Dirofilaria immitis is a mosquito-borne nematode that often infects dogs worldwide and causes what is commonly referred to as heartworm disease. The infection is recognized as being more prevalent in tropical and subtropical coastal regions; however, due to recent climate changes, it has been detected in regions previously considered free of infection. The asymptomatic animals presented in this case report had their infections detected opportunistically. One was presented for a routine checkup and the other for pre-operative evaluation. In the checkup case, heartworm disease was suspected after auscultation. In the presurgical case, microfilariae were found when cytology was performed. Both dogs had D. immitis infection confirmed by antigen detection using an enzyme-linked immunosorbent assay (ELISA) test. The microfilariae were confirmed to be D. immitis. This report highlights the unsuspected finding of the infection in a region where canine heartworm disease has not been a concern. It throws light on the importance of constant surveillance of animal vector-borne diseases in areas of ecotone. Surveillance must be reinforced when natural resources are disturbed, especially in the face of global climate change
