Dirofilaria immitis in a cat and update on the geographic distribution of the infection in domestic felines in Brazil.

Feline dirofilariosis caused by Dirofilaria immitis represents a diagnostic and clinical challenge in veterinary medicine. Heartworm-associated respiratory disease (HARD) is one of the clinical manifestations observed in infected cats. In many cases, cats may die suddenly without suggestive clinical signs. This report describes the first natural D. immitis infection in a cat from the state of Pernambuco, and provides an update on the geographic distribution of this infection in domestic felines in Brazil. In June 2024, the body of a cat that had died suddenly was submitted for necropsy. The main findings included interstitial pneumonia, characterized by a smooth, red, and shiny pulmonary surface, with irregular, darker areas in the cranial lobes. Blood‑tinged material extended from the bronchial region to the trachea. Five filarioid nematodes were found in the pulmonary artery. The parasites were submitted for molecular identification via amplification and sequencing of a fragment of the cytochrome c oxidase subunit 1 (COI) gene. The sequences showed 100% identity with D. immitis in the GenBank database. These findings underscore the importance of implementing preventive measures in cat populations residing in endemic areas to mitigate the risk of infection.