Managing ewes that abort
Tuesday February 26 2008
Over the past few weeks I have been receiving a few queries from farmers that have sheep aborting. It is important that appropriate action is taken to try and control the situation.
A certain number of abortion/slipped lambs will happen on most sheep farms -- this is accepted as normal. These may manifest themselves as abortions where the farmer finds an aborted foetus or simply a number of ewes that scanned in lamb but turn up dry at lambing time.
In general, an abortion level of less than 2pc is considered to be 'normal'. In fact, some experts believe that a low level of abortions demonstrates that some level of immunity against aborting agents is being maintained in the flock (where toxoplasmosis is the cause).
The problem is that when the first ewe aborts, it is not possible to know if this is just a 'normal' abortion or the start of an abortion storm.
So how do we control abortion in sheep? The first step is to find out what is causing it. Some reasons are to do with the physiology/hormone levels of the sheep. Others include injuries, malnutrition and stress. And then there are diseases such as toxoplasmosis, enzootic abortion, tick-borne fever, salmonella and Campylobacter to name but a few.
Results from material sent to the Regional Veterinary Laboratories in 2006 showed that 22.4pc of all samples submitted were positive for enzootic abortion, 18.4pc for toxoplasmosis and 3.2pc for bacterial abortion. These results show that in only 44pc of cases was a diagnosis found. Very often farmers stop sending aborted material to the laboratory because they did not get a result from a previous sample. This is a mistake. Often it will take a number of samples sent to the laboratory before a positive diagnosis is made.
Because you never know why a ewe has aborted, it is important that you treat each one as if it was the start of an abortion storm. Some organisms that cause abortions will spread to other ewes in the flock if preventative measures are not taken. Ewes that have aborted should not be mixed with ewe lambs to build up their immunity until a definite diagnosis of the aborting organism has been made.
Many diseases that cause abortion are carried and shed by sheep in subsequent years and continually infect naive sheep.
When an abortion takes place, the following plan should be implemented to reduce the risk of further abortions:
1. Isolate the affected ewe immediately.
2. Disinfect the area where the ewe aborted, using hydrated lime or other suitable disinfectants, and freshly bed the pen.
3. Place a bucket of disinfectant at the entrance to the area where aborted ewes are being held to avoid infection being spread by foot or machinery.
4. Remember that some abortion agents can be contracted by humans, therefore extreme caution in handling the aborted ewe and aborted material is advised.
5. Remove all aborted material and arrange with your vet to have the foetus and afterbirth tested in your regional veterinary laboratory. Continue to test subsequent abortions even if you get negative results.
6. Surplus aborted material that is not being submitted to the laboratory should be burned, buried or treated with copious amounts of lime.
7. Do not allow contact with wildlife and aborted material as this may cause a spread to other farms.
8. Never mix ewes that have aborted with any other sheep until the cause has been established and you have been advised that it is safe to do so.
9. Discuss with your vet any benefit in taking blood samples from aborted ewes to aid in identification of the cause.
10. If a causal agent has been identified, continue to send further cases for examination as often more than one causal agent may be involved.
11. Some diseases that cause abortion may also make the ewes very sick. Continue to keep a close eye on the aborted ewes.
12. Treating all the sheep in the flock with long-acting antibiotics in the face of an outbreak is very much a hit and miss affair as there is little evidence that it is of any benefit for most aborting agents (enzootic abortion being an exception).
Once you have identified what went wrong you, in conjunction with your vet, will be able to draw up a plan to eliminate or reduce the risk of abortion recurring the following year. Because abortions are relatively common on sheep farms, pregnant women and people with compromised immune systems should stay away from the lambing shed.
- Michael Gottstein
