Association between asymptomatic submicroscopic and microscopic malaria infections and anemia: A study in southern Benin.

INTRODUCTION

Recently, efforts to eliminate malaria have shifted focus from symptomatic cases alone to include asymptomatic carriers, who are now recognized as significant contributors to the disease's transmission and control. This study examines the relationship between asymptomatic malaria infection and hemoglobin levels in Benin.

METHODS

A cohort in Benin was enrolled and categorized into three age groups (under 5 years, 5-15 years, and over 15 years) for follow-up from August to November 2021. Participants were monitored over two months and assessed for malaria infection through microscopy and polymerase chain reaction (PCR) during their three visits. A questionnaire was employed to gather general and clinical characteristics. Multivariate models were utilized to analyze the associations between asymptomatic infection, anemia, and hemoglobin levels.

RESULTS

Among 393 participants, 58.2% were diagnosed at enrolment with malaria via PCR, and 30.5% through microscopy. Anemia, defined as hemoglobin levels < 11 g/dL, was observed in 40.5% of the cohort. The risk of anemia declined with increasing age (OR for ages 5-15: 0.64, 95% CI [0.37; 1.09]; OR for over 15 years: 0.34, 95% CI [0.20; 0.59]) compared to children under 5. Individuals with both microscopic and submicroscopic infections exhibited higher odds of anemia (respectively OR = 4.15, 95% CI [2.41; 7.13] and OR = 2.09 [1.22; 3.57]) relative to those uninfected. Hemoglobin levels were consistently lower in participants with microscopic malaria across all age groups (β = -2.73, 95% CI [-3.41; -2.05] for those under 5, β = -1.35, 95% CI [-1.89; -0.82] for ages 5-15, and β = -0.72, 95% CI [-1.34; -0.07]) compared to non-infected individuals.

DISCUSSION: Our findings suggest that asymptomatic malaria infections, including submicroscopic cases, are associated with anemia and decreased hemoglobin levels. This underscores the importance of employing ultrasensitive diagnostic methods for such infections and acknowledging their potential health implications.