Education

1. Abortion in Large
Animals
Dr. Karima Al salihi

2. Definition
Abortion is the termination of pregnancy
after organogenesis is complete but before
the expelled fetus can survive.
If pregnancy ends before organogenesis, it
is called early embryonic death.
A dead, full-term fetus is a stillbirth (its
lungs are not inflated). Many etiologies of
abortion also cause stillbirths,
mummification, and weak or deformed
neonates.

3. The etiologic diagnosis of abortion in livestock is a difficult
and often frustrating task.
• Numerous factors complicate diagnosis.
• Often, abortion follows initial infection by weeks or
months, so the causative agent is no longer apparent
when abortion occurs.
• Expulsion may follow fetal death by hours or days, with
lesions obscured by autolysis.
• Fetal membranes and the aborted fetus are usually
contaminated by environmental agents before
examination.
• Many sporadic abortions are likely the result of
noninfectious (ie, toxic or genetic) causes, about which
much less is known than infectious causes; many
diagnostic laboratories are not equipped or staffed to
deal with these causes of abortion.

4. Abortion's samples
• Another problem in determining the cause of abortions is improper or
inadequate specimen selection and handling.
• The best specimen is the complete feto-placental unit in fresh condition,
along with maternal serum.
• The placenta and fetus should be cleaned with water or saline, packed in
clean plastic bags, chilled (but not frozen), and rapidly transported to the
diagnostic laboratory.
• In most cases, autolysis proceeds at a much slower rate in fetuses than
in carcasses of animals born alive.
• If chilled as soon as possible, most fetuses will be suitable for
examination, even if they do not reach the laboratory for 1–2 days.
• Fetal pigs, sheep, and goats are usually small enough to transport or
ship whole with the placenta.
• If there are multiple fetuses, three to five should be submitted with their
placentas.
• It is best to submit calves and foals whole, but in many cases it is more
convenient to perform a necropsy and collect samples for submission.

5. • The specimens routinely used for testing includes stomach or
abomasal contents; heart blood or fluid from a body cavity; unfixed
lung, liver, kidney, and spleen (some laboratories also request
tissues such as thyroid glands, thymus, heart, brain, abomasum,
and stomach); placenta (if available); and dam’s serum.
• These should be submitted in sterile containers to allow for
microbiologic cultures.
• Because they are always contaminated, placentas should not be
mixed with other tissues.
• Representative samples of the following should also be submitted
in 10% buffered formalin for histopathologic examination: lung,
liver, heart, kidney, spleen, brain, skeletal muscle, thyroid, adrenal
glands, intestines, and placenta
• In a large majority of cases, gross lesions other than signs of
autolysis (increased pleural and peritoneal fluid and blood-tinged
subcutaneous edema) are not present.
• However, if lesions are found, fresh and formalin-fixed samples of
affected tissues should be included.

6. • Most agents, especially bacteria and fungi, infect the placenta
and thus gain entry into the amniotic fluid, which is swallowed
by the fetus.
• Stomach contents can be obtained aseptically, making it the
best specimen for detection of fungi and most bacteria.
• Isolation from the stomach contents is much easier than from
the placenta, which is always heavily contaminated.
• Lungs, liver, spleen, and kidneys are also good for culture.
• Several agents (eg, fungi, Chlamydia, Coxiella) primarily affect
the placenta; failure to include placenta decreases the
probability they will be identified.
• Fetuses sometimes produce antibodies to certain agents (eg,
bovine viral diarrhea virus, Neospora spp, Leptospira spp), and
fetal serum or fluid from a body cavity can be tested for
antibodies.
• The presence of precolostral antibodies is evidence of in utero
exposure.

7. •A single antibody titer in the dam rarely provides evidence of
abortion caused by a particular agent unless background herd titer
levels are known.
•High maternal titers may as likely be the reason an animal did not
abort due to that agent, but absence of a titer can be used to
exclude an agent.
•Antibody titers to agents with control programs (eg, Brucella
abortus, pseudorabies virus) are always significant, even if the
abortion was caused by something else.
•Demonstration of a 4-fold increase in antibody titer is required to
prove active infection by a specific agent.
• Often, abortion occurs weeks or months after initial infection of
the dam, and her titer is stable or declining at the time of abortion.
•Paired serum samples obtained 2 weeks apart from 10% of the
herd or a minimum of 10 animals often demonstrate
seroconversion and provide evidence of active infection in the
herd.

8. Causes of abortion
Noninfectious Causes Infectious causes

9. Non infectious causes
• The actual incidence of abortions in cows due to genetic factors is
unknown. Some genetically caused abortions may not have
phenotypically recognizable lesions. Most lethal genes cause
early abortion or early embryonic death.
• Vitamins A and E, selenium, and iron have been implicated in
bovine abortions, but documentation based on experiments is
available only for vitamin A.
• Heat stress causes fetal hypotension, hypoxia, and acidosis. High
maternal temperature due to pyrexia may be more important than
environmentally induced heat stress.
• Although severe trauma may rarely result in abortion (the bovine
fetus is well protected by the amniotic fluid), farmers undoubtedly
blame too many abortions on the cow “getting bumped.”

10. •A number of toxins can cause abortion in cows.
Ponderosa pine needles can cause abortion if
ingested in the last trimester; the cows may become
moribund after delivery and hemorrhage excessively.
•Broomweed (Guttierrezia microcephala) ingestion can
also cause abortion, as can coumarins from rat
poison, many grasses, or moldy sweet clover.
•Sodium iodide, IV, has been contraindicated in
pregnant cows, but no abortions or adverse effects
occurred in pregnant cows treated with a single high
dose in some studies.
• Mycotoxins, especially those with estrogenic activity,
have been implicated in bovine abortions.
•Nitrates or nitrites have also been incriminated, but
experimental evidence is controversial.

11. Infectious cause
1. Bacterial causes
Infectious factor
Common names
Abortion rate Abortion timing
Recurrence of
abortion
Foetal lesions Samples
Brucella abortus
Brucellosis
Bang’s disease
Zoonosis
Up to 80% of
unvaccinated animals
infected in 1st or 2nd
trimester
6-9 months
Abortion or stillbirth 2
wk to 5 mo after
infection
Majority abort
only once
Placenta: retained, cotyledons
necrotic, red-yellow,; area
between thickened
Calf: normal or autolytic with
bronchopneumonia
placenta, foetus, or uterine
discharge
Diagnosis: maternal serology,
IFAT for Abs in placenta,
bacteria isolation
Campylobacter fetus
venerealis
Vibriosis
>10% 5-8 months
Uncommon,
convalescent
cows resistant to
infection
Placenta: mild placentitis,
hemorrhagic cotyledons and
an edematous
intercotyledonary area.
Foetus: fresh or autolysed;
mild fibrinous pleuritis,
peritonitis,
bronchopneumonia.
Placenta, foetal abomasal
contents, vaginal flushing
Diagnosis: microscopic
detection, isolation
C fetus fetus
C jejuni
Sporadic 4-9 months
Uncommon,
convalescent
cows resistant to
infection
See above See above

12. Leptospira
interrogans,
serovarsgrippotyphos
a, pomona, hardjo, ca
nicola, icterohaemorr
hagiae
Zoonosis
5-40%
Last trimester
Abortion 2-5 weeks
after infection
Immunity to
the serotype
causing
abortion but
sensitive to
other types
Placenta: diffuse
placentitis with
avascular, light tan
cotyledons and
edematous, yellowish
intercotyledonary
areasFoetus: autolysed
Placenta, foetus
Diagnosis: IFAT foe Abs
or PCR testing
forLeptospira
Arcanobacterium
(Actinomyces)
pyogenes
Sporadic Any stage Not known
Placenta: endometritis
and diffuse placentitis,
reddish brown to brown
colour.
Foetus: autolysed,
fibrinous pericarditis,
pleuritis, or peritonitis
Placenta, foetus
Identification in bacterial
culture from placenta or
abomasal contents
Listeria
monocytogenes
Zoonosis
Usually sporadic
but can reach
50%
Last trimester May recur
Dam: fever,
inappetance
Placenta: retained
Foetus: autolysed
Fibrinous polyserositis
and white necrotic foci
in the liver and/or
cotyledons
Placenta, foetus
Identification in bacterial
culture from placenta or
abomasal contents

13. Aspergillus sp
(60-80%
Mucor sp, Absidia
, orRhizopus sp
Usually
sporadic
but can
reach
5-10%
4 months
to term
most
common
in winter
May recur
Placenta:
severe,
necrotising
placentitis
Cotyledons
enlarged,
necrotic,
intercotyledona
ry area is
thickened and
leathery.
Foetus:
autolysed~30%
have gray
ringworm-like
skin lesions
principally
involving the
head and
shoulders
Foetus, placenta
Diagnosis:
isolation from the
stomach contents,
placenta, and skin
lesions.
Fungal causes

14. Protozoan
Tritrichomonas
(Trichomonas)
foetus
Trichomoniasis
Sporadic
first half of
gestation
Animal gains
immunity but
probably not life-
long
Placenta: retained,
mild placentitis with
hemorrhagic
cotyledons and
thickened
intercotyledonary
areas covered with
flocculent exudates
Foetus: no specific
lesions
Placenta, foetus,
vaginal/uterine
discharge
Diagnosis: detection
in abomasal
contents, placental
fluids, and uterine
discharges
Neospora caninum
Neosporosis
High in first
gestation and when
infection enters the
naïve herd
Up to 30% first
outbreak
Enzootic: 5-10%
Any stage, but most
often 5-6 months
Decreases with
parity but always
possible
Placenta, foetus: no
specific gross
lesions, autolysed
Microscopic: focal
encephalitis with
necrosis and
nonsuppurative
inflammation,
hepatitis in
Placenta, foetus
(brain, heart, liver,
body fluids), serum
samples from the
dam
Diagnosis: detection
of antigen in brain
histology samples
Immunochemistry
in tissue samples
Abs - PCR, ELISA

15. Viral causes
ovine Viral Diarrhoea Virus
BVD-MD
Usually low
Complex pathology
Abortion usually up to 4
months
Uncommon, immunity
develops
Placenta: retained, no
specific lesions
Foetus: no specific lesions,
autolysed, mummified
Placenta, foetus (preferred -
spleen), dam and herdmates
serum
Diagnosis: isolation,
immunologic staining, PCR,
or detection of precolostral
antibodies in aborted calves
Bovine Herpesvirus type I
(BHV I)
Infectious Bovine
rhinotracheitis virus (IBRV)
IBR
IBR-IPV
5-60%
in non vaccinated herds
Possibly any stage but most
common
from 4 months to term
Uncommon, immunity
develops
In the majority of cases
there are no gross lesions in
the placenta or foetus
Placenta: necrotizing
vasculitis
Foetus: autolysed, foci of
necrosis in the liver
Placenta, foetus, serum
samples from the dam
Diagnosis:
Immunochemistry in
samples from kidney and
adrenal glands, blood
serology, PCR
Blue tongue virus
Blue tongue
Usually low Variable Unlikely
No specific
Foetus: autolysed
Placenta, foetus, serum
samples from the dam
Diagnosis: virus isolation
Epizootic Bovine Abortion
Foothill Abortion
etiologic agent has not been
definitively determined,
vector – tickOrnithodoros
coriaceus
Can reach 75%
Limited mainly to California
in the US
Usually in the last trimester Unlikely
Placenta: No specific
Foetus: hepatomegaly,
splenomegaly, and
generalized lymphomegaly.
Microscopically - marked
lymphoid hyperplasia in the
spleen and lymph nodes and
granulomatous inflammation
in most organs.
Anamnesis
Diagnosis: elevated foetal
Ig-G

16. Factors not typical for cattle or rarely occurring
Chlamydophila
abortus (Chlamydia
psittaciserotype 1)
enzootic abortion of ewes
Zoonosis
Sporadic
Near the end of the last
trimester
Unlikely
Placenta: placentitis,
thickening and yellow-
brown exudate adhered to
the cotyledons and
intercotyledonary areas.
Foetus: fresh, minimal
autolysis, pneumonia,
hepatitis
Placenta, foetus Diagnosis:
identification in stained
smears of the placenta or by
ELISA, fluorescent
antibody staining, PCR, or
isolation in embryonated
chicken eggs or cell culture.
Ureaplasma diversum
Usually sporadic, but
outbreaks possible
Third trimester Possible
Placenta: retained,
intercotyledonary areas
thickened, nonsuppurative
placentitis
Foetus: no gross lesions,
pneumonia
Placenta, foetus
Diagnosis: isolation from
the placenta, lungs, and/or
abomasal contents
Salmonella spp
Usually sporadic but can
take form of an abortion
storm
Any stage Possible
Cows: clinically ill
Placenta and foetus:
autolysed and
emphysematous.
Placenta, foetus
Diagnosis: isolation from
the abomasal contents other
tissues.
Other infectious factors that
potentially can cause
abortion in cattle:
Parainfluenza 3 Virus
(PI3V), Mycoplasma spp ,
Histophilus
somni (Haemophilus
somnus), Staphylococcus
spp, Streptococcus spp,
Pasteurella spp, E.coli,

17. Infectious cause
1. Neosporosis:
• Neospora caninum is found worldwide and is the most common cause of abortion in dairy and
beef cattle .
• Dogs and coyotes are definitive hosts for N caninum and can be the source of infection. Abortion
can occur any time after 3 mo of gestation but is most common between 4 and 6 mo of gestation.
• Neospora can be associated with sporadic abortions or abortion storms, and repeat abortions in
cows have been reported. Most infections result in an asymptomatic congenitally infected calf.
• Some infected calves are born with paralysis or proprioceptive deficits. Cows are not clinically ill,
and placental retention is not common.
• The fetus is usually autolyzed or, in a few cases, mummified and rarely has gross lesions.
Microscopically, nonsuppurative inflammation is common in the brain, heart, and skeletal muscles.
• Organisms can be identified in these tissues and the kidneys by immunohistochemical staining
and PCR.
• Many late gestation fetuses have precolostral antibodies.
• They remain infected for years and possibly for life.
• Vertical transmission is common.
• During pregnancy, Neospora organisms can become activated and infect the fetus. This is thought
to be the most common source of infection. There is no treatment. Strict hygiene to prevent fecal
contamination of feed by dogs or coyotes may aid in prevention. A commercial vaccine is
available.

18. Bovine Viral Diarrhea (BVD):
• In several surveys, BVD was the most commonly
diagnosed virus in bovine abortion cases.
• The pathology of BVD in the developing fetus is complex.
Infection before insemination or during the first 40 days of
pregnancy results in infertility or embryonic death.
• Infection between 40 and 125 days of pregnancy results
in birth of persistently infected calves if the fetus survives.
• Fetal infection during the period of organogenesis (100–
150 days) may result in congenital malformations of the
CNS (cerebellar hypoplasia, hydrancephaly,
hydrocephalus, microencephaly, and spinal cord
hypoplasia).
• Congenital ocular defects have also been seen (cataracts,
optic neuritis, retinal degeneration, microphthalmia).

19. •After 125 days of gestation, BVD may cause abortion, or
the fetal immune response may clear the virus.
•Diagnosis is by identification of BVD virus by isolation,
immunologic staining, PCR, or detection of precolostral
antibodies in aborted calves.
•The virus is present in a wide variety of tissues, but the
spleen is the tissue of choice. Rising antibody titers to BVD
in aborting animals or herdmates is diagnostic of recent
infection.
•BVD virus is immunosuppressive and is found in many
fetuses infected by other agents (eg, bacteria, N caninum).
•Outbreaks of abortions by organisms that normally cause
sporadic abortion should raise suspicion of possible
concurrent BVD virus infection. Prevention should focus on
removal of persistently infected cattle and herd
vaccination.

20. Infectious Bovine Rhinotracheitis (IBR, Bovine Herpesvirus 1):
• Infectious bovine rhinotracheitis (IBR) is a major cause of viral abortion in the
world, with abortion rates of 5%–60% in nonvaccinated herds.
• The virus is widespread, causes latent infections, and can recrudesce;
therefore, any cow with a positive IBR titer is a possible carrier.
• The virus is carried to the placenta in WBCs; over the next 2 wk to 4 mo, it
causes a placentitis, then infects the fetus and kills it in 24 hr. Abortion can
occur any time but usually is from 4 mo to term.
• Autolysis is consistently present. Occasionally, there are small foci of
necrosis in the liver, but in a large majority of cases there are no gross
lesions in the placenta or fetus.
• Microscopically, small foci of necrosis with minimal inflammation are
consistently present in the liver.
• Necrotizing vasculitis is common in the placenta. Diagnosis can be made by
immunologic staining of the kidney, lung, liver, placenta, and adrenal glands.
IBR virus can be isolated from ~50% of infected fetuses (most successfully
from the placenta).
• In most cases, maternal titers have peaked by the time of abortion. In
abortion storms, rising titers can often be demonstrated in herdmates.
Control is by herd vaccination; intranasal, modified-live virus, and killed
vaccines are available.

21. Leptospirosis
• The pathogenic leptospires were formerly classified as serovars of Leptospira interrogans,
but they have been reclassified into 7 species with >200 recognized
serovars. Leptospira serovars Grippotyphosa, Pomona, Canicola, and
Icterohaemorrhagiae usually cause abortions in the last trimester, 2–6 wk after maternal
infection.
• Serovar Hardjo is host adapted to cattle and can establish lifelong infections in the
kidneys and reproductive tracts.
• In addition to third trimester abortions, serovar Hardjo reduces conception rates in carrier
cows and cows bred to carrier bulls.
• Although dams may show clinical signs of leptospirosis, most abortions are in otherwise
healthy cattle.
• Abortion rates vary from 5%–40% or more. The leptospires cause a diffuse placentitis with
avascular, light tan cotyledons and edematous, yellowish intercotyledonary areas.
• The fetus usually dies 1–2 days before expulsion and therefore is autolyzed. Occasionally,
calves are born alive but weak. Fetuses infected with serovar Pomona may show icterus.
• There are no specific lesions, but placenta and fetus should be submitted to the laboratory
for fluorescent antibody staining or PCR testing for Leptospira. Although maternal titers
are probably waning by the time of abortion, an initial titer of >1:800 may be suspicious.
• Approximately one-third of cows aborting because of serovar Hardjo have titers of <1:100
at the time of abortion.
• Cows infected with serovar Hardjo can shed the organism in urine throughout life. For
other serovars, the dam’s urine can be cultured or examined for leptospires within 2 wk of
abortion.

22. • For control, sources of infection (such as feed or water
contaminated by dogs, rats, or wildlife) should be identified and
eliminated.
• Vaccination with a five-way bacterin every 6 mo provides good
protection against serovars Grippotyphosa, Pomona, Canicola, and
Icterohaemorrhagiae but does not protect against infection and
renal shedding by serovar Hardjo.
• New monovalent serovar Hardjo vaccines that prevent infection,
but do not cure existing infections, are available.
• The following treatments have been found to eliminate the renal
carrier state: a single injection of oxytetracycline (20 mg/kg, IM), a
single injection of tilmicosin (10 mg/kg, SC), ceftiofur (5 mg/kg/day,
IM, for 5 days or 20 mg/kg/day, IM, for 3 days), or amoxicillin (15
mg/kg, IM, two injections 48 hr apart).
• Leptospirosis is zoonotic, and urine and milk of dams may be
infective for up to 3 mo, except for Hardjo, in which case cows can
be infective for life if not treated.

23. Brucellosis:
• Brucellosis (Bang’s disease) is a threat in most countries where cattle are
raised. In the USA, active control programs, including test, slaughter, and
heifer vaccination, have greatly decreased its incidence.
• Brucellosis causes abortions in the second half of gestation (usually
~7 mo), and ~80% of unvaccinated cows in later gestation will abort if
exposed to Brucella abortus.
• The organisms enter via mucous membranes and invade the udder,
lymph nodes, and uterus, causing a placentitis, which may be acute or
chronic.
• Abortion or stillbirth occurs 2 wk to 5 mo after initial infection. Affected
cotyledons may be normal to necrotic, and red or yellow. The
intercotyledonary area is focally thickened with a wet, leathery
appearance.
• The fetus may be normal or autolytic with bronchopneumonia. Diagnosis
can be made by maternal serology combined with fluorescent antibody
staining of placenta and fetus or isolation of B abortus from placenta,
fetus (abomasal contents and lung), or uterine discharge. Prevention is by
calfhood vaccination of heifers.
• Brucellosis is a serious zoonosis and a reportable disease, and the
appropriate authorities should be contacted.

24. Mycotic Abortion:
• Fungal placentitis due to Aspergillus sp (septated fungi, 60%–80% of
cases), or to Mucor sp, Absidia, Rhizopus sp, and a few other
nonseptated fungi, is an important cause of bovine sporadic abortion.
• Abortions occur from 4 mo to term and are most common in winter. It is
believed the fungi gain entry through the oral or respiratory tracts and
travel hematogenously to the placenta.
• Placentitis is severe and necrotizing. Cotyledons are enlarged and
necrotic with turned-in margins. The intercotyledonary area is thickened
and leathery.
• Adventitious placentation is common. The fetus seldom is autolyzed,
although it may be dehydrated; ~30% have gray ringworm-like skin
lesions principally involving the head and shoulders.
• The diagnosis is based on the presence of fungal hyphae associated with
necrotizing placentitis, dermatitis, or pneumonia.
• Fungi can also be isolated from the stomach contents, placenta, and skin
lesions. Isolation must be correlated with microscopic and gross lesions
to exclude contamination after abortion.
• For control, moldy feed should be avoided.

25. Trichomoniasis:
• Tritrichomonas foetus infection causes a venereal disease that
usually results in infertility but occasionally causes abortion in the
first half of gestation.
• Placentitis is relatively mild, with hemorrhagic cotyledons and
thickened intercotyledonary areas covered with flocculent exudate.
The placenta is often retained, and there may be pyometra.
• The fetus has no specific lesions, although T foetus can be found in
abomasal contents, placental fluids, and uterine discharges.
Infected cows typically clear the organism within 20 wk, but bulls,
especially those infected after 3 yr of age, can become lifelong
carriers.
• There is no legal, effective treatment for individual animals. Herd
treatment is based on identifying and segregating pregnant females
from “at-risk" females for ≥5 mo and by identifying and culling all
infected bulls.
• Prevention is by artificial insemination or natural insemination using
noninfected bulls. A killed, whole-cell vaccine is available for use in
cows.

26. Campylobacteriosis:
• Campylobacter fetus venerealis causes venereal disease that usually
results in infertility or early embryonic death but occasionally causes
abortion between 4 and 8 mo of gestation. C fetus fetus and C
jejuni are transmitted by ingestion and subsequent hematogenous
spread to the placenta.
• Both cause sporadic abortions, usually in the last half of gestation. The
fetus can be fresh with partially expanded lungs or severely autolyzed.
• Mild fibrinous pleuritis and peritonitis may be noted, as well as
bronchopneumonia. Placentitis is mild with hemorrhagic cotyledons and
an edematous intercotyledonary area.
• Campylobacter spp can be identified by darkfield examination of
abomasal contents or culture of placenta or abomasal contents.
Isolation and identification of the species involved is important if
vaccination is to be instituted.
• Venereal campylobacteriosis can be controlled by artificial insemination
and vaccination.
• Campylobacter spp are zoonotic, and C jejuni is an important cause of
enteritis in people.

27. Listeriosis:
• Listeria monocytogenes can cause placentitis and fetal
septicemia. Abortions are usually sporadic but may affect
10%–20% of a herd.
• Abortion is at any stage of gestation, and the dam may
have fever and anorexia before the abortion; retained
placenta is common.
• The fetus is retained for 2–3 days after death, so
autolysis may be extensive. Fibrinous polyserositis and
white necrotic foci in the liver and/or cotyledons are
common.
• Diagnosis is by culture of Listeria from fetus or placenta.
There is no available bacterin.
• Listeriosis is a reportable disease in many areas and is
a serious zoonosis, with spread possible through
improperly pasteurized milk.

28. Chlamydiosis:
• Chlamydia abortus, the cause of enzootic abortion of ewes,
causes sporadic abortion in cattle.
• Most abortions occur near the end of the last trimester, but they
can occur earlier. Placental lesions consist of thickening and
yellow-brown exudate adhered to the cotyledons and
intercotyledonary areas.
• Histologically, placentitis is consistently present, and pneumonia
and hepatitis can be found in some cases. C abortus can be
identified by examination of stained smears of the placenta or by
ELISA, fluorescent antibody staining, PCR, or isolation in
embryonated chicken eggs or cell culture.
• Organisms can often be identified in the lungs and liver but not as
consistently as in the placenta.
• There are no vaccines for cattle, although they are produced for
sheep.
• The bacterium is zoonotic, occasionally producing life-threatening
disease and abortion in pregnant women.

29. Ureaplasma diversum Infection:
• Ureaplasma diversum is a common inhabitant of the vagina and
prepuce of cattle that also causes abortions. Abortions are
usually single, but severe outbreaks occur on occasion.
• The infection may also result in stillbirths and birth of weak
calves. Most fetuses are aborted in the third trimester and are
well preserved. The cows are not sick, but retained placentas
are common.
• Placentitis and a necrotic amniotic membrane are common
features. The intercotyledonary areas are usually thickened and
sometimes contain areas of fibrin deposition and hemorrhage.
• There are no gross lesions in the fetus. Microscopically, there is
nonsuppurative placentitis and pneumonia characterized by
accumulations of lymphocytes around bronchi and by diffuse
alveolitis.
• Diagnosis is by isolation of U diversum from the placenta, lungs,
and/or abomasal contents.

30. Blue tongue:
• Bluetongue is caused by an Orbivirus with 24 serotypes and is transmitted by biting
midges of the genus Culicoides.
• Historically, blue tongue occurred from approximately latitude 35°S to 40°N, except in
the western USA, where it occurs to 45°N.
• After introduction of an attenuated, live virus serotype 10 vaccine in the 1950s, abortion,
mummification, stillbirth, and the birth of live offspring with CNS malformations occurred
in cattle and sheep. Since then, multiple blue tongue serotypes have been identified as
causes of similar reproductive losses in cattle and sheep.
• Attenuation of blue tongue virus can increase its ability to cross the placenta.
• There is evidence that before 2007, reproductive losses were caused by attenuated
blue tongue vaccine viruses, either by vaccination of pregnant animals or by spread of
vaccine virus in nature by Culicoides spp.
• In 2006, serotype 8 blue tongue virus appeared, spread, and became endemic across
northwestern Europe (north of 50°N), where blue tongue was previously unknown.
• Beginning in 2007, abortions and birth of “dummy” calves with brain malformations
occurred in blue tongue-infected herds; affected calves were documented to have been
infected in utero. Since then, many such cases have been reported.
• Diagnosis is by identification of precolostral antibodies to blue tongue or identification
of the virus by PCR.
• Brain, spleen, and whole blood are the preferred samples from fetuses and neonates
for PCR. Control of blue tongue is by vaccination and management procedures to
reduce exposure to biting midges.
• Modified-live and inactivated vaccines are available, but their availability and use varies
between countries

31. Other Causes of Abortion:
• Akabane virus (where present) causes abortion and fetal
anomalies.
• Parainfluenza-3 virus causes abortion in experimentally
inoculated seronegative cattle, but is seldom, if ever,
diagnosed in field cases of abortion.
• Occasionally, Salmonella spp cause abortion storms. The
cows are usually sick, and the fetuses and placentas are
autolyzed and emphysematous. Salmonellae can be isolated
from the abomasal contents and fetal tissues and from uterine
fluids and the dams’ feces.
• Mycoplasma spp, Histophilus somni, and a wide variety of
other bacteria can also cause sporadic abortions in cattle.
• Schmallenberg virus, discovered in Europe in 2011, belongs
to the Simbu serogroup and has been associated with
infertility, abortion, and fetal malformation in several ruminant
species.