Rare but Dangerous Fungus Seen in Pacific Northwest

April 22, 2010

spores-basidia

(Joseph Heitman/ Duke University Medical Center)
By Amanda Gardner

THURSDAY, April 22, 2010 (Health.com) — A rare but life-threatening tropical fungus that causes lung infections in both people and animals has been seen in the Pacific Northwest and could spread, researchers are reporting.

The fungus, known as Cryptococcus gattii (or C. gattii), has infected dozens of humans and animals—including cats, dogs, and dolphins—in Washington and Oregon in the past five years. While rare, the fungus has been lethal in about 25% of the people in the U.S. who have developed infections, according to Edmond Byrnes III, a doctoral student in molecular genetics and microbiology at Duke University and one of the lead authors of a new study about the fungus.

In the study, Byrnes and his colleagues analyzed 18 cases in people and 21 in animals that occurred in the U.S. between 2005 and 2009.

The symptoms of infection include chest pain, a persistent cough, shortness of breath, fever, and weight loss. The fungus can also cause meningitis, or inflammation of the membranes lining the brain, but can be treated with antifungal drugs. C. gattii is found in soil and trees, but experts haven’t yet determined how humans breathe it in.

Byrnes and colleagues have discovered a new, especially dangerous strain of the fungus. This strain—which is confined to Oregon, for now—is “highly virulent,” says Byrnes. “Overall it’s a pretty low threat, and it’s still uncommon in the area, but as the range of the organism expands and the number of cases increases accordingly, it’s becoming more of a concern,” he says.

The new strain is likely to move into Northern California and other neighboring regions, the researchers say. Other strains of the fungus have been found in people in San Francisco and Los Angeles, and in a bottlenose dolphin as far south as San Diego.

The fungus hails from the tropics and may have been carried to North America on imported plants or trees, experts say. It first emerged on this continent in 1999, on Vancouver Island off the coast of British Columbia, where it ultimately infected more than 200 people, killing nearly 9% of them.

From there, the fungus is believed to have crossed the border into the U.S. on logging trucks or car tires sometime before 2005, when the first infections were reported in Washington and Oregon. The cases in California “indicate that C. gattii can survive in that habitat,” says Yonathan Lewit, a research technician at Duke and a co-author of the new study, which appears in the journal PLoS Pathogens.

Next page: New mutation “unnerving”


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