One Health Surveillance for Emerging Fungal Diseases in Washington State: Coccidioides Immitis and Cryptococcus Gattii

BACKGROUND:  Washington State residents are at risk from two emerging fungal pathogens in the region: Cryptococcus gattii and Coccidioides immitis. C. gattii is an environmental fungus that has been isolated in the Pacific Northwest; since 2006, animal and human cases have been detected yearly in Washington. Coccidioides is a pathogenic fungus endemic to the southwestern United States; recent data integrating human, animal, and environmental surveillance now indicates the presence of Coccidioides in Washington. For both pathogens, the most common route of exposure is inhalation from the environment; infection can cause severe disease. Delayed diagnosis is common in Washington and can lead to poor health outcomes. To track these emerging fungal infections, surveillance in humans, animals, and targeted environmental sampling has been ongoing since 2006 for C. gattii and since 2014 for C. immitis.

METHODS:  Current cryptococcosis and coccidioidomycosis surveillance strategies draw many parallels and include passive reporting of human and animal cases, and environmental sampling. GIS mapping and ecologic modeling are used to better understand geographic distribution and environmental niche. Whole genome or multilocus sequence typing (WGST or MLST) are used to genotype isolates, and, in combination with patient travel histories, identify locally acquired infections. C. gattii and C. immitis surveillance data from 2006-2015 were used to describe the epidemiology of both pathogens in Washington. Human cases meeting the CSTE confirmed case definition for either condition were included along with animal cases and soil positive locations.

RESULTS:  Cases of C. gattii infection remain stable in Washington; 2-10 reports are received each year, with 46 cases reported since 2006. Animals are disease sentinels; cats are the most commonly reported animals infected, and disease appears to cluster in specific geographic locations in Western Washington.  The epidemiology of coccidioidomycosis cases identified to-date differs from that reported from highly endemic areas; this is most likely due to underreporting of disease in Washington. Based on clinical presentation and hospitalization data only severe cases of coccidioidomycosis with Washington exposure are being diagnosed and reported. Targeted environmental sampling has confirmed the existence of both organisms in Washington. 

CONCLUSIONS:  Continued work is needed to increase awareness of fungal disease among healthcare providers and veterinarians to improve disease reporting and case finding, and to continue soil sampling and analysis to increase our understanding of the environmental niche and geographic ranges of the fungi. Collaborative planning, implementation, and evaluation will drive emerging fungal disease surveillance in the Pacific Northwest.