First Autochthonous Infection of a Cat with Dirofilaria immitis in Austria

This case report is about a seven-year-old male neutered European Shorthair cat infected by Dirofilaria immitis as the first reported autochthonous Dirofilaria immitis infection in Austria. There was no history of periods abroad. Echocardiography showed suspected D. immitis in the right cardiac chamber with increased pulmonary pressure and ascites. Surgical removal of the heartworms was performed. Twenty adult heartworms were removed by transvenous jugular approach under general anesthesia and stored in 4% formalin. Five out of 20 specimens were examined via light and stereomicroscopy and feline heartworm infection was confirmed. Amplification of a 203 bp or 724 bp fragment of the cytochrome c oxidase subunit I gene was unsuccessful. After surgery the cat developed acute renal failure but recovered quickly. One year later, the cat underwent a control examination including echocardiography and blood work. There were no more D. immitis detectable at echocardiography. Lung pressure was mildly increased. Complete blood count and creatinine were unremarkable. The Knott's test and Dirofilaria-Antigen-test produced negative results. The cat did not show any clinical signs during the follow-up period. The aim of this case report is to highlight the growing risk of acquiring infection with D. immitis not only for Austrian dogs, but also for cats. This case report represents the first report of autochthonous D. immitis infection in Austria. Moreover, even if the prognosis in cats with caval syndrome due to feline heartworm disease is guarded to poor, surgical removal of the filariae can be a successful treatment option.