Use of Dog Serologic Data for Improved Understanding of Coccidioidomycosis: A One Health Approach.

BACKGROUND

Coccidioidomycosis (Valley fever) occurs when animals and humans inhale spores of Coccidioides spp, soil-dwelling fungi of the southwestern United States (US). The spatial epidemiology of coccidioidomycosis is poorly understood due to irregular detection of Coccidioides in soil, disease underdiagnosis, and lack of nationwide mandatory reporting. Data on seroreactivity to Coccidioides among dogs-which are highly susceptible to coccidioidomycosis, widespread across the US, and have limited travel-may strengthen our understanding human disease risk.

METHODS

We analyzed serologic test results for 834 899 dogs between 2012 and 2022 from all known diagnostic laboratories conducting serologic testing for anti-Coccidioides antibodies in dogs in the US. We used testing date and county-level location data to estimate spatial and temporal trends in incidence and test positivity for dogs and compared them to human surveillance data.

RESULTS

The overall seropositivity rate among tested dogs was 37.6% (313 829/834 899). Average test positivity rates in states with ≥0.5 tests per annum per 10 000 households were 35.4% (Texas) to 74.1% (Montana). For these states, average annual incidence per 10 000 households was as follows: Arizona (86.8), New Mexico (0.89), Nevada (0.78), California (0.75), Montana (0.63), Colorado (0.41), Oregon (0.41), Texas (0.38), Idaho (0.37), Wyoming (0.34), Utah (0.32), and Washington (0.26). Human incidence in California and Arizona between 2012 and 2022 was significantly correlated with dog incidence (ρ = 0.75 and ρ = 0.65, respectively). The distribution of seropositive dogs expanded from 76 of 3144 counties (2.4%) in 2012 to 390 in 2022 (12.4%).

CONCLUSIONS

Further investment in human diagnostic infrastructure and provider knowledge may ameliorate significant underrecognition of this emerging fungal disease.