Since the research published last week about this lethal strain of fungus in PLoS Pathogens last week, there has been a plethora of media attention concerning the yeast, Cryptococcus gattii. Here I’d like to answer some questions about the fungus to help make it more digestible.
What is Cryptococcus gattii?
C.gattii is a fungus, more specifically yeast, which is considered an emerging pathogen in the Pacific Northwest.
Where is C. gattii found?
Historically the fungus was thought to be found only in geographic regions with a tropical or subtropical environment such as South America, Africa and Australia. But this long-held impression has been shattered by the isolation of C. gattii from temperate regions of North America, Europe and Asia.
What is the difference between C. gattii and Cryptococcus neoformans?
They are closely related but very distinct species. Though there is quite a bit of overlap, what appear to be the biggest differences of interest are the ecological niches for each and the types of patients that they cause disease in.
C.neoformans is notorious for being present in bird droppings, pigeon nests and soil while the presence of C. gattii is frequently isolated from tree bark and tree hollows.
C. neoformans is primarily a disease of people with a compromised immune system while the newest discovery of the genome found in the Pacific Northwest appears to cause pathology on healthy people who are immunocompetent.
What is the concern about the genome found in the Pacific Northwest?
The authors from the PLoS Pathogens study point out that the genomes (strains) of C. gatti found there, the novel VGIIc genotype and VGIIa/major isolates from the United States are highly virulent compared to similar isolates from non-outbreak regions.
They go on to call them hypervirulent strains (essentially highly pathogenic) that could possibly expand and spread further into the country.
How could this fungus spread?
Since it has been documented to be present in over 50 species of trees, activities such as forestry could contribute to its spread. It has also been isolated from wheel wells of vehicles and the soles of shoes; these could be a possible ways of dispersal.
C. gattii could possibly spread through the export of trees and wood products, air currents, water currents and through birds, insects and other animals.
Because the environment of Northern California is so similar to Oregon and Washington, experts believe it is realistic to see the fungus spread to this region.
What disease does C. gattii cause?
Like its sister, C. neoformans, C. gattii is picked up by inhalation of the fungus. Fortunately there is no person to person transmission. Symptoms appear after a couple months to a year.
Respiratory symptoms, which would include cough, chest pain and shortness of breath. Other non-specific symptoms include headache, night sweats and fever. Of course the worst case scenario would be meningitis.
Fortunately, this infection is treatable with anti-fungal medications.
What can be done to prevent this infection?
There is not a vaccine for C. gattii. Since it is contracted by inhalation, you would expect that avoidance of wooded areas and areas of forestry activity would decrease the risk. However, there have even been people infected who were not “walking through the woods” so at this point experts believe there is not any real protective measures available.
Fortunately, this disease is still quite rare. Also, since the medical community is more attuned to the possibility of C. gattii infections in this region, appropriate and timely treatment is more likely to be administered.