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UBC Theses and Dissertations

Occupational exposure to Cryptococcus gattii : evaluation of exposure to Cryptococcus gattii among arborists and CRD watershed employees on Vancouver Island Hingston, Adrian Owen


Cryptococcus gattii (C. gattii) has emerged as an infectious pathogen on Vancouver Island, B.C. The goal of this thesis is to describe exposure to C. gattii among workers who work outdoors under the canopies of trees on Vancouver Island, specifically arbor workers and Capital Regional District (CRD) Watershed maintenance workers. Environmental sampling of trees, soil, water and air was used to characterize the geographical distribution of the organism on Vancouver Island and the Southern Gulf Islands. Air sampling was performed in the breathing zone of workers carrying out woodland tasks. Task analysis and questionnaire data were used to characterize the work tasks performed by arbor workers and CRD Watershed Maintenance workers. This organism was found in varying concentrations on the east coast of Vancouver Island from Victoria in the south to Courtenay in the north. The highest concentrations of positive samples were found in Parksville (i.e. 35% of all samples obtained were positive for C. gattii), Duncan (24%), and Salt Spring Island (20%). A wide range of tree species have been colonized by the organism including economically important varieties such as Douglas fir, Red Cedar, and Alder. The highest levels of C. gattii occurred in the drier months of the year, with very few positive air samples occurring between the months of November and March. Relative humidity was significantly (negatively) associated with airborne C. gattii in non-working conditions, and the location where the sample was taken as well as the month in which it was taken were significant determinants of airborne C. gattii concentration. The highest levels of airborne C. gattii occurred under working conditions. With work tasks such as chain sawing and chipping C. gattii can become airborne in smaller particle sizes that are able to enter deeper portions of the human respiratory tract, which may enhance its ability to initiate disease. There is a risk of occupational exposure to C. gattii to workers performing woodland tasks on Vancouver Island. The risk of exposure is higher in the drier months of the year and when the worker performs tasks that create aerosols. Workers should be made aware of the existence of the pathogen as well as the signs and symptoms of cryptococcosis.

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