Abstract
            Introduction: Toxoplasma gondii is a protozoan parasite that is globally widespread and infects humans and animals. Obligate  intracellular parasites enter many organs and tissues through the bloodstream, where they invade and proliferate into cells,  eventually destroying them. The aim of this study was to evaluate the extent of cardiac tissue changes in rats infected with T.  gondii.  
  Methods: Male Wistar rats (n=30) were allocated to three groups as follows: control group (n=10), T1  group that received 0.3 mL  of T. gondii tachyzoite (IP) (n=10), and T2  group that received 0.6 mL of T. gondii tachyzoite (IP) (n=10). However, the control  group just received an equal volume of distilled water daily (IP). Animals were kept in standard condition. Forty days after  inducing toxoplasmosis, heart tissues of rat in all groups were removed and prepared for histopathological examinations of heart  tissue under optical microscopy after hematoxylin and eosin staining and calculation of heart tissue weight.  
  Results: Heart tissue weight significantly decreased in groups that received 0.3 and 0.6 mL of T. gondii tachyzoite in comparison  to control groups. In histopathological studies of heart tissue under optical microscopy, atrophy and necrosis were observed in  heart tissues in T. gondii groups.  
  Conclusion: Since this parasite caused necrosis of heart cells in rats in our study, it is suggested that in preventing T. gondii  infection, health measures should be taken to promote human and animal health.