Infection in Immunocompetent Adults and Children
Immunocompetent adults and children with toxoplasmic lymphadenitis do not require treatment unless symptoms are severe or persistent. Infections acquired by laboratory accident or transfusion of blood products are potentially more severe, and these patients should always be treated. The combination of pyrimethamine, sulfadiazine, and folinic acid for 4-6 weeks is the most commonly used and recommended drug regimen (Box 2). Treatment should be administered for 2-4 weeks, followed by reassessment of the patient’s condition.
The decision to treat active toxoplasmic chorioretinitis should be based on the results of an examination performed by an ophthalmologist. Pyrimethamine and sulfadiazine plus folinic acid are commonly used for this syndrome. Clindamycin has also been used with favorable clinical results. Systemic corticosteroids may be required in addition to the anti-Toxoplasma drugs.
Infection in Pregnant Women
Spiramycin is the drug of choice for pregnant women who have acquired primary T gondii infection during gestation (Box 3). It does not eliminate but does appear to decrease the incidence of fetal infection. Because there is usually a delay between acquisition of acute maternal infection, infection of the placenta, and subsequent infection of the fetus, identification of acute maternal infection warrants immediate institution of spiramycin [available from the U.S. Food and Drug Administration (301-827-2335)]. Maternal adverse effects associated with spiramycin include nausea, vomiting, anorexia, diarrhea, vertigo, dizziness, flushing of the face, feeling of coolness, and numbness. There is no evidence that spiramycin is teratogenic. Spiramycin should be continued throughout the pregnancy even if the amniotic-fluid PCR result is negative for fetal infection. If the amniotic-fluid PCR result is positive at = 18 weeks, the institution of pyrimethamine, sulfadiazine, and folinic acid is recommended to treat fetal infection in utero.
Pregnant women with toxoplasmic chorioretinitis from reactivation of infection do not experience a higher risk of parasite transmission to the fetus than do pregnant women with prior infection and no ocular disease. However, when toxoplasmic chorioretinitis is thought to be a manifestation of primary infection acquired during gestation, it should be treated, because of the risks to both the mother and the fetus. The advice of an ophthalmologist should be sought.
Congenital Toxoplasmosis
The combination of sulfadiazine, pyrimethamine, and folinic acid for = 12 months is a commonly advocated regimen for infants born to mothers with positive results in the amniotic fluid or in whom the disease is highly suspected or proven (Box 4).
Infection in Immunocompromised Patients
The regimens used to treat toxoplasmosis in immunocompromised patients are basically the same as those used in other clinical settings; however, the doses recommended for immunocompromised patients are usually higher. The standard regimen is the combination of pyrimethamine, sulfadiazine, and folinic (not folic) acid (Box 5). Clindamycin can be used instead of sulfadiazine in adult patients intolerant to sulfonamides. The recommended duration of treatment is 4-6 weeks after resolution of all signs and symptoms (often for a total of at least several months). The role of other drugs (eg, atovaquone, clarithromycin, azithromycin, trimethoprim-sulfamethoxazole, and dapsone) in the treatment of toxoplasmosis in immunocompromised patients has not been well established. If these drugs are used, they should be given preferably in combination with pyrimethamine. At the present time, monotherapy does not have a role in the treatment of toxoplasmosis.
In patients with AIDS, after treatment of the acute phase (primary or induction treatment), maintenance therapy (secondary prophylaxis) should be instituted. The maintenance regimen is the same as that used in the acute phase but with each drug at one-half the dose. Current recommendations suggest that maintenance therapy be continued for the life of the patient. It is not known at this time whether the immune reconstitution observed as a result of combination antiretroviral therapy in AIDS patients might allow the successful discontinuation of maintenance treatment. Some non-AIDS-immunocompromised patients may also require maintenance treatment as long as their immunosuppressive regimens continue to exert a significant impact on cell-mediated immunity.