Review/Oorsig Volume 23, Issue 02 - Page 6

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 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. chlamydophila-abortus Chlamydophila abortus- an overview 10. ChlamydialAbortions_Sheep_Goats.pdf · PDF file Chlamydial Abortions in Sheep and Goats