High prevalence of asymptomatic and sub-patentPlasmodium falciparuminfections in Urban Bouaké, Côte d’Ivoire, but nohrp2deletions: Implications for Malaria Control

AbstractAsymptomaticPlasmodium falciparuminfections are common in endemic settings, yet diagnosing these infections remains challenging because they are often below the limit of detection of conventional light microscopy (LM) or rapid diagnostic tests (RDTs). Deletions of thehrp2/3gene, encoding the protein detected by the most sensitive class of RDTs, present a further threat. In this study, the prevalence of asymptomatic and sub-patentP. falciparuminfections was characterized in the rainy season in the city of Bouaké, Central Côte d’Ivoire. A cross-sectional survey was conducted in nine neighborhoods of Bouaké, Côte d’Ivoire, in 2016. Matched LM, RDTs, andvarATS qPCR, were used to determine the prevalence ofP. falciparuminfections and to compare the performance of the different diagnostic methods.P. falciparum hrp2/3deletions were typed by digital PCR. Among 2313 individuals, malaria prevalence was 10.8% by microscopy, 13.0% by RDT, 35.1% by qPCR, and 37.3% (863/2313) when all three methods were combined. 96.4% (832/863) of individuals withP. falciparuminfections did not report a recent fever. 57.1% (493/863) of infections were sub-patent. The prevalence was highly heterogeneous across the neighborhoods, ranging from 15% to 55.2%, and differed among age groups (<5 years: 17.7%, 5-14 years: 42.7%, ≥15 years: 35.9%). Compared tovarATS qPCR, LM and RDT had a low sensitivity of 24.3% and 34.2%, respectively, although both methods were highly specific (>96%). Sub-microscopic malaria infections were more prevalent in ≥15-year-olds (69.9%, 349/499) and in the neighborhood of Dar es Salam (75.9%, 44/58). No hrp2 deletions were observed, and two samples carriedhrp3deletion/wild-type mixed infections. The high prevalence of asymptomatic and sub-patent infections prompts the implementation of strategies targeting these parasite reservoirs to achieve reductions in malaria burden in this high-transmission city of Côte d’Ivoire.