abortion in sheep Flashcards
what are the four MAIN causes of abortion in uk sheep flocks
- chlamydia abortus
- toxoplasma gondii
- compylobacter
- Borders disease
length of ovine gestation
147 days
what is the infection route of chlamydia and what is the source of infection
venero-oral
1. aborted material of infected ewes contaminate environment and is viable for weeks
2. carrier ewes may or may not abort but continually shed bacteria at lambing and oestrus
what is the outcome of exposure
if ewe >90 days pregnant = ABORT
if ewe <90 days pregnant =. may abort later on in pregnancy or become latently infected by harbouring agent in repro tract and aborting next pregnancy.
If ewe not pregnant when infected she will abort when eventually pregnant
ewe lambs born to infected ewes will abort their first lamb.
once aborted most ewes become immune. Some become carriers
what is the abortion rates in an endemic and epidemic flock
naiive flock will be almost unaffected in first year. 30% abortion storm the following year
endemic flock has 5-10% abortion rate year on year
what is the cause of abortion following chlamydia infection
severe placentitis with necrosis
how is chlamydia abortus diagnosed
culture, PCR or ziehl nielson staining on swab taken from aborted material
how is chlamydia abortus controlled
vaccinate all ewes pre tupping
treat all at risk ewes with oxytetracycline 2 weeks apart
what is toxoplasma gondii
protozoan parasite
zoonotic
sheep intermediate, cat definitive
what is the outcome of toxoplasma infection at different stages
non pregnant at infection= immunity
early pregnancy infection= fetal resorbtion
mid pregnancy infection= foetal death or mummification
late pregnancy infection= abortion or birth of weak lambs with high mortality
due to the nature of immunity which group would mainly be affected in an endemic flock
abortion would mainly be seen in the young ewes due to older ewes having immunity
how is toxoplasma gondii diagnosed
submit foetus or placenta for serology
‘frosty strawberries’ appearance on cotyledons of placenta
how is toxoplasma controlled
give toxovax vaccine 3 weeks prior to tupping
control rat and cat population
what is the source of infection of compylobacter
carrier sheep, aborted material, contaminated feed/drink, birds
what is the result of campylobacter infection
abortion during last 6 weeks of pregnancy. abortion occurs 1-4 weeks post infection.
ewes later become ill with metritis
cause abortion storms due to it being very contagious in the environment
