Diagnosis and Treatment of Dirofilaria immitis in Two Cats From Italy

Dirofilaria immitis is a mosquito-borne filarioid that primarily infects dogs. Infection of cats is infrequent, and diagnosis of feline cardiopulmonary dirofilariosis may be overlooked. Here we describe D. immitis infections in two cats from Central-Northern Italy, where heartworm disease is endemic in dogs. Both cats tested positive on a rapid heartworm point of care (POC) antigen test. Case 1, a 13-year-old male castrated domestic shorthair (DSH) cat was investigated for progressive respiratory signs, including cough, nasal discharge, dyspnea and reverse sneezing. By contrast, Case 2, a 7-year-old male entire free-roaming colony cat with a fractured right tibia, tested positive during pre-surgical screening tests. Both cases were seropositive for Dirofilaria species anti-IgG. A duplex real-time PCR (dqPCR) for D. immitis and D. repens was positive for D. immitis DNA in Case 1 and negative in Case 2. Conventional PCR and sequencing of partial cox1 and 12S rRNA genes confirmed D. immitis infection in Case 1. Echocardiography displayed the presence of adult heartworms in the right heart and main pulmonary artery in both cases. These clinical cases highlight the importance of using a combination of antigenic, serological and diagnostic imaging tests to confirm dirofilariosis in cats. Dirofilariosis should be included in the differential diagnoses for cats living in Dirofilaria spp. endemic areas. © 2025 The Author(s). Veterinary Medicine and Science published by John Wiley & Sons Ltd.