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Campyvax4® – why vaccinate mixed age ewes?

Campylobacteriosis is one of the leading causes of abortion in sheep in New Zealand.

Campylobacter or ‘Campy’ is often associated with abortions in the last six weeks of pregnancy. Abortion storms may result in lamb losses of up to 30% in naïve flocks. However, trial work has shown that ‘Campy’ can also cause losses at other times which will often go unobserved. In early pregnancy, infections can cause embryonic loss which results in dry ewes or late lambers. Campylobacter can also cause stillbirths or birth of weak lambs that die soon after birth.

To prevent abortion storms, it is common for farmers to vaccinate their maiden ewes with a sensitiser and booster of Campyvax4® four to eight weeks apart, ideally completed prior to mating. But what about your mixed-age ewe flock? Should you consider an annual Campyvax4® booster in the MA ewes?
A serological survey of Toxoplasma gondii and Campylobacter fetus fetus in sheep (analysing three years of blood test results), showed that 88% of NZ farms had Campylobacter present (100% of farms had Toxoplasma gondii present). In the farms that were found to have Campylobacter, around half (52%) of unvaccinated mixed-age ewes were still naïve.

Unlike Toxoplasmosis, where a large proportion (85%) of 4-tooth and older ewes have already been naturally exposed and therefore developed protective antibodies to ‘Toxo’, it does not appear to be the case for Campylobacter, and simply relying on natural exposure to “boost” immunity in mixed-age ewes is not necessarily effective across the entire flock.
Therefore, an annual booster premating with Campyvax4® is necessary to protect the mixed-age ewe flock as around half of them are still at risk of infection due to ‘Campy’. But is there a financial benefit?

From a recent field study conducted in the Hawkes Bay, the results showed that there was a 4% increase in lambing percentage in two-tooth ewes boosted with Campyvax4® compared to 2-tooth ewes not boosted (i.e., 134% vs 130%). This result occurred when the booster was given no more than a year after the primary course i.e., the primary course was completed as a hogget.

Putting this into perspective, this is a difference of 40 lambs per 1000 ewes. Even if the lamb price is $110, that’s approximately $3,300 extra return factoring in a 2% loss after lambing and the cost of the vaccine (estimated $1 incl. GST per head).

Although there has been no trial work performed in NZ showing significant benefits of vaccinating mixed-age ewes with Campyvax4®, there have been several reports from farmers claiming lifts in lambing percentage and lamb viability through boosting their mixed-age ewe flock with Campyvax4® annually. For instance, a farmer in the South Island reported a 10% reduction in lambing percentage in his mixed-age ewe flock after discontinuing his annual Campyvax4® booster vaccination. This occurred for two consecutive years before he reinstated the annual Campyvax4® booster programme and his lambing percentage returned to where it was before he had ceased boosting his MA ewe flock. He stopped seeing slipped lambs prior to lambing, and overall, the lambs seemed bigger and healthier. For more information on this case, visit

In summary, although further investigation is required to determine whether mixed-age ewes will benefit from an annual booster vaccination, there may be significant benefits in booster vaccinating ewes prior to mating that received a primary vaccination course in the previous year. Previous trials have suggested that Campylobacter could be contributing to lamb losses between scanning and docking on properties on which abortions have not been observed, and that reduced lamb viability from Campylobacteriosis could be of greater importance than abortion. Therefore, mixed-age ewe flocks which are experiencing such losses may well benefit from protection through annual vaccination.

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