Post-lambing blood sampling in ewes

Considering blood sampling some sheep which aborted or appeared empty? There are limitations to testing for infectious abortion after lambing season but in some cases it can be useful for flock health planning. 

Initially consider:

• How many ewes have aborted? If less than 2% there may be nothing infectious to worry about. However, bear in mind 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 2% 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.

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 3-4 weeks after abortion has occurred and may wane over time through the summer, so sampling as soon as possible is beneficial.    

Please note that if sheep have been vaccinated with the newer Inmeva vaccine (HIPRA) they may have antibodies for a year or possibly longer. This is according to work done by HIPRA looking into serological response. EAE serology in these sheep may be very difficult to interpret. With the live vaccines, ewes often test negative for antibodies by the time they are blood sampled. 

• EAE and Toxoplasmosis: Most useful in unvaccinated flocks where no or very few foetuses/placentas were examined.
• Border Disease antibodies: Some foetuses may already have been tested for virus. Worth checking if the flock buys replacements or the ewes had contact with cattle during pregnancy. Antibodies can persist for years so the timing of exposure is usually not known.
• TBF: This cannot be definitively diagnosed by examination of foetuses. Flock history is particularly relevant, specifically abortion in purchased sheep or in home-bred sheep if they have spent a long time on tick-free ground e.g. wintered away. A purple top (EDTA) tube is needed for the PCR test but remember that Anaplasma phagocytophilum is pretty ubiquitous where there are ticks so any positive result should be considered alongside the history. 

For monthly and quarterly disease surveillance reports from SRUC, visit www.sruc.ac.uk/vets

Posted by SRUC Veterinary Services on 23/05/2025