AN APPROACH TO THE DIAGNOSIS OF BOVINE ABORTION*

How is reproductive failure manifested ?
Reproductive failure may occur at any phase in the female reproductive cycle. The clinical outcome of such a dysfunction is determined by the stage of the cycle affected:

	dysfunction of the oestrus cycle may lead to anoestrus
	ovulation Þ infertility
	fertilization Þ infertility
	embryogenesis Þ early embryonic death, resorption or infertility
	foetal development Þ foetal death, abortion or mummification
	parturition Þ perinatal death
	post partum Þ neonatal death

Do we agree on terminology ?

	early embryonic death: before implantation is complete at day 16; resulting in resorption. Up to 25-40% of early embryonic deaths may be due to genetic faults
	foetal death: after implantation: results in mummification, maceration, abortion or stillbirth
	mummification: failure of abortion with resorption of placental fluids, foetal dehydration, and uterine involution. Subsequent abortion or expulsion during parturition may occur. Dried, shrunken, brown/black
	maceration: due to bacterial infection. Only the bones are intact in the liquefactive, foul-smelling remains of soft tissues. Often accompanied by pyometra, uterine abscesses and foetal emphysema
	abortion: spontaneous or induced premature cessation with expulsion of a foetus too immature for survival (< 260 days)
	perinatal death: Immediately prior to or during parturition, or within 72 h after normal pregnancy. Includes stillbirth (= a full term foetus born dead)

Why the low success rate?

	event occurred days/weeks or even months earlier and cause may be undetectable at time of abortion
	few, if any, clinical signs in the dam prior to abortion
	usually no gross lesions in foetus
	autolysis often obscures foetal lesions and test results may become difficult to interpret
	foetal membranes, often affected first and most consistently, often not available
	most causes still unknown; toxic and genetic factors generally not detectable
	histology, serology, pathology and ‘other tools’ often only of marginal assistance
	foetal immune system may react differently than that of adult (be careful with test results from foetal tissue and do not always rely on conventional wisdom)
	incorrect samples submitted

Causes of abortion (and foetal abnormality) in cattle in South Africa [For more information on most of the conditions see: Vet Clin North Am 9(2):343-368, 1993 and J Vet Diag Inv 4:374-379, 1992]
 

Data from South Africa (JSAVA 70:50-57, 1999)
194 bovine foetuses examined, 1993 - 1996, OVI; 113/194 positive diagnosis = 58%;

	42/113 (37%) non-infectious included 19 % dystokias (cause of abortion?) and 11% developmental anomalies
	71/113 (63%) infectious included 52% bacterial or suspected bacterial; 2% suspected viral; 0,5% fungal; and 9% protozoal (mainly Anaplasma)

Factors indicating viral aetiology

	multiple cases during breeding season
	explosive nature of outbreak
	increased incidence of congenital defects following epidemic of a specific disease
	malformations in offspring of young females
	malformations in animals in certain area or district
	increase in number of resorbed foetuses

	organism found in pure or nearly pure culture in foetal stomach content or foetal tissues or both
	inflammation in foetal tissues (especially lung = bronchopneumonia with light microscopy) and placenta
	no other likely cause for abortion

What tests are available to the diagnostician ?

	smears: blood and impression smears
	serology
	microbiology: bacteria, viruses and fungi
	immunofluorescence
	immunohistochemistry
	pathology
	molecular biology: PCR
	electron microscopy (cotyledons)
	toxicology
	genetic testing (blood)

Do not forget a detailed history!

Examine the entire placenta and umbilical cord. Recognise normal features such as amniotic plaques and mineralization. If lesions are noticeable, try to distinguish between non-infectious and infectious causes. With regards to non-infectious causes, look for:

	umbilical cord abnormalities (torsion, strangulation)
	deficient placentation (may result in inadequate blood supply to the foetus)
	premature separation, villous atrophy
	adventitial placentation (may be response to hydrops amnii/allantois)

In the case of placentitis, specifically look for:

	cotyledon necrosis => e.g. Campylobacter, Brucella, Leptospira, Chlamydia, Coxiella
	haemorrhage => e.g. Listeria, Coxiella
	intercotyledonary oedema => Brucella, Leptospira
	granulomatous inflammation => Actinomyces, Nocardia
	hyperplastic lesions => Coxiella, Mycoplasma, Chlamydia, mycosis
	purulent inflammation => A. pyogenes

Prepartum (prenatal) death; death of foetus preceding initiation of partus

	haemoglobin-stained tissues (reddish)
	prominent renal cortical autolysis
	no umbilical artery thrombus or haemorrhage

Intrapartal (natal) death; calves die during parturition

	no haemoglobin-staining
	no umbilical artery thrombus or haemorrhage
	early (death before active expulsion): variable renal cortical autolysis; no subcutaneous oedema
	late (death during active expulsion): no renal cortical autolysis; localised subcutaneous oedema of head, forelimbs, or perineum (indicating positive signs of heart or lung function)

	thrombus in umbilical artery
	lung aeration
	early: soft to firm umbilical thrombus with haemorrhage around stump; no milk in digestive tract and no intestinal absorption of milk; no wear of slippers
	late: firm umbilical thrombus or umbilicus dried out; body fat metabolism if starvation occurred; milk in gut possibly with milk in lacteals; some wear of slippers

	congenital malformations (including nervous system and cardiac defects), lethal defects, inherited conditions (chondrodysplasia), and nutritional conditions such as hypovitaminosis A
	pale streaky muscles (skeletal and myocardium: white muscle disease)

	degree of maturity: early (BVD, Trichomonas); middle (IBR, Campylobacter, Neospora); late (Brucella, A. pyogenes, Leptospira)
	degree of autolysis: foetal death in utero therefore autolysed (IBR, Leptospira, A. pyogenes) vs premature foetal expulsion with minimal autolysis (Aspergillus, Chlamydia): unreliable
	foetal anomalies: mainly viral such as cerebellar hypoplasia (BVD) and skeletal abnormalities (BVD, RVF)
	anaemia, icterus (Babesia, Leptospira)
	hepatic lesions + interstitial pneumonia (viral such as IBR, RVF or septicaemia)
	fibrin on serosal surfaces (septicaemia)
	omphalophlebitis
	pale streaky muscles (skeletal and myocardium; Neospora)

	subcutaneous oedema frequently involving the head
	lung aeration
	subdural haemorrhage
	ruptured liver
	staining by or aspiration of meconium
	amniotic haemorhage

There are two options:

	option 1: perform a detailed necropsy examination on the aborted foetus and send specimens to a lab
	option 2: submit entire foetus and portion of the placenta to a lab (preferred)

What specimens are required (option 1) ?

	blood smear from foetus and dam
	impression smears from cotyledon and abomasal content (Stamps staining)
	abomasal content, lung, spleen or liver, cotyledon and affected organs for bacterial culture (aerobic and Brucella): specimens on ice - sterile - separate containers - do not freeze
	spleen and lung for viral isolation (not routinely done; costs)
	spleen for BVD-antigen detection (ELISA)
	range of organs and tissues in formalin for histology and possibly IMP: submit lung (pneumonia), liver (necrosis), spleen, brain (Neospora), kidney, adrenal gland (necrosis), thyroid gland, myocardium, skeletal muscle (Neospora, WMD)
	pre-colostral fluid from foetus: determine antibody titres to exclude viral in utero infection. Use CSF (useful in cases of hydrocephalus or hydranenchephaly), thoracic or abdominal fluid - only of use in late abortion after foetus has reached immunocompetence
	materal serology has limited usefulness. Cannot reliably discriminate between vaccination and natural exposure. To differentiate between recent versus prior exposure, two different tests are used: complement fixation (CF): IgM = recent exposure; ELISA: IgG = prior exposure. Serology is only useful if a four-fold change in titre is detected from paired serum samples. This has been demonstrated in chlamydosis and for viruses (only when the abortion is acute). Collect serum at the time of abortion and 3 weeks later, from several animals including unvaccinated animals.