What can areas of low Dirofilaria immitis preventive governance teach us?

Dirofilaria immitis remains a significant canine pathogen in Brazil despite the long-standing availability of chemoprophylactic products. Higher infection rates in low-income areas, and the persistence of cases in populations with veterinary access, suggest gaps in preventive governance. A cross-sectional survey was conducted in two high-challenge areas of metropolitan Rio de Janeiro, Brazil, from June 2023 to January 2024. Dogs older than 1 year and not on heartworm prophylaxis during the previous 6 months were enrolled. Blood samples were tested for D. immitis antigen, and owner questionnaires captured demographic, environmental and clinical data. Risk factors were evaluated using binomial regression models. Among 526 dogs sampled, the overall antigen-positive rate was 22.6%, with a higher prevalence in Niterói-Maricá (27.0%) than in the Western area of the Rio de Janeiro municipality (18.15%). Male, short-coated, heavier or outdoor-living dogs had significantly higher odds of infection. Coughing was more frequent in antigen-positive dogs, while no significant associations with weight loss or lethargy were observed. Despite widespread veterinary recommendations, substantial infection rates persist, especially in low-income communities, underscoring failures in preventive governance. Integrated efforts from veterinarians, regulatory authorities and the animal-health industry are urgently needed to improve chemoprophylaxis uptake and protect canine health in endemic regions.