Oorsig/Review
(mid pregnancy) without foetal involvement and
many abortions may occur at this stage. In other
instances, this initial placentitis is followed by
spreading to the surrounding placenta and foetus
and resulting in a bacteriaemia.
Control
•
•
Fig 3. High magnification of a placenta invaded by numerous
chlamydia organisms
Animals which become infected and abort
often maintain protective immunity, explaining
the significant reduction in abortion rate in
endemically infected flocks. Rarely immune
animals may shed bacteria in uterine discharges
and placental tissues in subsequent pregnancies.
Pathology
Placental pathology is a hallmark of C. abortus
infection and is characterised by necrosis of the
cotyledon periphery with oedema and often
haemorrhages of the inter – cotoledonary tissue.
Numerous C. abortus organisms are present in
the affected placental tissue. Frequently only
placental pathology is evident in the absence of
any foetal pathology. Foetal lesions include an
interstitial pneumonia, hydrothorax and ascites,
haemorrhages of the subcutis, thymus and
lymph nodes, lymphadenopathy of mesenteric
lymph nodes and occasionally multifocal hepatic
necrosis.
Diagnosis
It is essential to confirm the diagnosis and
confirmatory tests include the following:
•
•
•
•
Impression smears of placenta for Gimenez
stains.
Placenta
(cotyledonary
and
inter-
cotyledonary), liver, spleen, lymph nodes,
lung and brain in 10% buffered formalin for
histopathology.
Immunohistochemistry (IHC) staining for
Chlamydia antigen on formalin fixed tissues.
Placenta and spleen (fresh tissue) for
Chlamydia antigen polymerase chain reaction
(PCR).
6
•
•
•
•
•
It is essential to vaccinate ewes 4 to 6 weeks
before the breeding season, as the vaccine will
not provide protection against abortion once
the foetus has been infected. An inactivated
vaccine is produced by Design Biologics to
prevent abortions caused by C. abortus. It is
not clear if this vaccine will protect animals
against C. pecorum infection. Laboratory
identification of the specific Chlamydia specie
is therefore vital in the control of the disease.
Vaccination of sheep already infected with
C. abortus will not prevent abortions but can
reduce the incidence.
Retaining sheep in herd after an abortion
episode is recommended by some authors.
Sheep that have aborted are immune,
probably for life, though they may shed
organisms in subsequent lambing’s.
Aborted material and infected bedding must
be removed and destroyed.
Biosecurity - Buying in latently infected sheep
is the principal initial source of infection.
Maintaining a closed flock policy or
purchasing sheep from known enzootic
abortion free flocks.
Medication - A long-acting oxytetracycline
injection (20 mg/kg) administered routinely
on approximately day 110 of pregnancy and
every two weeks for two to three occasions.
References
1.
Buxton D et al. 2002. Ovine chlamydial abortion:
Characterization of the inflammatory immune
response in placental tissues. Journal of
Comparative Pathology 127:133-141.
2. Coetzer, JAW et al. 2004. Infectious diseases of
livestock, 2nd edition, Volume 1: 550-564
3. Entrician G et al. 2001. Chlamydial infection in
sheep: immune control versus fetal pathology.
Journal of the Royal Society of Medicine. 94:273-
277.
4. Giannitti et al. 2016. Chlamydia pecorum:
fetal and placental lesions in sporadic caprine
abortion. Journal of Veterinary Diagnostic
Investigation 28:184-189.
5. Last R 2016 Update on Chlamydia abortion in
ruminants http://vet360.vetlink.co.za/update-
on-chlamydia-abortion-of-ruminants/
6. Njaa B L. 2012. Diagnosis of abortion and
neonatal loss in animals. 4th edn. Wiley-
Blackwell.
7. OIE Terrestrial Manual 2012. Enzootic Abortion
of Ewes.
8. Papp et al. 1993. Chlamydia psittaci infection and
associated infertility in sheep. Canadian Journal
of Veterinary Research. 57:1
9. https://www.sciencedirect.com/.../
chlamydophila-abortus Chlamydophila abortus-
an overview
10. https://faculty.tarleton.edu/.../
ChlamydialAbortions_Sheep_Goats.pdf · PDF file
Chlamydial Abortions in Sheep and Goats