Published in:
Open Access
01-12-2010 | Research article
The use of a geographic information system to identify a dairy goat farm as the most likely source of an urban Q-fever outbreak
Authors:
Barbara Schimmer, Ronald ter Schegget, Marjolijn Wegdam, Lothar Züchner, Arnout de Bruin, Peter M Schneeberger, Thijs Veenstra, Piet Vellema, Wim van der Hoek
Published in:
BMC Infectious Diseases
|
Issue 1/2010
Login to get access
Abstract
Background
A Q-fever outbreak occurred in an urban area in the south of the Netherlands in May 2008. The distribution and timing of cases suggested a common source. We studied the spatial relationship between the residence locations of human cases and nearby small ruminant farms, of which one dairy goat farm had experienced abortions due to Q-fever since mid April 2008. A generic geographic information system (GIS) was used to develop a method for source detection in the still evolving major epidemic of Q-fever in the Netherlands.
Methods
All notified Q-fever cases in the area were interviewed. Postal codes of cases and of small ruminant farms (size >40 animals) located within 5 kilometres of the cluster area were geo-referenced as point locations in a GIS-model. For each farm, attack rates and relative risks were calculated for 5 concentric zones adding 1 kilometre at a time, using the 5-10 kilometres zone as reference. These data were linked to the results of veterinary investigations.
Results
Persons living within 2 kilometres of an affected dairy goat farm (>400 animals) had a much higher risk for Q-fever than those living more than 5 kilometres away (Relative risk 31.1 [95% CI 16.4-59.1]).
Conclusions
The study supported the hypothesis that a single dairy goat farm was the source of the human outbreak. GIS-based attack rate analysis is a promising tool for source detection in outbreaks of human Q-fever.