Our Ewe Blood Sampling Event took place at our Markeaton practice on Wednesday 21st April. Sponsored by MSD, it was an opportunity for several clients to bring a selection of barren or aborted ewes to have blood samples taken, to see whether there had been any exposure to Enzootic Abortion or Toxoplasma gondii in their flock.
Over the course of the event, seven clients and their ewes were booked in for appointments. The COVID-secure session, led by Dr David Charles CertHE(Biol.) BVSc MRCVS meant that in total, 62 blood samples were taken throughout the course of the blood drive.
During the event, Dave was assisted by Lottie, one of our VetTechs. Emma and Rachel, final year veterinary students at the University of Nottingham were also present, both of which are currently undertaking a two-week farm placement.
The 62 blood samples were taken quickly from the vein, using vacutainers to provide minimal discomfort or irritation to the ewes.
What causes ‘Enzootic Abortion’?
Enzootic abortion is caused by a bacteria called Chlamydophila abortus. The main source of infection is from infected sheep at lambing time (predominantly afterbirth, discharge and aborted foetuses). This can be sheep that have aborted this year, or sheep that have aborted in previous years and are known as carriers. Occasionally, transient infection of rams is possible.
Ewes that are infected at lambing time will carry infection throughout the coming year and abort the following lambing season. This is the cause of ‘abortion storms’ the following year after an initial diagnosis if no action is taken.
Toxoplasma gondii – symptoms and spread
Toxoplasma gondii is a protozoan parasite that causes toxoplasmosis in sheep. The main infection source is cat faeces. Toxoplasmosis is zoonotic and can spread to humans as well so extreme care must be taken around aborting sheep and aborted material.
Toxoplasmosis is caused by the ingestion of T.gondii oocysts by ewes; usually through cat faeces contaminating feed, hay or pasture. Cats become infected after eating infected rodents, the number of oocysts is amplified in cats to the extent that 1 gram of cat faeces can contain enough oocysts to infected thousands of ewes. The oocysts can exist on feed or pasture for very long periods of time.
The stage of pregnancy will determine the outcome of the infection;
Days 1 – 60: the foetus is absorbed and the ewe will appear barren
Days 60 – 120: abortion in late pregnancy, often with mummified foetus, Alternatively, stillbirths or weak lambs that may fade can be seen.
Unlike enzootic abortion toxoplasmosis cannot spread from sheep to sheep, and therefore vaccination is advisable as mixing sheep prior to tupping will not result in control.
Why is sampling barren or aborted ewes important?
Blood sampling barren or aborted ewes can identify whether they have been exposed to C.abortus (causative agent of Enzootic Abortion) or T.gondii and suggest if this has been a likely cause of the barren/abortion ewes. Furthermore, it can help us work with clients and advise on vaccination strategies, biosecurity and control protocols. It can also be used as a screen test in ewes with abnormally small or weak lambs, although it is not as accurate a predictor for this type of ewe.
We recommend any client with more than 2% of their flock aborting or an unexpected number of barren ewes, warrants screening bloods or further outdoor investigation.
How can blood sampling improve your flock’s health?
Blood sampling can help improve your flock’s health as the samples taken will help our vets to advise on future plans for the ewes when breeding or vaccinating.
Are you concerned about barren or aborted ewes in your flock? If so, please call our team on 01332 29492.
Join our Flock Health Club
With access to a number of benefits including a free visit fee and up to 60 minutes of time to develop your flock management plan which includes advice on vaccination regimes and infectious agent control, our Flock Health Club is the easy way to break down veterinary consultancy costs on a range of flock issues, as well as offering you discounts. Join the flock health club today.
We would like to extend our thanks to MSD for funding the laboratory fees as well as our clients who attended our Ewe Blood Sampling Event. Please keep a look out via our social media channels for more event dates announced.