Proceedings of the Spatial Information Research Centre’s 10th Colloquium 119 An ecological approach to environmental sources of campylobacteriosis in New Zealand Mark Hearnden 1 , Phil Weinstein 1 , Peter Firns 2 , Chris Skelly 3 , Clare Salmond 1 , George Benwell 2 The rate of campylobacteriosis in New Zealand is now over 200 cases per 100,000 per year (CDC, 1997), making this the most common of our notifiable diseases. Campylobacteriosis occurs more than twice as commonly here as in England, and more than three times as commonly as in Australia and Canada (CDC, 1993). This differential between countries is also clearer for Campylobacteriosis than for other notified foodborne illnesses (Malcolm, 1994). The direct cost of Campylobacteriosis to the New Zealand community is estimated to be $4.48 million per annum with true costs possibly in the order of $40 million per annum (Withington and Chambers 1996), when underreporting is considered (Hudson, 1997). Recent epidemiological studies have focused on the modes of transmission of Campylobacter in New Zealand. The consumption of raw or undercooked chicken (Eberhart-Phillips et al. 1997, Ikram et al 1994) and contaminated drinking water (Brieseman, 1987; Stehr-Green et al, 1991, Bohmer, 1997) are known to be risk factors for infection. However acting on these risk factors may have limited effec- tiveness if interventions are focused solely on reducing human exposure without consideration of the environmental reservoirs of the bacteria. 1 Department of Public Health Wellington School of Medicine University of Otago, Wellington South, New Zealand Phone +64 4 385 5999 Fax +64 4 389 5319 whale@wnmeds.ac.nz 2 Spatial Information research Centre University of Otago, Dunedin, New Zealand Phone +64 3 479 7391 Fax +64 3 479 8311 pfirns@infoscience.ac.nz Abstract Only Presented at the 10th Colloquium of the Spatial Information Research Centre, University of Otago, New Zealand, 16-19 November, 1998 3 Ministry of Health Wellington, New Zealand Phone +64 4 496 2000 Fax +64 4 496 2340 Chris_Skelly@moh.govt.nz A more effective approach may be to reduce the frequency with which the organism contaminates food and water, thereby reducing the human expo- sure. Primary prevention of this kind requires a detailed knowledge of the ecology of the disease, including consideration of the natural and occupa- tional environment, animal reservoirs, and human hosts. An ecological approach of this kind can lead to recommendations for public health interventions that are not otherwise obvious. For example, when applied to the mosquito borne disease Ross River virus in Australia, this approach has led to a fundamental change in the recommendations for vector control (Weinstein, 1997). There are good grounds to believe that climatic and agricultural factors are important influences on the prevalence of the organism in the New Zealand environment (Bohmer 1996; Weir,1998). In NZ, outbreaks of campylobacteriosis which were linked to the water supply have followed heavy rain, and are likely to be related to nearby grazing animals (Brieseman, 1987; Stehr-Green et al, 1991). Overseas the importance of extreme rainfall events for water- borne gastroenteritis (Patz et al 1996) has also been demonstrated in study of Campylobacters in a river