Main Malaria Vector Research Articles

Intensity and different genes involved in the resistance of An. gambiae s.l. to pyrethroids in four districts representative of the different agricultural production zones of North Benin, West Africa

The different methods used for the control of An. gambiae s.l. have led to the deployment of several defensive weapons by these vectors. Indoor residual spraying (IRS) implemented annually in the northern part of the country, and the national distribution of long-lasting insecticide-treated nets (LLINs) carried out every 3 years are the main malaria vector control tools deployed by the NMCP. The toxicity of insecticides in these tools results from their interaction with their biological target in the insect. Thus, for the effectiveness of vector control tools in an area, the knowledge of different defense weapons of Anopheles present in the area is essential.The characterization of resistance mechanisms present on samples of pyrethroid-resistant Anopheles gambiae s.l. was carried out in four districts of northern Benin taking into account the different agricultural production zones. The different species, resistance gene and enzyme present in these districts were investigated.High resistance of Anopheles gambiae s.l. in the four communes was observed, surviving a high frequency of the kdr resistance gene. Mosquito mortality rates ranged from 56.80% (95% CI: 50.51 - 62.95) in Kandi, to 70.24% (95% CI: 64.61 - 75.45) in N'Dali with deltamethrin, from 57.14% (95% CI: 51.04 - 63.09) in Kandi, to 74.80% (95% CI: 68.94 - 80.06) in N'Dali with permethrin, and from 59.63% (95% CI: 51.76 - 67.17) in Kandi, to 72.90% (95% CI: 66.24 - 78.89) in Parakou with alphacypermethrin. The lowest frequency of the kdr gene was observed in An. coluzzii 64.00% (95% CI: 56.90 - 70.60) in Malanville and the highest frequency in Kandi in An. gambiae 88.33% (95% CI: (82.70 - 92.60). It should also be noted that An. gambiae s.l. from these four districts also use detoxification enzymes to eliminate pyrethroid toxicity. These are: the communes of Parakou, Kandi and N'Dali for α and β esterases (pα < 0.05 and pβ < 0.05), Kandi, Malanville and N'Dali (p

Malaria abrogates O'nyong-nyong virus pathologies by restricting virus infection in nonimmune cells.

O'nyongnyong virus (ONNV) is a re-emerging alphavirus previously known to be transmitted by main malaria vectors, thus suggesting the possibility of coinfections with arboviruses in co-endemic areas. However, the pathological outcomes of such infections remain unknown. Using murine coinfection models, we demonstrated that a preexisting blood-stage Plasmodium infection suppresses ONNV-induced pathologies. We further showed that suppression of viremia and virus dissemination are dependent on Plasmodium-induced IFNγ and are associated with reduced infection of CD45- cells at the site of virus inoculation. We further proved that treatment with IFNγ or plasma samples from Plasmodium vivax-infected patients containing IFNγ are able to restrict ONNV infection in human fibroblast, synoviocyte, skeletal muscle, and endothelial cell lines. Mechanistically, the role of IFNγ in restricting ONNV infection was confirmed in in vitro infection assays through the generation of an IFNγ receptor 1 α chain (IFNγR1)-deficient cell line.

Dispersion routes of the main vectors of human malaria in the Americas: Genetic evidence from the mitochondrial COI gene.

In America, of the 44 species of Anopheles, nine are main vectors of malaria and, of these, genetic information exists for seven. Hence, this study sought to know the gene flow and diversity of the seven principal vectors of malaria at the Americas level. For the seven species and the sequences of the mitochondrial cytochrome c oxidase I (COI) gene obtained from the GenBank and Bold System, genetic analyzes of populations and genetic structure were performed and haplotype networks and phylogenetic trees were obtained. For the seven species, 1440 sequences were analyzed and 519 haplotypes were detected. The Hd and π values were higher within a continental context than by countries. Neutrality tests indicated positive and negative values with most of these being significant (p < 0.05). Phylogenetic analyses for all the species recovered three clades with no geographic pattern among them. Studies suggest that native species of Anopheles from the Americas have greater haplotype diversity and low genetic differentiation due to the lack of physical barriers to impede gene flow among these populations. Moreover, all the species are interconnected by roadways. This scenario complicates the epidemiological picture of malaria in the Americas.

Advancements in Preventing and Treating Malaria

In India, where only a fifth of the overall population, especially in rural areas, receives free or severely subsidized healthcare, malaria presents a significant socioeconomic burden on society. At private institutions, where the condition is typically treated based on presumptions, the majority of people seek medical attention as a result. Given that malaria is a rapidly reproducing parasite that may grow to pandemic proportions within a few days of entering the circulation, early identification and treatment are crucial to averting serious consequences. Female Anopheles mosquitoes, which are most active at dawn and dusk, are the main vectors of malaria. The disease has spread all over India, except in cool places with low mosquito populations, and from 10 days after infection he often shows symptoms between 4 weeks. Treating malaria is difficult because different types of disease require different drugs. Traditional treatments for malaria include quinine, but some parasites have developed resistance to quinine. It is treated with various drugs such as pyrimethamine. Quinine is improved and chloroquine is more effective against some types of ailments.

Malaria vector sibling species distribution in different endemic districts of Punjab, India.

Malaria transmission in Punjab, India is mainly seasonal with variation in its endemicity that may be due to varying vector behaviour in different areas of the state, primarily attributed to the existence of sibling species complexes among the vector species. So far there is no report regarding the existence of malaria vectors sibling species in the state of Punjab, therefore, the present study was planned to investigate the status of sibling species of two main vectors of malaria viz. Anopheles culcifacies and Anopheles fluviatilis in different districts of Punjab. Mosquito collections were made through hand catch in the morning hours. Malaria vector species An. culicifacies and An. fluviatilis were morphologically identified and man hour density was calculated. Both the vector species were subjected to molecular assays for sibling species identification through amplification of D3 domain of 28S ribosomal DNA by allele-specific PCR. Four sibling species of An. culicifacies, were identified viz. A, B, C and E. Species A was identified from Bhatinda district, species B, C and E from. S.A.S. Nagar and species C from Hoshiarpur. Two sibling species S and T of An. fluviatilis were identified from districts S.A.S. Nagar and Rupnagar. Presence of four sibling species of An. culicifacies and two sibling species of An. fluviatilis in Punjab necessitates planning of longitudinal studies to ascertain their role in disease transmission so that appropriate interventions may be applied to achieve malaria elimination.

&amp;lt;i&amp;gt;Anopheles leesoni&amp;lt;/i&amp;gt; Evans 1931, a Member of the &amp;lt;i&amp;gt;Anopheles funestus&amp;lt;/i&amp;gt; Group, Is a Potential Malaria Vector in Cameroon

Background: Understanding the biology of Anopheles malaria vector species is essential to planning effective and sustainable malaria control strategies in endemic countries. This study reported the implication of Anopheles leesoni in malaria transmission in Cameroon, Central Africa. Methods: Mosquitoes were collected in three localities from May 2015 to March 2018 using electric aspirators and Centers for Disease Control light traps (CDC-LT). Anopheles funestus sensu lato (s.l.) mosquitoes were identified as species using polymerase chain reaction assay (PCR). Furthermore, Plasmodium falciparum infection status was determined using the enzyme-linked immunosorbent assay (ELISA) method. Results: A total of 12,744 Anopheles mosquitoes were collected by electric aspirator (N = 4844) and CDC-LT (N = 7900). Anopheles funestus s.l. (86.95%) was the major species and the main malaria vector in rural savannah and rural forest sites followed by A. gambiae s.l. (13.05%) whereas in urban areas, A. gambiae s.l. was by far the most abundant representing 91.45% of Anopheles mosquitoes collected. Two members of the A. funestus group were identified among 1389 analysed by PCR: 1307 A. funestus sensu stricto (s.s.) (94.10%) and 82 A. leesoni (5.9%). Plasmodium falciparum infection rate was 21.04% in A. funestus s.s. For the first time, A. leesoni was found positive for P. falciparum (infection rate: 10.98%) in Cameroon. Conclusion: A very high P. falciparum infection rate was observed in this study in A. funestus s.s., highlighting its high implication in malaria transmission in Cameroon. Furthermore, the detection of P. falciparum infection in A. leesoni calls for more attention towards this neglected vector species.

Pyrethroid Resistance Intensity in Anopheles gambiae s.l. from Different Agricultural Production Zones in Benin, West Africa.

Agricultural production activities usually occur in Benin with the use of a huge amount of insecticides including pyrethroids for pest control. It is therefore important to regularly monitor pyrethroid resistance intensity in Anopheles gambiae s.l., the main malaria vector. This study was conducted in cereal, cotton, rice growing, and urban market gardening areas throughout the country in 2018 and 2019. Females An. gambiae s.l. field-collected as larvae were exposed to deltamethrin 1 × (0.05%), 2 × (0.1%), 5 × (0.25%), and 10 × (0.5%) and permethrin 1 × (0.75%), 2 × (1.5%), 5 × (3.75%), and 10 × (7.5%). Synergist assays were also performed using World Health Organization articles combining piperonyl butoxide (PBO) (4%) + deltamethrin 1 × and, PBO (4%) + Permethrin 1 × . Molecular species and L1014F kdr mutation were identified using PCR. Expression of metabolic enzymes was also assessed through biochemical tests. After exposure to permethrin and deltamethrin 10 × , An. gambiae s.l. displayed mortality rates <98%. Synergist assays induced significantly higher mortality rates than pyrethroids alone (p < 0.05). An. gambiae s.l. complex was composed of An. gambiae s.s., Anopheles coluzzii, and Anopheles arabiensis, with mean frequency of the L1014F kdr mutation >75%. Overexpression of nonspecific α and β esterases was observed in the cereal, cotton, and urban market gardening areas, while an overexpression of mixed function oxidases was observed in the cotton and rice growing areas. Overall, An. gambiae s.l. showed high resistance intensity to both deltamethrin and permethrin. The synergist and biochemical tests performed suggest that PBO long-lasting insecticidal nets may provide a greater control of pyrethroid-resistant mosquitoes.

Anopheline species (Diptera: Culicidae) from the Maracá Ecological Station, Roraima State, Brazil

Anopheline species were sampled in different ecotones at Maracá Ecological Station and in Cantá municipality, both in Roraima State, Brazil, in June 2016. Nine species were recorded. Six species belong to the subgenus Nyssorhynchus and three species to the subgenus Anopheles. The most abundant species collected were Anopheles triannulatus s.l., Anopheles nuneztovari s.l. and Anopheles oswaldoi species B. The remaining species had frequencies lower than 10%. While A. triannulatus s.l. was the most frequent and the most widely distributed species in the studied area, Anopheles darlingi Root, the main malaria vector in the Brazilian Amazon region, was captured in two different ecotones and in low frequency. Our findings suggest that the risk of malaria outbreaks at Maracá Ecological Station may be low. This study also describes the first record of Anopheles costai Fonseca &amp; Ramos in Maracá Ecological Station, Roraima State, increasing the distribution range of this taxon.

Wolbachia Detection in Field-Collected Mosquitoes from Cameroon.

Simple SummaryWolbachia bacteria from different strains, carried by many insects and nematodes, can interact in many ways with their hosts by changing their biology in different ways, including by suppressing vector population and reducing parasite transmission. Consequently, Wolbachia play an important role in vector control strategies. This study assessed the prevalence of natural Wolbachia infections in mosquitoes collected in Cameroon. Despite the low prevalence that was revealed, Wolbachia spp. were found in eight species of field-collected mosquitoes and are closely related to clades A and B. Aedes aegypti and A. gambiae sl., the main vectors of dengue and malaria, respectively, were not infected in this study, while C. moucheti recorded a high prevalence (46.67%). Future characterisation of the Wolbachia bacteria obtained is needed.Wolbachia spp., known to be maternally inherited intracellular bacteria, are widespread among arthropods, including mosquitoes. Our study assessed the presence and prevalence of Wolbachia infection in wild mosquitoes collected in Cameroon, using the combination of 23s rRNA Anaplasmatacea and 16s rRNA Wolbachia genes. Mosquitoes that were positive for Wolbachia were sequenced for subsequent phylogenetic analysis. Out of a total of 1740 individual mosquitoes belonging to 22 species and five genera screened, 33 mosquitoes (1.87%) belonging to eight species (namely, Aedes albopictus, A. contigus, Culex quinquefasciatus, C. perfuscus, C. wigglesworthi, C. duttoni, Anopheles paludis and Coquillettidia sp.) were found to be positive for Wolbachia infections. Wolbachia spp. were absent in A. gambiae and A. aegypti, the main vectors of malaria and dengue, respectively. Phylogenetic analysis of the 16S RNA sequences showed they belong mainly to two distinct subgroups (A and B). This study reports the presence of Wolbachia in about eight species of mosquitoes in Cameroon and suggests that future characterisation of the strains is needed.

Population genetics of Anopheles arabiensis, the primary malaria vector in the Republic of Sudan

BackgroundAnopheles arabiensis is a member of Anopheles gambiae complex and the main malaria vector in Sudan. There is insufficient population genetics data available on An. arabiensis for an understanding of vector population structure and genetics, which are important for the malaria vector control programmes in this country. The objective of this investigation is to study the population structure, gene flow and isolation by distance among An. arabiensis populations for developing control strategies.MethodsMosquitoes were collected from six sites located in three different states in Sudan, Khartoum, Kassala and Sennar, using pyrethrum spray catch of indoor resting mosquitoes. Anopheline mosquitoes were identified morphologically and based on species specific nucleotide sequences in the ribosomal DNA intergenic spacers (IGS). Seven published An. gambiae microsatellite loci primers were used to amplify the DNA of An. arabiensis samples.ResultsPCR confirmed that An. arabiensis was the main malaria vector found in the six localities. Of the seven microsatellite loci utilized, six were found to be highly polymorphic across populations, with high allelic richness and heterozygosity with the remaining one being monomorphic. Deviation from Hardy–Weinberg expectations were found in 21 out of 42 tests in the six populations due to heterozygote deficiency. Bayesian clustering analysis revealed two gene pools, grouping samples into two population clusters; one includes four and the other includes two populations. The clusters were not grouped according to the three states but were instead an admixture. The genetic distances between pairs of populations ranged from 0.06 to 0.24. Significant FST was observed between all pairwise analyses of An. arabiensis populations. The Kassala state population indicated high genetic differentiation (FST ranged from 0.17 to 0.24) from other populations, including one which is also located in the same state. High gene flow (Nm = 1.6–8.2) was detected among populations within respective clusters but limited between clusters particularly with respect to Kassala state. There was evidence of a bottleneck event in one of the populations (Al Haj Yousif site). No isolation by distance pattern was detected among populations.ConclusionsThis study revealed low levels of population differentiation with high gene flow among the An. arabiensis populations investigated in Sudan, with the exception of Kassala state.

Resistance Status of Anopheles maculipennis and Anopheles superpictus to the Conventional Insecticides in Northeastern Caspian Littoral, Iran.

Background:Malaria resurgence has occurred in the northern half parts of Iran. The resurgence of malaria in the prone area could arise from various factors, e.g. wide use of pesticides in the agriculture sector and factors such as habitual patterns of movement of local people from problematic southeastern foci in Iran toward the Caspian Littoral. There are no new data on the resistance status of main malaria vectors in the Caspian Littoral, and this study was aimed at renewal data on conventional insecticides.Methods:The field strain of adult Anopheles superpictus and Anopheles maculipennis were collected using the hand catch method and transferred to the laboratory. The susceptibility tests were carried out against DDT 4%, Malathion 5%, Permethrin 0.75%, Deltamethrin 0.05%, and Lambda-cyhalothrin 0.05%, followed by the WHO’s procedure.Results:The primary malaria vector in Caspian Littoral is An. maculipennis, revealed to be still resistant to DDT and mortality rate, LT50 and LT90 of female mosquitoes were 75.0%, 54.2, minutes and 111.3 minutes. The under ‘verification required’ status of An. maculipennis was also revealed to Lambda-cyhalothrin based on recent WHO’s criteria. The malaria vector An. superpictus is also considered the second malaria vectors in the west parts of the studied area, which showed to be susceptible to all insecticides tested.Conclusion:DDT resistance is persisted in An. maculipennis despite stopping residual spraying with DDT since 1978 in the Caspian Littoral, but the occurrence of pyrethroid under ‘verification required’ status is a progressive threat to the possible development of cross-resistance in the future.

New Distribution Records of Anopheles darlingi in Quintana Roo, Southeastern Mexico.

Anopheles darlingi is considered the main vector of malaria in the Neotropical region, so knowledge of its distribution in the Americas is highly relevant for the design of strategies for prevention and control of the illness. In Mexico, An. darlingi was recorded for the first time in 1943, and currently its distribution covers the states of Campeche, Chiapas, Quintana Roo, and Tabasco. In this study, new distribution data and observations of the abundance of An. darlingi in 14 localities of Quintana Roo, southeastern Mexico, are presented.

Effect of wall type, delayed mortality and mosquito age on the residual efficacy of a clothianidin-based indoor residual spray formulation (SumiShield™ 50WG) in southern Mozambique.

Indoor residual spraying (IRS) is one of the main malaria vector control strategies in Mozambique alongside the distribution of insecticide treated nets. As part of the national insecticide resistance management strategy, Mozambique introduced SumiShield™ 50WG, a third generation IRS product, in 2018. Its residual efficacy was assessed in southern Mozambique during the 2018–2019 malaria season. Using a susceptible Anopheles arabiensis strain, residual efficacy was assessed on two different wall surfaces, cement and mud-plastered walls, using standard WHO (World Health Organization) cone bioassay tests at three different heights. Female mosquitoes of two age groups (2–5 and 13–26 day old) were exposed for 30 minutes, after which mortality was observed 24h, 48h, 72h, and 96h and 120h post-exposure to assess (delayed) mortality. Lethal times (LT) 90, LT50 and LT10 were estimated using Bayesian models. Mortality 24h post exposure was consistently below 80%, the current WHO threshold value for effective IRS, in both young and old mosquitoes, regardless of wall surface type. Considering delayed mortality, residual efficacies (mosquito mortality equal or greater than 80%) ranged from 1.5 to ≥12.5 months, with the duration depending on mortality time post exposure, wall type and mosquito age. Looking at mortality 72h after exposure, residual efficacy was between 6.5 and 9.5 months, depending on wall type and mosquito age. The LT50 and LT10 (i.e. 90% of the mosquitoes survive exposure to the insecticides) values were consistently higher for older mosquitoes (except for LT10 values for 48h and 72h post-exposure mortality) and ranged from 0.9 to 5.8 months and 0.2 to 7.8 months for LT50 and LT10, respectively. The present study highlights the need for assessing mosquito mortality beyond the currently recommended 24h post exposure. Failure to do so may lead to underestimation of the residual efficacy of IRS products, as delayed mortality will lead to a further reduction in mosquito vector populations and potentially negatively impact disease transmission. Monitoring residual efficacy on relevant wall surfaces, including old mosquitoes that are ultimately responsible for malaria transmission, and assessing delayed mortalities are critical to provide accurate and actionable data to guide vector control programmes.

Data-driven and interpretable machine-learning modeling to explore the fine-scale environmental determinants of malaria vectors biting rates in rural Burkina Faso

BackgroundImproving the knowledge and understanding of the environmental determinants of malaria vector abundance at fine spatiotemporal scales is essential to design locally tailored vector control intervention. This work is aimed at exploring the environmental tenets of human-biting activity in the main malaria vectors (Anopheles gambiae s.s., Anopheles coluzzii and Anopheles funestus) in the health district of Diébougou, rural Burkina Faso.MethodsAnopheles human-biting activity was monitored in 27 villages during 15 months (in 2017–2018), and environmental variables (meteorological and landscape) were extracted from high-resolution satellite imagery. A two-step data-driven modeling study was then carried out. Correlation coefficients between the biting rates of each vector species and the environmental variables taken at various temporal lags and spatial distances from the biting events were first calculated. Then, multivariate machine-learning models were generated and interpreted to (i) pinpoint primary and secondary environmental drivers of variation in the biting rates of each species and (ii) identify complex associations between the environmental conditions and the biting rates.ResultsMeteorological and landscape variables were often significantly correlated with the vectors’ biting rates. Many nonlinear associations and thresholds were unveiled by the multivariate models, for both meteorological and landscape variables. From these results, several aspects of the bio-ecology of the main malaria vectors were identified or hypothesized for the Diébougou area, including breeding site typologies, development and survival rates in relation to weather, flight ranges from breeding sites and dispersal related to landscape openness.ConclusionsUsing high-resolution data in an interpretable machine-learning modeling framework proved to be an efficient way to enhance the knowledge of the complex links between the environment and the malaria vectors at a local scale. More broadly, the emerging field of interpretable machine learning has significant potential to help improve our understanding of the complex processes leading to malaria transmission, and to aid in developing operational tools to support the fight against the disease (e.g. vector control intervention plans, seasonal maps of predicted biting rates, early warning systems).Graphical abstract

Pre-intervention characteristics of the mosquito species in Benin in preparation for a randomized controlled trial assessing the efficacy of dual active-ingredient long-lasting insecticidal nets for controlling insecticide-resistant malaria vectors.

This study provides detailed characteristics of vector populations in preparation for a three-arm cluster randomized controlled trial (RCT) aiming to compare the community impact of dual active-ingredient (AI) long-lasting insecticidal nets (LLINs) that combine two novel insecticide classes-chlorfenapyr or pyriproxifen-with alpha-cypermethrin to improve the prevention of malaria transmitted by insecticide-resistant vectors compared to standard pyrethroid LLINs. The study was carried out in 60 villages across Cove, Zangnanando and Ouinhi districts, southern Benin. Mosquito collections were performed using human landing catches (HLCs). After morphological identification, a sub-sample of Anopheles gambiae s.l. were dissected for parity, analyzed by PCR for species and presence of L1014F kdr mutation and by ELISA-CSP to identify Plasmodium falciparum sporozoite infection. WHO susceptibility tube tests were performed by exposing adult An. gambiae s.l., collected as larvae from each district, to 0.05% alphacypermethrin, 0.75% permethrin, 0.1% bendiocarb and 0.25% pirimiphos-methyl. Synergist assays were also conducted with exposure first to 4% PBO followed by alpha-cypermethrin. An. gambiae s.l. (n = 10807) was the main malaria vector complex found followed by Anopheles funestus s.l. (n = 397) and Anopheles nili (n = 82). An. gambiae s.l. was comprised of An. coluzzii (53.9%) and An. gambiae s.s. (46.1%), both displaying a frequency of the L1014F kdr mutation >80%. Although more than 80% of people slept under standard LLIN, human biting rate (HBR) in An. gambiae s.l. was higher indoors [26.5 bite/person/night (95% CI: 25.2-27.9)] than outdoors [18.5 b/p/n (95% CI: 17.4-19.6)], as were the trends for sporozoite rate (SR) [2.9% (95% CI: 1.7-4.8) vs 1.8% (95% CI: 0.6-3.8)] and entomological inoculation rate (EIR) [21.6 infected bites/person/month (95% CI: 20.4-22.8) vs 5.4 (95% CI: 4.8-6.0)]. Parous rate was 81.6% (95%CI: 75.4-88.4). An. gambiae s.l. was resistant to alpha-cypermethrin and permethrin but, fully susceptible to bendiocarb and pirimiphos-methyl. PBO pre-exposure followed by alpha-cypermethrin treatment induced a higher 24 hours mortality compared to alphacypermethrin alone but not exceeding 40%. Despite a high usage of standard pyrethroid LLINs, the study area is characterized by intense malaria transmission. The main vectors An. coluzzii and An. gambiae s.s. were both highly resistant to pyrethroids and displayed multiple resistance mechanisms, L1014F kdr mutation and mixed function oxidases. These conditions of the study area make it an appropriate site to conduct the trial that aims to assess the effect of novel dual-AI LLINs on malaria transmitted by insecticide-resistant vectors.

Modeling the Potential Distribution of the Malaria Vector Anopheles (Ano.) pseudopunctipennis Theobald (Diptera: Culicidae) in Arid Regions of Northern Chile.

The extreme north of Chile presents a subtropical climate permissive of the establishment of potential disease vectors. Anopheles (Ano.) pseudopunctipennis is distributed from the south of the United States to the north of Argentina and Chile, and is one of the main vectors of malaria in Latin America. Malaria was eradicated from Chile in 1945. Nevertheless, the vector persists in river ravines of the Arica and Tarapacá regions. The principal effect of climate change in the north of Chile is temperature increase. Precipitation prediction is not accurate for this region because records were erratic during the last century. The objective of this study was to estimate the current and the projected distribution pattern of this species in Chile, given the potential impact due to climate change. We compiled distributional data for An. (Ano.) pseudopunctipennis and constructed species distribution models to predict the spatial distribution of this species using the MaxEnt algorithm with current and RCP 4.5 and 8.5 scenarios, using environmental and topographic layers. Our models estimated that the current expected range of An. (Ano.) pseudopunctipennis extends continuously from Arica to the north of Antofagasta region. Furthermore, the RCP 4.5 and 8.5 projected scenarios suggested that the range of distribution of An. (Ano.) pseudopunctipennis may increase in longitude, latitude, and altitude limits, enhancing the local extension area by 38 and 101%, respectively, and local presence probability (>0.7), from the northern limit in Arica y Parinacota region (18°S) to the northern Antofagasta region (23°S). This study contributes to geographic and ecologic knowledge about this species in Chile, as it represents the first local study of An. (Ano.) pseudopunctipennis. The information generated in this study can be used to inform decision making regarding vector control and surveillance programs of Latin America. These kinds of studies are very relevant to generate human, animal, and environmental health knowledge contributing to the “One Health” concept.

Preparation of nanoemulsion of Cinnamomum zeylanicum oil and evaluation of its larvicidal activity against a main malaria vector Anopheles stephensi.

There is a growing need to use green and efficient larvicidal as alternatives for conventional chemicals in vector control programs. Nanotechnology has provided a promising approach for research and development of new larvicides. Larvicidal potential of a nanoemulsion of Cinnamomum zeylanicum essential oil reports against Anopheles stephensi. The nanoemulsion of was formulated in various ratios comprising of C. zeylanicum oil, tween 80, span 20 and water by stirrer. It was characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). All components of C. zeylanicum essential oil were identified by GC-MS analysis. The larvicidal potential of the oil and its nanoformulation were evaluated against larvae of An. stephensi. The stability and durability of nanoemulsion was observed over a period of time. Sixty one components in the oil were identified, cinnamaldehyde (56.803%) was the main component. The LC90 and LC50 values of C. zeylanicum essential oil were calculated as 49ppm and 37ppm, respectively. The nanoemulsion droplets were found spherical in shape. It was able to kill 100% of larvae in up to 3days. It was stable after dilution and increased its larvicidal activity up to 32% compared with the essential oil. A novel larvicide based on nanotechnology introduced. This experiment clearly showed increasing larvicidal activity and residual effect of the nanoformulation in comparison with the bulk essential oil. It could be concluded that this nanoemulsion may be considered as safe larvicide and should be subject of more research in this field.

Culicidae Larvae and Their Seasonal Dynamics in the Region of Fez-Meknes, Morocco

RésuméObjectifDans le cadre de la prévention des maladies vectorielles au centre du Maroc, une étude de la fluctuation saisonnière de la biodiversité culicidienne a été menée de novembre 2015 à novembre 2016 sur quatre sites de reproduction situés dans la ville de Fès au centre du Maroc (Jnan EL Alami, barrage de Lgaâda, Awinat Elhajaj, Source Douwar Lhandiya). L'étude visait à améliorer les connaissances sur la dynamique saisonnière et la période d'activité des moustiques culicidiens, afin de cibler la période de lutte.MéthodesLes larves ont été collectées par la méthode du dipping à un intervalle de 15 jours, au moins une fois par mois. Les analyses statistiques ont été réalisées à l'aide de la version 3.6.1 du logiciel de traitement statistique R.RésultatsAu cours de cette étude, neuf espèces ont été trouvées avec de fortes variations mensuelles et saisonnières du nombre de chaque espèce et d'un site à l'autre. Les espèces prédominantes sont des vecteurs de maladies: Culex pipiens, Cx. perexiguus, Cx. theileri, vecteurs connus du virus du Nil occidental, suivis par Anopheles maculipennis s. l. et An. sergentii qui sont les principaux vecteurs du paludisme au Maroc. Cx. pipiens et Cx. perexiguus ont atteint la plus forte densité en septembre, tandis que Cx. theileri a été trouvé en grand nombre en février et peut donc émerger à la fin de l'hiver et au milieu du printemps. Le nombre le plus faible d'An. sergentii a été collecté en novembre, mais il a augmenté en septembre, octobre et décembre. An. maculipennis s. l. est apparu en juin, avec des récurrences en mars et juillet. Culiseta longiareolata a été trouvé au printemps et en été et en abondance en juin. Cependant, Uranotaenia unguiculata n'était présent qu'en septembre et octobre. An. cinereus et Cx. hortensis étaient tous les deux présents en novembre et février.ConclusionLes résultats obtenus seront un outil important pour la gestion et le suivi de la prolifération des Culicidae et pourront être utilisés pour améliorer l'efficacité de la gestion de la lutte.

Ecology and larval population dynamics of the primary malaria vector Nyssorhynchus darlingi in a high transmission setting dominated by fish farming in western Amazonian Brazil.

Vale do Rio Juruá in western Acre, Brazil, is a persistent malaria transmission hotspot partly due to fish farming development that was encouraged to improve local standards of living. Fish ponds can be productive breeding sites for Amazonian malaria vector species, including Nyssorhynchus darlingi, which, combined with high human density and mobility, add to the local malaria burden.This study reports entomological profile of immature and adult Ny. darlingi at three sites in Mâncio Lima, Acre, during the rainy and dry season (February to September, 2017). From 63 fishponds, 10,859 larvae were collected, including 5,512 first-instar Anophelinae larvae and 4,927 second, third and fourth-instars, of which 8.5% (n = 420) were Ny. darlingi. This species was most abundant in not-abandoned fishponds and in the presence of emerging aquatic vegetation. Seasonal analysis of immatures in urban landscapes found no significant difference in the numbers of Ny. darlingi, corresponding to equivalent population density during the rainy to dry transition period. However, in the rural landscape, significantly higher numbers of Ny. darlingi larvae were collected in August (IRR = 5.80, p = 0.037) and September (IRR = 6.62, p = 0.023) (dry season), compared to February (rainy season), suggesting important role of fishponds for vector population maintenance during the seasonal transition in this landscape type. Adult sampling detected mainly Ny. darlingi (~93%), with similar outdoor feeding behavior, but different abundance according to landscape profile: urban site 1 showed higher peaks of human biting rate in May (46 bites/person/hour), than February (4) and September (15), while rural site 3 shows similar HBR during the same sampling period (22, 24 and 21, respectively). This study contributes to a better understanding of the larvae biology of the main malaria vector in the Vale do Rio Juruá region and, ultimately will support vector control efforts.

Species Composition, Parous Rate, and Infection Rate of Anopheles Mosquitoes (Diptera: Culicidae) in Bahir Dar City Administration, Northwest Ethiopia.

Anopheles mosquitoes are the main vectors of malaria. There is little information on the current entomological aspects of Anopheles mosquitoes in Amhara region of northwestern Ethiopia. Therefore, the aim of this study was to assess the prevailing species composition, parous rate, and infection rate of Anopheles mosquitoes in the Bahir Dar city administration. A community-based cross-sectional study was conducted from January through July 2020. For this, six Centers for Disease Control and Prevention light traps (three traps indoor and three traps outdoor) were used to collect adult female Anopheles mosquitoes. The species were morphologically identified, and the parous and infection rates were determined via dissection of ovaries and salivary gland, respectively. A total of 378 adult female Anopheles mosquitoes comprised of three species (Anopheles d'thali, Anopheles rhodesiensis, and Anopheles gambiae complex) were collected and identified at the study sites. Anopheles rhodesiensis was the predominant species accounting for 90% of all collections at the Zenzelima site, followed by An. gambiae complex (6.5%). In contrast, An. gambiae complex was the predominant species at the Tis Abay site, comprising 94% of captures. The overall parous and infection rates were 35 (62.5%) and 1 (2.9%), respectively.