Scientists try new Tb-control ideas

01:43, Jan 31 2009

Landcare Research scientists will trial new pest-control methods in Marlborough this spring which may pave the way for a dramatic reduction in 1080-poison use in New Zealand.

Landcare Research's wildlife ecology and epidemiology science team has been working on possum-control techniques on Marlborough's Molesworth Station for the past three years.

Lead scientist Graham Nugent said his team would test three new projects this spring aimed at breaking the tuberculosis (Tb) cycle in wildlife.

One, using 1080 poison and a Tb vaccine simultaneously, might be a global first.

"This idea is to use the smallest possible amount of toxin to knock numbers down and then use the vaccine to ensure that the Tb cycle is well and truly broken," Nugent told Landcare's Discovery newsletter. "The argument is they will work far better together than they would alone."

Scientists intend to mix 5 per cent of vaccine baits into the 1080 mix. They expect most of the local possums to be killed by the poison, and hope the remainder will eat the vaccine baits. That should halt the spread of Tb among possums and reduce its spread to cattle.

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Nugent said Landcare was also trialling vaccinating cattle against Tb.

"There is a vaccine available, BCG, which is the same as the one long-used in humans. We know it protects cattle against experimental challenge from Tb. What we don't know is whether it will protect cows from the natural challenge of Tb-infected possums, so this trial is the first ever real-world field trial of that."

The third project will see poison sowed at different rates in different areas to see which method is most effective in reducing rates of Tb in the wild.

"We'll use released pigs as `Judas' animals or sentinels, as a way of measuring the level at which Tb continues to cycle or persist in wildlife," Nugent said.

"Pigs are very good at this because they rarely pass on Tb but they move around over large areas and quickly pick up Tb by scavenging any Tb-infected possum carcasses that inevitably occur if possums are still becoming infected."

The number of infected pigs would reveal which rate of poison dropping was most cost-effective at stopping Tb transmission to cattle, Nugent said.

 

The Press