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 to BVD.

  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 dam’s 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 tool.

   -By Dr. James P. Orr, Pathologist

    Reprinted with permission from   the Animal Health Expositor,  Prairie Diagnostic Services,
    Saskatoon, Saskatchewan