Toxoplasma gondii: Toxoplasmosis
Clinical manifestation of toxoplasmosis
1.Adults
a. lmmunocompetant host
- Asymptomatic in 90% of patients.
- M.C. clinical feature is cervical lymphadenopathy.
- Other less common manifestations are pneumonia, myocarditis
- Encephalitis- rare
b. Immunocompromised host
- M.C. signs and symptoms are principally within CNS :
- Encephalopathy, Meningoencephalitis.
2. Children
a. Congenital
- May present with hydrocephalus, microcephaly mental retardation, deafness, blindness, epilepsy.
- Chorioretinitis
- Intracerebral calcification may occur
- NOT infective in 3″ trimester in pregnancy
b. Acquired
- Mostly asymptomatic
- C/Fs are
- Macular scarring
- Retinochoroiditis(Most common)
- Vitritis
Diagnosis of Toxoplasmosis
1.Tissue and Body fluids
- Subinoculation of sample.
- Demonstration of tachyzoites in lymphnodes establishes the diagnosis of acute toxoplasmosis.
2. Serology
Acute infection detected by presence of IgG by:
- Sabin Feldman dye test(gold standard)
- Indirect fluorescent antibody test
- ELISA
- Avidity test-measure the strength of antigen-antibody reaction for IgG antibody
IgM
- Double sandwich IgM ELISA and IgM immunosorbent assay
- Presence of IgA also favours diagnosis of acute infection.
- IgA ELISA is more sensitive than IgM ELISA for detecting congenital infection.
3.Molecular diagnosis
- Real-time PCR for either the B, gene or the 529-bp sequence.
A. lmmunocompetent adult or child
- Lymphadenopathy + positive IgM titre is an indication of acute infection and indication of therapy.
B. Immunocompromised host
- Test for IgG antibody after diagnosis of HIV infection.
- IgM serum antibody is usually not detectable.
4. Congenital infection
- Detection of IgM specific antibody in fetus
- Helpful in diagnosing congenital toxoplasmosis since it does not cross placenta.
- PCR of amniotic fluid
5. Ocular toxoplasmosis
- Positive IgG titer with typical eye lesions.
Treatment of Toxoplasmosis
- Congenital infection
- Pyrimethamine and sulfadiazine
- Spiramycin + prednisone
Infection in immunocompetent:
- Only lymphadenopathy: No treatment unless have severe persistent symptoms.
- Ocular toxoplasmosis: Pyrimethamine + sulfadiazine or clindamycin.
- Infection in pregnancy: Spiramycin (rovamycine) is DOC.
Infection in Immunocompromised:
- Prophylaxis for AIDS who are seropositive for T. gondii and have CD4 T cell
- Trimethoprim + sulfamethoxazole/Dapsone + Pyrimethamine.
- Pyrimethamine + Sulfadiazine (preferr.ed but not widely available).
Exam Question
Clinical manifestation of toxoplasmosis
1.Adults
a. lmmunocompetant host
- M.C. clinical feature is cervical lymphadenopathy.
- Other less common manifestations are pneumonia, myocarditis
- Encephalitis- rare
2. Children
a. Congenital
- May present with hydrocephalus, microcephaly mental retardation, deafness, blindness, epilepsy.
- Chorioretinitis
- Intracerebral calcification may occur
- NOT infective in 3″ trimester in pregnancy
b. Acquired
- C/Fs are
- Macular scarring
- Retinochoroiditis(Most common)
- Vitritis
Diagnosis of Toxoplasmosis
Serology
Acute infection detected by presence of IgG by:
- Sabin Feldman dye test(gold standard)
- Avidity test-measure the strength of antigen-antibody reaction for IgG antibody
- IgA ELISA is more sensitive than IgM ELISA for detecting congenital infection.
Congenital infection
- Detection of IgM specific antibody in fetus
- Helpful in diagnosing congenital toxoplasmosis since it does not cross placenta.
Treatment of Toxoplasmosis
- Congenital infection
- Pyrimethamine and sulfadiazine
- Infection in pregnancy: Spiramycin (rovamycine) is DOC.
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