Cryptococcus gattii Spreading in North America

The Centers for Disease Control reported late last year that Cryptococcus gattii fungal infections were diagnosed in Alabama (1), California (13), Florida (1), Georgia (5), Hawaii (1), Michigan (1), Montana (1), and New Mexico (2) since 2009.  This is surprising because the fungus only first emerged in North America in British Columbia in 2009.  Shortly after, it spread to the Pacific Northwest, and it has now reached the North American East Coast.

C. gattii infections are contracted by inhalation of fungal spores after encountering areas of decaying forest matter or areas near pigeon droppings, which support the growth of the fungus2.  The resulting cryptococcosis infection can lead to pulmonary irritation/infection and potential pneumonia or, more seriously, central nervous system infection1.  Animals present symptoms similar to humans, and the wide array of species that have been affected includes cats, dogs, birds, ferrets, llamas, alpacas, goats, sheep, horses, and porpoises.2

Fungal infections have been known to generally threaten only immunocompromised humans and animals, and infections of this type have usually been associated with the opportunistic pathogen Cryptococcus neoformans rather than C. gattii.  These recent North American infections have been reported in otherwise clinically healthy people and animals, and the C. gattii infections have been more difficult treat than C. neoformans3.  According to microbiologists such as Joseph Heitman, Director for Center for Microbial Pathogenesis at Duke University Medical Center,4 these developments and the changes in geographic spread could be due to C. gattii participating in sexual reproduction and forming previously unseen and more virulent strains.  Additionally, global climate changes could be playing a role in providing new ideal environments for the fungus.  This is thought to be the case in British Columbia, where Douglas fir trees were discovered to be hosting the organism after several years during which the average temperature in the area was consistently one degree higher than normal3. The new North American cases were not always connected with travel to places in which the fungus is endemic within the expected incubation period of 2-13 months1.  Such instances could suggest that the C. gattii strains arrived years earlier from endemic regions, but are just now causing illnesses as the climates in their new habitats have become more favorable3.  

Authored by Paige Meier

References:

1. Harris JR, SR Lockhart, G Sondermeyer, DJ Vugia, MB Crist, MT D’Angelo, et al. 2013. “Cryptococcus gattii infections in multiple states outside the US Pacific Northwest.” Emerg Infect Dis [Internet]. 19.10 (Oct 2013). Accessed 20 Jan 2014. http://wwwnc.cdc.gov/eid/article/19/10/13-0441_article.htm 
2. Nielsen K, AL De Obaldia, J Heitman. 2007. “Cryptococcus neoformans mates on pigeon guano: implications for the realized ecological niche and globalization.” Eukaryot Cell. 6.6 (Jun 2007): 949-59. Accessed 20 Jan 2014. http://www.ncbi.nlm.nih.gov/pubmed/17449657
3. Frazer, J. 2013. “Fungi on the March.” Scientific American. 309(Nov 2013): 50-57. Accessed 20 Jan 2014. http://www.nature.com/scientificamerican/journal/v309/n6/full/scientificamerican1213-50.html.
4. Heitman, J. 2013. “Sexual reproduction and the emergence and evolution of microbial pathogens.” Duke University Medical Center for Microbial Pathogenesis. Accessed 20 Jan 2014. http://mgm.duke.edu/microbial/mycology/heitman/.
5.  Naureen I, EE DeBess, R Wohrle, B Sun, RJ nett, AM Ahlquist, T Chiller, SR Lockhart. 2009. “Correlation of genotype and in vitro susceptibilities of Cryptococcus gattii strains from the Pacific Northwest of the United States.” J. Clin. Micorobiol. 48.2 (Dec 2009): 539. Accessed 20 Jan 2014. http://jcm.asm.org/content/48/2/539.full.pdf+html.
6. Duncan CG, C Stephen, J Campbell. 2006. “Evaluation of risk factors for Cryptococcus gattii infection in dogs and cats.” J Am Vet Med Assoc. 228.3 (Feb 2006): 377-82. Accessed 20 Jan 2014. http://avmajournals.avma.org/doi/abs/10.2460/javma.228.3.377?prevSearch=allfield%253A%2528c.%2Bgatti%2529&searchHistoryKey.