The aims of this study determined to investigate the pathological changes induced by streptococcus pyogen associated with modified immune model of rats, twenty different samples of urine and feces were collected from patients infected with Streptococcus pyogenes in local hospitals of Salaheddin and Kirkuk, after conformation the samples were then followed by Vitek2 analysis. The results was showing that 98% of the samples were Streptococcus pyogenes bacteria, After confirmation, the samples were then taken to the central laboratories of Tikrit University to determine challenge dose of infection in the rats, The animal groups  divided into 4 groups, each group :having 5 animals, and the fourth group was negative control group, as follows The first , second and third groups injected 0.5 ml of Streptococcus pyogenes challenge dose. After 3 days, the first group that was injected with 0.5 was killed. As for the second group, after 24 hours they had a strong allergic reaction with itching in all parts of the body. However, movement rate of third group was affected. In conclusion, this study provides an understanding of the pathophysiology and importance of S. pyogenes infection, information that will be useful for future investigations and treatments aimed at reducing the negative effects of this bacterium on human health.