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Also known as: '''''EAE — Ovine Enzootic Abortion — Chlamydophila abortus'''''

Also known as: '''''EAE — Ovine Enzootic Abortion — Chlamydophila abortus'''''

==Introduction==

==Introduction==

It is important due to its '''zoonotic potential''' and is a serious infection in pregnant women.

It is important due to its '''zoonotic potential''' and is a serious infection in pregnant women.

==Epidemiology and transmission==

==Epidemiology and Transmission==

Infection occurs by the '''oral route''' and is not apparently until the next pregnancy, when the organism invades the placenta at 90 days' gestation causing a '''suppurative necrotising placentitis''' at the time of rapid foetal growth.

Infection occurs by the '''oral route''' and is not apparent until the next pregnancy, when the organism invades the placenta at 90 days' gestation causing a '''suppurative necrotising placentitis''' at the time of rapid foetal growth.

In some flocks ewes may become infected and abort in the same pregnancy if infection occurs at least 6 weeks before they are due to lamb.

In some flocks ewes may become infected and abort in the same pregnancy if infection occurs at least 6 weeks before they are due to lamb.

Ewes which '''abort or drop stillborn or weak lambs''' shed vast numbers of the organism in the diseased placentas and uterine discharges. The ''Chlamydiae'' organisms remain viable for several days and allow '''spread of infection'''. Survival is longer if temperatures drop or freeze.

Ewes which '''abort or drop stillborn or weak lambs''' shed vast numbers of the organism in the diseased placenta and uterine discharges. The [[:Category:Chlamydophila species|''Chlamydiae'']] organisms remain viable for several days and allow '''spread of infection'''. Survival is longer if temperatures drop or freeze.

In rams, infection can be seen as '''orchitis''' and the organism is excreted in the semen, though venereal spread is thought to be uncommon.

In rams, infection can be seen as '''orchitis''' and the organism is excreted in the semen, though venereal spread is thought to be uncommon.

'''Clean flocks''' usually become infected through the introduction of replacement breeding females which contaminate the flock during parturition. The following year can bring a serious outbreak with up to 30% of ewes aborting. Ewes have solid immunity post-abortion and thereafter, only younger females will pick up the infection and an '''annual incidence of 10-20%''' can be expected if no control measures are put in place.

'''Clean flocks''' usually become infected through the introduction of replacement breeding females which contaminate the flock during parturition. The following year can bring a serious outbreak with up to 30% of ewes aborting. Ewes have solid immunity post-abortion and thereafter, only younger females will pick up the infection and an '''annual incidence of 10-20%''' can be expected if no control measures are put in place.

==Clinical signs==

==Clinical Signs==

'''Abortion storms''' are a feature of EAE, especially in housed, intensively managed flocks. Aborting ewes may have '''vague malaise''' for up to 24 hours but are not noticeably sick.

'''Abortion storms''' are a feature of EAE, especially in housed, intensively managed flocks. Aborting ewes may have '''vague malaise''' for up to 24 hours but are not noticeably sick.

The diagnostic method of choice is '''examination of fresh placentas'''. The organism is demonstrated in smears from intercotyledonary areas of the placenta using a '''modified Ziehl-Neelsen stain'''.

The diagnostic method of choice is '''examination of fresh placentas'''. The organism is demonstrated in smears from intercotyledonary areas of the placenta using a '''modified Ziehl-Neelsen stain'''.

'''Vaginal swabs''' or swabs from the coat of the aborted foetus can be used if placenta is not avaiable.

'''Vaginal swabs''' or swabs from the coat of the aborted foetus can be used if placenta is not available.

It is important to note that ''Yersinia'' and ''Coxiella burnetti'' also stain red with the Ziehl-Neelsen stain and may complicate the diagnosis.

It is important to note that ''[[Yersinia]]'' and ''[[Coxiella burnetti]]'' also stain red with the Ziehl-Neelsen stain and may complicate the diagnosis.

'''Histopathology''' reveals an inflammatory infiltrate and intracytoplasmic inclusions in chorionic epithelial cells. Immuno-histo chemistry can be used to demonstrate antigen in the tissues if necessary.

'''Histopathology''' reveals an inflammatory infiltrate and intracytoplasmic inclusions in chorionic epithelial cells. Immuno-histo chemistry can be used to demonstrate antigen in the tissues if necessary.

'''PCR testing''' has also been developed for use on vaginal swabs and placental tissue from sheep.

'''PCR testing''' has also been developed for use on vaginal swabs and placental tissue from sheep.

==Prevention and control==

==Prevention and Control==

There are three '''vaccines''' available in the UK that provide protection against EAE.

There are three '''vaccines''' available in the UK that provide protection against EAE.

The two live-attenuated vaccines can only be used in '''non-pregnant females''' but the inactivated vaccine can be used '''during pregnancy'''.

The two live-attenuated vaccines can only be used in '''non-pregnant females''' but the inactivated vaccine can be used '''during pregnancy'''.

The inactivated vaccine has been shown to '''reduce the number of abortions in a flock of already-infected sheep''' and it can be '''used during an outbreak''' to control the number of abortions.

The inactivated vaccine has been shown to '''reduce the number of abortions in a flock of already infected sheep''' and it can be '''used during an outbreak''' to control the number of abortions.

Whole-flock treatment with '''long-acting oxytetracycline''' can be used 3-6 weeks before lambing to increase the number of viable lambs born to ewes known to be infected with EAE. Repeat injections might be necessary and ewes still excrete the organism if the lambs are born alive.

Whole-flock treatment with '''long-acting oxytetracycline''' can be used 3-6 weeks before lambing to increase the number of viable lambs born to ewes known to be infected with EAE. Repeat injections might be necessary and ewes still excrete the organism if the lambs are born alive.

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