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