Pathogistological changes in the lungs of Felis silvestris catus when infected with Aelurostrongylus abstrusus

Aelurostrongylus abstrusus is a parasite that belongs to Nematoda type, Metastrongyloidea superfamily, Angiostrongylidae family, Aelurostrongylus genus and is known as feline helminth, whose intermediate hosts are slugs and snails and reservoir hosts are mice and birds. In cats, Aelurostrongylus abstrusus parasitizes in bronchioles and alveoli, causing specific inflammatory changes in the lower respiratory tract and enables the development of such clinical signs as cough, shortness of breath as well as mucous-purulent discharge from the nasal cavity, when complicated by bacterial infections. Females of parasite lay eggs, which the larvae of L1 hatch from. Subsequently, these larvae cough with bronchial mucus and are swallowed by an animal. They pass through the digestive channel without changes and together with the faeces are released into the environment. The first stage larvae actively penetrate into the body of the slugs, fade twice and are becoming invasive. Duration of larvae development from the stage L1 to L3 depends on the biological cycle of intermediate hosts – slugs and snails. Cats are becoming infected by eating slugs or snails with invasive larvae of the third stage (L3), which are transmitted from the digestive channel of the definitive host (cat) with blood flow to the lungs. Usually, the pathogen has low pathogenicity and invasions are primarily detected after animal’s death, during pathoanatomical dissection. Acute clinical signs of the disease have not been described much up to date. The article presents the results of pathomorphological examination of the cat's lungs infected by Aelurostrongylus abstrusus. The severity of pathomorphological changes of the cat’s pulmonary tissue depends on the intensity of the invasion. When dissected, the lungs appear unevenly coloured, dark red with light and slightly denser areas, where focal parasitic nodules are clearly distinct, surrounded by pink halo and different in size but mostly round, dense consistency. Main morphological characteristic of Aelurostrongylus abstrusus infection is the presence of numerous eggs and L1 larvae in the alveoli but also in the bronchi. Helminth eggs accumulated in the alveolar lumps, surrounded by a thin shell; a severe cellular reaction from lymphocytes, macrophages and histiocytes occurred around this shell. An inflammatory reaction resulted in the thickening of the interstitial tissue with a strong vascular response, characterized by fraying and edema of the vessel walls. The results of pathomorphological researches have shown that the main changes were localized in the lungs and bronchial tubes with diffuse damage of the pulmonary tissue parenchyma and development of croupous pneumonia.