In New Zealand the two main causes of sheep abortions are campylobacter and toxoplasmosis. Luckily for us, vaccines are available to help prevent these diseases.
What is Campylobacter and where does it come from?
Campylobacter fetus is a bacterium that is spread mostly by infected, carrier ewes or aborted material. Carrier ewes can propagate the disease from season to season, keeping the infection in your flock. Up to 88% of New Zealand farms have the bug, so it’s safest to assume it’s on your property (or very close by!).
Once ingested by a pregnant ewe, it localises in the intestine and then spreads via the bloodstream to the placenta. Typically, ewes will abort 1-3 weeks after they’re infected and most of them don’t appear to get ‘sick.’
Due to the way it is spread, we tend to see sporadic abortions earlier in gestation, gathering momentum to result in abortion ‘storms’ in late pregnancy (the last 6 weeks or so). As the infected material is spread, more ewes are exposed and therefore more abortions are seen.
Which stock should I vaccinate and when?
We recommend all breeding ewes are vaccinated. Previously unvaccinated ewes need a sensitizer dose and a booster dose, 4 -6 weeks apart. Thereafter, an annual booster dose is recommended and can be given pre-tup or at ram withdrawal.
How can vaccinating against Campylobacter affect production on my farm?
Putting it bluntly – vaccinating can increase your lambing percentage by 9%. As outlined earlier, the disease is widespread in New Zealand so vaccinating is an excellent option to improve performance.
This disease causes increased losses throughout pregnancy, typically in maiden ewes. Rather than obvious abortions in late pregnancy, you may notice a decreased scanning percentage – especially in your maiden ewes – or an increased number of dry/dry ewes at weaning. Just like campy, ewes do not appear to get ‘sick.’
Toxoplasma gondii: a complicated little bug with an interesting lifecycle!
Toxoplasma gondii is a protozoan parasite: a hardy bug that has a complicated lifestyle involving several animals such as rodents, birds and cats as well as sheep (and even humans!). With regards to ovine abortions, when cats are infected, they shed huge numbers of the bug via their faeces, contaminating feed and/or water that is then ingested by sheep. In the pregnant ewe, the bug moves from the gut to the placenta and foetus, causing foetal resorption (in early pregnancy), or foetal death, mummification and abortion (in mid-late pregnancy). Unlike with campylobacter, sheep are not infective to one another. Once a ewe has been infected, she’ll develop life-long immunity and won’t abort due to toxoplasmosis again.
How wide-spread is the problem?
It is estimated that 64% of New Zealand cats (feral AND pets) are infected with toxoplasmosis by the time they’re approaching adulthood. Given the large number of feral cats in New Zealand, it’s hardly surprising to find out that 99% of New Zealand farms have it.
Will vaccinating help? When do I do it?
By vaccinating a previously unvaccinated flock, on average we see a decrease in the dry ewes by 14% and a 3% increase in overall lambing percentage. Vaccinating is simple: one dose will protect ewes for life. It is a live vaccine, which means it has some special instructions around handling and storage and needs to be ordered well in advance. An important point to make is that this vaccine must be given at least four weeks prior to tupping.
Want further information or support?
Protecting your flock against campy and toxo is straightforward and very cost-effective. Give us a call at your local Anexa vet clinic if you have any questions or to plan your flocks’ vaccination schedule.
Down the track, if you become concerned about a lower than normal scanning percentage or start to experience heavy losses, give us a ring. Timeliness is key when it comes to sussing the problem. Bringing us entire aborted foetuses and placentas will give us the best chance of finding the cause, though blood tests and post-mortems of the ewes may also help.