Plasmodium falciparum malaria runs a more severe course in splenectomized patients at comparable levels of parasitemia: a retrospective matched case-control study.

Abstract

Background: The spleen plays a vital role in combating Plasmodium infections, particularly during the erythrocytic stage of the infection. Asplenia may notably affect disease progression and parasite clearance dynamics. More insight is needed as to whether asplenic malaria patients - beyond considerations of parasite load - also face a higher burden of disease caused by malaria-specific manifestations of organ dysfunction and/or metabolic deterioration.

Methods: A case-control study was conducted comparing splenectomized malaria patients with non-splenectomized individuals at comparable parasitemia levels. Control subjects were sourced from the Rotterdam Malaria Cohort Study. Due to the cohort's limited asplenic cases, a systematic literature review identified 13 additional asplenic malaria cases. Each case was matched for age and P. falciparum parasitemia level with 3 control subjects resulting in 45 case-control paired observations.

Findings: The study included a total of 60 P.falciparum malaria patients, comprising 15 splenectomized patients (cases) and 45 non-splenectomized patients (controls). Eleven of 15 cases (73%) met WHO criteria for severe disease, in contrast to 21 of 45 (47%) matched controls. Cases had significantly longer median duration of hospitalizations (10 versus 5.5 days) and higher rates of hemodynamic instability. Splenectomized malaria patients had a significantly 3-fold higher odds of experiencing WHO-defined severe disease malaria (OR 3.14 (95% CI 1.30-7.60)) than matched controls.

Conclusion: The findings of this case-control study suggest that - at comparable levels of parasitemia - P. falciparum malaria infections in asplenic individuals may run a more severe course as compared with individuals who have not undergone splenectomy.