Wolfgang Richard Mukabana

BackgroundIdentification of malaria vectors is an important exercise that can result in the deployment of targeted control measures and monitoring the susceptibility of the vectors to control strategies. Although known to possess distinct biting behaviours and habitats, the African malaria vectors Anopheles gambiae and Anopheles arabiensis are morphologically indistinguishable and are known to be discriminated by molecular techniques. In this paper, Raman spectroscopy is proposed to complement the tedious and time-consuming Polymerase Chain Reaction (PCR) method for the rapid screening of mosquito identity.MethodsA dispersive Raman microscope was used to record spectra from the legs (femurs and tibiae) of fresh anaesthetized laboratory-bred mosquitoes. The scattered Raman intensity signal peaks observed were predominantly centered at approximately 1400 cm−1, 1590 cm−1, and 2067 cm−1 …

Accurate identification of disease vectors is crucial when collecting epidemiological data. In mosquitoes, which transmit diseases like malaria, yellow fever, chikungunya, and dengue fever, identification mainly relies on the observation of external morphological features at different life cycle stages. This process is tedious and labor‐intensive. In this paper, the utility of Raman spectroscopy to discriminate and classify three mosquito species, namely, Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus, is presented. The three species were chosen to represent two subfamilies of medically important mosquitoes, that is, the Anophelinae and the Culicinae. The study is primarily a proof of concept on the potential of Raman spectroscopy in mosquito taxonomy. A dispersive Raman microscope was used to record spectra from the legs (femur and tibia) of fresh anesthetized laboratory‐bred mosquitoes …

Background Leading transmission-blocking vaccine candidates such as Plasmodium falciparum surface protein 25 (Pfs25 gene) may undergo antigenic alterations which may render them ineffective or allele-specific. This study examines the level of genetic diversity, signature of selection and drivers of Pfs25 polymorphisms of parasites population in regions of western Kenya with varying malaria transmission intensities. Methods Dry blood spots (DBS) were collected in 2018 and 2019 from febrile outpatients with malaria at health facilities in malaria-endemic areas of Homa Bay, Kisumu (Chulaimbo) and the epidemic-prone highland area of Kisii. Parasites DNA were extracted from DBS using Chelex method. Species identification was performed using real-time PCR. The 460 base pairs (domains 1–4) of the Pfs25 were amplified and sequenced for a total of 180 P. falciparum-infected blood samples. Results Nine of ten polymorphic sites were identified for the first time. Overall, Pfs25 exhibited low nucleotide diversity (0.04×10−2) and low mutation frequencies (1.3% to 7.7%). Chulaimbo had the highest frequency (15.4%) of mutated sites followed by Kisii (6.7%) and Homa Bay (5.1%). Neutrality tests of Pfs25 variations showed significant negative values of Tajima’s D (-2.15, p<0.01) and Fu’s F (-10.91, p<0.001) statistics tests. Three loci pairs (123, 372), (364, 428) and (390, 394) were detected to be under linkage disequilibrium and none had history of recombination. These results suggested that purifying selection and inbreeding might be the drivers of the observed variation in Pfs25. Conclusion Given the low level of nucleotide diversity, it is …

Given the stagnating progress in the fight against malaria, there is an urgent need for areawide integrated vector management strategies to complement existing intra-domiciliary tools, ie, insecticide-treated bednets and indoor residual spraying. In this study, we describe a pilot trial using drones for aerial application of Aquatain Mosquito Formulation (AMF), a monomolecular surface film with larvicidal activity, against the African malaria mosquito Anopheles arabiensis in an irrigated rice agro-ecosystem in Unguja island, Zanzibar, Tanzania. Nine rice paddies were randomly assigned to three treatments:(a) control (drone spraying with water only),(b) drone spraying with 1 mL/m2, or (c) drone spraying with 5 mL/m2 of AMF. Compared to control paddies, AMF treatments resulted in highly significant (p< 0.001) reductions in the number of larvae and pupae and> 90% fewer emerging adults. The residual effect of AMF treatment lasted for a minimum of 5 weeks post-treatment, with reductions in larval densities reaching 94.7% in week 5 and 99.4% in week 4 for the 1 and 5 mL/m2 AMF treatments, respectively. These results merit a review of the WHO policy regarding larval source management (LSM), which primarily recommends its use in urban environments with ‘few, fixed, and findable’breeding sites. Unmanned aerial vehicles (UAVs) can rapidly treat many permanent, temporary, or transient mosquito breeding sites over large areas at low cost, thereby significantly enhancing the role of LSM in contemporary malaria control and elimination efforts.

Background: Behavioural responses of mosquito vectors to insecticide-treated materials are critical aspects of disease control and for insecticide resistance management. Physiological resistance to insecticides may change mosquitoes’ behavioural response to insecticide-treated materials such as bed nets.Methods: Using free-flying bioassay conducted in cubic-shape cages with different net materials on different sides of the cage, we examined the behavioural responses of insecticide-resistant (Bungoma strain) and susceptible (Kisumu strain) Anopheles gambiae sensu stricto mosquitoes to different types of long-lasting insecticidal nets (LLINs) including the piperonyl butoxide treated (PBO) LLIN using untreated nets as control. We conducted video tracking of mosquito flying paths and analysed landing attempts, resting preference and resting duration on treated and untreated netting materials. Kisumu susceptible strain (An. gambiae ss) was used as a control.Results: We found that for both field and susceptible strain mosquitoes PBO nets caused significantly higher mortalities. Direct observation found that the resistant strain mosquitoes showed significant inactive overall compared to susceptible mosquitoes regardless of net material. Direct observations found that resistant mosquitoes showed 5-10 fold higher proportion of resting on the non-treated nets (10~ 20% resting rate) compared to treated nets (< 2% resting rate), whereas, susceptible mosquitoes resting equally on treated and untreated nets (~ 5%). Based on video tracking results, mosquito landing attempts on the nets were low in the control cages and similar for both strains of …

Jigger infestation, also referred to as Tungiasis, is a skin health problem usually associated with poor people. It is caused by penetration of female jigger flea, Tunga penetrans into the skin of a disposed host and, the consequent hypertrophy of the parasite. The disease is zoonotic in nature. The objective of this survey was to assess the role that housing conditions play in aggravating tungiasis in Kandara Sub-County of Murang’a County. This was a 50:50 case-control survey involving 776 participants. The participants filled questionnaires with the assistance of community health extension workers. Univariate regression analysis was conducted between case and control variables. Variables showing significant differences were then analyzed in a multivariate regression to identify those that were independent in abetting jigger problem. The results showed that the infested participants were 1.6 times more likely to live in earthen houses while the floors of their houses were 4.2 times more likely to be earthen when compared to the control. About 54% of these house floors were also cracked and dusty while 49 % of them had cracked rough walls. There was no single parameter that stood out as an independent variable. The findings of the study demonstrated a high relationship between dilapidated housing and jigger infestation in Kandara Sub- County. These results will enable efficacious interventional measures to ultimately control jigger infestation.

Malaria control programs in Africa encounter daunting challenges that hinder progressive steps toward elimination of the disease. These challenges include widespread insecticide resistance in mosquito vectors, increasing outdoor malaria transmission, lack of vector surveillance and control tools suitable for outdoor biting vectors, weakness in malaria surveillance, and an inadequate number of skilled healthcare personnel. Ecological and epidemiological changes induced by environmental modifications resulting from water resource development projects pose additional barriers to malaria control. Cognizant of these challenges, our International Center of Excellence for Malaria Research (ICEMR) works in close collaboration with relevant government ministries and agencies to align its research efforts with the objectives and strategies of the national malaria control and elimination programs for the benefit of local …

Background: Malaria elimination and eradication efforts can be advanced by including transmission-blocking or reducing vaccines (TBVs) alongside existing interventions. Key transmission-blocking vaccine candidates, such as Pfs230 domain one and Pfs48/45 domain 3, should be genetically stable to avoid developing ineffective vaccines due to antigenic polymorphisms. We evaluated genetic polymorphism and temporal stability of Pfs230 domain one and Pfs48/45 domain three in Plasmodium falciparum parasites from western Kenya. Methods: Dry blood spots on filter paper were collected from febrile malaria patients reporting to community health facilities in endemic areas of Homa Bay and Kisumu Counties and an epidemic-prone area of Kisii County in 2018 and 2019. Plasmodium speciation was performed using eluted DNA and real-time PCR. Amplification of the target domains of the two Pfs genes was performed on P. falciparum positive samples. We sequenced Pfs230 domain one on 156 clinical isolates and Pfs48/45 domain three on 118 clinical isolates to infer the levels of genetic variability, signatures of selection, genetic diversity indices and perform other evolutionary analyses. Results: Pfs230 domain one had low nucleotide diversity (π = 0.15 × 10–2) with slight variation per study site. Six polymorphic sites with nonsynonymous mutations and eight haplotypes were discovered. I539T was a novel variant, whereas G605S was nearing fixation. Pfs48/45 domain three had a low π (0.063 × 10–2), high conservation index, and three segregating sites, resulting in nonsynonymous mutation and four haplotypes. Some loci of Pfs230 D1 …