Sheep abortions with no diagnosis
Following on from our previous blog post, the information below focuses on when there has been significant reproductive loss in a flock and no diagnosed cause. For future health planning and when considering pre-tupping abortion vaccine programmes, now is a good time to take stock.
Various things should be considered and questions asked before deciding what, if anything, to do next:
- Were foetuses and placentas examined at the lab or a complete set of samples (FSC, foetal fluid and placenta) collected and sent? If no placentas were checked then EAE cannot be ruled out.
- How many ewes have aborted? If less than two per cent there may be nothing infectious to worry about. However, bear in mind though that EAE could start small.
- Submission of whole foetuses plus placentas from more than one ewe increases the diagnostic rate. If foetuses/placentas from several ewes have been examined with no diagnosis reached, and more than two per cent of the flock have aborted then consider further investigation. EAE, Toxoplasmosis and bacterial causes such as Campylobacter, Salmonella and Listeriosis should already have been ruled out in these flocks.
Further testing options are available but there are some limitations. As with other serological tests the detection of antibody does not prove a definite link with abortion. Sampling both aborted and lambed ewes is an option to see if there is a difference. Antibody levels will be highest three to four weeks after abortion has occurred and may wane over time through the summer, so sampling as soon as possible is beneficial.
- EAE and Toxoplasmosis: Most useful in unvaccinated flocks where no or very few foetuses/placentas were examined.
- Border Disease: Some foetuses may already have been tested. It is worth checking if the flock buys replacements or the ewes had contact with cattle during pregnancy.
- TBF: This cannot be definitively diagnosed by examination of foetuses. Flock history is particularly relevant specifically abortion in purchased sheep or in homebred sheep if they have spent a long time on tick free ground e.g. wintered away. Management changes such as tree planting in the area could have resulted in an increase in tick numbers on farms where they previously weren’t a problem? A purple top (EDTA) tube is needed for the PCR test but remember that Anaplasma phagocytophilum is fairly ubiquitous where there are ticks so any positive result should be considered alongside the history.
- Liver fluke: Abortions can occur secondary to liver disease or severe anaemia caused by chronic liver fluke. Thin ewes, small lambs and ewes with no milk may also have been reported.
- Q Fever: Recognised as a cause of abortion in sheep and like EAE can only reliably be ruled in or out if placenta is examined. Serology on aborted ewes is of use as part of a wider investigation.
Posted by SRUC Veterinary Services on 18/07/2023
