{Toxic Indoor Mold Central} New Strain of Virulent Airborne Fungi, Unique to Oregon, Is Set to Spread

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Apr 23, 2010, 1:03:17 PM4/23/10
to Toxic Indoor Mold Central
ScienceDaily (Apr. 22, 2010) — A newly discovered strain of an
airborne fungus has caused several deaths in Oregon and seems poised
to move into California and other adjacent areas, according to
scientists at Duke University Medical Center.

"This novel fungus is worrisome because it appears to be a threat to
otherwise healthy people," said Edmond Byrnes III, a graduate student
in the Duke Department of Molecular Genetics and Microbiology.
"Typically, we see this fungal disease associated with transplant
recipients and HIV-infected patients, but that is not what we are
seeing." Byrnes and other Duke co-authors work in the laboratory of
senior author Joseph Heitman, M.D., Ph.D., and chair of the Department
of Molecular Genetics and Microbiology.
Their new work on the emergence and virulence of the new genotypes of
Cryptococcus gattii fungi in the United States was published online in
PLoS Pathogens on April 22.
The mortality rate for recent C. gattii cases in the Pacific Northwest
is running at approximately 25 percent out of 21 cases analyzed in the
United States, compared to a mortality rate of 8.7 percent out of 218
cases in British Columbia, Canada, the researchers said. Most have a
more complicated clinical course than people infected with the more
common Cryptococcus neoformans.
Because the strain is so virulent when it infects some humans and
animals, the researchers are calling for greater awareness and
vigilance. Testing involves culturing the fungus and then sequencing
its DNA to learn whether it is the virulent or more benign strain,
which could affect treatment plans.
Some strains of C. gattii are not more virulent than C. neoformans,
for example, but doctors need to know what type they are dealing with,
Byrnes said. Using molecular techniques, the geneticists uncovered
clues that showed the Oregon-only fungal type most likely arose
recently, in addition to an outbreak of C. gattii that began in Canada
in 1999 that has now spread into Washington and Oregon.
Symptoms can appear two to several months after exposure, and may
include a cough lasting weeks, sharp chest pain, shortness of breath,
headache (related to meningitis), fever, nighttime sweats and weight
loss. In animals the symptoms are a runny nose, breathing problems,
nervous system problems and raised bumps under the skin. While C.
gattii can be treated, it cannot be prevented; there is no vaccine.
The new type of Cryptococcus gattii reproduces both sexually and
asexually. The more virulent strain may have genetically recombined
with related but less harmful strains. This novel genotype is highly
virulent compared with similar isolates of Cryptococcus that are not
causing disease outbreaks.
The researchers found that the novel genotype (VGIIc) is now a major
source of Cryptococcus gattii illness in Oregon. Because C. gattii
types had been found in tropical areas before, co-lead author Wenjun
Li, M.D., Ph.D., of Duke Molecular Genetics and Microbiology,
speculates that environmental changes may be responsible for the
evolution and emergence of this pathogen.
Determining the exact origin of the VGIIc type is difficult, and
sampling thus far has failed to turn up isolates in Oregon soil, water
or trees.
"We are trying to put together the evolutionary story of where these
types come from by closely studying the genetics of all samples
possible," said Yonathan Lewit, a research associate also in Duke
Molecular Genetics and Microbiology. He said that cell components
called mitochondria may play a role in the increased virulence of
certain types.
VGIIc, the new Oregon strain, has yielded dozens of isolates in many
specimens, including from domesticated animals: cats, dogs, an alpaca
and a sheep. "Most of those are nonmigratory animals," Byrnes said,
explaining that the animals probably didn't bring the pathogen from
some other region, and most likely acquired it locally.
Other authors include Hansong Ma, Kerstin Voelz and Robin May of the
Department of Molecular Pathobiology at the University of Birmingham,
United Kingdom; Ping Ren and Vishnu Chaturvedi of the Mycology
Laboratory at Wadsworth Center in Albany, N.Y.; Dee Carter of the
Department of Molecular and Microbial Biosciences, the University of
Sydney, Australia; and Robert Bildfell of the Department of Biomedical
Sciences, Oregon State University, Corvallis.
This work was supported by National Institutes of Health/National
Institute of Allergy and Infectious Diseases grants.

Story Source:

Adapted from materials provided by Duke University Medical Center.

Journal Reference:

Edmond J. Byrnes, Wenjun Li, Yonathan Lewit, Hansong Ma, Kerstin
Voelz, Ping Ren, Dee A. Carter, Vishnu Chaturvedi, Robert J. Bildfell,
Robin C. May, Joseph Heitman. Emergence and Pathogenicity of Highly
Virulent Cryptococcus gattii Genotypes in the Northwest United States.
PLoS Pathogens, 22 Apr 2010 DOI: 10.1371/journal.ppat.1000850

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