Coccidioidomycosis (Valley fever) is caused by inhaling spores of Coccidioides fungi found in the southwestern U.S. Thus, it affects humans and various animals, including dogs and horses.
Coccidioidomycosis incidence is expected to rise due to climate change, population growth, and soil disturbance from agriculture. Dogs may reveal trends, spatial disease emergence, and the burden of coccidioidomycosis not reported in humans. In 2020, approximately 45% of U.S. households owned at least one dog, for a total of 83.7 million, which offers insights into disease risk by nationality.
This study aimed to analyze dog incidence trends, compare them to human data, and investigate spatial clustering of infection in endemic areas to assess dogs as potential sentinels for human disease. These findings were detailed in a recent study published in The Journal of Infectious Diseases.
Laboratories were found through internet searches and communication with the University of California-Davis, the University of Arizona, and diagnostic centers. Digitally archived test results from January 2012 to August 2023 include data on all animal species, covering age, breed, sex, testing dates, and locations.
A total of 2,141,055 test results were received. Records were excluded for non-dog species, non-serologic results, duplicates, non-U.S. dogs, ages over 20 years, and inconclusive, insufficient, or cancelled tests.
For each dog, the first positive test result was retained; otherwise, the first negative result was used. State-level trends in incidence and test positivity from 2012 to 2022 were analysed through a random-effect meta-analysis, pooling county-level estimates for trends.
To assess whether dogs serve as sentinels for human disease, researchers calculated Pearson correlation coefficients for dog incidence 1-6 months before and after human incidence. The Getis-Ord Gi* statistic identified significant spatial clusters of cold and hot spots for incidence in states with sufficient testing levels.
Data cleaning and analysis were conducted in R (version 4.3.2), with chi-square analyses performed using GraphPad Prism (version 10.3.0). ArcGIS Pro (version 3.4.0) was used to create maps and perform spatial analysis.
The average annual incidence per 10,000 households was observed in Arizona at 87.8, New Mexico at 0.89, Nevada at 0.79, California at 0.75, Texas at 0.38, Idaho at 0.37, Utah at 0.32, and Washington at 0.26.
A total of 98.7% of test results were geocoded, with 13.8% owner resistance and the remaining 86.2% from the clinic location. Around 1,075 entries used gel immunodiffusion (gel ID), and others are enzyme immunoassay (EIA) from laboratory 5. The reported seropositive dogs jumped from 21,085 in 2012 to 38,079 in 2021.
Texas experienced a decline in test positivity rates (-1.3% [95% Confidence interval (CI): -2.5%, -0.1%] each year) along with California (-4.4% [95% CI: -6.3%, -2.5%] each year), while other endemic states experienced stable rates during 2012 to 2022.
In California, the correlation between monthly dog and human incidence rates was 0.75 (95% CI: 0.66–0.82), while in Arizona it was 0.65 (95% CI: 0.53–0.74). In California, dog-human incidence correlation in the following month was 0.75 (95% CI: 0.67,0.82), and in Arizona, it was 0.63 (95% CI: 0.51, 0.73), indicating a strong connection between the two species.
Canine serologic data improve our understanding of coccidioidomycosis epidemiology in areas without human reporting. Travel exposure, regional dog ownership differences, and breed susceptibility these are main limitations.
This study incorporates dog testing for public health surveillance and targeted interventions.
These findings support future research on risks and promote preventive strategies such as education and vaccination. Animal health data integration enhances the One Health strategy against fungal disease. Further investment in diagnostic infrastructure and training may improve fungal disease recognition.
Reference: Sykes JE, Camponuri SK, Weaver AK, Thompson GR, Remais JV. Use of dog serologic data for improved understanding of coccidioidomycosis: A One Health approach. J Infect Dis. 2025; jiaf184. doi:10.1093/infdis/jiaf184
