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Arthropod-borne viruses (Arboviruses) replicate in vertebrates and invertebrates and are mainly transmitted by mosquitoes. Between 2000 and 2021, several arbovirus outbreaks were recorded in African countries, including dengue, yellow fever, Chikungunya, Zika, and O'nyong nyong. Most often, the causes and factors involved in these outbreaks are unknown. We aimed to understand current knowledge regarding factors responsible for the persistent transmission and emergence of mosquito-borne arboviruses in Africa and to identify critical research gaps important for preventing future outbreaks. We used a systematic literature review between 2020 and 2021, to show that the main identified factors favoring the arbovirus outbreak in Africa are low vaccination coverage, high density and diversity of competent mosquitoes, insecticide resistance of mosquito vectors, and a scarcity of data on arboviruses. Further studies on arboviruses may include studies of competence to viral strains and the susceptibility of mosquito vectors to insecticides. Because of the detrimental effects of insecticides on human health and the environment, viral paratransgenesis and other biological control methods should be explored as alternatives or as supplements to insecticides.Illustration of factors identified for promoting the transmission of arbovirus in Africa. The main factors are the lack of drugs and vaccines, low coverage of vaccination when a vaccine exists, competence of mosquitoes to viruses, diversity and high density of vectors. Climate change, urbanization, deforestation and agricultural practices, lead to a richness and high density of vectors.

Aedes albopictus (Skuse) is native to Southeast Asia and has colonized tropical and temperate regions worldwide in the last three to four decades. In Africa, data on its distribution is incomplete. Most studies having focused on the abundance, competition to other species, and phylogenetics of this vector are from the central African region. Here, we report the first detection of Ae. albopictus in Benin, West Africa. A total of 13 specimens were collected during the study period in 2021. The phylogenetic analysis of a cytochrome oxidase c subunit I gene fragment revealed a close relationship to populations from tropical India. Because of its close geographical proximity to areas where it has been found, it is assumed that the species was introduced several years before and is currently widely distributed in Benin. Additional studies are needed to explore its distribution, expansion range, and competitive effects on native species.

Severe acute respiratory syndrome coronavirus 2 Delta variant epidemiology in Africa is unknown. We found Delta variant was introduced in Benin during April–May 2021 and became predominant within 2 months, after which a steep increase in reported coronavirus disease incidence occurred. Benin might require increased nonpharmaceutical interventions and vaccination coverage.

The geographic and evolutionary origins of the SARS-CoV-2 Omicron variant (BA.1), which was first detected mid-November 2021 in Southern Africa, remain unknown. We tested 13,097 COVID-19 patients sampled between mid-2021 to early 2022 from 22 African countries for BA.1 by real-time RT-PCR. By November-December 2021, BA.1 had replaced the Delta variant in all African sub-regions following a South-North gradient, with a peak Rt of 4.1. Polymerase chain reaction and near-full genome sequencing data revealed genetically diverse Omicron ancestors already existed across Africa by August 2021. Mutations, altering viral tropism, replication and immune escape, gradually accumulated in the spike gene. Omicron ancestors were therefore present in several African countries months before Omicron dominated transmission. These data also indicate that travel bans are ineffective in the face of undetected and widespread infection.

BackgroundMany SARS-CoV-2 seroprevalence surveys since the end of 2020 have disqualified the first misconception that Africa had been spared by the pandemic. Through the analysis of three SARS-CoV-2 seroprevalence surveys carried out in Benin as part of the ARIACOV project, we argue that the integration of epidemiological serosurveillance of the SARS-COV2 infection in the national surveillance package would be of great use to refine the understanding of the COVID-19 pandemic in Africa.MethodsThree repeated cross-sectional surveys have been carried out in Benin, two in Cotonou, the economic capital in March and May 2021, and one in Natitingou, a semi-rural city in North in August 2021. The global and by age-groups weighted seroprevalences have been estimated and the risk factors of the infection by SARS-COV-2 have been assessed by using logistic regression.ResultsIn Cotonou, a slight increase in overall age-standardized SARS-CoV-2 seroprevalence from 29.77% (95% CI: 23.12-37.41%) at the first survey to 34.86% (95% CI: 31.57-38.30%) at the second survey was observed. In Natitingou the global adjusted seroprevalence was 33.34% (95% CI: 27.75-39.44%), much higher than expected. Adults over 40 seemed to be more at risk than the youngest during the first survey in Cotonou but no longer in the second survey, showing the persistence of the SARS-COV-2 virus circulation outside the epidemic waves.ConclusionsA routine serological surveillance on strategic sentinel sites and / or populations could constitute a cost / effective compromise to better anticipate the onset of new waves and define public health strategies.

Intense transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Africa might promote emergence of variants. We describe 10 SARS-CoV-2 lineages in Benin during early 2021 that harbored mutations associated with variants of concern. Benin-derived SARS-CoV-2 strains were more efficiently neutralized by antibodies derived from vaccinees than patients, warranting accelerated vaccination in Africa.

We used commercially available ELISAs to test 68 samples from coronavirus disease cases and prepandemic controls from Benin. We noted

Background: The blood-feeding patterns are crucial in incriminating disease vectors as well as facilitating the design and consolidation of effective vector control interventions in an area. Objective: This study aimed to establish if prolonged use of insecticide-treated bed nets (ITNs) caused a shift in the preferred hosts of the common malaria vectors as the hosts were under the bed net. Such a shift would render ITNs less effective and would probably explain the continued morbidity and mortality due to malaria in the highly endemic Kamuli district. Methods: A total of 3,519 indoor and outdoor human biting female Anopheles gambiae sensu lato and An. funestus mosquitoes were collected from 48 households using human-baited bed net traps. All 187 indoor resting blood-fed anophelines collected were tested by direct enzyme-linked immunosorbent assay (ELISA) for blood meal host identification. Of these, 73 mid guts came from 24 households in villages with a 69% ITNs coverage, while 114 mid guts were from 24 households in non-ITN villages. Results: Blood meal hosts were identified in only 10.96% (n = 8) and 14.91% (n = 17) of the Anopheles blood meals from the intervention and non-intervention zones, respectively. Other blood meals could not be clearly identified. Eight (100%) blood meals in the intervention zone were from humans, while in the non-intervention zone, 15 (88.24%), one (5.88%) and one (5.88%) came from humans, cattle and goat, respectively. These findings demonstrated that the malaria vectors in Kamuli district are anthropophilic, with nearly all the mosquitoes collected from both zones feeding on humans during every blood meal (p = 0.82). This indicated high vector-human contacts, and thus implicating these species as important in the transmission of Plasmodium species and probably other infections. Conclusion: The use of insecticide-treated bed nets is effective for controlling malaria vectors inside houses, evoking universal coverage of houses in the area.

Lassa virus has been identified in 3 pygmy mice, Mus baoulei, in central Benin. The glycoprotein and nucleoprotein sequences cluster with the Togo strain. These mice may be a new reservoir for Lassa virus in Ghana, Togo, and Benin.

Background Long-lasting insecticidal nets (LLINs) are the primary malaria prevention and control intervention in many parts of sub-Saharan Africa. While LLINs are expected to last at least 3 years under normal use conditions, they can lose effectiveness because they fall out of use, are discarded, repurposed, physically damaged, or lose insecticidal activity. The contributions of these different interrelated factors to durability of nets and their protection against malaria have been unclear. Methods Starting in 2009, LLIN durability studies were conducted in seven countries in Africa over 5 years. WHO-recommended measures of attrition, LLIN use, insecticidal activity, and physical integrity were recorded for eight different net brands. These data were combined with analyses of experimental hut data on feeding inhibition and killing effects of LLINs on both susceptible and pyrethroid resistant malaria vectors to estimate the protection against malaria transmission—in terms of vectorial capacity (VC)—provided by each net cohort over time. Impact on VC was then compared in hypothetical scenarios where one durability outcome measure was set at the best possible level while keeping the others at the observed levels. Results There was more variability in decay of protection over time by country than by net brand for three measures of durability (ratios of variance components 4.6, 4.4, and 1.8 times for LLIN survival, use, and integrity, respectively). In some countries, LLIN attrition was slow, but use declined rapidly. Non-use of LLINs generally had more effect on LLIN impact on VC than did attrition, hole formation, or insecticide loss. Conclusions There is much more variation in LLIN durability among countries than among net brands. Low levels of use may have a larger impact on effectiveness than does variation in attrition or LLIN degradation. The estimated entomological effects of chemical decay are relatively small, with physical decay probably more important as a driver of attrition and non-use than as a direct cause of loss of effect. Efforts to maximize LLIN impact in operational settings should focus on increasing LLIN usage, including through improvements in LLIN physical integrity. Further research is needed to understand household decisions related to LLIN use, including the influence of net durability and the presence of other nets in the household.

Information on severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spread in Africa is limited by fragile surveillance systems and insufficient diagnostic capacity. We assessed the coronavirus disease-19 (COVID-19)-related diagnostic workload in Benin, Western Africa, characterized SARS-CoV-2 genomes from 12 acute cases of COVID-19, used those together with public data to estimate SARS-CoV-2 transmission dynamics in a Bayesian framework, validated a widely used diagnostic dual target RT-PCR kit donated to African countries, and conducted serological analyses in 68 sera from confirmed COVID-19 cases and from febrile patients sampled before the predicted SARS-CoV-2 introduction. We found a 15-fold increase in the monthly laboratory workload due to COVID-19. Genomic surveillance showed introductions of three distinct SARS-CoV-2 lineages. SARS-CoV-2 genome-based analyses yielded an R0 estimate of 4.4 (95% confidence interval: 2.0-7.7), suggesting intense spread of SARS-CoV-2 in Africa. RT-PCR-based tests were highly sensitive but showed variation of internal controls and between diagnostic targets. Commercially available SARS-CoV-2 ELISAs showed up to 25% false-positive results depending on antigen and antibody types, likely due to unspecific antibody responses elicited by acute malaria according to lack of SARS-CoV-2-specific neutralizing antibody responses and relatively higher parasitemia in those sera. We confirm an overload of the diagnostic capacity in Benin and provide baseline information on the usability of genome-based surveillance in resource-limited settings. Sero-epidemiological studies needed to assess SARS-CoV-2 spread may be put at stake by low specificity of tests in tropical settings globally. The increasing diagnostic challenges demand continuous support of national and supranational African stakeholders. Funding This work was supported by the Deutsche Gesellschaft fur Internationale Zusammenarbeit (GIZ) GmbH.

Objective Post-harvest shrimp losses are a big problem due to the proliferation of spoilage bacteria. Presence and multiplication of these bacteria promotes the emergence of food-borne diseases. This study was carried out to characterize some spoilage bacteria from tropical brackish water shrimps and black tiger shrimps stored in ambient temperature (25 °C). Results 22 isolates of Bacillus spp; 09 isolates of Coagulase Negative Staphylococci (CNS) and 04 isolates of enterobacteria such as Pantoea spp (01); Serratia plymutica (01) and Serratia rubidaea (02) have been identified. Resistance and virulence genes were then detected. All isolates expressed resistance to at least three of antibiotics tested. 03 isolates of enterobacteria were susceptible to cetfazidim and amoxicillin-clavulanic acid. Bacillus spp showed total susceptibility to cefixim, ertapenem and cetfazidim. Staphylococci were susceptible to clindamycin. Pantoea spp was resistant to all antibiotics but exhibited intermediate susceptibility to amoxicillin-clavulanic acid. 04 isolates of Staphylococci were positive to mecA resistances genes. All the enterobacteria harbor no tetracycline resistance genes. All the isolates of Bacillus exhibited the presence of enterotoxin genes. Also, a high prevalence of 21 isolates to hemolytic enterotoxins was noted. 17 isolates from them kept ability to cell-lyse factor production like sphingomyelinase activities. The majority of Bacillus isolates identified by the present study poses a potential risk of food poisoning due to the prevalence of toxin genes found.

Additional file 1: Table S1. Primers of resistance genes. Table S2. Primers of virulence genes. Figure S1. Microbial population present in tropical shrimps.

Background: Information on severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spread in Africa is limited by fragile surveillance systems and insufficient diagnostic capacity. Methods: We assessed the coronavirus disease-19 (COVID-19)-related diagnostic workload in Benin, Western Africa, characterized SARS-CoV-2 genomes from 12 acute cases of COVID-19, used those together with public data to estimate SARS-CoV-2 transmission dynamics in a Bayesian framework, validated a widely used diagnostic dual target RT-PCR kit donated to African countries, and conducted serological analyses in 68 sera from confirmed COVID-19 cases and from febrile patients sampled before the predicted SARS-CoV-2 introduction. Findings: We found a 15-fold increase in the monthly laboratory workload due to COVID-19. Genomic surveillance showed introductions of three distinct SARS-CoV-2 lineages. SARS-CoV-2 genome-based analyses yielded an R0 estimate of 4.4 (95% confidence interval: 2.0-7.7), suggesting intense spread of SARS-CoV-2 in Africa. RT-PCR-based tests were highly sensitive but showed variation of internal controls and between diagnostic targets. Commercially available SARS-CoV-2 ELISAs showed up to 25% false-positive results depending on antigen and antibody types, likely due to unspecific antibody responses elicited by acute malaria according to lack of SARS-CoV-2-specific neutralizing antibody responses and relatively higher parasitemia in those sera. Interpretation: We confirm an overload of the diagnostic capacity in Benin and provide baseline information on the usability of genome-based surveillance in resource-limited settings. Sero-epidemiological studies needed to assess SARS-CoV-2 spread may be put at stake by low specificity of tests in tropical settings globally. The increasing diagnostic challenges demand continuous support of national and supranational African stakeholders. Funding: This work was supported by the Deutsche Gesellschaft fur Internationale Zusammenarbeit (GIZ) GmbH. Declaration of Interests: The authors declare no conflict of interests. Ethics Approval Statement: This study was approved by the ethics committee of the Ministry of Health (Arrete 2020 No. 030/MS/DC/SGM/DNSP/CJ/SA/027SGG2020) and followed the Declaration of Helsinki. Written consent was obtained from all the patients participating in the study.

Background: Biological larviciding is an additional tool that can help address the current dilemma in malaria control, namely vector resistances to pyrethroids and shifting of biting activity to times when people are not protected. Although malaria interventions primarily target Anopheles mosquitoes, there might be an impact on populations of other mosquito genera that share the same breeding sites. In this study we research to what extent Culex and Aedes mosquitoes, the primary vectors of numerous zoonotic diseases, are affected by larviciding interventions against malaria mosquitoes. Methods: We researched the impact of different larviciding choices with Bacillus thuringiensis israelensis on non-target mosquitoes in 127 rural villages and a semi-urban town in a health district in Northwestern Burkina Faso. All villages were distributed into a total of three study arms with different larviciding choices: full, selective and untreated control. Geographically close villages were distributed into clusters to avoid contamination between treated and untreated villages. Adult mosquitoes were captured in light traps inside and outside houses during the rainy seasons of a baseline and an intervention year. A negative binomial regression was used to determine the reductions achieved through larviciding among different mosquito genera.Results: Larviciding interventions against malaria showed only limited or no impact against Culex mosquitoes, while against Aedes, reductions of up to 34% were achieved when all detected breeding sites in the public space were treated. While the semi-urban setting showed high abundance of Culex, in the rural villages we captured more Aedes. Conclusions: Future larviciding programs should be evaluated for including the treatment of Aedes and Culex breeding habitats. Since the major cost components of such programs are labor and transport, other disease vectors could be targeted at little additional cost.

Au Benin, la diversite bioclimatique du sud forestier au nord savanicole induit des facies de transmission de paludisme tres varie. Mais peu de travaux ont ete realises sur la transmission du paludisme en zone de savane seche au nord du pays. C’est dans ce cadre qu’une etude sur la variation saisonniere de la transmission du paludisme en prelude a la mise en place d’une Pulverisation Intra Domiciliaire (PID) a grande echelle dans la commune de Corpargo au Nord-Est du Benin a ete initiee. Dans un premier temps, des captures de moustiques sur appât humain ont ete effectuees dans deux villages a un rythme de 2 nuits consecutives par mois. Ces captures sur appât humain ont ete completees par des captures au pyrethre effectuees a l’interieur des maisons et ceci 2 fois par mois dans 10 habitations choisies egalement dans les memes zones de capture afin de connaitre la diversite de la faune culicidienne. Dans un deuxieme temps, le thorax des moustiques captures sur appât humain a ete utilise pour rechercher la positivite en proteines Circum sporozoite (CS) de Plasmodium falciparum par la methode de titrage immunoenzymatique (ELISA-CSP). Cette etude a revele la presence de plusieurs especes de moustiques dont Anopheles gambiae s.s (30% de la population collectee) avec une densite agressive moyenne mensuelle de 3,65 piqures par homme et par nuit. Cette espece de An. gambiae retrouvee est responsable de la transmission du paludisme tout au long de l’annee. Cette etude montre une fois encore que An. gambiae s.s reste le principal vecteur de la transmission du paludisme avec de fortes densites agressives dans cette commune. Ces donnees de base seront d’une grande utilite dans la mise en place des strategies de la PID, gage de la reduction du taux de mortalite dȗ au paludisme dans cette region. Mots cles: Anopheles gambiae , paludisme, transmission, Copargo, Benin.

Thanks to recent advances in random amplification technologies, metagenomic surveillance expanded the number of novel, often unclassified viruses within the family Rhabdoviridae. Using a vector-enabled metagenomic (VEM) tool, we identified a novel rhabdovirus in Aedes cantans mosquitoes collected from Germany provisionally named Ohlsdorf virus (OHSDV). The OHSDV genome encodes the canonical rhabdovirus structural proteins (N, P, M, G and L) with alternative ORF in the P gene. Sequence analysis indicated that OHSDV exhibits a similar genome organization and characteristics compared to other mosquito-associated rhabdoviruses (Riverside virus, Tongilchon virus and North Creek virus). Complete L protein based phylogeny revealed that all four viruses share a common ancestor and form a deeply rooted and divergent monophyletic group within the dimarhabdovirus supergroup and define a new genus, tentatively named Ohlsdorfvirus. Although the Ohlsdorfvirus clade is basal within the dimarhabdovirus supergroup phylogeny that includes genera of arthropod-borne rhabdoviruses, it remains unknown if viruses in the proposed new genus are vector-borne pathogens. The observed spatiotemporal distribution in mosquitoes suggests that members of the proposed genus Ohlsdorfvirus are geographically restricted/separated. These findings increase the current knowledge of the genetic diversity, classification and evolution of this virus family. Further studies are needed to determine the host range, transmission route and the evolutionary relationships of these mosquito-associated viruses with those infecting vertebrates.

La lutte anti-vectorielle basee sur l’utilisation des rideaux impregnes (RII) au cours des deux dernieres decennies a permis de reduire le fardeau du paludisme dans bon nombre de pays africains. A l’heure actuelle ou Anopheles gambiae , principal vecteur du paludisme en Afrique a developpe une resistance vis-a-vis des insecticides recommandes par l’Organisation Mondiale de la Sante (OMS), est-il opportun d’introduire ces RIIs dans les pays endemiques du paludisme comme le Benin? C’est pour repondre a cette question que le present travail a ete realise pour evaluer l’efficacite des RIIs qui seront destines aux populations. Dans un premier temps, les RIIs ont ete soumis au test en cone et en tunnel suivant le protocole de l’OMS ou 24 heures apres, les taux de mortalite de la souche sensible de An. gambiae kisumu et de la population sauvage en provenance de Ladji ont ete compares a la valeur standard de l’OMS. Dans un deuxieme temps, nous avons evalue l’efficacite des RIIs en fonction des savons et des frequences de lavage. Il ressort des travaux que les resultats des bioessais des tests en cone ont montre que la mortalite induite apres un contact de 3min est de 48,85% avec la souche sensible Kisumu et 6,96% pour la population sauvage Ladji. Aussi, l’efficacite des rideaux a donne 65,5% de taux de mortalite avec la souche de Kisumu et 40% pour la population sauvage de terrain Ladji. Tous les savons utilises (klin, fanico, palmida, kogui et koto) ont provoque une baisse d’efficacite des RIIs a partir du 1er lavage. Des resultats obtenus de cette etude, il ressort que les rideaux impregnes a la bifenthrine ont ete peu efficaces comme moyen de lutte contre le paludisme. Dans un contexte de resistance des vecteurs du paludisme aux insecticides, l’introduction de rideaux impregnes aux pyrethrinoides ne jouerait aucun role de barriere chimique pour limiter ou reduire la transmission du paludisme. Il serait souhaitable d’eviter la vulgarisation de tel outil dans la lutte contre le paludisme. Mots cles : Rideaux impregnes, Anopheles gambiae, efficacite, savon, Benin.

Anopheles gambiae sensu stricto Giles (formerly A. gambiae S molecular form), the largely anthropophilic species, is reportedly the most important malaria vector in Uganda among the A. gambiae complex species. Indoor and outdoor human-biting mosquitoes were caught for four consecutive nights in each of 48 households in Kamuli district using human-baited bed net traps for subsequent identification of the principal Anopheles sibling species responsible for transmitting malaria. Sibling species under the A. gambiae complex were characterized by polymerase chain reaction using species specific single nucleotide polymorphism (SNPs) in the intergenic spacer region (IGS) with primers specific for A. gambiae s.s., Anopheles arabiensis, Anopheles melas, Anopheles merus and Anopheles quadriannulatus . Molecular forms of the A. gambiae s.s. were further discriminated using primers specific for Mopti and Savannah forms. Out of 300 A. gambiae s.l. amplified, 98% (n= 294) were A. gambiae s.s. Out of 142 A. gambiae s.s. samples analyzed for molecular forms, 78.9% (n=112) were identified as A. gambiae s.s. Giles ( A. gambiae Savannah (S) form, while the other 21.1% were not identifiable. the presence of A. gambiae s.s. Giles in Kamuli was also reported. Considering the anthropophilic, endophagic and endophilic behavior of A. gambiae s.s. (and of the molecularly similar A. gambiae s.s. Giles), the combined use of insecticide-treated nets (ITNs), indoor residual spraying, larval source management and improved house design in the context of integrated vector management, may be the appropriate vector control strategies in the area. There is also need for regular monitoring of the vector species composition, distribution and behavior for proper planning of appropriate vector control interventions in the future. Key words : Sibling species, molecular forms, Anopheles gambiae complex, anthropophily, IPM.

Background Since 2008, the National Malaria Control Program (NMCP) has been engaged in the implementation of indoor residual spraying (IRS) in Benin. The first and second round was a success with a drastic decrease of malaria transmission in areas under IRS. We present here the results of the third round. The purpose of this study was to compare the results of the third round of IRS to those achieved during the first two rounds. A second success of IRS will enable the Government of Benin to extend the strategy to other areas. Methods Mosquito collections were carried out in the department of Ouémé where the homes of four districts were treated with bendiocarb. In these districts, more than 350 000 inhabitants were protected by IRS. A fifth untreated district served as control. In the five districts, mosquito collections were organized to follow the dynamics of malaria transmission and possible changes in the behavior of mosquitoes. Results A significant reduction in human biting rate was recorded after the third round of IRS, specifically in Adjohoun (89.78%), Dangbo (56.8%) and Missérété (93.22%) where an inhabitant received less than 2 bites of An. gambiae per night. During this same time, the entomological inoculation rate (EIR) declined dramatically in all areas under intervention (74.26% reduction). We also noted a significant reduction in longevity, the blood feeding rate of the vectors and an increase in exophily induced by bendiocarb on An. gambiae and Mansonia spp. Conclusion The present study showed, once again, the effectiveness of bendiocarb on anopheles populations resistant to pyrethroids. This product can be recommended in combination with other insecticides for the management of vector resistance to insecticides.

Background In many parts of Africa as in Benin, the main strategies of vector control are based on the scaling-up of Long Lasting Insecticide Treated Nets (LLITNs) and indoor residual spraying (IRS). The need to understand the biological implications of IRS in large scale and full coverage of LLITNs is paramount. It is in this context that the present study was conducted. It aims to evaluate the effect of a large scale IRS using a non-pyrethroid insecticide and full coverage of deltamethrin treated nets on the behavior of An. gambiae s.l. in the intervention areas compared to untreated areas used as controls. Methods Mosquitoes were collected using human landing catches, pyrethrum spray catches and window exit traps to assess reduction of entry rate, endophily rate, endophagy rate and overall mortality rate in natural populations of An. gambiae s.l. before IRS and LLITNs intervention (2007) and after in 2008 and 2010. Results In the IRS arm, endophily rate was 67.13% before intervention and 4.5% after intervention, whereas in the control arm it was stable at 51.67% (P > 0 .05). In the LLITN arm endophily rates also decreased after intervention. After the IRS, no gravid mosquitoes were collected from all treated localities, but LLITN performance was not that spectacular. The proportion of mosquitoes biting indoors in the IRS arm decreased from 67.09% before intervention to 42.85% after intervention, compared to a low but significant decrease (71.31% to 57. 46%) in the LLITN arm. The use of vector control tools and behavior of the host would be the main factors that modify the behavior of taking a human blood meal observed on An. gambiae s.l. inside human dwellings. Conclusion The impact on the behavior of An. gambiae s.l. observed with the bendiocarb used in IRS was highly effective compared with the free distribution of LLITNs in terms of mortality and the decrease of proportions of indoor feeding. Despite this efficacy, there is a need for complementary tools and research of alternative strategy oriented on effective health education, and the use of powerful tools such as IRS, LLITNs, larviciding and repellents.

Introduction: To overcome the problems of periodic re-impregnation of mosquito nets and low rates of treatment, the commune of Aguegues was chosen to evaluate the effects of Olyset® nets on malaria transmission and against An. gambiae. Methods: 87 old Olyset® nets installed five years ago were identified in the village ‘Akpadon’. 10 untreated nets were installed in 10 structures of type “a bedroom and parlour” in the village ‘Akodji’. Four rooms without nets were identified in the village ‘Donoukpa’. Entomological and epidemiological evaluations were conducted during the May to October 2011. 24 sessions of capture or 2088 men-nights resulted in the capture of 30,608 mosquitoes. Results: The entrance of anopheles was significantly reduced in the village with Olyset® nets. 45% of mosquitoes captured inside rooms with Olyset® nets were found dead after 24 hrs of obser¬vation. Overall, parasitemia was very low in the treated village (4.52%). 18 (4.64%) cases of malaria fever were from Akpadon with 7.5% positive blade smear, 29 (10.98%) were from Akodji with 8.37% positive blade smear, and 80 (95.23%) come from Donoukpa with 38.09% positive blade smear. The Olyset® nets and untreated net were adjusted hemoglobin levels. Conclusion: Olyset® net had a very high knock down effect and is an alternative in malaria control., BioImpacts; ISSN 2228-5660

Background Pyrethroid insecticides, carbamate and organophosphate are the classes of insecticides commonly used in agriculture for crop protection in Benin. Pyrethroids remain the only class of insecticides recommended by the WHO for impregnation of bed nets. Unfortunately, the high level of pyrethroid resistance in Anopheles gambiae s.l., threatens to undermine the success of pyrethroid treated nets. This study focuses on the investigation of agricultural practices in cotton growing areas, and their direct impact on larval populations of An. gambiae in surrounding breeding sites. Methods The protocol was based on the collection of agro-sociological data where farmers were subjected to semi-structured questionnaires based on the strategies used for crop protection. This was complemented by bioassay tests to assess the susceptibility of malaria vectors to various insecticides. Molecular analysis was performed to characterize the resistance genes and the molecular forms of An. gambiae. Insecticide residues in soil samples from breeding sites were investigated to determine major factors that can inhibit the normal growth of mosquito larvae by exposing susceptible and resistant laboratory strains. Results There is a common use by local farmers of mineral fertilizer NPK at 200 kg/ha and urea at 50 kg/hectare following insecticide treatments in both the Calendar Control Program (CCP) and the Targeted Intermittent Control Program (TICP). By contrast, no chemicals are involved in Biological Program (BP) where farmers use organic and natural fertilizers which include animal excreta. Susceptibility test results confirmed a high resistance to DDT. Mean mortality of An. gambiae collected from the farms practicing CCP, TICP and BP methods were 33%, 42% and 65% respectively. An. gambiae populations from areas using the CCP and TICP programs showed resistance to permethrin with mortality of 50% and 58% respectively. By contrast, bioassay test results of An. gambiae from BP areas gave a high level of susceptibility to permethrin with an average mortality of 94%. Molecular analysis identified An. gambiae s.s, and An. arabiensis with a high predominance of An. gambiae s.s (90%). The two molecular forms, M and S, were also determined with a high frequency of the S form (96%). The Kdr gene seemed the main target- site resistance mechanism detected in CCP, TICP, and BP areas at the rates ranging from 32 to 78%. The frequency of ace-1R gene was very low (< 0.1). The presence of inhibiting factors in soil samples under insecticide treatments were found and affected negatively in delaying the development of An. gambiae larval populations. Conclusions This research shows that Kdr has spread widely in An. gambiae, mainly in CCP and TICP areas where pyrethroids are extensively used. To reduce the negative impact of pesticides use in cotton crop protection, the application of BP-like programs, which do not appear to select for vector resistance would be useful. These results could serve as scientific evidence of the spread of resistance due to a massive agricultural use of insecticides and contribute to the management of pesticides usage on cotton crops hence reducing the selection pressure of insecticides on An. gambiae populations.

Background Anopheles gambiae, the main malaria vector in Benin has developed high level of resistance to pyrethroid insecticides, which is a serious concern to the future use of long-lasting insecticidal nets (LLIN) and indoor residual spraying (IRS). In this context, one of the pathways available for malaria vector control would be to investigate alternative classes of insecticides with different mode of action than that of pyrethroids. The goal of this study was to evaluate under field conditions the efficacy of a carbamate (bendiocarb) and an organophosphate (fenitrothion) against pyrethroid-resistant An. gambiae s.s. Methods Wild populations and females from laboratory colonies of five days old An. gambiae were bio-assayed during this study. Two pyrethroids (deltamethrin and alphacypermethrin), an organophosphate (fenitrothion), a carbamate (bendiocarb) and a mixture of an organophosphate (chlorpyriphos + a pyrethroid deltamethrin) were compared in experimental huts as IRS treatments. Insecticides were applied in the huts using a hand-operated compression sprayer. The deterrency, exophily, blood feeding rate and mortality induced by these insecticides against An. gambiae were compared to the untreated control huts. Results Deltamethrin, alphacypermethrin and bendiocarb treatment significantly reduced mosquito entry into the huts (p < 0.05) compared to untreated huts. Blood feeding rates in huts treated with fenitrothion and the mixture chlorpyriphos/deltamethrin were reduced from 10.95% respectively to 3.7% and 4.47% three months after treatment and from 10.20% to 4.4% and 2.04% four months after treatment. Exophily rates in huts with deltamethrin, alphacypermethrin and the mixture chlorpyriphos/deltamethrin were significantly higher than in the huts with fenitrothion. Deltamethrin and alphacypermethrin had the lowest mortality rate while fenitrothion killed 100% of An. gambiae (in the first month) and 77.8% (in the fourth month). Bendiocarb and the mixture chlorpyriphos/deltamethrin mortality rates ranged from 97.9 to 100% the first month and 77.7-88% the third month respectively. Conclusion After four months, fenitrothion, bendiocarb and the mixture chlorpyriphos/deltamethrin performed effectively against pyrethroid-resistant Anopheles. These results showed that bendiocarb could be recommended as an effective insecticide for use in IRS operations in Benin, particularly as the mixture chlorpyriphos/deltamethrin does not have WHOPES authorization and complaints were mentioned by the sleepers about the safety and smell of fenitrothion.

Background The emergence of pyrethroid resistance in Anopheles gambiae has become a serious concern to the future success of malaria control. In Benin, the National Malaria Control Programme has recently planned to scaling up long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) for malaria prevention. It is, therefore, crucial to monitor the level and type of insecticide resistance in An. gambiae, particularly in southern Benin where reduced efficacy of insecticide-treated nets (ITNs) and IRS has previously been reported. Methods The protocol was based on mosquito collection during both dry and rainy seasons across forty districts selected in southern Benin. Bioassay were performed on adults collected from the field to assess the susceptibility of malaria vectors to insecticide-impregnated papers (permethrin 0.75%, delthamethrin 0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. The species within An. gambiae complex, molecular form and presence of kdr and ace-1 mutations were determined by PCR. Results Strong resistance to permethrin and DDT was found in An. gambiae populations from southern Benin, except in Aglangandan where mosquitoes were fully susceptible (mortality 100%) to all insecticides tested. PCR showed the presence of two sub-species of An. gambiae, namely An. gambiae s.s, and Anopheles melas, with a predominance for An. gambiae s.s (98%). The molecular M form of An. gambiae was predominant in southern Benin (97%). The kdr mutation was detected in all districts at various frequency (1% to 95%) whereas the Ace-1 mutation was found at a very low frequency (≤ 5%). Conclusion This study showed a widespread resistance to permethrin in An. gambiae populations from southern Benin, with a significant increase of kdr frequency compared to what was observed previously in Benin. The low frequency of Ace-1 recorded in all populations is encouraging for the use of bendiocarb as an alternative insecticide to pyrethroids for IRS in Benin.

International audience; We report two outbreaks of Lassa fever that occurred in Benin in 2014 and 2016 with 20 confirmed cases and 50% (10/20) mortality. Benin was not previously considered to be an endemic country for Lassa fever, resulting in a delay to diagnose the disease and its human transmission. Molecular investigations showed the viral genomes to be similar to that of the Togo strain, which is genetically very different from other known strains and confirms the existence of a new lineage. Endemic circulation of Lassa virus in a new territory and the genetic diversity thus confirm that this virus represents a growing threat for West African people. Given the divergence of the Benin strain from the prototypic Josiah Sierra Leone strain frequently used to generate vaccine candidates, the efficacy of vaccine candidates should also be demonstrated with this strain.

Background Urban agricultural practices are expanding in several cities of the Republic of Benin. This study aims to assess the impact of such practices on transmission of the malaria parasite in major cities of Benin. Method A cross sectional entomological study was carried out from January to December 2009 in two vegetable farming sites in southern Benin (Houeyiho and Acron) and one in the northern area (Azèrèkè). The study was based on sampling of mosquitoes by Human Landing Catches (HLC) in households close to the vegetable farms and in others located far from the farms. Results During the year of study, 71,678 female mosquitoes were caught by HLC of which 25% (17,920/71,678) were Anopheles species. In the areas surveyed, the main malaria parasite, Plasmodium falciparum was transmitted in the south by Anopheles gambiae s.s. Transmission was high during the two rainy seasons (April to July and October to November) but declined in the two dry seasons (December to March and August to September). In the north, transmission occurred from June to October during the rainy season and was vehicled by two members of the An. gambiae complex: Anopheles gambiae s.s. (98%) and Anopheles arabiensis (2%). At Houeyiho, Acron and Azèrèkè, the Entomological Inoculation Rates (EIRs) and the Human Biting Rates (HBRs) were significantly higher during the dry season in Households Close to Vegetable Farms (HCVF) than in those located far from the vegetable areas (HFVF) (p < 0.05.). However, there were no significant differences in HBRs or EIRs between HCFV and HFVF during the rainy seasons at these sites (p > 0.05). The knock-down resistance (kdr) mutation was the main resistance mechanism detected at high frequency (0.86 to 0.91) in An. gambiae s.l. at all sites. The ace-1R mutation was also found but at a very low frequency (< 0.1). Conclusion These findings showed that communities living close to vegetable farms are permanently exposed to malaria throughout the year, whereas the risk in those living far from such agricultural practices is limited and only critical during the rainy seasons. Measures must be taken by African governments to create awareness among farmers and ultimately decentralize farming activities from urban to rural areas where human-vector contact is limited.

Background A fast development of urban agriculture has recently taken place in many areas in the Republic of Benin. This study aims to assess the rapid expansion of urban agriculture especially, its contribution to the emergence of insecticide resistance in populations of Anopheles gambiae. Methods The protocol was based on the collection of sociological data by interviewing vegetable farmers regarding various agricultural practices and the types of pesticides used. Bioassay tests were performed to assess the susceptibility of malaria vectors to various agricultural insecticides and biochemical analysis were done to characterize molecular status of population of An. gambiae. Results This research showed that: (1) The rapid development of urban agriculture is related to unemployment observed in cities, rural exodus and the search for a balanced diet by urban populations; (2) Urban agriculture increases the farmers' household income and their living standard; (3) At a molecular level, PCR revealed the presence of three sub-species of An. gambiae (An. gambiae s.s., Anopheles melas and Anopheles arabiensis) and two molecular forms (M and S). The kdr west mutation recorded in samples from the three sites and more specifically on the M forms seems to be one of the major resistance mechanisms found in An. gambiae from agricultural areas. Insecticide susceptibility tests conducted during this research revealed a clear pattern of resistance to permethrin (76% mortality rate at Parakou; 23.5% at Porto-Novo and 17% at Cotonou). Conclusion This study confirmed an increase activity of the vegetable farming in urban areas of Benin. This has led to the use of insecticide in an improper manner to control vegetable pests, thus exerting a huge selection pressure on mosquito larval population, which resulted to the emergence of insecticide resistance in malaria vectors.