Enzootic Abortion of Ewes

• Ovine enzootic abortion/EAE
• Especially in intensive systems
• Ewe lambs may acquire infection at birth and abort in their first pregnancy
• Pathogenesis:
  • Infection via ingestion or inhalation causes a bacteraemia
  • Bacteria localise in placenta and cause placentitis, leading to late abortion or premature weak lambs
  • Necrosis of cotyledons and oedema of adjacent tissue, as well as dirty pink uterine discharge
  • Aborted lambs well preserved
  • Large numbers of chlamydiae shed in placenta and uterine discharges; survive in environment for several days
  • Abortion rates may reach 30% in susceptible flock
  • Ewes infected late in pregnancy may not abort, but may abort during the next pregnancy
  • No other clinical signs in aborting ewes
  • Fertility not impaired
• Transmission:
  • Survival of elementary bodies in faeces and wild birds are a source of infection from one lambing season to the next
  • Ewes may be carriers for several years
  • Venereal transmission from infected rams
  • Some immunity develops after infection, protecting ewes from subsequent disease
• Vaccination:
  • Live attenuated vaccines prior to breeding or inactivated vaccines during pregnancy
  • Vaccines prevent infection but will not clear infection from persistently-infected animals
  • Vaccination of ewe lambs prior to breeding
• Treatment: long-acting oxytetracyclines during an outbreak to protect in-contact pregnant ewes
• Control: isolate aborted ewes; destroy placentas, thorough cleaning
• Also abortion in cattle, goats and pigs
• Serious infection in pregnant women

Enzootic abortion of ewes. Causes late abortion, premature lambing, retained foetal membranes. Infection is by ingestion. Immunity develops following exposure therefore abortion only in ewes not previously exposed. Aborted foetus may be oedematous with blood tinged fluid in body cavities. Cotyledons are necrotic, covered with exudate while foetal membranes may be thickened and oedematous.