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Proceedings of the First Symposium on Marsupials in New Zealand

The Success of Tb/Possum Control

page 218

The Success of Tb/Possum Control

Success in Tb/possum control can ultimately only be measured in terms of a reduced incidence of tuberculosis amongst cattle herds. This has been most accurately documented for the "Block 1" test area near Westport (Fig. 4, from Stockdale, 1975, Report AH26-1175). In that area, tuberculin testing of herds at three monthly intervals revealed incidences amongst reactor and tuberculous cattle of 5–6% and 2–3% respectively. Reduced incidences of cattle of either status were obtained only with the attempted elimination of infective animals outside of individual herds. Control of possums, initially by aerially applied toxin and later by repeated ground operations has led to a steady reduction in the incidence in both reactor and tuberculous cattle. In at least two instances, viz. the Monument area on Banks Peninsula and the Matiri Valley near Murchison, repeated possum control has led indirectly to disease-free herds.

Long term changes in the disease status of possum populations have not been monitored. However, in the two instances quoted above - the Monument area and the Matiri valley - it is reasonable to infer that a dramatic reduction if not a total elimination of all foci of infection amongst possums occurred in each area.

Short term changes have been monitored at least once, viz. in the Hohonu region, central Westland, by the author. In that instance, the possum kill obtained by aerial poisoning was estimated to be 67± 14% (C.L.) while the percent incidence of tuberculous possums remained unchanged.