Trusted medical expertise in seconds.

Access 1,000+ clinical and preclinical articles. Find answers fast with the high-powered search feature and clinical tools.

Try free for 5 days
Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer.

Toxoplasmosis

Last updated: September 28, 2020

Summarytoggle arrow icon

Toxoplasmosis is a disease caused by the obligate intracellular parasite Toxoplasma gondii. Transmission occurs either through ingestion of cysts found, for example, in raw meat or cat feces, or from mother to fetus through the placenta. The clinical presentation depends on the patient's immune status: In immunocompetent individuals, 90% of cases are harmless and asymptomatic, with the remaining 10% displaying mild mononucleosis-like symptoms. In immunosuppressed patients (e.g., those who are HIV-positive), infection may result in cerebral toxoplasmosis (headache, confusion, focal neurologic deficits) or toxoplasmic chorioretinitis (eye pain, reduced vision). Treatment is indicated for immunosuppressed patients, infected mothers, congenital toxoplasmosis, and immunocompetent patients with more severe symptoms. The treatment of choice is usually a combination of pyrimethamine, sulfadiazine, and leucovorin (folinic acid), with the exception of new infections during pregnancy, which are treated with spiramycin.

For the congenital variant and how to manage infection in pregnant women, see toxoplasmosis during pregnancy.

  • Prevalence
    • In the US: ∼ 10% of adults
    • In some tropical climates: up to 95%

References:[1]

Epidemiological data refers to the US, unless otherwise specified.

  • Pathogen: Toxoplasma gondii, an obligate intracellular, single-celled protozoan
  • Route of transmission
    • Oral ingestion: The oocysts are excreted in the feces of cats (final host) and are orally ingested by other mammals such as humans, hoofed animals, and birds (intermediate hosts). Primary modes of transmission include the following:
      • Cat feces
      • Raw or insufficiently cooked meat (most common)
      • Unpasteurized milk (especially goat milk)
    • Transplacental transmission: see toxoplasmosis during pregnancy
    • Via organ transplantation or blood transfusion

References:[2]

References:[3]

Cerebral toxoplasmosis

Ocular toxoplasmosis

  • Chorioretinitis
    • Acute toxoplasmosis; (current focal infection): yellow-white retinal lesion; , marked vitreous reaction; , concomitant vasculitis; , defects in the visual field at the site of inflammation
    • Previous toxoplasmosis (previous focal infection): formation of scars with white atrophic areas and surrounding dark, sharply-defined pigmentation
    • Recurrent focal infection usually develops at chorioretinal scars.
    • Congenital toxoplasmosis is almost always accompanied by the formation of scars of the macula and corresponding visual impairment.

References:[4][5]

  • Immunocompetent patients usually do not require treatment.
  • Medical therapy

References:[7]

  1. Parasites - Toxoplasmosis (Toxoplasma infection): Epidemiology & Risk Factors. https://www.cdc.gov/parasites/toxoplasmosis/epi.html. Updated: March 26, 2015. Accessed: March 13, 2017.
  2. Toxoplasma gondii: from animals to humans. https://www.ncbi.nlm.nih.gov/pubmed?term=11113252. Updated: November 1, 2000. Accessed: March 13, 2017.
  3. Clinical spectrum in 107 cases of toxoplasmic lymphadenopathy. https://www.ncbi.nlm.nih.gov/pubmed?term=3326123. Updated: July 1, 1987. Accessed: March 13, 2017.
  4. Agabegi SS, Agabegi ED. Step-Up To Medicine. Wolters Kluwer Health ; 2015
  5. Gandhi RT. Toxoplasmosis in HIV-infected patients. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/toxoplasmosis-in-hiv-infected-patients.Last updated: July 21, 2016. Accessed: March 16, 2017.
  6. Resources for Health Professionals. https://www.cdc.gov/parasites/toxoplasmosis/health_professionals/index.html. Updated: October 26, 2018. Accessed: May 21, 2019.
  7. Pyrimethamine-clindamycin vs. pyrimethamine-sulfadiazine as acute and long-term therapy for toxoplasmic encephalitis in patients with AIDS. https://www.ncbi.nlm.nih.gov/pubmed?term=8838183. Updated: February 1, 1996. Accessed: March 13, 2017.
  8. Toxoplasmosis in the adult. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1749356/pdf/bullnyacadmed00169-0109.pdf. Updated: February 1, 1974. Accessed: March 13, 2017.