Ovine abortion season 2022 so far

_{Toxoplasmosis has been the leading cause of ovine abortion so far this year.}

The pie chart below summaries the breakdown of diagnoses reached so far this spring from ovine abortion material received at Dumfries. The data is from 70 submissions of which approximately half was made up of whole foetuses and the other half abortion kits. A diagnosis was reached in 60% of submissions with the figure slightly higher when carcases were received.

Unusually there are many more diagnoses of toxoplasma than EAE. Toxovax supply issues combined with promotion of vaccination to prevent EAE may have played a role. The 'bacteria-other' category includes single diagnoses of sporadic abortions caused by Streptococcus uberis, Yersinia enterocolitica, Trueperella pyogenes and Mannheimia haemolytica. We have not diagnosed Schmallenberg virus so far.

Comprehensive screening for the most common causes of ovine abortion could not be completed in 50% of submissions where no diagnosis was reached. This was due to certain samples being unavailable (for example, no placenta or foetal fluids). Mummified foetuses are unrewarding to test in most cases.

If you have clients with significant numbers of abortions and no diagnosis reached, then it is always worth submitting more foetal samples if they are available. If routine screening has already been carried out, then consider extending testing to include Border disease (FF for antibody and spleen in VTM for virus PCR). If testing on foetal material has been limited, and no abortion vaccines are used, then negative ewe serology can be useful to rule out EAE, toxoplasmosis and Border disease. Proving a diagnosis of abortion due to tick borne fever can be challenging and usually hinges on positive ewe PCR results (EDTA sample required), plus a history of naïve animals being introduced to an area of tick habitat. Histopathology may detect lesions of anoxia or placentitis but, in foetuses with no diagnosis on routine screening, the changes are usually not specific enough to pinpoint the cause.

If you would like to discuss specific cases please get in touch.

Posted by SRUC Veterinary Services on 05/04/2022