Toxoplasma prophylaxis in haematopoietic cell transplant recipients: a review of the literature and recommendations.

Purpose of review Toxoplasmosis in haematopoietic cell transplant (HCT) recipients is associated with high morbidity and mortality rates. Prophylaxis following HCT is recommended for high-risk pre-HCT toxoplasma-seropositive (pre-HCTSP) recipients. However, there is no agreement or consistency among programmes on whether to adopt prophylaxis or not, or if used, on the chosen antitoxoplasma prophylactic regimen. This review discusses the role of prophylaxis, and preemptive treatment, for toxoplasmosis in the setting of HCT. Recent findings Approximately two-thirds of toxoplasmosis cases following HCT are reported in allogeneic pre-HCTSP (allo pre-HCTSP) patients. This finding confirms a major role of reactivation of latent infection in the pathogenesis of toxoplasmosis in this patient population. Toxoplasma disease-related mortality in allo pre-HCTSP patients was reported at 62%, but it can be significantly decreased with early detection and treatment of toxoplasma infection. There are no randomized trials comparing the efficacy of different prophylactic agents to prevent toxoplasmosis after HCT. Several observational studies have demonstrated the efficacy of trimethoprim-sulfamethoxazole (TMP/SMX) in decreasing the incidence of toxoplasmosis following HCT. There is limited information regarding efficacy of other prophylactic agents. Preemptive treatment using routine blood PCR monitoring seems to be beneficial in detecting infection early and preventing disease in several observational studies and has been adopted for allo pre-HCTSP HCT patients when universal prophylaxis is not possible. Universal prophylaxis with TMP/SMX in allo pre-HCTSP patients should be implemented by all transplant programmes. Preemptive treatment with routine blood PCR monitoring is an option if prophylaxis cannot be used.