Early Lambing – Investigating abortions in sheep

Early lambing is less popular than it was in our part of the world, but we have had some cases of sheep aborting in recent weeks. This mainly has been in pedigree lambing flocks where early lambing is still popular. One recent case involved a hogget delivering two malformed lambs which were premature and partially decomposed. The other ewe presented with a waterbag protruding from a prolapsed vagina, with incomplete dilation of the cervix. This meant that the ewe had to have a caesarean section, resulting in the delivery of two weak lambs which looked premature, and while born alive, died before the ewe’s operation was completed.

In both cases, we took samples from the ewe’s placenta and the surface of the lamb. The placenta samples were taken by rubbing a cotton swab on a placental cotyledon (button). A separate sample can be taken from the fluids on the surface of the lamb. The samples were tested using a specialised testing method called PCR. This test can identify low levels of infectious material in the test material. The sample from the first hogget tested positive for toxoplasmosis, while the second ewe had been infected with Enzootic abortion (EAE). This method of testing differs from a blood sample as it demonstrates the presence of the actual abortion-causing organism in the ewe’s uterus, rather than demonstrating the ewe’s immune response.

Toxoplasmosis is a parasitic disease which can be spread by cats. Ewes aborting due to toxoplasmosis are therefore not directly infectious to other ewes. EAE, on the other hand, is contagious and the early identification of ewes aborting due to EAE can help in control by ensuring aborted ewes are kept isolated and allow for the preventative use of antibiotics in at-risk comrade animals. However, as with any disease, antibiotics should not be relied upon for long term control.

Early, accurate diagnosis of infectious abortion in ewes can help in the management of the disease and the selection of appropriate vaccination programmes. Some sheep owners believe that ewes “slinging” lambs at the start of the season are normal, but with proper diagnosis and vaccination, it doesn’t have to be!

Irish Farmers Journal231019

John Gilmore is a practising veterinary surgeon and Managing Director of FarmLab Diagnostics, an animal health testing laboratory, www.farmlab.ie, in Elphin, Co.Roscommon

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