Canine heartworm disease in Brazil: diagnostic challenges, prevention gaps, and One Health implications

Abstract

Canine heartworm disease, caused by the nematode Dirofilaria immitis and transmitted by mosquitoes, remains an important cardiopulmonary parasitosis in dogs and a growing zoonotic concern in Brazil. Higher prevalences have historically been reported in coastal and warm, humid areas, with infection rates exceeding 40–60% in some local canine populations, although more recent data indicate heterogeneous and, in some regions, increasing patterns of occurrence. This narrative review synthesizes current evidence on etiology, life cycle, epidemiology, clinical presentation, diagnosis, treatment and prevention of canine heartworm disease in Brazil, highlighting regional prevalence data and recent international guidelines from the American Heartworm Society and the Companion Animal Parasite Council. Particular emphasis is placed on diagnostic challenges related to occult infections and variable test performance, therapeutic limitations in routine practice, and poor adherence to continuous chemoprophylaxis in endemic settings. In addition, we discuss the role of infected dogs as key reservoirs for mosquito-borne transmission, the documented risk of human dirofilariasis, and the need to frame heartworm prevention within a One Health approach that integrates small animal practice, vector control and public health surveillance. Strengthening preventive veterinary medicine, including home-based care in high-risk areas, and enforcing annual testing and year‑round prophylaxis are essential to reduce the burden of heartworm disease and its zoonotic impact in Brazil.