Health Care Providers
Diagnosis
Diagnosis of toxoplasmosis is usually made by detection of Toxoplasma-specific IgG, IgM, or IgA antibodies. There are several tests available that detect these immunoglobulin antibodies within several weeks of infection:
- dye test (DT)
- indirect fluorescent antibody test (IFA)
- enzyme immunoassays (ELISA, immunoblots)
If acute infection is suspected, the patient's serum should be tested for IgG and IgM Toxoplasma-specific antibodies. For a testing results algorithm, see CDC's DPDx Toxoplasmosis: Antibody Detection page.
Serologic tests are sometimes unreliable in immunosuppressed patients. Because of the persistence of Toxoplasma cysts and antibody in asymptomatic chronic latent infections, immunosuppressed persons with both positive PCR and serologic results should have their diagnostic testing results interpreted in relation to clinical features of an active infection. A negative PCR does not rule out active infection. PCR can also be performed on amniotic fluid which can be helpful in determining fetal infection following acute acquired infection of the mother.
Diagnosis can be made by direct observation of the parasite in stained tissue sections, cerebrospinal fluid (CSF), or other biopsy material. These techniques are used less frequently because of the difficulty of obtaining these specimens. Parasites can also be isolated from blood or other body fluids (for example, CSF) but this process can be difficult and requires considerable time.
Treatment
Toxoplasma-infected patients with illness should be given combinations of pyrimethamine with either sulfadiazine or trisulfapyrimidines, plus folinic acid in the form of leucovorin calcium to protect the bone marrow from the toxic effects of pyrimethamine.
(For dosages, see The Medical Letter's Drugs for Parasitic Infections 
[PDF - 33 KB, 1 page]).
If the patient experiences a hypersensitivity reaction to the combination therapy, pyrimethamine plus clindamycin can be used instead. The fixed combination of trimethoprim with sulfamethoxazole has been used as an alternative when the primary drugs of choice are unavailable.
Management of maternal and fetal infection varies depending on the treatment center. In general, spiramycin is recommended (for the first and early second trimesters) or pyrimethamine/sulfadizaine and folinic acid (for late second and third trimesters) for women with acute T. gondii infection (diagnosed at a reference laboratory) during gestation. PCR is often performed on the amniotic fluid at 18 gestation weeks or more to determine if the infant is infected. If the infant is likely to be infected, then treatment with drugs such as pyrimethamine, sulfadizaine, and folinic acid is typical. Congenitally infected newborns are treated with pyrimethamine and a sulfonamide. (For dosages, see Montoya JG, Liesenfeld O. Toxoplasmosis. Lancet. 2004 Jun 12;363:1965-1976).
Persons with AIDS who are newly infected with Toxoplasma, or who have a recrudescence, need treatment that must be taken until a significant immunologic improvement is achieved as a result of antiretroviral therapy. For details, see Treating opportunistic infections among HIV-infected adults and adolescents and Guidelines for the prevention of opportunistic infections among HIV-infected persons — 2002.
Related Links
Guidelines for the prevention of opportunistic infections among HIV-infected persons — 2002
Treating opportunistic infections among HIV-infected adults and adolescents
Preventing congenital toxoplasmosis
Montoya JG, Liesenfeld. Toxoplasmosis. Lancet. 2004 Jun 12;363:1965-1976.
To access this article online via the Lancet website you must either be a subscriber or choose the pay-per-view option.
The Medical Letter's Drugs for Parasitic Infections (PDF - 33 KB, 1 page)
Toxoplasmosis Brochures (Educational Material for Patients)
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Page last reviewed: January 10, 2008
Content Source: Division of Parasitic Diseases (DPD)
National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED)