedurecan be performed either under sedation and local anesthesia or under general anesthesia andtypically takes less than 30 minutes. There areseveral surgical methods available, namely use ofa transnasal endoscopically guided laser, transendoscopic electrosurgical instrument, or transnasal
or transoral curved surgical knife. Surgical excision
can also be performed via incision into the airway
via the pharynx or larynx, however, these methods
will result in an external scar and can contributeto surgical site complications. These procedures
are therefore typically reserved for cases with additional complications.
The potential complications of surgical intervention include thermal trauma to the epiglottis, adhesions, and cicatrix (scar) formation. To
reduce the risk of these occurring, horses should
receive systemic and topical anti-inflammatory
medications. Dorsal displacement of the soft palate can occur regardless of the treatment method
employed, particularly when epiglottic hypoplasia
is present.
Local inflammation is common following surgical correction of epiglottic entrapment. Horses
should therefore receive transnasal endoscopic
evaluation each week following surgery until thelarynx has a normal appearance. Throat sprays containing anti-inflammatory agents are also strongly
recommended. In order to reduce inflammationin the laryngeal region; horses require a period ofrest following surgery. Depending on the severity of the condition and the treatment method
employed, horses can return to work 3-8 weeks
post-operatively, providing transnasal endoscopic
evaluation is normal. Reoccurrence is not uncommon and can be treated by surgical excision of theexcess subepiglottic mucosa. The majority of horses
with epiglottic entrapment without epiglottic
hypoplasia are able to return to their original levelof activity.
CONTACT:
Alex Gillen, MA, MS, VetMB, CertAVP,
DipACVS, DipECVS, MRCVS
alexandra.gillen@liverpool.ac.uk
Phillip Leverhulme Equine Hospital
University of Liverpool
United Kingdom

causesFigure 1. Infectious Infectious
causes of abortion.
Infectious
causes ofof abortion
abortion
14.00%
14.00%
12.00%
12.00%
10.00%
10.00%
8.00%
8.00%
6.00%
6.00%
4.00%
4.00%
2.00%
2.00%
0.00%
0.00%

MucoidMucoidplacentitis
placentitis

E

FungalUnidentified Leptospirosis
Fetal
FungalUnidentified Leptospirosis
Fetal
placentitis
bacterial
bacteremia
placentitis
bacterial
bacteremia
placentitis
placentitis
2016
2016

2017
2017

2018
2018

EHV‐1
EHV‐1

2019
2019

Noninfectious
Figure 2. Non-infectious
causes of causes
abortion.of
Noninfectious
causesof abortion
abortion
10.00%
10.00%
9.00%
9.00%
8.00%
8.00%
7.00%
7.00%
6.00%
6.00%
5.00%
5.00%
4.00%
4.00%
3.00%
3.00%
2.00%
2.00%
1.00%
1.00%
0.00%
0.00%

Umbilical cord
Umbilical cord
torsiontorsionFetal stress
Fetal stress
2016
2016

Cervical pole
Cervical pole
necrosis
necrosis
2017
2017

2018
2018

Twinning
Twinning
2019
2019

Miscellaneous
Miscellaneousquine abortion is a common and frustrating
condition with a variety of infectious andnoninfectious causes. Evaluation of the fetoplacental unit can aid in understanding the cause ofindividual foal loss, allow early detection of infectious causes of abortion, and identify trends overmultiple years that can help predict future causesof fetal loss. Following changes in the causes ofabortion over multiple years may help to elucidate
environmental risk factors or changes in diseaseprevalence over time.
Causes of abortion over the last four breeding
seasons from 2016 to 2019 are presented in Figure
1 (infectious causes) and Figure 2 (non-infectious
causes). A review of the 2016 and 2017 seasons canbe found in the January 2018 issue of the Equine
Disease Quarterly. Total submission numbers were570, 328, 408, and 304 for 2016, 2017, 2018,and 2019, respectively. The overall submission
numbers vary based on numbers of mares bredthat year and incidence of diseases which create
noticeable placental lesions (such as nocardioform placentitis). General trends in abortion haveremained consistent over time, with placentitis
being the most commonly diagnosed cause ofabortion in all years. Placentitis cases represented
24.6%, 20.2%, 34.5%, and 25% for 2016, 2017,2018, and 2019. Typically, non-infectious causesof abortion (umbilical cord torsion, twins, fetal
and maternal stress, and abortions of unknown
etiology) are more common than infectious causes(viral, bacterial, and fungal infections) with the
exception of 2016, which had 145 cases of mucoid(nocardioform) placentitis, increasing the total

percentage of infectious abortions to 55%.
Evaluation of the last four breeding seasonsshows that cases of mucoid placentitis and abortionof undetermined cause have the most variation
between years. Abortions due to fungal infection,
fetal bacteremia, umbilical cord torsion, and fetal
stress have remained fairly stable. An increase in
miscellaneous causes of abortion and undetermined causes occurred in 2018 and 2019. Miscellaneous causes include a variety of conditions
including congenital malformations, fetal andmaternal stress, cervical pole necrosis, fetal organ
necrosis or inflammation, hydrops and Potomac
horse fever. This increase may reflect normal variation between years. Alternatively, monitoring andintervention for early placentitis and vaccination
for infectious cases of abortion such as leptospirosis and EHV-1 may be decreasing the incidenceof these recognized diseases and result in a corresponding increase in the percentage of cases ofabortion without an identified cause. Abortions of
undetermined cause increased each year at 14.9%
in 2016, 27.5% and 38.2% in 2017 and 2018 andpeaking at 44% in 2019. Continued monitoringof trends will help to determine the significanceof these variations.
CONTACT:
Alan Loynachan, DVM, PhD, DACVP
alan.loynachan@uky.edu
Rebecca Ruby, MSc, BVSc, DAVCP
rebecca.ruby@uky.edu(859) 257-8283
University of Kentucky Veterinary Diagnostic Laboratory,
Lexington, Kentucky

KENTUCKY

Nocardioform Placentitis: A Continuing Enigma

Nocardioform placentitis was first diagnosed incentral Kentucky in 1986 with subsequent
increased case incidences occurring in 1998, 1999,
and 2011. Cases of nocardioform placentitis havealso been reported sporadically in Florida, South
Africa, Italy, and most recently in New Zealand.

Nocardioform placentitis is characterized by lateterm abortions, premature foals, neonatal deaths,
and weak foals born at term. Nocardioform placentitis may involve large regions of the chorion
that can result in fetal growth retardation due toplacental insufficiency. The distribution of theEquine Disease Quarterly Newsletter

5

lesion in the placenta is distinct from ascending
bacterial placentitis with lesions of nocardioform
placentitis commonly distributed in the cranial,
ventral portion of the placenta near the junctionof the uterine horns and body. The lesion is often
sharply demarcated from the surrounding normal
placenta, and the affected placenta is frequently
covered with thick, tan mucoid material.
Nocardioform placentitis is associated with
Gram-positive, branching actinomycetes including multiple Amycolatopsis spp., Crossiella equi,and, more recently, Streptomyces atriruber andStreptomyces silaceus. Characterization of actinomycetes associated with abortions during the 2011
outbreak of nocardioform placentitis in central
Kentucky revealed that Amycolatopsis spp. (49%of cases) were most commonly identified followedby Crossiella equi (29% of cases). Nocardioform
placentitis results in episodic abortions. A major
epizootic of nocardioform placentitis was recorded
in 2010-11, consisting of 390 confirmed cases ofplacentitis with 76 confirmed abortions. These
abortions occurred primarily between December
2010 and April 2011 and were diagnosed almost
exclusively during the last trimester of pregnancy.
Nocardioform placentitis is primarily characterized as a mucoid placentitis in which the bacterial
infection is limited to the chorionic surface of theventral placenta without infection of the fetus. To
date, the pathogenesis remains poorly understood.
Attempts to induce infection in mares by intrauterine inoculation of Crossiella equi at breeding
and in pregnant mares via oral, intravenous, andintranasal routes with this organism have been

350

350

300

300

250

250

200

200

150

100

50

50

1

2

3

4

5

6

Mean Aug-Sept rainfall

Mean Aug-Sept rainfall

7

8

Nocardioform placentitis abortions occur from
November to June, with a peak incidence in January and February. The majority of aborted fetuses
are in the last trimester of pregnancy, and the identification of nocardioform lesions on the placentaof term pregnancies is a common presentation. A
retrospective epidemiologic study of on-farm risk
factors associated with the 2010-11 epizootic ofnocardioform placentitis identified a number ofassociations with nocardioform placentitis. Larger
farms, higher mare numbers and higher animal
density on farms was positively associated with
the incidence of nocardioform placentitis. Longer grazing times during late winter, prebreedingadministration of progesterone to mares, humanchorionic gonadotropin (hCG) administration
post-breeding and nonsteroidal anti-inflammatory
drugs (NSAIDs) were negatively associated with
the incidence of nocardioform placentitis. Retrospective evaluation of monthly climate data(precipitation and average temperature) for central
Kentucky and the number of nocardioform placentitis cases seen by the University of Kentucky
Veterinary Diagnostic Laboratory for the period of
1990-2018 was conducted to evaluate climatologic
associations with nocardioform placentitis (Figures
1 and 2). This analysis demonstrated a moderately
strong negative association (ρ = -0.57; P = 0.001)

150

100

0

Epidemiology

Figure 2. Relationship between the number of nocardioform
placentitis cases seen by the UKVDL and average temperature(°F) in August and September preceding that foaling season.

NP cases

NP cases

Figure 1. Relationship between the number of nocardioform
placentitis cases seen by the UKVDL and average rainfall(inches) in August and September preceding that foaling
season.

unsuccessful. Likewise, the ecology and biologyof the causative agents, Crossiella equi and Amycolatopsis spp. remains unknown as these causative
organisms have only been isolated from affected
placentae in mares.

9

0

67

68

69

70

71

72

73

Mean Mean
Aug-Sept
temperature
Aug-Sept

74

75

76

Presorted Standard
US Postage Paid
Permit 51
Lexington KY

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

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

APRIL 2020
Volume 29, Number 2

C O M M E N TA RY
IN THIS ISSUE
Commentary
International
Fourth Quarter2019  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2Epiglottic
Entrapment  .  .  .  .  .  .  .  .  . 3National
Equine Abortion .  .  .  .  . 4Kentucky

between August and September rainfall and thenumber of nocardioform placentitis cases submitted for the subsequent foaling season. Likewise,
there was a moderately strong positive association(ρ = 0.47; P = 0.001) between mean temperaturesin August and September and the number of nocardioform placentitis cases submitted the next
foaling season. Because average temperatures inAugust and September 2019 were 5.3% above
the long-term average and average rainfall was
only 52% of long-term average, the 2020 foaling
season seems likely to have a higher incidence of
nocardioform placentitis. Although there does
seem to be an association between a hot and dry
August and September preceding an increase innocardioform cases, the causal relationship is lessclear. Other members of the actinomycetes, such as
Rhodococcus equi, are soil-dwelling pathogens thatare associated with hot, dry, dusty environments.
It is worth considering that the actinomycetes
responsible for nocardioform placentitis may also
originate as soil-borne organisms, despite thefailure thus far to isolate these pathogens fromenvironmental sources. Related members of Amycolatopsis and Streptomyces are well characterized
as soil-associated microorganisms, and a likely
environmental association (hot, dry periods in latesummer) may be associated with the disease.
It appears likely that the pathogenesis of nocardioform placentitis is multifactorial and may
involve environmental conditions (hot, dry periods in late summer) and possibly effects related
to host susceptibility. Pregnancy in many species,
including the mare, involves some degree of immunosuppression, and many actinomycetes are more
pathogenic in immunocompromised hosts. Moreresearch is needed to better unravel this complex
disease process in the mare.
CONTACT:
Barry A. Ball, DVM, PhD, DACT
b.a.ball@uky.edu(859) 218-1141
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky

Nocardioform
Placentitis .  .  .  .  .  .  .  .  .  .  . 4

College of Agriculture,
Food and Environment
Department of
Veterinary Science

Lloyd’s—An international
insurance market forbloodstock and otherspecialist insurance.

One benefit of being older is the ability toreflect on many equine medical crises. Contagious equine metritis was the first notable crisisof my career, but I have unfortunately witnessed
numerous others including: equine viral arteritis,
leptospirosis, mare reproductive loss syndrome,
track breakdowns, and more recently nocardioform placentitis. With each of these crises, scientists have stepped up to search for solutions, andI have seen first-hand the positive results that takeplace when practitioners work with scientists on
the medical issues facing our horses.
This year central Kentucky has again been confronted with a substantial increase in the numberof nocardioform placentitis cases. As with any caseof placentitis, and certainly with nocardioform
placentitis, the first clinical sign that the mare’s
pregnancy may be compromised is evident with“bagging up” early, which is horseman’s lingo forpremature lactation or increased udder size. Unlike
ascending placentitis, there is usually no vulvar
discharge in mares with nocardioform placentitis.
For the most part, it is relatively easy to diagnose nocardioform placentitis after the mare has
either aborted or foaled, as the placenta is usually
covered by a very characteristic brown mucoid
discharge—many people think it looks like peanutbutter. A diagnosis of nocardioform placentitis
is more challenging before the mare delivers her
foal (or fetus) and is made based on clinical signs

and abdominal ultrasound scans. Nocardioform
placentitis frequently forms lesions on the ventral
aspect of the placenta. This unique location negates
the usefulness of the standard placentitis ultrasound measurement of the combined thickness of
the uterus and placenta (CTUP), which is taken byrectal ultrasound of the uterus and placenta near
the cervix.
With suspect nocardioform placentitis cases,
one may see a range of abnormalities on transabdominal ultrasound scans. These include pockets
of separation with apparent exudate between theuterus and placenta and signs of placental inflammation. It is important to note that not all lesions
will be apparent by this method, and placental
examination for lesions should still be done after
abortion or parturition.
The greatest incidence of nocardioform placentitis occurs in December, January, and February.
As we enter March, the number of cases should
soon decrease. While we have unfortunately seen
an increased incidence of nocardioform placentitis
this year, one positive is that more cases have been
examined and increased samples have been collected to better understand this unique condition.
CONTACT:Tom Riddle, DVM
triddle@roodandriddle.com(859) 233-0371
Rood and Riddle Equine Hospital
Lexington, Kentucky

Equine Disease Quarterly Newsletter

5

lesion in the placenta is distinct from ascending
bacterial placentitis with lesions of nocardioform
placentitis commonly distributed in the cranial,
ventral portion of the placenta near the junctionof the uterine horns and body. The lesion is often
sharply demarcated from the surrounding normal
placenta, and the affected placenta is frequently
covered with thick, tan mucoid material.
Nocardioform placentitis is associated with
Gram-positive, branching actinomycetes including multiple Amycolatopsis spp., Crossiella equi,and, more recently, Streptomyces atriruber andStreptomyces silaceus. Characterization of actinomycetes associated with abortions during the 2011
outbreak of nocardioform placentitis in central
Kentucky revealed that Amycolatopsis spp. (49%of cases) were most commonly identified followedby Crossiella equi (29% of cases). Nocardioform
placentitis results in episodic abortions. A major
epizootic of nocardioform placentitis was recorded
in 2010-11, consisting of 390 confirmed cases ofplacentitis with 76 confirmed abortions. These
abortions occurred primarily between December
2010 and April 2011 and were diagnosed almost
exclusively during the last trimester of pregnancy.
Nocardioform placentitis is primarily characterized as a mucoid placentitis in which the bacterial
infection is limited to the chorionic surface of theventral placenta without infection of the fetus. To
date, the pathogenesis remains poorly understood.
Attempts to induce infection in mares by intrauterine inoculation of Crossiella equi at breeding
and in pregnant mares via oral, intravenous, andintranasal routes with this organism have been

350

350

300

300

250

250

200

200

150

100

50

50

1

2

3

4

5

6

Mean Aug-Sept rainfall

Mean Aug-Sept rainfall

7

8

Nocardioform placentitis abortions occur from
November to June, with a peak incidence in January and February. The majority of aborted fetuses
are in the last trimester of pregnancy, and the identification of nocardioform lesions on the placentaof term pregnancies is a common presentation. A
retrospective epidemiologic study of on-farm risk
factors associated with the 2010-11 epizootic ofnocardioform placentitis identified a number ofassociations with nocardioform placentitis. Larger
farms, higher mare numbers and higher animal
density on farms was positively associated with
the incidence of nocardioform placentitis. Longer grazing times during late winter, prebreedingadministration of progesterone to mares, humanchorionic gonadotropin (hCG) administration
post-breeding and nonsteroidal anti-inflammatory
drugs (NSAIDs) were negatively associated with
the incidence of nocardioform placentitis. Retrospective evaluation of monthly climate data(precipitation and average temperature) for central
Kentucky and the number of nocardioform placentitis cases seen by the University of Kentucky
Veterinary Diagnostic Laboratory for the period of
1990-2018 was conducted to evaluate climatologic
associations with nocardioform placentitis (Figures
1 and 2). This analysis demonstrated a moderately
strong negative association (ρ = -0.57; P = 0.001)

150

100

0

Epidemiology

Figure 2. Relationship between the number of nocardioform
placentitis cases seen by the UKVDL and average temperature(°F) in August and September preceding that foaling season.

NP cases

NP cases

Figure 1. Relationship between the number of nocardioform
placentitis cases seen by the UKVDL and average rainfall(inches) in August and September preceding that foaling
season.

unsuccessful. Likewise, the ecology and biologyof the causative agents, Crossiella equi and Amycolatopsis spp. remains unknown as these causative
organisms have only been isolated from affected
placentae in mares.

9

0

67

68

69

70

71

72

73

Mean Mean
Aug-Sept
temperature
Aug-Sept

74

75

76

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

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

APRIL 2020
Volume 29, Number 2

C O M M E N TA RY
IN THIS ISSUE
Commentary
International
Fourth Quarter2019  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2Epiglottic
Entrapment  .  .  .  .  .  .  .  .  . 3National
Equine Abortion .  .  .  .  . 4Kentucky

between August and September rainfall and thenumber of nocardioform placentitis cases submitted for the subsequent foaling season. Likewise,
there was a moderately strong positive association(ρ = 0.47; P = 0.001) between mean temperaturesin August and September and the number of nocardioform placentitis cases submitted the next
foaling season. Because average temperatures inAugust and September 2019 were 5.3% above
the long-term average and average rainfall was
only 52% of long-term average, the 2020 foaling
season seems likely to have a higher incidence of
nocardioform placentitis. Although there does
seem to be an association between a hot and dry
August and September preceding an increase innocardioform cases, the causal relationship is lessclear. Other members of the actinomycetes, such as
Rhodococcus equi, are soil-dwelling pathogens thatare associated with hot, dry, dusty environments.
It is worth considering that the actinomycetes
responsible for nocardioform placentitis may also
originate as soil-borne organisms, despite thefailure thus far to isolate these pathogens fromenvironmental sources. Related members of Amycolatopsis and Streptomyces are well characterized
as soil-associated microorganisms, and a likely
environmental association (hot, dry periods in latesummer) may be associated with the disease.
It appears likely that the pathogenesis of nocardioform placentitis is multifactorial and may
involve environmental conditions (hot, dry periods in late summer) and possibly effects related
to host susceptibility. Pregnancy in many species,
including the mare, involves some degree of immunosuppression, and many actinomycetes are more
pathogenic in immunocompromised hosts. Moreresearch is needed to better unravel this complex
disease process in the mare.
CONTACT:
Barry A. Ball, DVM, PhD, DACT
b.a.ball@uky.edu(859) 218-1141
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky

Nocardioform
Placentitis .  .  .  .  .  .  .  .  .  .  . 4

College of Agriculture,
Food and Environment
Department of
Veterinary Science

Lloyd’s—An international
insurance market forbloodstock and otherspecialist insurance.

One benefit of being older is the ability toreflect on many equine medical crises. Contagious equine metritis was the first notable crisisof my career, but I have unfortunately witnessed
numerous others including: equine viral arteritis,
leptospirosis, mare reproductive loss syndrome,
track breakdowns, and more recently nocardioform placentitis. With each of these crises, scientists have stepped up to search for solutions, andI have seen first-hand the positive results that takeplace when practitioners work with scientists on
the medical issues facing our horses.
This year central Kentucky has again been confronted with a substantial increase in the numberof nocardioform placentitis cases. As with any caseof placentitis, and certainly with nocardioform
placentitis, the first clinical sign that the mare’s
pregnancy may be compromised is evident with“bagging up” early, which is horseman’s lingo forpremature lactation or increased udder size. Unlike
ascending placentitis, there is usually no vulvar
discharge in mares with nocardioform placentitis.
For the most part, it is relatively easy to diagnose nocardioform placentitis after the mare has
either aborted or foaled, as the placenta is usually
covered by a very characteristic brown mucoid
discharge—many people think it looks like peanutbutter. A diagnosis of nocardioform placentitis
is more challenging before the mare delivers her
foal (or fetus) and is made based on clinical signs

and abdominal ultrasound scans. Nocardioform
placentitis frequently forms lesions on the ventral
aspect of the placenta. This unique location negates
the usefulness of the standard placentitis ultrasound measurement of the combined thickness of
the uterus and placenta (CTUP), which is taken byrectal ultrasound of the uterus and placenta near
the cervix.
With suspect nocardioform placentitis cases,
one may see a range of abnormalities on transabdominal ultrasound scans. These include pockets
of separation with apparent exudate between theuterus and placenta and signs of placental inflammation. It is important to note that not all lesions
will be apparent by this method, and placental
examination for lesions should still be done after
abortion or parturition.
The greatest incidence of nocardioform placentitis occurs in December, January, and February.
As we enter March, the number of cases should
soon decrease. While we have unfortunately seen
an increased incidence of nocardioform placentitis
this year, one positive is that more cases have been
examined and increased samples have been collected to better understand this unique condition.
CONTACT:Tom Riddle, DVM
triddle@roodandriddle.com(859) 233-0371
Rood and Riddle Equine Hospital
Lexington, Kentucky

2

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

The fourth quarter saw an additional 35
outbreaks of vesicular stomatitis reported by the
USA on premises in eight states. No new affected
premises have been identified since late November.

Fourth Quarter 2019T

Equine Disease Quarterly
Editors

Peter Timoney
Alan Loynachan
Rebecca Ruby

Staff

Diane Furry
Tawana Brown
Dennis Duross
Anita HatchettCorrespondence 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 equine disease outbreaks.
The Republic of South Africa (RSA) reported
sporadic cases of African Horse Sickness inFree State, Gauteng, and North West Province.
These represented the first cases recorded in the
2019/2020 season.
Three separate outbreaks of glanders were confirmed in Turkey. These were associated with illegal
movement of horses without identification orveterinary certification. Of 1,375 horses tested, 63
were positive and 18 suspect; all were euthanized.
Equine influenza was confirmed in France,
Germany, the Netherlands, the UK, and the USA.
With the exception of the USA, the number ofoutbreaks ranged from 1-3, the majority in unvaccinated horses. The disease is endemic in theUSA, with outbreaks diagnosed in seven states andmultiple outbreaks in one state.
Belgium, France, Germany, the Netherlands,
Switzerland, and the USA recorded strangles. The
number of outbreaks varied from four (Belgium),
21 (France), three (Germany), 12 (the Netherlands), one (Switzerland) to 40 in the USA, where
the disease is endemic.
Equine herpesvirus 1 (EHV-1) related diseases
were recorded by Belgium, Canada, France, Germany, the Netherlands, RSA, UK, and the USA.
Respiratory disease outbreaks were diagnosed in
France (two), the Netherlands (one), RSA (one),
UK (four), and in several states in the USA. EHV-1
abortion was reported by France (one case) and theNetherlands (one case). EHV-1 neurologic disease
was confirmed in Belgium (one outbreak involving five horses), Canada (two cases), France (twooutbreaks), Germany (one case), the Netherlands(three outbreaks, one involving 11 affected horses
and the other two, single cases), and the USA (17outbreaks in 10 states, one involving eight cases
and the remainder, single cases).
Equine herpesvirus 4 (EHV-4) respiratory disease outbreaks were reported by France (41, themajority involving single cases), Germany (three,
all single cases), Japan (one outbreak involving
two horses), the Netherlands (five, involving one
to five animals apiece), and the UK (11). While
the majority were represented by single cases, one

outbreak involved 32 weanlings and another eight
yearlings. France (two outbreaks) and the USA(three outbreaks) reported single cases of EHV-4
abortion. Numerous cases of EHV-2 and EHV-5
infection were confirmed by the USA, a percentageof which were associated with clinical respiratory
disease.
France and the USA reported two outbreaks ofequine infectious anemia apiece. Each involved asingle case.
Only a single report of equine piroplasmosis wasreceived in the fourth quarter of 2019. The RSA
reported that the disease was endemic throughout
the country.
A total of 19 cases of nocardioform placentitis
and abortion were diagnosed in Kentucky, USA
during the period under review. A range of bacterial organisms were identified with cases of the disease. Contagious equine metritis was reported byseveral countries. Denmark, France and Germany
each detected Taylorella equigenitalis in a stallion.
South Korea recorded three positive animals outof 2,269 samples tested, the gender of the animals
was not identified.
Other causes of abortion reported by Kentucky,
USA included Neorickettsia risticii (two cases).
The USA recorded one case of Salmonella
infection in Kentucky; several cases of rotavirus
infection in three states, two involving strainsof the G3 genotype and four the G14 genotype;nine cases of Lawsonia enteropathy; and 10 casesof infection with Clostridium perfringens Toxin A
genotype.
Eastern equine encephalomyelitis (EEE) was
reported by the USA, with 30 cases diagnosed in
the fourth quarter, 10 in Michigan and nine in
Indiana. The majority were in unvaccinated horsesthat died or were euthanized.
France, Germany, Portugal, and the USA
confirmed cases of West Nile (WN) encephalitis.
Outbreaks in France (seven), Germany (three), andPortugal (one) involved one or two cases. A totalof 25 cases were recorded in the USA, of which
10 were in Colorado and six in Florida. One casewas positive for both EEE virus and WN virus.
The RSA confirmed one case of equine encephalosis, and the USA diagnosed three cases of equine
protozoal myelitis during the period under review.

The USA confirmed two outbreaks of Rhodococcus equi infection, but this significantly underrepresents the incidence of this endemic disease in
the country.

3

4

N AT I O N A L

Equine Abortion:
The 2016-2019 Breeding Seasons in Central Kentucky

Epiglottic EntrapmentThe epiglottis is a triangular shaped cartilage
located in the throat at the base of the entrance
to the airways. During normal breathing, it is situated above the soft palate and facilitates air movement. When eating, the epiglottis moves upwards
and backwards to allow swallowing and to prevent
food from entering the airways. To allow for such
movement, the lower surface of the epiglottis has
a loosely attached, elastic mucosa (subepiglottic
mucosa). Epiglottic entrapment occurs when the
subepiglottic mucosa becomes positioned above
the epiglottis, restricting movement.
The most common presenting sign in casesof epiglottic entrapment is abnormal respiratory
noise. The abnormally positioned subepiglottic
mucosa creates a slightly narrowed airway, as
well as increased air turbulence, which creates aharsh respiratory noise. Horses in a higher planeof work, racehorses for example, can also present
with exercise intolerance. In horses performing athigh speeds, even mild narrowing of the airway can
result in decreased athletic performance, and, asa result, decreased earnings. Coughing and nasal
discharge occur in some cases, as an abnormallyfunctional epiglottis can contribute to disruptionof airflow and slightly interfere with the swallowing process. As none of these changes indicate a
specific cause of disease, transnasal endoscopy isoften used to further investigate horses exhibitingthese clinical signs. This procedure is commonly
done in many cases with suspected upper airway
disease and involves the passage of a small, flexible
camera up the horse’s nose to visualize the airway.
Most horses tolerate this intervention well withminimal restraint or sedation.
The majority of cases have persistent epiglottic
entrapment; however, a small number of horses
experience intermittent epiglottic entrapment,
which is relieved when the horse swallows. The
membrane entrapping the epiglottis can vary inthickness, width, and can become ulcerated. In
addition to endoscopic evaluation, a radiograph ofthe laryngeal region can also be obtained to assess
the patient for epiglottic hypoplasia (a smaller thannormal epiglottis) as this can be an uncommon
cause of epiglottic entrapment.
Surgery is the most common treatment option
for this condition. An incision is made throughthe abnormally positioned subepiglottic mucosa
to release the entrapped epiglottis. The procedurecan be performed either under sedation and local anesthesia or under general anesthesia andtypically takes less than 30 minutes. There areseveral surgical methods available, namely use ofa transnasal endoscopically guided laser, transendoscopic electrosurgical instrument, or transnasal
or transoral curved surgical knife. Surgical excision
can also be performed via incision into the airway
via the pharynx or larynx, however, these methods
will result in an external scar and can contributeto surgical site complications. These procedures
are therefore typically reserved for cases with additional complications.
The potential complications of surgical intervention include thermal trauma to the epiglottis, adhesions, and cicatrix (scar) formation. To
reduce the risk of these occurring, horses should
receive systemic and topical anti-inflammatory
medications. Dorsal displacement of the soft palate can occur regardless of the treatment method
employed, particularly when epiglottic hypoplasia
is present.
Local inflammation is common following surgical correction of epiglottic entrapment. Horses
should therefore receive transnasal endoscopic
evaluation each week following surgery until thelarynx has a normal appearance. Throat sprays containing anti-inflammatory agents are also strongly
recommended. In order to reduce inflammationin the laryngeal region; horses require a period ofrest following surgery. Depending on the severity of the condition and the treatment method
employed, horses can return to work 3-8 weeks
post-operatively, providing transnasal endoscopic
evaluation is normal. Reoccurrence is not uncommon and can be treated by surgical excision of theexcess subepiglottic mucosa. The majority of horses
with epiglottic entrapment without epiglottic
hypoplasia are able to return to their original levelof activity.
CONTACT:
Alex Gillen, MA, MS, VetMB, CertAVP,
DipACVS, DipECVS, MRCVS
alexandra.gillen@liverpool.ac.uk
Phillip Leverhulme Equine Hospital
University of Liverpool
United Kingdom

causesFigure 1. Infectious Infectious
causes of abortion.
Infectious
causes ofof abortion
abortion
14.00%
14.00%
12.00%
12.00%
10.00%
10.00%
8.00%
8.00%
6.00%
6.00%
4.00%
4.00%
2.00%
2.00%
0.00%
0.00%

MucoidMucoidplacentitis
placentitis

E

FungalUnidentified Leptospirosis
Fetal
FungalUnidentified Leptospirosis
Fetal
placentitis
bacterial
bacteremia
placentitis
bacterial
bacteremia
placentitis
placentitis
2016
2016

2017
2017

2018
2018

EHV‐1
EHV‐1

2019
2019

Noninfectious
Figure 2. Non-infectious
causes of causes
abortion.of
Noninfectious
causesof abortion
abortion
10.00%
10.00%
9.00%
9.00%
8.00%
8.00%
7.00%
7.00%
6.00%
6.00%
5.00%
5.00%
4.00%
4.00%
3.00%
3.00%
2.00%
2.00%
1.00%
1.00%
0.00%
0.00%

Umbilical cord
Umbilical cord
torsiontorsionFetal stress
Fetal stress
2016
2016

Cervical pole
Cervical pole
necrosis
necrosis
2017
2017

2018
2018

Twinning
Twinning
2019
2019

Miscellaneous
Miscellaneousquine abortion is a common and frustrating
condition with a variety of infectious andnoninfectious causes. Evaluation of the fetoplacental unit can aid in understanding the cause ofindividual foal loss, allow early detection of infectious causes of abortion, and identify trends overmultiple years that can help predict future causesof fetal loss. Following changes in the causes ofabortion over multiple years may help to elucidate
environmental risk factors or changes in diseaseprevalence over time.
Causes of abortion over the last four breeding
seasons from 2016 to 2019 are presented in Figure
1 (infectious causes) and Figure 2 (non-infectious
causes). A review of the 2016 and 2017 seasons canbe found in the January 2018 issue of the Equine
Disease Quarterly. Total submission numbers were570, 328, 408, and 304 for 2016, 2017, 2018,and 2019, respectively. The overall submission
numbers vary based on numbers of mares bredthat year and incidence of diseases which create
noticeable placental lesions (such as nocardioform placentitis). General trends in abortion haveremained consistent over time, with placentitis
being the most commonly diagnosed cause ofabortion in all years. Placentitis cases represented
24.6%, 20.2%, 34.5%, and 25% for 2016, 2017,2018, and 2019. Typically, non-infectious causesof abortion (umbilical cord torsion, twins, fetal
and maternal stress, and abortions of unknown
etiology) are more common than infectious causes(viral, bacterial, and fungal infections) with the
exception of 2016, which had 145 cases of mucoid(nocardioform) placentitis, increasing the total

percentage of infectious abortions to 55%.
Evaluation of the last four breeding seasonsshows that cases of mucoid placentitis and abortionof undetermined cause have the most variation
between years. Abortions due to fungal infection,
fetal bacteremia, umbilical cord torsion, and fetal
stress have remained fairly stable. An increase in
miscellaneous causes of abortion and undetermined causes occurred in 2018 and 2019. Miscellaneous causes include a variety of conditions
including congenital malformations, fetal andmaternal stress, cervical pole necrosis, fetal organ
necrosis or inflammation, hydrops and Potomac
horse fever. This increase may reflect normal variation between years. Alternatively, monitoring andintervention for early placentitis and vaccination
for infectious cases of abortion such as leptospirosis and EHV-1 may be decreasing the incidenceof these recognized diseases and result in a corresponding increase in the percentage of cases ofabortion without an identified cause. Abortions of
undetermined cause increased each year at 14.9%
in 2016, 27.5% and 38.2% in 2017 and 2018 andpeaking at 44% in 2019. Continued monitoringof trends will help to determine the significanceof these variations.
CONTACT:
Alan Loynachan, DVM, PhD, DACVP
alan.loynachan@uky.edu
Rebecca Ruby, MSc, BVSc, DAVCP
rebecca.ruby@uky.edu(859) 257-8283
University of Kentucky Veterinary Diagnostic Laboratory,
Lexington, Kentucky

KENTUCKY

Nocardioform Placentitis: A Continuing Enigma

Nocardioform placentitis was first diagnosed incentral Kentucky in 1986 with subsequent
increased case incidences occurring in 1998, 1999,
and 2011. Cases of nocardioform placentitis havealso been reported sporadically in Florida, South
Africa, Italy, and most recently in New Zealand.

Nocardioform placentitis is characterized by lateterm abortions, premature foals, neonatal deaths,
and weak foals born at term. Nocardioform placentitis may involve large regions of the chorion
that can result in fetal growth retardation due toplacental insufficiency. The distribution of the