Clinical findings in migrants with asymptomatic Plasmodium infections

Background Migrants from malaria endemic areas may have asymptomatic parasitemia that persists after relocating to non-endemic countries. Recommendations on malaria screening and treatment of asymptomatic infections in migrants are lacking. The aim of this study was to explore the clinical features of sub-clinical blood stage Plasmodium infections in migrants, to inform screening and management strategies. Methods A retrospective observational study was performed to evaluate clinical data from medical records of asymptomatic sub-Saharan African (SSA) migrants identified with parasitic infection within a screening study in Stockholm, Sweden. Clinical data from hospital outpatient visits were compared between malaria PCR-positive and PCR-negative individuals, the latter assessed for schistosomiasis and/or strongyloidiasis. Results Clinical features and chemistry tests from 65 Plasmodium PCR-positive individuals were compared with data from 54 PCR-negative individuals. Study participants with Plasmodium infection had a higher proportion of anemia (21.1% vs 6.1%, p=0.048), elevated erythrocyte sedimentation rate (ESR) (58.1% vs 25.0%, p=0.008), raised plasma/serum IgM (30.5% vs 10.5%, p=0.030) and splenomegaly (25.4% vs 2.5%, p=0.002). After antimalarial treatment, splenomegaly and laboratory parameters improved in Plasmodium infected individuals. Conclusion Migrants with subclinical Plasmodium infection have a high proportion of splenomegaly and abnormal laboratory findings, such as anemia and elevated ESR. Screening and treatment of subclinical malaria infections could prevent adverse outcomes and should be considered both in endemic and non-endemic settings.