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Causes focal CNS lesions and encephalopathy best seen on MRI which improve with treatment

About

• Toxoplasmosis is a Intracellular protozoan (toxoplasma gondii) infection
• 22% of the UK population are seropositive for previous exposure
• Over 90% of French population are seropositive
• T. gondii was discovered by Charles Nicolle and L. Manceaux in 1908 in a North African rodent,Ctenodactylus gondii

Source

• Foodborne: Raw or undercooked meat
• Zoonotic: Cats, birds, and other animals or soil contaminated by cat faeces
• Congenital: From infected mother to fetus
• Blood tranfusion

Risks

• Pregnancy - harmful to fetus
• Seen in 10 percent of untreated AIDS patients
• Immunocompromised e.g. HIV when CD4 < 100/mm³
• Immunosuppressant therapy

Clinical - worse the earlier in gestation

• Lymphadenopathy: can involve cervical glands. Similar to glandular fever. Seen in immunocompetent individuals. Glands can be up to 3 cm.
• Toxoplasmic encephalitis: fever, severe headache, seizures, coma, seizures, neurology usually in immunocompromised e.g. HIV
• Congenital Toxoplasmosis: Infection before or during pregnancy. Microcephaly and Hydrocephalus, Chorioretinitis, Mental retardation
• Systemic Toxoplasmosis - dry cough, fever, SOB, CXR changes. Causes myocarditis, pneumonia, pleuritis, hepatitis with hepatomegaly, splenomegaly, bone marrow infiltration and CNS infection. Rare if normal immune system.
• Ocular toxoplasmosis: progressive retinochoroiditis - multiple, yellow-white, cotton-like patches with indistinct margins located in small clusters in the posterior pole. Pain and visual loss
• Immunocompetent adults: Almost always asymptomatic

Investigations

• Sabin–Feldman indirect fluorescent antibody test is used in immunocompetent patients. A x 4 ↑ IgG or the presence of IgM indicates acute infection. The presence of high-avidity IgG excludes infection in the past 3–4 mths, which is important in pregnancy.
• May cause a heterophile antibody-negative glandular fever-like illness
• HIV test, CD4 < 200, Test for Lymphoma
• Pulmonary : fungal pneumonia, pneumonitis can resemble PCP, Effusions. Get CXR/CT chest
• CT/MRI - multiple ring contrast-enhancing lesions (Primary brain lymphoma also seen with AIDs causes a single lesion). Toxoplasmosis is unlikely if a single and solitary disease.

Diagnostic criteria

• Specific IgG seroconversion; or
• Clinical features typical for toxoplasmosis, detection of specific serum IgA/IgM, and high levels of low-avidity specific IgG (<20%); or
• Epithelioid cells and lymphoid follicular hyperplasia found on histologic examination of an enlarged lymph node, presence of specific IgM, and increasing or elevated levels of specific IgG; or
• Isolation of the parasite in cultures or detection of its genetic material in blood, body fluids, or tissues.
• Lymph node tissue may be used as a source of T. gondii DNA to be amplified by PCR, or be stained with T. gondii antisera to demonstrate treponemes histochemically.

Management

• Immunocompetent, nonpregnant patients typically do not require treatment
• HIV/CNS/Systemic disease consider a trial of Sulfadiazine and Pyrimethamine for 6 weeks and rescan and clinically reassess. Consider HAART as soon as stable. Risk of IRIS.
• It should result in improvement in 3 weeks. If not consider Primary CNS lymphoma, Tuberculoma, Focal cryptococcal infection

References

• Toxoplasmosis