Toxoplasmosis is caused by the parasite Toxoplasma gondii which infects both birds and mammals.

Epidemiology

• Hot, arid climates have a low incidence of toxoplasmosis
• Transmission
  • Usually oral (ingestion of raw or undercooked meat contaminated with infectious oocysts or tissue cysts)
  • May occur via blood transfusion, organ transplant and transplacentally from mother to infant

Organism

• Obligate intracellular parasite

Risk Factors

• Predisposition to severe toxoplasmosis infection is common in persons with acquired immunodeficiency syndrome (AIDS) or in persons who are otherwise immunocompromised

Clinical Presentation

• Usually a mild or asymptomatic disease in adults
• Constitutional signs and symptoms - prolonged fever, headache, lymph node enlargement, myalgias
• Gastrointestinal signs and symptoms - hepatomegaly, hepatitis
• Toxoplasmosis acquired in utero can result in blindness, encephalomyelitis, mental retardation, convulsions and death in infected neonates (TORCH syndrome)
• Transplant patients - most common in heart transplant patients

Treatment

• Toxoplasmosis can be treated
• Early detection of the disease is crucial for effective therapy
• Recommend treatment with antibiotics for patient with congenital infection or for a patient who is immunocompromised
• Complete eradication of the parasite becomes difficult after long-term chronic infection

Diagnosis

• Indications for testing - pregnant female with suspected exposure; immunocompromised patient with undiagnosed flu-like illness
• Laboratory testing
  • IgG, lgM antibodies in pregnant women

    • Caution should be exercised in the use of IgM antibody levels in prenatal screening. Any positive results in pregnant patients that are confirmed positive by a reference laboratory that specializes in toxoplasmosis testing should be evaluated by amniocentesis and PCR testing for Toxoplasma gondii.

  • PCR in immunocompromised patients
  • As suggested by the CDC, any equivocal or positive result should be retested using a different assay (IgG Dye test, IgM ELISA, reflex to Avidity and/or other tests) from another reference laboratory specializing in toxoplasmosis testing
  • Recommend paired acute and convalescent antibody testing to confirm the presence of disease
  • Sabin Feldman dye test - performed only in reference labs and detects either a change in antibody titers or a significantly high single titer

Differential Diagnosis

• Bartonella
• Brucella
• Coxiella
• Ehrlichiosis
• Mononucleosis
• Rickettsia