By Linda Weiford, WSU News
PULLMAN, Wash. – A fungus found in semiarid parts of the Southwest that sometimes launches a lethal illness has been identified for the first time in Washington state soil, leading public health officials and an internationally known fungal expert at Washington State University to believe the organism is quietly spreading to the Northwest.
Valley fever occurs when the soil-dwelling Coccidioides fungus, or “cocci,” becomes airborne, releasing invisible spores that get inhaled and lodged in the lungs of humans and certain animals, especially dogs. Sixty percent of people exposed don’t fall ill; however, 150,000 face ailments ranging from flu- and pneumonia-like symptoms each year, according to the U.S. Centers for Disease Control and Prevention.
In the most severe form, cocci spores break from the lungs and cycle through the bloodstream, setting up infections that destroy bones, cause skin abscesses and inflame the brain. The CDC estimates it kills 160 people annually.
Illness in Washington
Valley fever is not new to certain regions of Arizona and the San Joaquin Valley of central California where it’s most prevalent in the United States. But the disease originating from spores in Washington soil is new.
Three unrelated cases were diagnosed in the eastern part of the state 2010-11. And recently, soil samples taken from the vicinity tested positive for the fungus, proving that cocci can survive there, said Tom Chiller, medical doctor with the CDC in Atlanta who specializes in fungal diseases and who collaborated with Washington state in its investigation.
This, coupled with the three patients’ histories of not traveling to the Southwest before falling ill, “make us quite certain that the people who got sick didn’t acquire valley fever elsewhere and that the fungus has moved beyond its normal geographical range,” said Chiller.
“Whether in the Southwest or in eastern Washington, we know that more people are being exposed. While the majority of these people will do just fine, it poses a significant health threat to others,” he said.
Regents Professor Emeritus Jack D. Rogers, a mycologist who has studied fungi at WSU for a half-century and is considered an international expert in the field, said he was surprised to learn of Coccidioides’ presence in Washington.
In deserts, the fungal tube-shaped cells growing in the soil can break into spores that go air-borne and are carried long distances in the wind. But whether spores are transported in a dust storm or within dirt stuck to the bottom of a hiker’s boot, “once deposited on the ground, they need the right climactic and soil conditions to support growth,” Rogers said.
“It’s long been believed that those conditions were geographically maintained in the desert Southwest and parts of Mexico, Central America and South America,” he said. “Because valley fever is hard to detect and often misdiagnosed by physicians who are not acquainted with it, it’s important to know where cocci’s range is expanding.”
Changing weather conditions, population sprawl that disrupts the soil and a possible rodent host moving northward in search of habitat could explain cocci’s presence in Washington, he said.
The fungus has landed
However the fungus made its way to Washington soil, Chiller of the CDC speculates its presence illustrates an emergent public health issue, not a one-time fluke.
“Do I think it just showed up and made three people sick? No. I think it has probably been in the soil for some time,” he said.
The persons diagnosed with valley fever had lived within a 60-mile radius straddling Benton, Franklin and Walla Walla counties. They spent a lot of time outdoors, according to “Coccidioidomycosis acquired in Washington State,” published in the journal Clinical Infectious Diseases (July 2012).
A 12-year-old boy originally diagnosed with pneumonia may have contracted the fungal infection while playing in a dirt canyon near his home; a 15 year-old boy is believed to have been infected through skin lacerations he suffered when his ATV crashed on a dirt track; and a 58-year-old man may have gotten sick after inhaling spores during his work as a construction excavator, according to the report.
The adult’s illness, which at first mimicked pneumonia and later developed into meningitis, was the most severe.
“We surmise that Coccidioides either has established or is establishing a new niche in eastern Washington,” stated the authors, who included state and county public health experts and Chiller.
Now that soil isolates sent to the CDC have tested positive for cocci – including one with the same DNA of isolates obtained from a patient – “we’re no longer speculating,” said Chiller. “We know.”
Doctors, veterinarians alerted
In early April, Washington’s health department sent advisories to physicians and veterinarians statewide to inform them.
“Valley fever is not known to be contagious and there’s no reason for the public to be alarmed, but it is important to understand its cause and symptoms. Early diagnosis and treatment can ward off serious complications in humans and animals alike,” said Washington state public health veterinarian Ron Wohrle who, working with multiple agencies, will conduct more soil testing as part of a surveillance plan that is being devised.
“The idea here is to draw on the expertise of a variety of health specialists and environmental scientists with knowledge of how cocci is maintained in soil in other parts of the country to determine the environmental conditions that may support the survival of this fungal pathogen in Washington soils,” he said.
Contacts:
Jack D. Rogers, WSU mycologist, rogers@wsu.edu
Tom Chiller, U.S. CDC, tnc3@cdc.gov
Ron Wohrle, Washington public health veterinarian, Ron.Wohrle@doh.wa.gov
Linda Weiford, WSU News, 509-335-7209, linda.weiford@wsu.edu