Screening

HIV-infected patients

HIV-infected patients with severe immunosuppression (CD4+ T lymphocyte count near 100 cells/microlitre) who are unable to take trimethoprim/sulfamethoxazole for Pneumocystis jiroveci prophylaxis should be tested for prior exposure by measuring anti-Toxoplasma immunoglobulin (Ig) G.[41]

Adults and adolescents living with HIV with CD4 counts <200 cells/microlitre should be tested for the IgG antibody to Toxoplasma gondii soon after the diagnosis of HIV infection to detect latent infection.[24]​ Patients with HIV and CD4+ T lymphocyte counts <100 cells/microlitre with detectable anti-Toxoplasma IgG are at risk for re-activation of latent infection and should receive prophylactic treatment.[24]

Transplant recipients

In the US, Toxoplasma IgG testing is required for all donors, regardless of organ.[42]

Among organ transplant recipients, toxoplasmosis is most commonly seen in heart recipients but can also occur in recipients of other solid organs or stem cell transplants.[41] Thus, the serostatus of all donors and recipients should be checked prior to transplantation.[25] Cardiac transplant patients who have detectable anti-Toxoplasma IgG or who are recipients of hearts from seropositive donors should receive prophylaxis, as should all solid organ transplant recipients who are high risk for toxoplasmosis (donor Toxoplasma IgG+, recipient Toxoplasma IgG negative).

Additionally, all recipients of allogeneic haematopoietic stem cell transplants should have baseline anti-Toxoplasma IgG testing. Prophylaxis prior to haematopoietic stem cell transplantation is recommended for all Toxoplasma seropositive recipients.[43]

For Toxoplasma seropositive individuals undergoing allogeneic haematopoietic stem-cell transplant who are unable to tolerate trimethoprim-sulfamethoxazole prophylaxis, weekly monitoring of blood for Toxoplasma polymerase chain reaction (PCR) for the first 3 months post-transplant is recommended.[44]

Consideration should also be given to performing a PCR at regular intervals in other patients who are at high risk of disseminated disease (e.g., heart transplant recipients with seropositive donors who are not able to tolerate trimethoprim-sulfamethoxazole). While there is no consensus on the optimal treatment of patients who are asymptomatic and PCR positive (i.e., trimethoprim/sulfamethoxazole prophylaxis versus treatment dosing of pyrimethamine plus sulfadiazine), centres utilising this surveillance strategy have higher survival rates than centres that do not screen with PCR.[40]

Pregnant women and newborns

The American College of Obstetricians and Gynecologists does not recommend universal screening for toxoplasmosis in women of childbearing age or those who are already pregnant.[45] Instead, it is advised to focus on targeted screening for individuals exhibiting symptoms indicative of acute infection or those who have had high-risk exposures. Understanding the limitations of serological testing, including the possibility of false-positive or negative results, is essential.[31]​ Some countries with a higher seroprevalence for Toxoplasma gondii, such as France, perform routine screening for women of childbearing age and during pregnancy.[11]

Certain US states (Massachusetts and New Hampshire) screen for toxoplasmosis in newborns by checking anti-Toxoplasma IgM.[46]

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