Toxoplasmosis during pregnancy can cause transplacental infection and brain injury to the fetus. Adults have asymptomatic infections, lymphadenopathy only, or mononucleosis-like illnesses. Only cats have infectious feces. Cats acquire infection by eating infected rodents or birds.

225,000 (US); 4,500,000 (Global)
Toxoplasma gondii infection;
10-23 days in one outbreak (ingestion of undercooked meat); 5-20 days in another outbreak associated with infected cats; [CCDM]
Infected adults may have an asymptomatic infection, have lymphadenopathy only, or have a mononucleosis-like illness. [CCDM]
Standard; "Transmission from person to person is rare; vertical transmission from mother to child, transmission through organs and blood transfusion rare." [CDC 2007 Guideline for Isolation Precautions]
In normal hosts, asymptomatic lymphadenopathy, usually cervical, is the most common manifestation of infection. A maculopapular rash may occur. Enlarged lymph nodes do not suppurate. About 3% to 7% of clinically significant lymphadenopathy cases are caused by T. gondii. All symptoms of acute infection usually resolve within a few months to a year. Occasional complications in normal hosts are myocarditis (arrhythmias, pericarditis, and heart failure) pneumonitis, pleural effusions, empyema, liver infection, and encephalitis. T. gondii is the most common cause of retinal infections in immunocompetent patients. Patients who acquired the infection in utero usually present at the age of 10-30 with both eyes infected and the macula involved, while patients with acute infections usually present after the age of 30 with one eye infected and the macula not involved. In AIDS patients, a Pneumocystis-like pulmonary infection has been reported. [PPID, p. 3364-8] A minority of immunocompetent patients have nontender cervical lymphadenopathy. Generalized lymphadenopathy with fever, headache, and fatigue occurs in 20-40% of symptomatic patients. [Harrisons, p. 619] Complications of patients with AIDS or other immune diseases include maculopapular rash, chorioretinitis, cerebritis, myocarditis, and pneumonia. [CCDM, p. 614] In adults, the four main types of disease are acute, CNS, ocular, and disseminated with non-CNS involvement. Most cases of ocular toxoplasmosis are contracted as congenital infections and then reactivated, usually in the second or third decades of life. Acute toxoplasmosis may resemble infectious mononucleosis, and findings may include hepatosplenomegaly, anemia, atypical lymphocytosis, leukopenia, elevated liver enzymes, and less commonly, pharyngitis. A severe, disseminated form of toxoplasmosis is rare except in immunocompromised patients. Findings may include pneumonitis, myocarditis, brain lesions, and meningoencephalitis. [Merck Manual, p. 1559-63] Cervical lymphadenopathy is the most common finding in acute toxoplasmosis. Fever and abdominal pain may accompany mesenteric lymphadenitis. Other lymph nodes frequently involved are suboccipital, supraclavicular, axillary, and inguinal. Urticaria may be associated with toxoplasmosis. Parotitis is a possible complication. [ID, p. 1513-14, 1213] Orchitis is a complication in infected AIDS patients. CNS toxoplasmosis in the immunocompromised presents with altered consciousness, seizures, headache, fever, and focal neurologic deficits. [Guerrant, p. 725]

A primary infection during pregnancy can cause transplacental infection and brain injury to the fetus. Only cats have infectious feces. Cats acquire infection by eating infected rodents or birds. Other intermediate hosts are sheep, goats, swine, cattle, and chickens. Human infection occurs after: 1.) ingestion of undercooked meat (pork, mutton, or rarely, beef); 2.) ingestion of soil, food, or water contaminated with feces from infected cat; 3.) ingestion of raw goat's milk; 4.) blood transfusion or organ transplantation; and 5.) inhalation (reported in one outbreak). "Oocysts shed by cats sporulate and become infective 1-5 days later, and may remain infective in water or moist soil for over a year." [CCDM, p. 615] Dogs that roll in cat feces may spread infection while being groomed by their owners. [Guerrant, p. 722] Higher risks occur in developing and tropical countries, especially if increased exposure to undercooked meat, untreated drinking water, and contaminated soil. [CDC Travel, p. 351] Raw oysters, clams, and mussels are potential sources of infection. Working with meat is another risk factor. The seroprevalence of T. gondii infection varies from 7% in England, to 11% in the United States, to 78% in Brazil. [Cecil, p. 2095] Contaminated equipment (e.g., needles and glassware) and tissue are potential sources of infection for laboratory personnel. [Harrison ID, p. 1111] Immunosuppressed patients most commonly affected by life-threatening toxoplasmosis are those with AIDS and on immunosuppressive therapy (e.g. Hodgkin's disease, leukemia, and organ transplant). [ID, p. 1515]
Paired sera; Identify agent in tissue or body fluids; [CCDM] Reference lab ( can determine recent vs. old infection based on IgM, IgG, and antibody avidity levels; Ocular disease is clinical dx + IgG titer; [Harrisons, p. 619-20]
  • >arthralgia
  • >fatigue, weakness
  • >fever
  • >myalgia
  • E pharyngitis
  • G abdominal pain
  • G hepatomegaly
  • G liver function test, abnormal
  • G nausea, vomiting
  • H anemia
  • H leukocytosis
  • H leukopenia
  • H lymphadenopathy
  • H splenomegaly
  • N confusion, delirium
  • N headache
  • N lethargy
  • N muscle weakness
  • N seizure
  • N stiff neck
  • R cough
  • R dyspnea
  • S lymphadenitis, acute
  • S papules or plaques
  • S rash (exanthem)
  • S urticaria
  • X lung infiltrates
  • *ARDS
  • *blindness
  • *brain abscess or lesion
  • *cranial neuropathy
  • *encephalitis
  • *epididymo-orchitis
  • *erythema nodosum
  • *glomerulonephritis
  • *hepatitis
  • *meningitis
  • *myelitis
  • *myocarditis
  • *pancreatitis
  • *paralysis
  • *parotitis
  • *pericarditis
  • *pneumonia
  • *pneumonitis
  • *shock
  • *stupor, coma
  • *uveitis




Inhalation, Ingestion, Needle (Includes Drug Abuse), Scalpel or Transfusion
Fecally Contaminated Soil, Animal Excreta, Animal Tissue, Soil or Dust (Ingesting or Inhaling), Eating Contaminated Food, Eating Contaminated or Infected Meat, Eating Contaminated Mollusks or Crustacean, Eating Unpasteurized Milk or Cheese, Eating Contaminated Produce, Waterborne (Ingesting, Inhaling, or Swimming)
Birds and Poultry, Cattle, Goats and Sheep, Cats, Dogs, Rodents, Swine, Wild Animals
  • AIDS patients
  • Cancer patients
  • Consume unpasteurized milk/cheese
  • Eat undercooked meat or fish
  • Have a blood transfusion
  • Ingest infectious agents in food/water
  • Touch infected meat or poultry
  • Work in a medical or research lab
No treatment necessary for most immunocompetent patients with only lymphadenopathy; [Harrisons, p. 620]
1. (US) Seroprevalence varies by location (from 3% to >50% in US and up to 90% in tropical countries and parts of Western Europe); In areas of high seroprevalence, 25-50% of AIDS patients not taking antiretroviral drugs develop CNS toxoplasmosis. [Gorbach, p. 384] Estimated 225,000 cases in 1997; [Mead1999: PMID 10511517]
2. (Global) Cases reported in England & Wales: 405 (2008), 422 (2009), 345 (2010), 341 (2011), 311 (2012); [Public Health England website] 20 X US cases/yr;