Transplantation activity is increasing, leading to a growing number of patients at risk for toxoplasmosis. We reviewed toxoplasmosis prevention practices, prevalence, and outcomes for hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT; heart, kidney, or liver) patients in Europe. We collected electronic data on the transplant population and prevention guidelines/regulations and clinical data on toxoplasmosis cases diagnosed during 2010–2014. Serologic pretransplant screening of allo-hematopoietic stem cell donors was performed in 80% of countries, screening of organ donors in 100%. SOT recipients were systematically screened in 6 countries. Targeted anti-Toxoplasma chemoprophylaxis was heterogeneous. A total of 87 toxoplasmosis cases were recorded (58 allo-HSCTs, 29 SOTs). The 6-month survival rate was lower among Toxoplasma-seropositive recipients and among allo-hematopoietic stem cell and liver recipients. Chemoprophylaxis improved outcomes for SOT recipients. Toxoplasmosis remains associated with high mortality rates among transplant recipients. Guidelines are urgently needed to standardize prophylactic regimens and optimize patient management.

Background: It is becoming increasingly clear that, during successful highly active antiretroviral therapy (HAART), a proportion of treated patients develop opportunistic infections (OIs), referred to in this setting as immune restoration disease (IRD). We examined the risk of developing IRD in HAART‐treated HIV‐infected patients.Methods: A retrospective study of a cohort including all 389 patients treated with HAART between 1 January 1998 and 31 May 2004 in our HIV unit was performed to evaluate the occurrence of and risk factors for IRD during HAART. Baseline and follow‐up values of CD4 T‐cell counts and plasma viral loads (pVLs) were compared to assess the success of HAART.Results: During successful HAART (significant increase in CD4 T‐cell counts and decrease in pVL), at least one IRD episode occurred in 65 patients (16.7%). The median time to IRD was 4.6 months (range 2–12 months). IRDs included dermatomal herpes zoster (26 patients), pulmonary tuberculosis (four patients), tuberculous exudative pericarditis (two patients), tuberculous lymphadenitis (two patients), cerebral toxoplasmosis (one patient), progressive multifocal leucoencephalopathy (PML) (one patient), inflamed molluscum (one patient), inflamed Candidaalbicans angular cheilitis (three patients), genital herpes simplex (two patients), tinea corporis (two patients), cytomegalovirus (CMV) retinitis (two patients), CMV vitritis (one patient) and hepatitis B (three patients) or C (fifteen patients). A baseline CD4 T‐cell count below 100 cells/μL was shown to be the single predictor [odds ratio (OR) 2.5, 95% confidence interval (CI) 0.9–6.4] of IRD, while a CD4 T‐cell count increase to >400 cells/μL, but not undetectable pVL, was a negative predictor of IRD (OR 0.3, 95% CI 0.1–0.8).Conclusions: To avoid IRD in advanced patients, HAART should be initiated before the CD4 T‐cell count falls below 100 cells/μL.

Toxoplasmosis is paradigmatic of the One Health approach, as the causative parasite Toxoplasma gondii infects virtually all warm-blooded animals, including humans. This makes T. gondii one of the most successful parasites on earth, infecting up to a third of the global human population. Moreover, the T. gondii disease burden has been ranked among the highest of all parasitic diseases. To reduce the disease burden of toxoplasmosis in humans, interventions are needed in the animal reservoirs, necessitating close collaboration between both the human and veterinary medical sectors. In the present special issue of FAWPAR, several of the most pertinent topics related to the impact and control of toxoplasmosis are addressed by leading experts in the field. This collection of papers highlights state-of-the-art knowledge, gaps in knowledge and future perspectives, as well as the benefits of current and proposed future activities to tackle toxoplasmosis within the One Health context.

The efficacy of atovaquone (ATO) combined with clindamycin (CLI) against Toxoplasma gondii was examined in murine models of infection with a mouse-non-virulent (Me49) strain. Swiss-Webster mice inoculated by mouth with 10 or 20 cysts were treated with ATO and CLI alone or combined at dosages of ATO 5–100 and CLI 25–400 mg/kg/day for 2–4 weeks. Drug treatment was initiated (i) day 4 post-infection (acute infection), (ii) 3 months post-infection (chronic infection) and (iii) following a 2–3 week course of treatment with dexamethasone (DXM) alone or combined with cortisone-acetate (CA) introduced 3 months post-infection (reactivated toxoplasmosis). In acute infection, whereas treatment with any drug or drug combination significantly enhanced survival and reduced the brain cyst burden, in mice treated with ATO alone or combined with CLI, the cyst counts were significantly lower than in mice treated with CLI alone. In chronic infection, the decrease in the cyst burden observed 2 weeks after treatment with either drug alone was significant only in mice treated with the combined drugs. Most importantly, in reactivated toxoplasmosis, whereas an effect for the combined drugs was shown in mice suppressed with both DXM alone and combined with CA, in mice pre-treated with DXM a 3 week course of ATO ≥25 and CLI 50 mg/kg/day significantly increased survival and markedly decreased the cyst burden. The latter effect was long-term, since the cyst burdens in treated mice continued to decrease up to 3 months later, whereas they increased in the untreated mice. The results warrant clinical evaluation of the combination of ATO and CLI in the treatment of toxoplasmosis in both immunocompetent and, more importantly, immunosuppressed patients.