Pathomorphological manifestations of pulmonary tissue lesions in cats with aelurostrongylosis

The prevalence of Aelurostrongylus abstrusus infection in domestic cats has significantly increased in recent years. This rise is attributed to both greater awareness among veterinary professionals and improvements in diagnostic methods. The disease is characterized by lung damage, which is related to the parasite's life cycle, particularly the deposition of eggs and the development of larvae in the lung tissue. These processes are accompanied by an inflammatory reaction, leading to structural and functional impairments of the lung tissue in infected animals. During the macroscopic examination of the lungs in infected cats, discoloration, increased size, and a nodular surface due to the formation of nodular foci are noted. The lung tissue appears reddish with grayish-pink foci, where on the cut surface, grayish-creamy firm nodules of varying sizes are visible. Microscopic examination of the lung tissue revealed that in areas of intense infestation by A. abstrusus parasites, an inflammatory reaction develops in a staged manner. In the initial phase, when the parasite's eggs are deposited and localized, degenerative processes predominate. These are characterized by the marked dilation of alveolar spaces, disruption of the elastic framework of alveolar septa and their rupture, compression of the capillary loops, dystrophic-necrotic changes in the alveolar epithelium and bronchial mucosa, interstitial edema around blood vessels, and fragmentation of collagen fibers. With prolonged exposure and activity of the parasite larvae, proliferative processes dominate, leading to the formation of non-specific granulomas. Alveolar spaces show infiltration by histiocytes and polymorphonuclear cells, with fewer leukocytes. Around blood vessels and bronchi, there is infiltration by lymphocytic and macrophage cellular elements. As the number of macrophage cells in the alveolar spaces increases, the presence of larval forms of the parasite decreases, and alveolar wall thickening, due to hyperelastosis, is observed. In such foci of productive inflammation, progressive productive-destructive vasculitis, bronchitis with bronchial obstruction by parasite larvae and desquamated epithelium, and localized serous-productive pleuritis are noted. Clinically, cats infected with aelurostrongylosis exhibit chronic coughing, dyspnea, and cloudy mucous nasal discharge, indicative of a severe course of the disease. A histological hallmark of A. abstrusus infection is the presence of eggs and larvae in the bronchi and alveoli, which triggers both degenerative and proliferative processes in the lung tissue. The distinctive characteristics of the parasite larvae, particularly their shape and size, enable veterinary professionals to identify the helminth during examination. The pathological changes in the lungs caused by A. abstrusus highlight the need to consider this infection during the differential diagnosis of respiratory diseases in cats, especially those belonging to high-risk groups.