Emergence of the Pathogen
Before the discovery of Cryptococcus gattii in BC, the pathogen was thought to be restricted to tropical and subtropical areas. A number of investigators have tried to explain the emergence and dispersion of the microorganism in BC.
How C. gattii was originally introduced into the region is not known, but we do know the yeast is transmitted in air, water, and soil. This means it can be easily transported on shoes or vehicle wheels and when products are moved from place to place. Climate change impacts, including cycles of warmer summers and reduced snow cover, are thought to have supported the yeast's emergence on Vancouver Island and its spread to other parts of the Pacific Northwest.12
Researchers have mapped out the current geographical distribution of human and animal cases of C. gattii in British Columbia (Figure 1).3 Mak and colleagues (2010) have also developed ecological niche models to predict the possible future geographical distribution and colonization of C. gattii in the Pacific Northwest (Figure 2).3 These models are based on data about human and animal cases and environmental sampling, as well as on climate projections for the region. The maps developed from these projections are useful tools for public health officials.
They indicate that C. gattii may eventually colonize the heavily populated areas of BC's Lower Mainland, although to date only small numbers of people and animals in the Lower Mainland, Washington, and Oregon have contracted cryptococcosis from somewhere other than Vancouver Island.456
- 1. Kidd SE, Hagen F, Tscharke RL, et al. A Rare Genotype of Cryptococcus Gattii Caused the Cryptococcosis Outbreak on Vancouver Island (British Columbia, Canada). PNAS. 2004; 101(49): 17258-17263. http://www.pnas.org/content/101/49/17258.abstract.
- 2. Bartlett KH, Kidd SE, Kronstad JW. The emergence of Cryptococcus gattii in British Columbia and the Pacific Northwest. Curr Infect Dis Rep. 2008;10(1):58-65.
- 3. a. b. Mak S, Klinkenberg B, Bartlett K, et al. Ecological niche modeling of Cryptococcus gattii in British Columbia, Canada. Environ Health Perspect. 2010;118(5):653-658. http://ehp03.niehs.nih.gov/article/info:doi/10.1289/ehp.0901448.
- 4. Upton A, Fraser JA, Kidd SE, et al. First contemporary case of human infection with Cryptococcus gattii in Puget Sound: evidence for spread of the Vancouver Island outbreak. J Clin Microbiol. 2007;45(9):3086-3088. http://jcm.asm.org/content/45/9/3086.
- 5. MacDougall L, Kidd SE, Galanis E, et al. Spread of Cryptococcus gattii in British Columbia, Canada, and detection in the Pacific Northwest, USA. Emerg Infect Dis. 2007;13(1):42-50. http://wwwnc.cdc.gov/eid/article/13/1/06-0827_article.htm.
- 6. Byrnes EJ III, Li W, Lewit Y, et al. Emergence and pathogenicity of highly virulent Cryptococcus gattii genotypes in the northwest United States. PLoS Pathog. 2010;6(4):e1000850. http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat....