Anopheles gambiae, An. coluzzii and An. arabiensis are the three major vectors of malaria in Nigeria. These mosquitoes have developed resistance to different insecticides. Insecticides resistance intensity assay was recently introduced to provide insight into the potential operational significance of insecticide resistance. Here, we present data on pyrethroids resistance intensity and resistance mechanisms from six vector surveillance sites (Lagos, Ogun, Edo, Anambra, Kwara and Niger) in Nigeria. Adult Anopheles reared from larval collections were tested using WHO insecticides susceptibility protocol with 1x concentration of permethrin and deltamethrin followed with intensity assays with 5x and 10x concentrations of both insecticides. Synergistic and biochemical assays were carried out and underlying resistance mechanisms determined following standard protocols. Anopheles gambiae constituted >50% samples tested in five sites. Permethrin and deltamethrin resistance was observed at all the sites. The Kdt50 varied from 15 minutes (CI = 13.6–17.2) in deltamethrin to 42.1 minutes (CI = 39.4–44.1) in permethrin. For both insecticides, Kdt95 was >30 minutes with 25% to 87% post exposure mortality at the different sites. The West Africa knock down resistance (kdr-w) mechanism was found at each site. Resistant An. gambiae from Lagos, Ogun and Niger synergized prior to permethrin or deltamethrin exposure showed significant mortality (89–100%) compared to unsynergized mosquitoes (Lagos, p = 0.031; Ogun, p = 0.025; Niger, p = 0.018). Biochemical analyses revealed significant increased levels of P450 enzymes in resistant Anopheles gambiae from Lagos (p = 0.038); Ogun (p = 0.042) and Niger (p = 0.028) in addition to GST in Lagos (p = 0.028) and Ogun (p = 0.033). Overall, the results revealed high pyrethroid resistance associated with increased activities of metabolic enzymes (P450 + GST) in An. gambiae and An. coluzzii from Lagos and Ogun. The presence of kdr + P450 conferred moderate resistance whereas low resistance was the case where kdr was the sole resistance mechanism. Findings thus suggests that elevated levels of cytochrome P450 enzymes together with GST were responsible for high or severe pyrethroid resistance.

Malariometric surveys generate data on malaria epidemiology and dynamics of transmission necessary for planning and monitoring of control activities. This study determined the prevalence of malaria and the knowledge, attitude, and practice (KAP) towards malaria infection in Ibeshe, a coastal community. The study took place during the dry season in 10 villages of Ibeshe. All the participants were screened for malaria. A semistructured questionnaire was used to capture sociodemographic data and KAP towards malaria. A total of 1489 participants with a mean age of 26.7 ± 20.0 years took part in the study. Malaria prevalence was 14.7% (95% CI 13.0–16.6%) with geometric mean density of 285 parasites/μL. Over 97% of participants were asymptomatic. Only 40 (2.7%) of the participants were febrile, while 227 (18.1%) were anemic. Almost all the participants (95.8%) identified mosquito bite as a cause of malaria, although multiple agents were associated with the cause of malaria. The commonest symptoms associated with malaria were hot body (89.9%) and headache (84.9%). Window nets (77.0%) were preferred to LLIN (29.6%). Malaria is mesoendemic in Ibeshe during the dry season. The participants had good knowledge of symptoms of malaria; however, there were a lot of misconceptions on the cause of malaria.

The observation of limited diversity of malaria parasites may imply that the use of antigenic markers as genotyping tools for distinguishing recrudescence and re-infections with P. falciparum during drug trials is subjective.

BackgroundGenetic diversity studies provide evidence of Plasmodium falciparum differentiation that could affect fitness and adaptation to drugs and target antigens for vaccine development. This study describes the genetic structure of P. falciparum populations in urban and rural sites from southwestern Nigeria.MethodologyTen neutral microsatellite loci were genotyped in 196 P. falciparum infections from three localities: Aramoko-Ekiti, a rural community; Lekki, an urban location and Badagry, a peri-urban border settlement. Analysis was performed on the genetic diversity, linkage disequilibrium, population structure and inter-population differentiation.ResultsAllelic diversity values were similar across all populations, with mean expected heterozygosity (HE) values between 0.65 and 0.79. No matching multilocus haplotypes were found and analysis of multilocus LD showed no significant index of association. Genetic differentiation between populations was low (ΦPT = 0.017).ConclusionThe absence of detectable population structure of P. falciparum in southwestern Nigeria is evident in the lack of significant differentiation between populations separated by about 200 km. This implies that a fairly uniform malaria control strategy may be effective over a wide geographic range in this highly endemic region. However, more wide-scale survey across the country will be required to inform malaria control in this large and densely populated endemic region.

Background: Vaccines are the most reliable alternative to elicit sterile immunity against malaria but their development has been hindered by polymorphisms and strain-specificity in previously studied antigens. New vaccine candidates are therefore urgently needed. Highly conserved Plasmodium falciparum reticulocyte-binding protein homologue-5 (PfRH5) has been identified as a potential candidate for anti-disease vaccine development. PfRH5 is essential for erythrocyte invasion by merozoites and crucial for parasite survival. However, there is paucity of data on the extent of genetic variations on PfRH5 in field isolates of Plasmodium falciparum. This study described genetic polymorphisms at the high affinity binding polypeptides (HABPs) 36718, 36727, 36728 of PfRH5 in Nigerian isolates of P. falciparum. This study tested the hypothesis that only specific conserved B and T cell epitopes on PfRH5 HABPs are crucial for vaccine development. Methods:One hundred and ninety-five microscopically confirmed P. falciparum samples collected in a prospective cross-sectional study of three different populations in Lagos, Nigeria. Genetic diversity and haplotype construct of Pfrh5 gene were determined using bi-directional sequencing approach. Tajima's D and the ratio of nonsynonymous vs synonymous mutations were utilized to estimate the extent of balancing and directional selection in the pfrh5 gene.Results: Sequence analysis revealed three haplotypes of PfRH5 with negative Tajima's D and dN/dS value of − 1.717 and 0.011 ± 0.020, respectively. A single nucleotide polymorphism, SNP (G → A) at position 608 was observed, which resulted in a change of the amino acid cysteine at position 203 to tyrosine. Haplotype and nucleotide diversities were 0.318 ± 0.016 and 0.0046 ± 0.0001 while inter-population genetic differentiation ranged from 0.007 to 0.037. Five polypeptide variants were identified, the most frequent being KTKYH with a frequency of 51.3%. One B-cell epitope, 151 major histocompatibility complex (MHC) class II T-cell epitopes, four intrinsically unstructured regions (IURs) and six MHC class I T-cell epitopes were observed in the study. Phylogenetic analysis of the sequences showed clustering and evidence of evolutionary relationship with 3D7, PAS-2 and FCB-2 RH5 sequences. © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article' s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article'