A model of pulmonary toxoplasmosis in rats as potential impact on immune deficient diseases

Abstract

Toxoplasma gondii is an obligate intracellular zoonotic protozoan. Pulmonary involvement is common in immunocompromised hosts but rarely occurs in immunocompetent ones. Rat pulmonary involvement could be considered as a good representative model for study of human toxoplasmosis infection to either acute toxoplasmosis, chronic toxoplasmosis, or disseminated toxoplasmosis in human immunodeficiency virus (HIV) patients. Forty Swiss-Webster rats were divided into four groups each ten rats: group 1, non-infected and untreated (normal); group 2, acute infected non-treated; and groups 3 and 4, chronic infected non-treated and corticosteroid treated respectively. Lung tissue and blood samples were taken during acute and chronic stages for parasitological and histopathological study and serological assay. Acute and chronic states revealed the presence of viable toxoplasma tachyzoites and bradyzoites in lung tissue respectively. Serological assay showed different results in acute and chronic infections. The histopathological changes in acute rat group showed that per alveolar septa has been swollen due to swelling of the pneumocystis type I and II and the lining cells of the alveoli became low cuboidal in shape. The histopathological changes in chronic untreated rat group showed that the majority of alveolar walls were thickened due to swelling of the alveolar epithelial cells and mononuclear inflammatory cells and the bronchioles due to hyperplasia of its lining epithelium. Some of the blood vessel wall contained large number of chronic Toxoplasma cysts and surrounded by mononuclear cells. While chronic corticosteroid-treated rat group showed perivascular and alveolar edema with congested per alveolar blood capillaries and alveolar edema with compensatory emphysema of some others. The study concluded that toxoplasmosis is a great of interest, serious, and often a life-threatening disease in immune-deficient patients and sometimes in immunocompetent ones. Pulmonary toxoplasmosis should be considered in the differential diagnosis in potentially HIV-infected patients with respiratory symptoms and bilateral pulmonary infiltrates. Early diagnosis and initiating specific good therapy is essential.