How ferrets help track TB

New Zealand's TBfree programme is focused on the eventual eradication of bovine tuberculosis.  

Almost any wild animal can acquire bovine tuberculosis - some become infected incidentally; some harbour disease and can transmit it to livestock.  

Possums are proven hosts and vectors of TB, and TBfree's pest control is aimed largely at possums. 

But what about ferrets? The ferret is a cat-sized mustelid predator that inhabits grassy tussock and scrubland.  

Generally, where you find rabbits, you'll find ferrets.  

They breed like rabbits too - one mother can produce four to eight kits each spring and roam over several square kilometres. 

Ferrets are carnivorous and cannibalistic. They readily scavenge carcasses, including animals that have died from TB. That makes them useful to TB researchers surveying areas of farmland and wilderness for evidence of the presence or absence of TB in wildlife.  

A TB-infected ferret can become disorientated and wander close to livestock. That poses a transmission risk for farmed animals. Inquisitive cattle or deer will investigate a sick ferret's abnormal behaviour, similar to the way livestock are thought to acquire TB when they investigate sick possums. But ferrets are really more useful as a research tool. They show where TB-infected possums are.  

Ferrets are usually trapped using kill-traps, tunnel traps or leg-hold traps baited with fresh rabbit meat. 

In the Mackenzie Country in the middle of the South Island, for example, ferrets are trapped by contractors. Their carcasses are examined in the lab to check signs of TB infection.  

Infection is usually found in the lymph nodes. In the earlier stages, ferrets will carry infection without showing signs of disease of TB lesions.  

Tissue taken from the lymph nodes is cultured to check for signs of TB. 

Ferret surveys help to identify where TB is present in wildlife and where possum control is needed to eradicate TB.  

They also indicate where disease has been successfully cleared. Using ferrets for TB research is a cheaper and more efficient way of finding TB than surveying possums. 

Ferrets are introduced predators which do nothing for New Zealand's environment.  

Helping OSPRI track and eradicate bovine TB is one useful contribution ferrets can make.  

For more information on using ferrets for TB research, read the factsheets at ospri.co.nz 

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