New Zealand Journal of Agricultural Research abstracts
Evaluating potential sources of bovine tuberculosis infection in a New Zealand
cattle herd
J. M. KEAN
N. D. BARLOW*
AgResearch
Canterbury Agriculture & Science Centre
Gerald Street
P.O. Box 60
Lincoln, New Zealand
G. J. HICKLING
Department of Entomology and Animal Ecology
P.O. Box 84
Lincoln University
Canterbury, New Zealand
Abstract In New Zealand, a major source of bovine
tuberculosis (Mycobacterium bovis, Tb) infection in farmed cattle is
thought to be transmission from infected wildlife, primarily the brushtail
possum (Trichosurus vulpecula). At Hohotaka, central North Island,
control work from 1988 to 1994 achieved a sustained mean reduction of 87.5% in
the density of Tb-infected possums. As expected, annual Tb incidence in local
cattle herds consequently declined by a similar amount (83.4%). This decline
was gradual, due to within-herd transmission of residual infection and
imperfect detection of infected animals. By fitting models to the observed rate
of decline in Hohotaka Tb reactors, we are able to deduce the contributions to
reactor rates of possums and cattle-to-cattle Tb transmission. Our results
suggest that Tb transmission between cattle within the herd may have
contributed around 20% to 32% of infections prior to the wildlife control
programme. Nevertheless, our estimate for the rate of within-herd transmission
is well below that required to maintain cattle Tb in the absence of infectious
wildlife. Our analysis supports the policy of wildlife control as the most
effective method for reducing cattle Tb in areas such as Hohotaka.
Keywords Mycobacterium bovis; wildlife; brushtail
possum; disease transmission; models
New Zealand Journal of Agricultural Research, 1999, Vol. 42: 101-106
0028-8233/99/4201-0101 $7.00/0 (c) The Royal Society of New Zealand
1999
PDF file of entire paper: medium quality (541K); (scanned from paper original: notes about this process)
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