Pigs Point To Presence Of Tb Possums

December 6, 2000

Implanting a radio transmitter into an anaesthetised pig prior to release.

Landcare Research has just completed an Animal Health Board funded pilot trial which shows that deliberately released pigs can be used to detect bovine Tb in possums, and are likely to be effective indicators of the presence and persistence of the disease.

Possums pose an immense threat to the beef and dairy industries by spreading Tb, so possum populations have been reduced to low densities in increasingly large parts of New Zealand in efforts to eliminate the disease. However, these successful control efforts have made it much harder to know if and where Tb persists, particularly when there are few livestock to indicate the disease s presence. Possum populations can be surveyed directly, but surveys are difficult and costly. An alternative is to use other wildlife as sentinels of Tb s existence.

Landcare Research scientists have concluded a pilot trial to see whether the pigs are effective sentinels. In February, they caught pigs from the Marlborough Sounds area, which is Tb free, radio-tagged them, and released them into a forest where Tb is present. Over the next eight months, pigs were killed at different times, and checked for Tb. The last pig was checked just a few days ago. All of the pigs developed Tb despite the relatively short time they were in the area; even the two caught just two months after release.

An animal ecologist, Graham Nugent, says there was a steady progression of the severity of the pigs Tb lesions over the course of time. “The pigs we checked a few days ago had bigger lesions than the ones we checked earlier. This suggests that all of the pigs became infected very soon after release, and therefore that pigs can be particularly sensitive indicators of Tb presence.

“The next stage of our research will be to see where and how this knowledge can be applied for Tb management” says Mr Nugent. “ This trial has shown that it is practical to use pigs as sentinels, and the early indications are that they could be extremely useful in identifying Tb trouble-spots.

“In many ways, the use of pigs as sentinels is like setting a thief to catch a thief”.

For further information, contact: Graham Nugent Landcare Research Lincoln wk: (03) 325 6701 x 2256 hm: (03) 332 9445

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