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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
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**Infection via ingestion or inhalation causes a bacteraemia
*Necrosis of cotyledons and oedema of adjacent tissue, as well as dirty pink uterine discharge
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**Bacteria localise in placenta and cause placentitis, leading to late abortion or premature weak lambs
*Aborted lambs well preserved
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**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
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**Aborted lambs well preserved
*Abortion rates may reach 30% in susceptible flock
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**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
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**Abortion rates may reach 30% in susceptible flock
*No other clinical signs in aborting ewes
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**Ewes infected late in pregnancy may not abort, but may abort during the next pregnancy
*Fertility not impaired
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**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
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**Fertility not impaired
*Ewes may be carriers for several years
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*Transmission:
*Venereal transmission from infected rams
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**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
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**Ewes may be carriers for several years
*Live attenuated vaccines prior to breeding or inactivated vaccines during pregnancy
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**Venereal transmission from infected rams
*Vaccines prevent infection but will not clear infection from persistently-infected animals
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**Some immunity develops after infection, protecting ewes from subsequent disease
*Vaccination of ewe lambs prior to breeding
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*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
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