Medical Encyclopedia: Toxoplasmosis (Print Version)
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Medical Encyclopedia: Toxoplasmosis
URL of this page: http://www.nlm.nih.gov/medlineplus/ency/article/000637.htm
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:
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mild illness with fever, resembling mononucleosis
enlarged lymph nodes in the head and neck
headache
sore throat
muscle pain
In congenital infection:
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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:
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brain lesions are associated with fever, headache, confusion, seizures, and abnormal neurological findings
retinal inflammation causing blurred vision
http://www.nlm.nih.gov/medlineplus/print/ency/article/000637.htm
10/10/2007
Medical Encyclopedia: Toxoplasmosis (Print Version)
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Signs and tests
Tests to determine infection or presence of cysts:
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serologic titers for toxoplasmosis
MRI of head
cranial CT scan
brain biopsy
slit lamp examination reveals characteristic retinal lesions
Treatment
No treatment is recommended for people without symptoms, except children, to prevent retinal inflammation.
Treatment of women in pregnancy is controversial because of the toxicity of the medications, but treatment is still
advocated.
Medications to treat the infection include: pyrimethamine, sulfonamide drugs, folinic acid, clindamycin, and
trimethoprim-sulfamethoxazole. Treatment in AIDS patients is continued as long as the immune system is weak,
to prevent reactivation of the disease.
Expectations (prognosis)
Acute infection in children may cause retinochoroiditis (inflammation of the retina). Toxoplasmosis in adults has a
good prognosis (probable outcome) if the immune system is healthy. Chronic infection without any symptoms is
usually benign (harmless).
Complications
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spread of the infection in immunocompromised hosts (can be fatal)
permanent disability in infants (blindness, learning disorders, and so on)
recurrence of the disease
Calling your health care provider
Call for an appointment with your health care provider if symptoms of toxoplasmosis occur. Urgent or emergency
conditions exist if the disorder occurs in an immunosuppressed person or in a baby, or if confusion, seizures, or
other severe symptoms develop.
Prevention
Avoid undercooked meats, or freeze meat to -20 degrees Celsius for 2 days. Protect children's play areas from
cat and dog feces. Wash the hands thoroughly after contact with soil that may be contaminated with animal feces.
Pregnant women should have their blood examined for Toxoplasma antibody -- and those with negative results
should take measures to prevent infection by avoiding exposure to cat feces (including not cleaning litter boxes),
cooking meat thoroughly, and washing hands thoroughly after handling raw meat.
Patients with HIV disease should have toxoplasma antibody titers checked. If the results of the blood test are
positive and if the CD4 count is less than 100, patients should be given prophylactic antibiotics (trimethoprimsulfamethoxazole is the medication of choice) with antiretroviral therapy until the CD4 cell count has risen.
References
Cohen J, Powderly WG. Infectious Diseases. 2nd ed. New York, NY: Elsevier; 2004.
Mandell GL, Bennett JE, Dolin R. Principles and Practice of Infectious Diseases. 6th ed. London: Churchill
Livingstone; 2005.
Update Date: 2/13/2006
http://www.nlm.nih.gov/medlineplus/print/ency/article/000637.htm
10/10/2007
Medical Encyclopedia: Toxoplasmosis (Print Version)
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Updated by: Monica Gandhi, M.D., M.P.H., Assistant Professor, Division of Infectious Diseases, UCSF, San Francisco, CA. Review provided
by VeriMed Healthcare Network.
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http://www.nlm.nih.gov/medlineplus/print/ency/article/000637.htm
10/10/2007