Temporality of early-term abortions associated with mare reproductive loss syndrome in horses.
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.


METHODS
2,314 mares confirmed pregnant at approximately 28 days after breeding from 36 farms in central Kentucky, including 515 mares that had early-term abortions.


METHODS
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 80%).


CONCLUSIONS
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.
Cohen
Noah D
ND
Department of Large Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4475, USA.
Carey
Vincent J
VJ
Donahue
James G
JG
Seahorn
Janyce L
JL
Brown
Stuart E
SE
Riddle
Thomas W
TW
D000034:Abortion, Veterinary / Q000453:epidemiology / Q000662:veterinary*; D000818:Animals; D004196:Disease Outbreaks / Q000662:veterinary*; D005260:Female; D005313:Fetal Death / Q000453:epidemiology / Q000662:veterinary*; D006734:Horse Diseases / Q000453:epidemiology*; D006736:Horses; D007407:Interviews as Topic; D007629:Kentucky / Q000453:epidemiology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D012307:Risk Factors; D013577:Syndrome; D013997:Time Factors