The present report describes the first clinically manifested and serologically proven case of Dirofilaria immitis infection in a cat in Bulgaria. A 10-year-old intact male cat was referred to the Small Animal Clinic, Trakia University with a history of anorexia, weight loss, intermittent coughing and itching skin lesions on the head and neck. Physical examination revealed abnormal heart sounds and respiration, cyanosis of the mucous membranes, and generalized enlargement of the lymph nodes. Mild infestation with hard ticks and fleas was also detected during the initial skin inspection. In addition, adult Otodectes cynotis mites were observed in the skin lesions. The fecal sample was positive for larvae of Aelurostrongylus abstrusus and eggs of Toxocara cati. Blood serology revealed antigens of D. immitis as well as antibodies against both feline immunodeficiency virus and D. immitis. Thoracic radiographic findings included a pronounced generalized reticular interstitial pattern; alveolar and bronchial shades with multiple nodular thickenings throughout the lungs. Electrocardiography demonstrated a sinus tachycardia, a peaked P-wave (P-pulmonale) and an abnormally low ST-segment. The clinical signs disappeared after treatment with selamectin, doxycycline and corticosteroids. Despite the improvement in general health condition, the cat suddenly died several months later.
