ABSTRACT
The majority of Plasmodium falciparum malaria diagnoses in Africa are made using rapid diagnostic tests (RDTs) that detect histidine-rich protein 2. Increasing reports of false-negative RDT results due to parasites with deletions of the pfhrp2 and/or pfhrp3 genes (pfhrp2/3) raise concern about existing malaria diagnostic strategies. We previously identified pfhrp2-negative parasites among asymptomatic children in the Democratic Republic of the Congo (DRC), but their impact on diagnosis of symptomatic malaria is unknown. We performed a cross-sectional study of false-negative RDTs in symptomatic subjects in 2017. Parasites were characterized by microscopy; RDT; pfhrp2/3 genotyping and species-specific PCR assays; a bead-based immunoassay for Plasmodium antigens; and/or whole-genome sequencing. Among 3627 symptomatic subjects, 427 (11.8%) had RDT-/microscopy + results. Parasites from eight (0.2%) samples were initially classified as putative pfhrp2/3 deletions by PCR, but antigen testing and whole-genome sequencing confirmed the presence of intact genes. 56.8% of subjects had PCR-confirmed malaria. Non-falciparum co-infection with P. falciparum was common (13.2%). Agreement between PCR and HRP2-based RDTs was satisfactory (Cohen's kappa = 0.66) and superior to microscopy (0.33). Symptomatic malaria due to pfhrp2/3-deleted P. falciparum was not observed. Ongoing HRP2-based RDT use is appropriate for the detection of falciparum malaria in the DRC.
Subject(s)
Malaria/diagnosis , Molecular Diagnostic Techniques/standards , Plasmodium falciparum/genetics , Adolescent , Antigens, Protozoan/genetics , Antigens, Protozoan/immunology , Child , False Negative Reactions , Humans , Malaria/parasitology , Molecular Diagnostic Techniques/methods , Plasmodium falciparum/immunology , Plasmodium falciparum/isolation & purification , Plasmodium falciparum/pathogenicity , Polymerase Chain Reaction/methods , Polymerase Chain Reaction/standards , Protozoan Proteins/genetics , Protozoan Proteins/immunology , Reagent Kits, Diagnostic/standards , Serologic Tests/methods , Serologic Tests/standardsABSTRACT
BACKGROUND & OBJECTIVES: Insecticide resistance in mosquitoes at Kinshasa may jeopardize the efficacy and usage of long-lasting insecticidal nets (LLINs). Entomological impact, user acceptance and bioefficacy of a combination LLIN (PermaNet® 3.0) and a standard LLIN (OlysetNet®) were evaluated at two sites in Kinshasa characterized by high densities of either Anopheles gambiae s.s. (Kindele) or Culex spp (Kimbangu). METHODS: Insecticide susceptibility (permethrin, deltamethrin, bendiocarb, propoxur and DDT) was determined via tube tests and bottle assays. Entomological impact of unwashed and washed LLINs and untreated nets was assessed via Latin square, based on rotation of nets and their users through selected houses at each site. User acceptability was evaluated through interviews using a questionnaire and net bioefficacy was measured via cone bioassays with field-derived An. gambiae s.s. RESULTS: The An. gambiae s.s. population from Kindele was resistant to DDT and permethrin with mortality rate of 27.3 and 75.8%, respectively, and kdr mutations (L1014F) plus suspected metabolic resistance. The Culex spp population was resistant to all five insecticides tested. No differences in entomological indices were observed for the five net treatments, but bioefficacy against An. gambiae was significantly higher for unwashed and washed PermaNet 3.0 (100 and 71% mortality) than for OlysetNet (56 and 36%). Householders reported a good sleep most often when using unwashed and washed PermaNet (94 and 88%) and least often with unwashed OlysetNet (46%). INTERPRETATION & CONCLUSION: High bioefficacy via cone bioassays against an An. gambiae s.s. population with kdr and suspected metabolic resistance was observed with PermaNet 3.0. Lower biting rates and a higher chance of a good night of sleep were reported when using PermaNet 3.0 compared to OlysetNet.
