New vaccine against ovine enzootic abortion in development in MIdlothian

A new vaccine being developed against ovine enzootic abortion by scientists at the Moredun Research Institute is more effective than any commercial vaccine currently available in protecting animals from the disease.
Stock photo by John DevlinStock photo by John Devlin
Stock photo by John Devlin

Ovine enzootic abortion is the most common infectious cause of abortion in sheep in the UK and many countries worldwide. It is caused by the bacteria Chlamydia abortus which invades the placenta during pregnancy and can also cause life-threatening illness and abortion in humans.

Although there are vaccines currently available on the market to control infection, they are not always effective. Commercial live vaccines, which use a weakened form of C. abortus, have been shown to cause both abortion in some of the hosts and transmission to other unvaccinated animals, presenting a health risk to both the wider flock and to people. Meanwhile, their inactivated counterparts, which use a killed form of C. abortus, have also been shown to be less effective in protecting animals from infection and immunity is more short-lived.

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However, a team of researchers led at Pentland Science Park near Penicuik by Moredun’s Dr David Longbottom have recently completed the first stage in the development of a new vaccine that is akin to the live variation, but without the ability to grow and cause infections in the host animal. This provides an important step towards tackling C. abortus transmission.

Dr Longbottom said: “We are very encouraged that the new vaccine results in a similar protective response to that generated following a natural infection or resulting from the live vaccines but importantly without the ability to cause disease.”

Future work stemming from this study will look to optimise the vaccine formulation further.

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