Equine Abortion
A Timetable Guide to Diagnosis by Lauri Robinson, Diagnostic
Pathology Clerk edited by Wm. Van AIstine,DVM,PhD
| Cause of Abortion/ Time of
Gestation |
Gross Findings and Clinical
Signs |
Diagnosis: Samples to Submit
and Lab
Procedures (see note) |
Early Embryonic Death (EED)
0-40 d Eariy Fetal Death
|
Maternal malnutrition, twin pregnancy, history
of maternal stress, uterine disease, poor conformation
of vulva, vagina, cervix
Early (EED) signs: often none
Later (EFD) signs: aborted fetus |
Repeated gynecologic exams, fetal and maternal
serum samples, antigen/ antibody compatibility |
Equine Viral Arteritis
(EVA) 5-10 mo
| Mare: depression, fever,
anorexia,leukopeniakeratitis, diarrhea, colic, edema of
limbs and ventral abdomen, generalized vascular necrosis
Fetus: aborted 7-10 d after first signs of illness in
mare, usually autolyzed because death 2-4 d prior to abortion,
± pleural effusion, petechial hemorrhage, if non-autolyzed-
usually no gross lesions |
Histopath
-Serology
-Virus isolation
-Check stallion since virus can be transmitted via semen |
| Twinning 6-9 mo (=most
common non-infectious cause) |
Fetus: 2 feti, one in all of 1 horn and most
of body. and the other in a small portion of the body
and in the other horn
Placenta: large smooth area between the chorions
of the twins
Mare: ± history of double ovulations |
None needed |
| Placental Defects |
Pathologic Twisting of the
Cord
6-9 mo |
Fetal anoxia due to pathologic
twisting of the cord diagnosed by twisting of the cord
and localized swelling and discoloration of the cord,
causing vascular obstruction. Cord is usually abnormally
long (>90 cm). |
Histopath Optional |
Body Pregnancy
7-9 mo
|
Fetus: in the body of the
uterus with stunted growth
Placenta:Placential insufficiency: homs
have failed to expand and the chorioallantoic homs
are undeveloped |
None Necessary |
EHV-1
(Rhinopneumonitis)
9-1 Imocan be 5-11 mo
(#1 cause of abortion)
|
Fetus: Aborted 3 wks -
4 mo post mare exposure
-Liver: enlarged with subcapsular pinpoint to 5mm grey/
white foci of necrosis
-Lungs: severe edema,esp.interlobular septa, ± white foci
of necrosis (like liver)
-Pleural/Abdominal cavities: excessive yellow fluid
± Pericardial effusion and epicardialpetchiae
± jaundice of mucous membrane
If bom alive - dies within hours to days
Placenta:±edematous, ± no rupture of cervical star,fetus
usually still attached to fetal membranes,
± premature placental separation
Mares/Farm; asymptomatic/abortion storms |
-Tissues in formalin for histopath-intranuclear
inclusion bodies
-Virus isolation (fetal lung, liver, adrenal, lymph nodes)
-FA
-Fetal serology
|
| Cause of Abortion/ Time of Gestation
|
Gross Findings and Clinical Signs
|
Diagnosis: Samples to Submit and Lab Procedures
(see note) |
MycoticS-11mo (can be 5-11 mo) Most common:
Aspergillusfumigatus
(canbeA/ycor,Allescheria, Candida,Coccidiodes,Histoplasma,
Cryptococcus |
Fetus: not autolytic, small, emaciated,
if bom alive-dies soon after birth, ± bronchopneumonia±grey
nodules on lung, ±mycotic dermatitis
Placenta: thickened, necrotic placenta ± necrotic plaques on maternal chorionic surface and
on endometrium.
Note: it is normal for the equine placenta
to have 1-2 mm hyperkeratotic nodules on the fetal side
of the allantoamnionnear the major vessels of the cord.
Mares: post-abortion: purulent vulval
discharge that resolves spontaneously |
-Histopath
-fungal culture of placenta
|
Premature Placental Separation
late in gestation |
Fetus: death by anoxia
Mares:allantochorion bulges out of vulvawith
cervical star intact. Cause unknown |
None necessary |
Bacterial anytime most common:
Strep.zaoepidemicus
others: E.coli, Pseudomonas,Staph., Klebsiella,Enterobacter,
Taylorellaequigenitalis(CEM) |
Usually ascending infection
Fetus: gross lesions are non-specific, ± enlarged liver, ± increased fluid in body cavities;
organisms most consistently isolated from fetal stomach
contents
Placenta: area of the chorioallantois around
the cervical star is edematous and thickened, ± chorion
covered in brown exudate, line of demarcation between
the diseased
placenta and normal chorioallantois, ± cloudy
fluid in amniotic cavity
Length of pregnancy before abortion depends
on the presence of absence of septicemia and the amount
of placental involvement
|
-Fetal stomach contents, placenta, liver,
kidney, and lung for culture
-Histopath |
| Leptospirosis 6-11 mo |
Fetus:icterus, enlarged/yellow liver
Placenta: thickened allantochorion
or exudate |
-Histopath
-Immunofluorescencefor spirochetes in aborted
tissues (kidney, liver, placenta) |
Other Causes of Equine Abortion:
Hormones: Progesterone deficiency, prostaglandin
F2a, oxytocin,glucocorticoidsPoisonous Plants, Drugs:
Fescue, locoweed, sudan
grass, sorghum, phenothiazine,organophosphates thiabendazole
Notes: The best method of diagnosing equine
abortions is to submit the entire fetus and placenta to a
diagnostic laboratory. However, this is not always practical.
If a field necropsy is performed, it is important that the
practitioner send the following tissues to the diagnostic
laboratory: placenta, lung, liver, spleen kidney, stomach
contents, lymph nodes, thymus, fetal adrenal, and fetal serum.
References:
Kobluk,C,etal. The Horse: Diseases and Clinical
Management. Philadelphia:
WBSaunders, 1995. McKinnon,AO and JLVoss.Equine Reproduction.
Philadelphia:
Lea & Febiger, 1993.
|
