الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
T. gondii is an obligate intracellular apicomplexan parasite which is a highly successful and remarkable global pathogen due to its ability to infect almost any nucleated cell in any warm-blooded animal. The life cycle of T. gondii involves two hosts. Domestic cats and other felines serve as definitive hosts, while man and other animals (sheep, cow, pig …) act as intermediate hosts. Infection can occur through the consumption of contaminated water or food, infected imperfectly cooked meat, accidentally in the laboratory, congenitally, blood transfusion or through organ transplantation.
Most infections with T. gondii in immunocompetent hosts are asymptomatic. Specific groups of patients including congenitally infected fetuses, and immunologically impaired individuals are at high risk for severe or may be lethal Toxoplasma infection. In the immunocompromised patients, infection with T. gondii causes generalized lesions as encephalitis, pneumonitis and myocarditis and frequently lead to death of the patients.
There is no effective vaccine against toxoplasmosis in humans so, an effective chemotherapy constitutes the only alternative to control the disease. Treatment regimens for infected patients have not essentially changed for years. The most common drugs used in the therapy of toxoplasmosis are a combination of pyrimethamine and sulfadiazine or a combination of pyrimethamine with lincosamide or macrolide antibiotics in addition to folic acid. The recommended drugs act by different mechanisms of action to limit replication of T. gondii. However, they cannot eliminate it from the host organism as they are active only against tachyzoites of T. gondii and they don’t affect the tissue cysts of the parasite located predominantly in brain and muscles. Besides, they can cause numerous and sometimes severe side effects such as bone marrow suppression and hypersensitivity. Therefore, there is an urgent need to develop new drugs and establish “gold standard” treatment.