While Nait is not perfect it has enabled the eradication attempt that otherwise might not have been possible, Ministry for Primary Industries intelligence group manager Alix Barclay says.
That head-start has, over time, meant changes to the design of surveillance and how it is implemented, Barclay said.
The intelligence team is responsible for tracing the disease, surveillance, targeting of sampling, data management and the diagnostic laboratory systems.
“Simply it’s about tracking it down and once tracked finding out if, in fact, there’s infection and identifying farms at risk and finding out which way they fit the tracing puzzle.
“So, in the intelligence team we have a wide variety of tasks and a lot of specialist groups targeting specific aspects of our responsibilities.
“The team includes different breeds of epidemiologists, some also contracted to specifically support the surveillance teams.”
Barclay said the fact M bovis had a head-start on the tracing has become significant in how the surveillance is structured and how it is implemented now, compared to 14 months ago.
“Given the head-start bovis had on us, perhaps here in NZ as long as a couple of years so we are now learning, in the beginning our ability to catch up with farms was much slower as we gained tracing patterns, meaning in many cases a farm could have been infected for several months before we started tracing it.
“That meant a lot more tracing work from each at-risk property and we had a lot of catching up to do.”
Now farms have more often than not been infected for only a month when they are identified, making tracing much quicker under a new design that’s intercepting likely spread much sooner.
“But still, every farm is different with its own individual challenges whether it be calves, beef cattle or dairy so the pressure doesn’t really ease at all for the tracing team.
“We are just catching it sooner and implementing surveillance in a new design learned from experiences of the past 14 months.”
In tracing the movement of animals MPI is also tracing business networks and business relationships.
“Once we have determined an infected property we look at all movements from that farm and onto that farm and once we have all those movements logged we will know when that farm got infected.”
Essentially, given the greatest risk of spread is through animal movements, the initial tracing is forward.
“But we also trace back, mapping out business relationships to determine the level of risk from the infected property and to develop a link to the rest of the response.
“Once we have identified a business relationship, that needs to be investigated and that’s significant ongoing surveillance.
“It’s one big puzzle but unlike a jigsaw puzzle the problem with tracing is you don’t have everything you want to start and you have got to gather the pieces, piece by piece to put it together.”
Barclay said while Nait has not proved to be everything it was thought to be, it has given the response the ability to design tracing and surveillance.
“If bovis had got here before Nait we wouldn’t be doing this.
“We don’t think we would have been able to attempt eradication the way we are.
“It may not be a perfect tool but it’s given us a chance to start.”
With 12,000 risk events in the tracing network it’s effectively mapping a community.
“That’s not 12,000 farms but actual risk events where a farm may have bought this year from an infected property and then popped up again having bought again next year.
“Risk events are multiple on some farms.”
Surveillance is about getting the full picture of what’s happening on each infected farm.
“Diagnostic testing around forming that picture is an area we have learned a lot about as the response has gone on.
“There’s been no template, no text book to do this.
“We have been working from a clean slate to develop systems.
“That’s why things have changed over time and we appreciate that’s been confusing for farmers along the way.
“Farms we are tracing now are presenting diagnostically different to the very first farms.
“We expected that given the first farms had been infected for at least a year.”
Working from the temporary Wallaceville MPI laboratory the testing team has completed 180,000 M bovis diagnostic tests alone over the past 12 months.
The laboratory’s normal work is 25,000 tests a year.
