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Introduction
1. Anatomy
2. Microbiology
2.1 General bacteriology
2.2 Introduction to systemic bacteriology
2.3 Gram positive cocci
2.4 Gram negative cocci
2.5 Gram positive bacilli
2.6 Gram negative bacilli
2.7 Other important bacteria
2.8 Virology
2.9 Parasitology
2.9.1 Entamoeba histolytica
2.9.2 Acanthamoeba
2.9.3 Naegleria fowleri
2.9.4 Giardia lamblia
2.9.5 Cryptosporidium parvum
2.9.6 Trichomonas
2.9.7 Plasmodium spp.
2.9.8 Babesia
2.9.9 Toxoplasma gondii
2.9.10 Taenia
2.9.11 Hymenolepis nana
2.9.12 Enterobius vermicularis
2.9.13 Trichuris
2.9.14 Trichinella
2.9.15 Ascaris
2.9.16 Hookworms
2.9.17 Strongyloides
2.9.18 Additional information
2.10 Mycology
3. Physiology
4. Pathology
5. Pharmacology
6. Immunology
7. Biochemistry
8. Cell and molecular biology
9. Biostatistics and epidemiology
10. Genetics
11. Behavioral science
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2.9.9 Toxoplasma gondii
Achievable USMLE/1
2. Microbiology
2.9. Parasitology

Toxoplasma gondii

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Toxoplasma gondii

Toxoplasma gondii is a protozoan parasite. You can acquire infection in several ways:

  • Eating or drinking food and water contaminated with cysts containing bradyzoites (a stage in the life cycle of Toxoplasma)
  • Eating undercooked pork, lamb, shellfish, etc.
  • Drinking unpasteurised goat’s milk (may contain tachyzoites)
  • Exposure to cats: the parasite infects cats, and oocysts in cat feces can spread infection to humans. Clinical vignettes often mention “cleaning the cat litter box” as a clue to toxoplasmosis.
  • Maternal infection close to pregnancy can be transmitted to the fetus
  • Rarely, blood transfusions and organ transplants can transmit toxoplasmosis

Clinically, toxoplasmosis commonly presents with fever, flu like symptoms, and lymphadenopathy.

Congenital toxoplasmosis presents with microcephaly, seizures, chorioretinitis, intracranial calcifications, blindness, and maculopapular rash. It can also cause stillbirths and miscarriages.

In immunocompromised individuals, it can present as encephalitis, intracranial mass lesions, myocarditis, and pneumonitis.

Diagnosis is made by demonstrating trophozoites using Giemsa stain in smears from CSF, bone marrow, etc. Serology can be done using IgM and IgG by ELISA, indirect immunofluorescence, CFT, and indirect haemagglutination tests. PCR can be done in amniotic fluid.

Transmission of Toxoplasma gondii

  • Ingestion of cysts in contaminated food/water
  • Eating undercooked pork, lamb, shellfish
  • Drinking unpasteurized goat’s milk (tachyzoites)
  • Exposure to cat feces (oocysts); cleaning litter box
  • Maternal-fetal transmission if infection during pregnancy
  • Rare: blood transfusion, organ transplant

Clinical Presentation

  • Common: fever, flu-like symptoms, lymphadenopathy
  • Congenital toxoplasmosis:
    • Microcephaly, seizures, chorioretinitis
    • Intracranial calcifications, blindness, maculopapular rash
    • Stillbirths, miscarriages
  • Immunocompromised: encephalitis, intracranial mass lesions, myocarditis, pneumonitis

Diagnosis

  • Giemsa stain for trophozoites in CSF, bone marrow, etc.
  • Serology: IgM, IgG (ELISA, indirect immunofluorescence, CFT, indirect haemagglutination)
  • PCR in amniotic fluid

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Toxoplasma gondii

Toxoplasma gondii

Toxoplasma gondii is a protozoan parasite. You can acquire infection in several ways:

  • Eating or drinking food and water contaminated with cysts containing bradyzoites (a stage in the life cycle of Toxoplasma)
  • Eating undercooked pork, lamb, shellfish, etc.
  • Drinking unpasteurised goat’s milk (may contain tachyzoites)
  • Exposure to cats: the parasite infects cats, and oocysts in cat feces can spread infection to humans. Clinical vignettes often mention “cleaning the cat litter box” as a clue to toxoplasmosis.
  • Maternal infection close to pregnancy can be transmitted to the fetus
  • Rarely, blood transfusions and organ transplants can transmit toxoplasmosis

Clinically, toxoplasmosis commonly presents with fever, flu like symptoms, and lymphadenopathy.

Congenital toxoplasmosis presents with microcephaly, seizures, chorioretinitis, intracranial calcifications, blindness, and maculopapular rash. It can also cause stillbirths and miscarriages.

In immunocompromised individuals, it can present as encephalitis, intracranial mass lesions, myocarditis, and pneumonitis.

Diagnosis is made by demonstrating trophozoites using Giemsa stain in smears from CSF, bone marrow, etc. Serology can be done using IgM and IgG by ELISA, indirect immunofluorescence, CFT, and indirect haemagglutination tests. PCR can be done in amniotic fluid.

Key points

Transmission of Toxoplasma gondii

  • Ingestion of cysts in contaminated food/water
  • Eating undercooked pork, lamb, shellfish
  • Drinking unpasteurized goat’s milk (tachyzoites)
  • Exposure to cat feces (oocysts); cleaning litter box
  • Maternal-fetal transmission if infection during pregnancy
  • Rare: blood transfusion, organ transplant

Clinical Presentation

  • Common: fever, flu-like symptoms, lymphadenopathy
  • Congenital toxoplasmosis:
    • Microcephaly, seizures, chorioretinitis
    • Intracranial calcifications, blindness, maculopapular rash
    • Stillbirths, miscarriages
  • Immunocompromised: encephalitis, intracranial mass lesions, myocarditis, pneumonitis

Diagnosis

  • Giemsa stain for trophozoites in CSF, bone marrow, etc.
  • Serology: IgM, IgG (ELISA, indirect immunofluorescence, CFT, indirect haemagglutination)
  • PCR in amniotic fluid