Lung strongyloidoses in cats are caused by members of superfamily Metastrongyloidea. The most frequently encountered species Aelurostrongylus abstrusus (Railliet, 1898) (Rhabditida; Angiostrongylidae) parasitises in the lung tissue of both domestic and wild cats. They become infected by eating paratenic hosts or food contaminated by snail slime. The present study aims to establish the changes in circulating blood proteins: total protein, albumin, globulins and fibrinogen, as well as albumin/globulin (A/G), fibrinogen/albumin (F/A) and fibrinogen/total protein (F/TP) ratios in cats with chronic A. abstrusus infection. The research was performed in cats from both sexes, 4 months to 8 years of age, regardless of the breed. All animals were reared outdoor and had a history of respiratory illness. The diagnosis was made on the basis of analysis by the method of Baermann funnel technique. Statistically significant (P < 0.05) increase in total protein (0.048), fibrinogen (0.032), F/TP (0.048) and F/A (0.019), as well as a statistically significant (P= 0.017) reduction in albumin were found compared to the control group.