Abortions Why Have Them Necropsied?
The success rate in identifying causes of abortion by
conducting a post mortem on the fetus and placenta is low
compared to other diseases. This is particularly true for
cattle, sheep and pigs, the species most frequently submitted
to laboratories for fetal pathological analysis. A unique
diagnostic feature of abortions lies in the intimate relationship
existing between dam and fetus, simultaneously involved
and affected by the event, often unequally. While the fetus
is ultimately affected and prematurely expelled, the triggering
cause of abortion in many cases is disease involving the
dam and her environment. The diagnostic conundrum presented
by abortion requires critical examination of these relationships.
Why examine fetus and placenta?
For owners of affected animals, negative results are
of equal importance to positive ones. Clearly it becomes
important to know if an aborted calf is affected with IBR
or Neospora, or that lambs were aborted because of toxoplasmosis
or coxiellosis. An accurate diagnosis allows the practitioner
to respond using solid medical information in determining
treatment and preventative measures for specific diseases.
On the other hand, negative results despite full
pathological and microbiological examination-offer reassurance
that several infectious diseases, including important zoonoses,
have been partially or completely ruled out.
Examination of the aborted fetus can provide insight
into noninfectious diseases affecting the unborn like congenital
anomalies incompatible with fetal survival, placental hemorrhage
arising from trauma, fetal heart failure caused by dietary
selenium deficiency and hemorrhage as a result of sweet
clover poisoning. A full term, underdeveloped fetus may
reveal maternal problems like inadequate nutrition through
the later half of pregnancy, or placental disease. The
detailed necropsy supplemented by histology and other tests
involving virus isolation or immunohistochemistry help differentiate
noninfectious disease from things like congenital exposure
Genetic defects in livestock are occasionally expressed
as fetal deformities that result in death of the fetus and
abortion. A few specific genetic defects may be identified
through examination of fetal tissue. Osteopetrosis, arthrogryposis
of cattle and spider-lamb chondrodysplasia in
sheep are in this category. Non-heritable chromosomal defects
with malformation of multiple body systems may be diagnosed
by karyotyping viable cells collected from fetal tissue.
Autolysis is a major enemy of the pathologist. Fetal
submissions are received in various states of autolysis
more frequently than any other type of specimen, due in
large part to in utero decomposition of the dead
fetus that may not be expelled for a period of time while
maintained at the dams body temperature. Despite
this reality, pathologists are repeatedly surprised to find
characteristic lesions of IBR (liver), Neospora (brain)
and other infections when autolyzed tissue is examined histologically.
Even the autolyzed fetus can be a valuable diagnostic
-By Dr. James P. Orr, Pathologist
Reprinted with permission from the Animal Health
Expositor, Prairie Diagnostic Services,