Anyone can be affected by sheep measles, anytime, and it's not always easy to confirm the cause.
That's the message from the co-owners of a large Poverty Bay sheep and beef business which breeds and finishes several-thousand lambs a year.
They're speaking from experience. Last winter, two lines of trading lambs killed out with what for them was a massive infection rate, up to 28per cent in one case. It was an isolated blowout but it has prompted a rethink on how they manage the risk of ovis across their whole business.
"It hasn't cost us a lot, but it could really cost the industry .. when diners in a high-end restaurant find a lesion in their lamb."
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Sam and Gemma Hain are partners in the 10,000 stock unit Waikura Station, which comprises just over 1000ha of mainly medium to steep hill country west of Gisborne.
As well as commercial sheep and cattle breeding, the Hain family have for many years also bred stud Hereford, Shorthorn and Angus cattle, along with stud Romneys. They own a further 135ha at Te Karaka on the Poverty Bay flats, where they winter bought in trading lambs, then lease the land out for summer squash and sweet corn production.
There are nine working dogs on the station, and several pet dogs. Up until now, they've been wormed every three months with all-wormer tablets mailed out by the vet.
"I've been comfortable with that system; we've never had a problem before," Sam says.
"The more I read, and talk to vets and other people, however, the more I think we should change to worming every month."
But dogs can't be blamed with certainty for the July ovis incidence blowout, even though this occurred on the lower finishing farm where the risk posed by wandering dogs is believed to be higher.
That's because only some of the bought-in lambs grazing there had ovis. When the Hains found out 28 were infected from a line of 345 drafted in July, they set up a test for the next draft.
"When the results came back from the first draft, I thought that's terrible. So with the next lot of lambs we killed, we divided them up according to where they had come from, and killed them all on the same day. Out of one line of 146 lambs, 41 had cysts. The other line still had ovis, but the incidence rate was about 1per cent, not 28per cent."
Subsequent drafts had either no ovis, or only one or two lambs affected.
Sam says that, in some ways, it would have been easier to understand the situation if all the lambs grazing at Te Karaka had been affected. As it stands, there is no immediate or easily identifiable cause of the outbreak.
He spoke to the farmer the infected lambs came from and he stated he regularly wormed his dogs. Sam thought it was important to have the conversation, even if the farmer wasn't the source of the infection because many farmers who only sell store stock don't get feedback from the works on their ovis incidence.
Only one of their finishing lambs was condemned, so financially it could have been worse. But that's not the point, he says.
"It hasn't cost us a lot, but it could really cost the industry. What we as farmers and rural dwellers have to understand is that a big proportion of ovis lesions aren't discovered; they go into the marketplace and they cause big reputational damage to our product, when diners in a high-end restaurant find a lesion in their lamb.
"One of the problems with ovis is that it doesn't cost us very much as producers. We had what I think is a massive outbreak, and it cost us one sheep. For attitudes to change, it needs to have a bigger financial impact."
One thing that has changed as a result of the experience is his attitude to dog dosing, as well as his knowledge of ovis.
"There hasn't been bovine TB found in Gisborne for 20 years, and because of that none us of know a lot about TB any more. If a reactor got back into Gisborne, suddenly we'd all get clued up again.
"It's the same in this case. Suddenly I've learned a lot about ovis. And one of the things I've learned is that the parasite has a 35-day life cycle. Every time we worm our dogs we break the cycle. If we're worming every three months there is a big window where the dogs can potentially get re-infected and start spreading eggs again.
"By worming every month, you break the cycle before there's a risk of re-infection."
Dan Lynch, project manager for Ovis Management, says more farmers are moving to monthly dosing.
National incidence rates in the season ending October were the lowest in 10 years, but Ovis Management is closely monitoring higher prevalence in trading lambs compared to those bred and finished on the same property.
"We are looking to target back down the production chain to ensure lamb breeders who kill few, if any lambs, are aware of the need to have an effective on-farm control programme in place."
For more details, visit www.sheepmeasles.co.nz.