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Professional Keeper of animals, Veterinary surgeon, Veterinary nurse, Veterinary student, Pharmacist or SQP

Abortion is a significant animal welfare, human health and economic threat to the sheep industry. It is widespread globally and, whilst some cases are caused by poor management or nutritional factors, infectious agents are responsible for much of the problem.

Enzootic Abortion of Ewes (EAE) is the most prevalent cause of abortion in the UK sheep flock, responsible for around 50% of abortion cases (EBLEX, 2012). EAE is caused by the bacterium Chlamydophila abortus, and is therefore also known as chlamydial abortion.

EAE is characterised by late term abortions, stillbirths and weak lambs, and also by an inflamed, reddish brown placenta. The disease is transmitted by ingestion following exposure to infected foetal membranes and lambing discharges. Infection does not result in abortion in that pregnancy unless the ewe is less than 14 weeks pregnant. Instead, the infection remains latent in the ewe until the next pregnancy when it causes abortion.


Mydiavac® provides proven protection for naïve breeding ewes against Enzootic abortion (Chlamydophila abortus) infection when administered before tupping.

If a pre-tupping dose has not been administered — either due to due to lack of time or purchasing animals with unknown vaccine status — Mydiavac® can be used at any stage of pregnancy.

If you unfortunately encounter an EAE outbreak in your flock, Mydiavac® administration in the face of an outbreak has been proven to reduce the level of abortion in infected pregnant ewes. If a high population of ewes are naive when their flock-mates are aborting, Mydiavac administration in the face of an outbreak can also reduce the number becoming latently infected and result in fewer EAE abortions the following year.


Pre-tupping vaccination with Mydiavac® is considered best practice, but because it is an inactivated vaccine it may also be administered at many other stages of the sheep calendar:

  • Winter or Spring: when EAE first strikes in the flock pre-lambing, to achieve quick protection for non EAE exposed ewes.
  • Spring or Summer: when gathering ewes and lambs to minimise handling and labour requirements.
  • Summer: when ewe replacements chosen or purchased.
  • Summer or Autumn: with a live toxoplasmosis vaccine.
  • Autumn: up to 3-4 weeks pre-tupping.
  • Autumn or Winter: after removal of the tup.
  • Winter: following scanning of ewes.


  • 1ml dose for ease of storage and administration.
  • 100 dose (100ml) or 20 dose (20ml) packs to minimise waste.
  • Once broached the contents of the vial may be used for the whole working day.
  • Sealed 100ml Mydiavac® vials have a 14 month shelf life, and 20ml vials have 12 months.
  • Mydiavac® is provided ready to use: no mixing with solvents required.
  • Mydiavac® can be given at the same time as a commercial Toxoplasma gondii vaccine containing live tachyzoites of the S48 strain, providing different syringes and injection sites are used.

Product data sheet

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