Toxoplasmosis (Toxoplasma gondii)
المؤلف:
Cornelissen, C. N., Harvey, R. A., & Fisher, B. D
المصدر:
Lippincott Illustrated Reviews Microbiology
الجزء والصفحة:
3rd edition , p222-223
2025-08-12
321
Toxoplasma gondii is an intracellular sporozoan, distributed worldwide, that infects all vertebrate species, although the definitive host is the cat. Humans can become infected by the accidental ingestion of oocysts present in cat feces, by eating raw or undercooked meat, congenitally from an infected mother, or from a blood transfusion.
1. Pathology and clinical significance:
There are two kinds of Toxoplasma trophozoites found in human infections: rapidly growing tachyzoites (“tachy-” = rapid) that are seen in body fluids in early, acute infections, and slowly growing bradyzoites (“brady-” = slow) that are contained in cysts in muscle and brain tissue and in the eye. Tachyzoites directly destroy cells, particularly parenchymal and reticuloendothelial cells, whereas bradyzoites released from ruptured tissue cysts cause local inflammation with blockage of blood vessels and necrosis. Infections of normal human hosts are common and usually asymptomatic. However, they can be very severe in immunocompromised individuals, who may also suffer recrudescence (relapse) of the infection. Congenital infections can also be severe, resulting in stillbirths, brain lesions, and hydrocephaly, and they are a major cause of blindness in new borns.
2. Diagnosis and treatment:
The initial diagnostic approach involves detection of parasites in tissue specimens, but this may often be inconclusive. With the recent availability of commercial diagnostic kits, serologic tests to identify toxoplasma are now routinely used. These include tests for Toxoplasma-specific immunoglobulin (Ig) G and IgM. The treatment of choice for this infection is the antifolate drug pyrimethamine, given in combination with sulfadiazine. For patients who cannot receive sulfa drugs, clindamycin can be added to pyrimethamine.
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