Zoom in at African Country level: Potential Climate Induced Changes in Areas of Suitability for Survival of Malaria Vectors

Predicting anopheles vectors’ population densities and boundary shifts is crucial in preparing for malaria risks and unanticipated outbreaks. Although shifts in the distribution and boundaries of the major malaria vectors (Anopheles gambiae s.s. and An. arabiensis) across Africa have been predicted, quantified areas of absolute change in zone of suitability for their survival have not been defined. In this study, we have quantified areas of absolute change conducive for the establishment and survival of these vectors, per African country, under two climate change scenarios and based on our findings, highlight practical measures for effective malaria control in the face of changing climatic patterns. We develop a model using CLIMEX simulation to estimate the potential geographical distribution and seasonal abundance of these malaria vectors in relation to climatic factors 9temperature, rainfall and relative humidity). The model yielded an eco climatic index (EI) describing the total favorable geographical locations for the species. The EI value were classified and exposed to a GIS package. Using ArcGIS, the EI shape points clipped to the extent of Africa and then converted to a raster layer using inverse Distance Weighted (IDW) interpolation method. Generated maps wre then transformed into polygon-based geo-referenced data set and areas computed and expressed in square kilometers (km2). Five classes of EI were derived indicating the level of survivorship of these malaria vectors. The proportion of areas increasing or decreasing in level of survival of these malaria vectors will be more pronounced in eastern and southern African countries than those in western Africa. Angola, Ethiopia, Kenya, Mozambique, Tanzania, South Africa and Zambia appear most likely to be affected in terms of absolute change of malaria vectors suitability zones under the selected climate change scenarios. The potential shifts of these malaria vectors have implications for human exposure to malaria, as recrudescence of the disease is likely to be recorded in several new areas and regions. Therefore, the need to develop, compile and share malaria preventive measures, which can be adapted to different climatic scenarios, remains crucial. \u

Expression of the cytochrome P450s, CYP6P3 and CYP6M2 are significantly elevated in multiple pyrethroid resistant populations of Anopheles gambiae s.s. from Southern Benin and Nigeria

Background: Insecticide resistance in Anopheles mosquitoes is threatening the success of malaria control programmes. This is particularly true in Benin where pyrethroid resistance has been linked to the failure of insecticide treated bed nets. The role of mutations in the insecticide target sites in conferring resistance has been clearly established. In this study, the contribution of other potential resistance mechanisms was investigated in Anopheles gambiae s.s. from a number of localities in Southern Benin and Nigeria. The mosquitoes were sampled from a variety of breeding sites in a preliminary attempt to investigate the role of contamination of mosquito breeding sites in selecting for resistance in adult mosquitoes. Results: All mosquitoes sampled belonged to the M form of An. gambiae s.s. There were high levels of permethrin resistance in an agricultural area (Akron) and an urban area (Gbedjromede), low levels of resistance in mosquito samples from an oil contaminated site (Ojoo) and complete susceptibility in the rural Orogun location. The target site mutation kdrW was detected at high levels in two of the populations (Akron f = 0.86 and Gbedjromede f = 0.84) but was not detected in Ojoo or Orogun. Microarray analysis using the Anopheles gambiae detox chip identified two P450s, CYP6P3 and CYP6M2 up regulated in all three populations, the former was expressed at particularly high levels in the Akron (12.4-fold) and Ojoo (7.4-fold) populations compared to the susceptible population. Additional detoxification and redox genes were also over expressed in one or more populations including two cuticular pre-cursor genes which were elevated in two of the three resistant populations. Conclusion: Multiple resistance mechanisms incurred in the different breeding sites contribute to resistance to permethrin in Benin. The cytochrome P450 genes, CYP6P3 and CYP6M2 are upregulated in all three resistant populations analysed. Several additional potential resistance mechanisms were also identified that warrant further investigation. Metabolic genes were over expressed irrespective of the presence of kdr, the latter resistance mechanism being absent in one resistant population. The discovery that mosquitoes collected from different types of breeding sites display differing profiles of metabolic genes at the adult stage may reflect the influence of a range of xenobiotics on selecting for resistance in mosquitoes

Genome-Wide Transcription and Functional Analyses Reveal Heterogeneous Molecular Mechanisms Driving Pyrethroids Resistance in the Major Malaria Vector Anopheles funestus Across Africa.

Pyrethroid resistance in malaria vector, An. funestus is increasingly reported across Africa, threatening the sustainability of pyrethroid-based control interventions, including long lasting insecticidal nets (LLINs). Managing this problem requires understanding of the molecular basis of the resistance from different regions of the continent, to establish whether it is being driven by a single or independent selective events. Here, using a genome-wide transcription profiling of pyrethroid resistant populations from southern (Malawi), East (Uganda), and West Africa (Benin), we investigated the molecular basis of resistance, revealing strong differences between the different African regions. The duplicated cytochrome P450 genes (CYP6P9a and CYP6P9b) which were highly overexpressed in southern Africa are not the most upregulated in other regions, where other genes are more overexpressed, including GSTe2 in West (Benin) and CYP9K1 in East (Uganda). The lack of directional selection on both CYP6P9a and CYP6P9b in Uganda in contrast to southern Africa further supports the limited role of these genes outside southern Africa. However, other genes such as the P450 CYP9J11 are commonly overexpressed in all countries across Africa. Here, CYP9J11 is functionally characterized and shown to confer resistance to pyrethroids and moderate cross-resistance to carbamates (bendiocarb). The consistent overexpression of GSTe2 in Benin is coupled with a role of allelic variation at this gene as GAL4-UAS transgenic expression in Drosophila flies showed that the resistant 119F allele is highly efficient in conferring both DDT and permethrin resistance than the L119. The heterogeneity in the molecular basis of resistance and cross-resistance to insecticides in An. funestus populations throughout sub-Saharan African should be taken into account in designing resistance management strategies

Typologie Des Gîtes Larvaires Et Résistance Des Vecteurs Du Paludisme A La Deltaméthrine Dans les Milieux Urbain Et Rural Du Département De l’Atlantique Au Sud Du Bénin: Données Préliminaires

La lutte antilarvaire récemment recommandée par l’OMS, requiert une connaissance approfondie de la distribution et de la typologie des gîtes larvaires des vecteurs du paludisme. L’objectif de cette étude est d’identifier les différents gîtes larvaires des anophèles et leur mécanisme de résistance à la deltaméthrine. Des prospections larvaires ont été effectuées en 2017 durant les saisons pluvieuses et sèches dans trois communes au sud du Bénin. Les moustiques issus de l’émergence des larves ont été soumis à la deltaméthrine et au bendiocarb selon le protocole de l’OMS. L’identification moléculaire des anophèles et le génotypage de la mutation Kdr ont été réalisés par PCR et l’expression des oxydases, des estérases α et β, et des GST ont été mesurées. Les prospections larvaires ont permis de répertorier 37 gîtes larvaires regroupés en 13 types. La majorité des gîtes étaient anthropiques. La densité larvaire variait d’un type de gîtes à l’autre. An. coluzzii et An. gambiae étaient les deux vecteurs du paludisme vivant en sympatrie dans lestroissites d’étude. Ils sont fortement résistants à la deltaméthrine avec la présence de la mutation kdr à des fréquences très élevées et une augmentation des activités des estérases dans les populations d’anophèles collectés à Zè et des GST à Abomey-Calavi et Allada. La prolifération des vecteurs du paludisme serait imputable à l’insalubrité de l’environnement immédiat et aux activités anthropiques qui créent et assurent le maintien des gîtes larvaires. Ces données pourraient servir au renforcement des stratégies de lutte contre le paludisme déjà en cours. Anopheles larval control, recently recommended by WHO, requires a deep knowledge of the distribution and typology of larval breeding sites. The objective of this study is to identify the different larval habitats colonized by Anopheles and their insecticide resistance mechanism. Larval surveys were carried out in three Districts in south of Benin in 2017, during the rainy and dry seasons. Mosquitoes breeding sites have been characterized and mapped. Mosquitoes from the emergence of larvae were tested to deltamethrin and bendiocarb according to the WHO protocol. The molecular identification of anopheles and the genotyping of the kdr mutation were performed by PCR and the expression of oxidases, esterases, and GSTs was measured. Larval surveys have identified 37 breeding sites categorized into 13 types. Most of the larval habitats were anthropogenics. An. coluzzii and An. gambiae were the two malaria vectors found in sympatric in the three study sites. These two vectors were highly resistant to deltamethrin with the presence of the kdr L1014F mutation at very high frequencies and an increase in esterase activities in anopheline populations collected in Zè and GST in Abomey-Calavi and Allada. The proliferation of malaria vectors is attributable to the unhealthy environment and human activities that create and maintain mosquito breeding. This study highlighted diversity in the type of breeding site of An. gambiae s.s in the Atlantic Department, suggesting the adaptation of this species in its environment. These results could be used to develop an antilarval control strategy in Abomey-Calavi, Zè and in Allada

Malaria transmission and prevalence in rice-growing versus non-rice-growing villages in Africa: a systematic review and meta-analysis.

BACKGROUND: Rice fields in Africa are major breeding sites for malaria vectors. However, when reviewed in the 1990s, in settings where transmission was relatively intense, there was no tendency for malaria indices to be higher in villages with irrigated rice fields than in those without. Subsequently, intervention coverage in sub-Saharan Africa has been massively scaled up and malaria infection prevalence has halved. We re-examined this rice-malaria relationship to assess whether, with lower malaria transmission, malaria risk is greater in rice-growing than in non-rice-growing areas. METHODS: For this systematic review and meta-analysis, we searched EMBASE, Global Health, PubMed, Scopus, and Web of Science to identify observational studies published between Jan 1, 1900, and Sept 18, 2020. Studies were considered eligible if they were observational studies (cross-sectional, case-control, or cohort) comparing epidemiological or entomological outcomes of interest between people living in rice-growing and non-rice-growing rural communities in sub-Saharan Africa. Studies with pregnant women, displaced people, and military personnel as participants were excluded because they were considered not representative of a typical community. Data were extracted with use of a standardised data extraction form. The primary outcomes were parasite prevalence (P falciparum parasite rate age-standardised to 2-10-year-olds, calculated from total numbers of participants and number of infections [confirmed by microscopy or rapid diagnostic test] in each group) and clinical malaria incidence (number of diagnoses [fever with Plasmodium parasitaemia confirmed by microscopy or rapid diagnostic test] per 1000 person-days in each group). We did random-effects meta-analyses to estimate the pooled risk ratio (RR) for malaria parasite prevalence and incidence rate ratio (IRR) for clinical malaria in rice-growing versus non-rice-growing villages. RRs were compared in studies conducted before and after 2003 (chosen to mark the start of the mass scale-up of antimalaria interventions). This study is registered with PROSPERO (CRD42020204936). FINDINGS: Of the 2913 unique studies identified and screened, 53 studies (including 113 160 participants across 14 African countries) were eligible for inclusion. In studies done before 2003, malaria parasite prevalence was not significantly different in rice-growing versus non-rice-growing villages (pooled RR 0·82 [95% CI 0·63-1·06]; 16 studies, 99 574 participants); however, in post-2003 studies, prevalence was significantly higher in rice-growing versus non-rice growing villages (1·73 [1·01-2·96]; seven studies, 14 002 participants). Clinical malaria incidence was not associated with residence in rice-growing versus non-rice-growing areas (IRR 0·75 [95% CI 0·47-1·18], four studies, 77 890). Potential limitations of this study include its basis on observational studies (with evidence quality rated as very low according to the GRADE approach), as well as its omission for the effects of seasonality and type of rice being cultivated. Risk of bias and inconsistencies was relatively serious, with I2 greater than 90% indicating considerable heterogeneity. INTERPRETATION: Irrigated rice-growing communities in sub-Saharan Africa are exposed to greater malaria risk, as well as more mosquitoes. As increasing rice production and eliminating malaria are two major development goals in Africa, there is an urgent need to improve methods for growing rice without producing mosquitoes. FUNDING: Wellcome Trust Our Planet Our Health programme, CGIAR Agriculture for Nutrition and Health

Pathogenicity of Beauveria bassiana (Balsamo-Crivelli) and Metarhizium anisopliae (Metschnikof) isolates against life stages of Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae)

Background Entomopathogenic fungi are primary pathogens that naturally afect insect pests by suppressing their populations and considered as an ecofriendly agents. The present study aimed to evaluate in vitro activity of diferent isolates of Beauveria bassiana and Metarhizium anisopliae against the development of larval stages of the Cucurbit fruit fy, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae). Results Larval mortality was signifcantly high with B. bassiana isolate Bb337 (5.82–21.70%) and with the lowest in M. anisopliae isolate MaD (1.49–6.33%). Pupal mortality rate was comparatively higher with more than 50%. The cadavers of all host instars produced conidia (sporulation). Sporulated dead larvae were signifcantly higher in Bb337 (61.10%) than at the least in MaD (18.60%) at 105 conidia/ml. At 108 conidia/ml, MaD induced the highest pupal cadavers with mycosis (32.42%). Regardless of applied fungal species, host instars mortality signifcantly increased with increasing concentration of B. bassiana isolates, suggesting a concentration-dependent response of Z. cucurbitae. Conclusion The tested isolates demonstrated their pathogenicity through vertical transmission of mycosis from one instar to another, regardless of the concentrations used

Capture of high numbers of simulium vectors can be achieved with host decoy traps to support data acquisition in the onchocerciasis elimination endgame

Onchocerciasis elimination is within reach in many countries but requires enhanced surveillance of the Simulium vectors of Onchocerca volvulus. Collection of sufficient numbers of adult Simulium to detect infective O. volvulus larvae is hindered by limited sampling tools for these flies. Here, we tested for the first time the Host Decoy Trap (HDT), an exposure free method previously developed for Anopheles vectors of malaria parasites, as a potential sampling tool for adult Simulium. In three replicates of a randomized Latin square experimental design, the HDT was compared to Human Landing Catches (HLC) and the Esperanza Window Trap (EWT). A total of 8,531 adult S. damnosum sensu lato blackflies (S. squamosum group) were found in catches from the three different trapping methods. The HDT (mean catch 533 ± 111) caught significantly more S. squamosum than the EWT (mean catch 9.1 ± 2.2), a nearly 60-fold difference. There was no significant difference between the HLC (mean catch 385.6 ± 80.9) and the HDT. Larvae indistinguishable from those of O. volvulus were dissected from 2.86% of HDT samples (n=70) and 0.35% of HLC samples (n=285); a single infective third-stage larvae (L3) was found during dissection of a sample from the HDT. Owing to its very high capture rate, which was comparable to the HLC and significantly greater than EWT, alongside the presence of infected flies in its catch, the HDT represents a potentially valuable new tool for blackfly collection in elimination settings, where thousands of flies are needed for parasite screening

Multiple insecticide resistance in an infected population of the malaria vector Anopheles funestus in Benin.

BACKGROUND Knowledge on the spread and distribution of insecticide resistance in major malaria vectors such as Anopheles funestus is key to implement successful resistance management strategies across Africa. Here, by assessing the susceptibility status of an inland population of An. funestus Giles (Kpome) and investigating molecular basis of resistance, we show that multiple resistance and consistent plasmodium infection rate are present in Anopheles funestus populations from Kpome. METHODS The insecticide susceptibility level of collected Anopheles funestus was assessed. Synergist (PBO) was used to screen resistance mechanisms. The TaqMan technique was used for genotyping of insecticide resistant alleles and detecting plasmodium infection levels. The nested PCR was used to further assess the plasmodium infection rate. RESULTS The TaqMan analysis of plasmodial infections revealed an infection rate (18.2 %) of An. funestus in this locality. The WHO bioassays revealed a multiple phenotypic resistance profile for An. funestus in Kpome. This population is highly resistant to pyrethroids (permethrin and deltamethrin), organochlorines (DDT), and carbamates (bendiocarb). A reduced susceptibility was observed with dieldrin. Mortalities did not vary after pre-exposure to PBO for DDT indicating that cytochrome P450s play little role in DDT resistance in Kpome. In contrast, we noticed, a significant increase in mortalities when PBO was combined to permethrin suggesting the direct involvement of P450s in pyrethroid resistance. A high frequency of the L119F-GSTe2 DDT resistance marker was observed in the wild DDT resistant population (9 %RS and 91 %RR) whereas the A296S mutation was detected at a low frequency (1 %RS and 99 %SS). CONCLUSION The presence of multiple resistance in An. funestus populations in the inland locality of Kpome is established in this study as recently documented in the costal locality of Pahou. Data from both localities suggest that resistance could be widespread in Benin and this highlights the need for further studies to assess the geographical distribution of insecticide resistance across Benin and neighboring countries as well as a more comprehensive analysis of the resistance mechanisms involved

Mineral analysis reveals extreme manganese concentrations in wild harvested and commercially available edible termites

Termites are widely used as a food resource, particularly in Africa and Asia. Markets for insects as food are also expanding worldwide. To inform the development of insect-based foods, we analysed selected minerals (Fe-Mn-Zn-Cu-Mg) in wild-harvested and commercially available termites. Mineral values were compared to selected commercially available insects. Alate termites, of the genera Macrotermes and Odontotermes, showed remarkably high manganese (Mn) content (292-515mg/100gdw), roughly 50-100 times the concentrations detected in other insects. Other mineral elements occur at moderate concentrations in all insects examined. On further examination, the Mn is located primarily in the abdomens of the Macrotermes subhyalinus; with scanning electron microscopy revealing small spherical structures highly enriched for Mn. We identify the fungus comb, of Macrotermes subhyanus, as a potential biological source of the high Mn concentrations. Consuming even small quantities of termite alates could exceed current upper recommended intakes for Mn in both adults and children. Given the widespread use of termites as food, a better understanding the sources, distribution and bio-availability of these high Mn concentrations in termite alates is needed

Does the spillage of petroleum products in Anopheles breeding sites have an impact on the pyrethroid resistance?

<p>Abstract</p> <p>Background</p> <p>The emergence of <it>Anopheles </it>populations capable of withstanding lethal doses of insecticides has weakened the efficacy of most insecticide based strategies of vector control and, has highlighted the need for further studies on the mechanisms of insecticide resistance and the various factors selecting resistant populations of mosquitoes. This research targeted the analysis of breeding sites and the oviposition behaviour of susceptible and resistant populations of <it>Anopheles </it>in localities of spilled petroleum products. The aim was to establish the possible contribution of oil spillage in the selection of pyrethroid resistance in malaria vectors.</p> <p>Methods</p> <p><it>Anopheles </it>breeding sites were identified and the insecticide susceptibility of the <it>Anopheles gambiae </it>populations mapped in 15 localities of South Western Nigeria. The presence of oil particles as well as the turbidity, the dissolved oxygen and the pH of each identified breeding site was recorded. Data were cross-analysed to correlate the habitat types and the insecticide susceptibility status of emerging mosquitoes. The second phase of this study was basically a laboratory model to provide more information on the implication of the spillage of petroleum on the selection of pyrethroid resistance in <it>An. gambiae</it>.</p> <p>Results</p> <p>Moderate levels of resistance following exposure to permethrin-impregnated papers were recorded with the majority of <it>An. gambiae </it>samples collected in the South Western Nigeria. Data from this study established a link between the constituency of the breeding sites and the resistance status of the emerging <it>Anopheles</it>.</p> <p>Conclusion</p> <p>This study has revealed the segregational occupation of breeding habitats by pyrethroid resistant and susceptible strains of <it>An. gambiae </it>in south-western Nigeria. Compiled results from field and laboratory research point out clear relationships between oil spillage and pyrethroid resistance in malaria vectors. The identification of this factor of resistance could serve as strong information in the management of insecticide resistance in some West African settings.</p