Abortion in the Horse

Most common bacterial cause - bacterial species , treatment

-Streptococcal species

-E. coli

-tx: antimicrobials, anti inflammatories, meds for maintaining uterine quiescence

Most common viral cause of abortion - when it causes abortion, vaccines/admin

-Equine herpesvirus type 1 (EHV 1)

-abortion in latter gestation

-EHV-1 vaccine admin at 5,7,9 months

Most common non infectious cause of abortion

-twin fetuses

-placenta can’t maintain two feti, which are typically aborted during gestation

-some may be born alive

Placentitis - route, causative orgs, effects of infection

-during the latter stages of pregnancy (7-11 months)

-route: bacteria are introduced to the uteroplacental unit via ascending infections → inflammation and placental detachment at the cervical star region

-hematogenous infection are poss → Strep zooepidemicus, E. coli, P. aeruginosa, Klebsiella

-fungal: Aspergillus

-placental thickening occurs along with separation from the endometrium, resulting in abortion from uteroplacental insufficiency → inflammation promotes uterine activity

Placentitis treatments and outcomes

-antimicrobial therapy

-non steroidal anti inflammatories (Flunixin meglumine)

-Altrenogest (progesterone) to promote uterine quiescence

-Clenbuterol (sympathomimetic) to suppress uterine motility

-pentoxyfylline to decrease inflammatory mediators and increase uterine blood flow

-outcomes range from abortion to healthy foal birth to septic foal

-early intervention can improve outcome

Viral abortions - causative orgs, vaccination, infection effects, fetal effect

-EHV -1 is most common

-EHV-4 (equine viral arteritis)

-EHV-1 vaccine given at 5,7,9 months of preg

-EHV-1 results in subclinical to clinically relevant respiratory infections

-abortion can occur soon after mare infection or several weeks after

-viremia infection of fetus → rapid placental detachment

-fetus can become infected by: amniotic fluid inhalation or chorionic vasculature

viral abortions - diagnosis

-aborted fetus examination: small necrotic foci on liver, necrotizing bronchiolitis, intranuclear inclusion bodies on histologic examination

-some fetuses are born alive and have neonatal herpes: many of these foals don’t survive for more than a few hours or days and demonstrate signs of resp distress, icterus, fever, lethargy

-viral neutralization test, indirect immunoflourescence, PCR, and viral isolation for confirmation of EHV

viral abortions - treatment

-no direct treatment

-acyclovir and valacyclovir may be beneficial

-vaccination protocols for prevention are most effective

List of non infectious causes of abortion

-twin fetuses

-umbilical torsion

Twin fetuses - effects, consequences, outcome

-diffuse microcotyledonary placentation of the mare makes it unlikely a twin preg will carry to full term→ limited endometrial surface available for allantochorion to attach

-two fetuses compete for adequate nutrition and placentation

-if it is maintained to latter gestation, fetal growth is more rapid and demandning on mare until one or both twins become emaciated and die → death of one or both commonly is followed by abortion

-if twins are carried to full term, one or both, have stunted growth and size from intrauterine growth retardation

-it is poss for twins to survive, but its also common for one or both to have disorders of development

Umbilical torsion - effect, consequence

-not common

-fetus rotates in the amniotic sac and causes excessive twisting of the umbilical cord

-normal flow through the umbilicus is constricted = edema, hemorrhage, ecchymosis