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For further information, see CMDT Part 37-06: Toxoplasmosis
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Essentials of Diagnosis
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Fever, malaise, headache, sore throat
Lymphadenopathy
Positive IgG and IgM serologic tests
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Infection in immunocompromised persons
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Reactivation leads to encephalitis, retinochoroiditis, pneumonitis, myocarditis
Positive IgG but negative IgM serologic tests
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General Considerations
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T gondii, an obligate intracellular protozoan, is found worldwide in humans and in many species of mammals and birds
Definitive hosts are cats
Humans are infected after ingestion of cysts in raw or undercooked meat, ingestion of oocysts in food or water contaminated by cats, transplacental transmission of trophozoites or, rarely, direct inoculation of trophozoites via blood transfusion or organ transplantation
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Toxoplasma seroprevalence
Varies widely
< 20% in the United States
However, it is much higher in other countries in both the developed and developing worlds, where it may exceed 80%
In the United States, T gondii is estimated to infect 1.1 million persons each year, with resultant chorioretinitis developing in 21,000 and vision loss in 4800
In the United States, an estimated 400 to 4000 congenital infections occur yearly
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Primary infection in the immunocompetent person
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After ingestion, T gondii infection progresses from the gastrointestinal tract to lymphatics, and then dissemination
Most acute infections are asymptomatic
About 10–20% are symptomatic after an incubation period of 1–2 weeks
Typically present as mild, febrile illnesses that resemble infectious mononucleosis
Nontender cervical or diffuse lymphadenopathy may persist for weeks to months
Systemic findings may include
Fever
Malaise
Headache
Sore throat
Rash
Myalgias
Hepatosplenomegaly
Atypical lymphocytosis
Severe manifestations are rare and include
Pneumonitis
Meningoencephalitis
Hepatitis
Myocarditis
Polymyositis
Retinochoroiditis
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Fetal infection follows maternal infection in 30–50% of cases, but this risk varies by trimester
10–25% during the first trimester
30–50% during the second trimester
60% or higher during the third trimester
Early fetal infections commonly lead to
Neurologic findings can include
Seizures
Psychomotor retardation
Deafness
Hydrocephalus
Systemic findings include
Fever or hypothermia
Jaundice
Vomiting
Diarrhea
Hepatosplenomegaly
Pneumonitis
Myocarditis
Rash
Retinochoroiditis and other sight-threatening eye lesions may develop
Retinochoroiditis presents weeks to years after congenital infection, commonly in teenagers or young adults
Uveitis is also seen
Disease presents with pain, photophobia, and visual changes, usually without systemic symptoms
Signs and symptoms eventually improve, but visual ...