Objective—To characterize the temporality of dates
of breeding and abortion classified as mare reproductive
loss syndrome (MRLS) among mares with abortions
during early gestation.
Animals—2,314 mares confirmed pregnant at
approximately 28 days after breeding from 36 farms in
central Kentucky, including 515 mares that had earlyterm
Procedure—Farm veterinarians and managers were
interviewed to obtain data for each mare that was
known to be pregnant to determine pregnancy status,
breeding date, last date known to be pregnant, and
date of abortion.
Results—Mares bred prior to April 1, 2001,
appeared to be at greatest risk of early-term abortion,
both among and within individual farms.
Mares bred in mid-February appeared to be at
greatest risk of abortion, with an estimated weekly
incidence rate of abortion of 66% (95% CI, 52% to
Conclusions and Clinical Relevance—Mares in
central Kentucky bred between mid-February and
early March were observed to be at greatest risk of
early-term abortion, and risk gradually decreased to
a background incidence of abortion of approximately
11%. Mares bred after April 1, 2001, appeared to
be at markedly less risk, indicating that exposure to
the cause of MRLS likely occurred prior to this
date. (Am J Vet Res 2005;66:1792–1797)
Objective—To estimate spatial risks associated with
mare reproductive loss syndrome (MRLS) during
2001 among horses in a specific study population and
partition the herd effects into those attributable to
herd location and those that were spatially random
and likely attributable to herd management.
Animals—Pregnant broodmares from 62 farms in 7
counties in central Kentucky.
Procedure—Veterinarians provided the 2001 abortion
incidence proportions for each farm included in the
study. Farms were georeferenced and data were analyzed
by use of a fully Bayesian risk-mapping technique.
Results—Large farm-to-farm variation in MRLS incidence
proportions was identified. The farm-to-farm
variation was largely attributed to spatial location
rather than to spatially random herd effects
Conclusions and Clinical Relevance—Results indicate
that there are considerable data to support an
ecologic cause and potential ecologic risk factors for
MRLS. Veterinary practitioners with more detailed
knowledge of the ecology in the 7 counties in
Kentucky that were investigated may provide additional
data that would assist in the deduction of the
causal factor of MRLS via informal geographic information
systems analyses and suggest factors for
inclusion in further investigations. (Am J Vet Res 2005;66:17–20)
Objective—To identify factors associated with abortions
during early gestation classified as mare reproductive
loss syndrome (MRLS).
Animals—324 broodmares from 43 farms in central
Kentucky, including 121 mares from 25 farms that
had early-term abortions (ETAs) associated with
MRLS (case horses), 120 mares from the same farms
but that did not abort, and 83 mares from 18 farms
that were not severely impacted by MRLS.
Procedure—Farm managers were interviewed to
obtain data on various management practices and
environmental exposures for the mares. Data for case
and control horses were compared to identify risk factors
for mares having MRLS-associated ETAs.
Results—Several factors increased the risk of MRLS-associated
ETAs, including feeding hay in pasture,
greater than usual amounts of white clover in pastures,
more eastern tent caterpillars in pastures, abortion
during a previous pregnancy, and sighting deer or
elk on the premises.
Conclusions and Clinical Relevance—Analysis indicates
that certain characteristics of pastures predisposed
mares to MRLS-associated ETAs. Methods for
limiting exposure to pasture (keeping mares in stalls
longer) during environmental conditions similar to
those of 2001 (ie, sudden freezing in mid-April following
warmer-than-usual springtime temperatures and
larger-than-usual numbers of eastern tent caterpillars
in and around pastures) should reduce the risk of
mares having MRLS-associated ETAs. It was not possible
to determine whether exposure to white clover
or caterpillars were causal factors for MRLS or were
merely indicators of unusual environmental conditions
that resulted in exposure of mares to a toxic or infectious
agent. (J Am Vet Med Assoc 2003;222:210–217)
Objective—To determine whether the concentration of airborne virulent Rhodococcus equi varied by location (stall vs paddock) and month on horse farms.
Sample—Air samples from stalls and paddocks used to house mares and foals on 30 horse breeding farms in central Kentucky.
Procedures—Air samples from 1 stall and 1 paddock were obtained monthly from each farm from January through June 2009. Concentrations of airborne virulent R equi were determined via a modified colony immunoblot assay. Random-effects logistic regression was used to determine the association of the presence of airborne virulent R equi with location from which air samples were obtained and month during which samples were collected.
Results—Of 180 air samples, virulent R equi was identified in 49 (27%) and 13 (7%) obtained from stalls and paddocks, respectively. The OR of detecting virulent R equi in air samples from stalls versus paddocks was 5.2 (95% confidence interval, 2.1 to 13.1). Of 60 air samples, virulent R equi was identified in 25 (42%), 18 (30%), and 6 (10%) obtained from stalls during January and February, March and April, and May and June, respectively. The OR of detecting virulent R equi from stall air samples collected during May and June versus January and February was 0.22 (95% confidence interval, 0.08 to 0.63).
Conclusions and Clinical Relevance—Foals were more likely to be exposed to airborne virulent R equi when housed in stalls versus paddocks and earlier (January and February) versus later (May and June) during the foaling season.