Toxoplasmosis
Toxoplasmosis: Excerpt from Professional Guide to Diseases (Eighth Edition)
Toxoplasmosis, one of the most common infectious diseases, is caused by the protozoa Toxoplasma gondii. Distributed worldwide, it's less common in cold or hot, arid climates and at high elevations. It usually causes localized infection but may produce significant generalized infection, especially in neonates and patients who are immuno-deficient. Congenital toxoplasmosis, characterized by lesions in the central nervous system, may result in stillbirth or serious birth defects. For this reason, pregnant women are advised to avoid cleaning cat litter boxes because fecal-oral contamination from infected cats transmits toxoplasmosis.
Causes
T. gondii exists in trophozoite forms in the acute stages of infection and in cystic forms (tissue cysts and oocysts) in the latent stages. In addition to possible fecal-oral transmission from infected cats, ingestion of tissue cysts in raw or uncooked meat (heating, drying, or freezing destroys these cysts) can also transmit toxoplasmosis. However, toxoplasmosis also occurs in vegetarians who aren't exposed to cats, so other means of transmission may exist. Congenital toxoplasmosis follows transplacental transmission from a chronically infected mother or one who acquired toxoplasmosis shortly before or during pregnancy.
Signs and symptoms
Toxoplasmosis acquired in the first trimester of pregnancy commonly results in stillbirth. About one-third of infants who survive have congenital toxoplasmosis. The later in pregnancy that maternal infection occurs, the greater the risk of congenital infection in the infant. Obvious signs of congenital toxoplasmosis include retinochoroiditis, hydrocephalus or microcephalus, cerebral calcification, seizures, lymphadenopathy, fever, hepatosplenomegaly, jaundice, and rash. Other defects, which may become apparent months or years later, include strabismus, blindness, epilepsy, and mental retardation. (See Ocular toxoplasmosis.)
Acquired toxoplasmosis may cause localized (mild lymphatic) or generalized (fulminating, disseminated) infection. Localized infection produces fever and a mononucleosis-like syndrome (malaise, myalgia, headache, fatigue, and sore throat) and lymphadenopathy. Generalized infection produces encephalitis, fever, headache, vomiting, delirium, seizures, and a diffuse maculopapular rash (except on the palms, soles, and scalp). Generalized infection may lead to myocarditis, pneumonitis, hepatitis, and polymyositis.
Diagnosis
CONFIRMING DIAGNOSIS Identification of T. gondii in an appropriate tissue specimen confirms the diagnosis of toxoplasmosis.
Serologic tests may be useful and, in patients with toxoplasmosis encephalitis, computed tomography scans and magnetic resonance imaging disclose lesions.
Treatment
Treatment of acute disease consists of drug therapy with sulfonamides, pyrimethamine, folinic acid, clindamycin, or co-trimoxazole. In patients who also have acquired immunodeficiency syndrome, treatment continues indefinitely. No safe, effective treatment exists for chronic toxoplasmosis or toxoplasmosis occurring in the first trimester of pregnancy.
Special considerations
When caring for patients with toxoplasmosis, monitor drug therapy carefully and emphasize thorough patient teaching to prevent complications and control spread of the disease.
❑Because sulfonamides cause blood dyscrasias and pyrimethamine depresses bone marrow, closely monitor the patient's hematologic values. Also emphasize the importance of regularly scheduled follow-up care.
❑Teach all patients to wash their hands after working with soil (because it may be contaminated with cat oocysts); to cook meat thoroughly and freeze it promptly if it isn’t for immediate use; to change cat litter daily (cat oocysts don’t become infective until 1 to 4 days after excretion); to cover children’s sandboxes; and to keep flies away from food (flies transport oocysts).
❑Advise all pregnant women to avoid cleaning and handling of cat litter boxes. If this can't be avoided, advise them to wear gloves.
❑Patients who are receiving immunosuppressants are very susceptible to toxoplasmosis. Warn them of the risks and suggest having all cats that go outdoors tested for toxoplasmosis.
❑Report all cases of toxoplasmosis to your local public health department.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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