Toxoplasma Gondii Flashcards
What are the general features of the phylum Apicomplexa?
- Obligate intracellular parasites. 2. Apical complex (polar rings, rhoptries, conoids, micronemes). 3. Complex life cycle (sexual & asexual cycles). 4. Coccidian parasites. 5. Includes T. gondii, Plasmodium spp., Babesia spp., etc. 6. No organ of locomotion.
What are the two asexual forms of Toxoplasma gondii?
- Tachyzoite (actively multiplying, pyriform, obligate intracellular, divides by endodyogeny). 2. Bradyzoite (resting, slow-growing, in cysts).
What is the sexual form of Toxoplasma gondii?
Oocyst: Oval, unsporulated when immature; sporulated oocyst contains 2 sporocysts with 4 sporozoites each.
What is the definitive host of Toxoplasma gondii?
Cats (felidae) – both sexual and asexual reproduction occur.
What are the intermediate hosts of Toxoplasma gondii?
Humans, mammals, and birds (asexual reproduction only, humans are dead-end hosts).
What are the infective stages of Toxoplasma gondii?
- Oocyst (from cat feces). 2. Bradyzoite (from infected meat). 3. Tachyzoite (from blood transfusion, transplacental transmission, organ transplant).
What are the modes of transmission for Toxoplasma gondii?
- Ingesting raw/undercooked meat (bradyzoites). 2. Food/water contaminated with cat feces (oocysts). 3. Blood transfusion (tachyzoites). 4. Transplacental transmission (tachyzoites). 5. Organ transplantation (cysts). 6. Contaminated mucous membranes/skin abrasions (tachyzoites).
What are the two types of life cycles in Toxoplasma gondii?
- Enteric cycle (only in cats, involves sexual reproduction in intestinal epithelium). 2. Exo-enteric cycle (asexual replication in humans & intermediate hosts, leading to tissue cyst formation).
What are the clinical types of toxoplasmosis?
- Acquired toxoplasmosis (mostly asymptomatic; mild cases with fever, myalgia, lymphadenopathy; severe cases can cause encephalitis, hepatitis, myocarditis). 2. Congenital toxoplasmosis (risk depends on maternal immunity and fetal age). 3. Recrudescence toxoplasmosis (in immunocompromised patients).
What are the risk factors for severe congenital toxoplasmosis?
- Maternal infection during pregnancy. 2. Lack of protective maternal immunity. 3. Gestational age (earlier infection leads to more severe outcomes).
What are the key features of congenital toxoplasmosis?
- Intracerebral calcifications (leading to mental retardation, convulsions). 2. Hydrocephalus or microcephalus. 3. Retinochoroiditis (can develop later in life). 4. Hepatosplenomegaly, jaundice, lymphadenopathy. 5. Risk of abortion/stillbirth in severe cases.
How is toxoplasmosis diagnosed?
- Serology (IgM indicates recent infection; rising IgG titer indicates recent infection; IgG persistence suggests past infection). 2. Sabin-Feldman dye test (stains live tachyzoites). 3. IFAT, CFT, PCR.
What are the treatments for toxoplasmosis?
- Pyrimethamine + sulfadiazine (not for pregnant women). 2. Spiramycin (for pregnant women). 3. Clindamycin (for AIDS patients or sulfur allergy).
