Canine Coccidioidomycosis in Argentina: Epidemiological Trends and Evaluation of a Rapid Diagnostic Assay

Coccidioidomycosis is an endemic fungal infection in northwestern Argentina, where domestic dogs serve as epidemiological sentinels. This study updates the epidemiology of canine coccidioidomycosis from 2015 to 2024 and assesses the performance of a lateral flow assay (LFA) for antibody detection. During this period, 1,734 serum specimens were evaluated by agar gel immunodiffusion (ID) at the hospital in the main endemic region, of which 506 (29%) tested positive, representing an increase compared with the previous decade. This rise reflects strengthened surveillance, improved access to reagents through the National Mycology Network, and heightened veterinary awareness. In two years of active surveillance (2019-2021), we obtained clinical and epidemiological information from 72 seropositive dogs, showing that musculoskeletal signs, particularly limb pain and lameness, were the most frequent presentations, consistent with disseminated disease. More than 60% of dogs were primarily indoor animals, suggesting local acquisition of infection and emphasizing the potential risk of human exposure. To compare serological methods, 225 sera sent for diagnosis by ID were tested by LFA and counterimmunoelectrophoresis. The LFA demonstrated very good agreement with both reference methods and provided the shortest turnaround time, supporting its utility as a rapid screening tool in veterinary practice. However, limitations include the lack of specimens from dogs with other mycoses and the inability to evaluate test performance in acute disease, where sensitivity may be reduced. Overall, these findings highlight the importance of canine surveillance, clinician awareness, and accessible diagnostic tools to improve the early recognition and management of coccidioidomycosis in endemic regions.