Toxoplasmosis

Definition

Toxoplasmosis is an infection with the protozoan intracellular parasite Toxoplasma gondii.

Causes, incidence, and risk factors

Toxoplasmosis is found in humans worldwide, and in many species of animals and birds. Cats are the definitive host of the parasite.

Human infection results from ingestion of contaminated soil, careless handling of cat litter, ingestion of raw or undercooked meat (lamb, pork, and beef), transmission from a mother to a fetus through the placenta (congenital infection), or by blood transfusion or solid organ transplantation.

Over 80-90% of primary infections produce no symptoms. The incubation period for symptoms is 1 to 2 weeks.

Congenital toxoplasmosis is caused by infection with Toxoplasma gondii in a pregnant woman, with up to 50% of such infections transmitted to the fetus. Signs of congenital infection may be present at birth or develop over the first few months of life.

Infants may show signs of central nervous system disorders, enlargement of the liver and spleen, Blindness, and mental retardation. Toxoplasmosis also affects people who are immunosuppressed (as a result of AIDS, cancer, or immunosuppressive therapies). The disease may affect the brain, lung, heart, eyes, or liver.

Symptoms

In non-immunosuppressed people:

• mild febrile illness resembling mononucleosis
  
• enlarged Lymph nodes in the head and neck
  
• headache
  
• sore throat
  
• muscle pain
  

In congenital infection:

• central nervous system disorders
  
• Enlarged liver or spleen
  
• rash, fever, jaundice, anemia
  
• inflammation of the retina of the eye
  
• psychomotor and learning disorders (may not appear until later)
  

In an immunosuppressed person:

• brain lesions are associated with fever, headache, confusion, seizures, and abnormal neurological findings
  
• retinal inflammation causing blurred vision