Semi-field studies to better understand the impact of eave tubes on mosquito mortality and behaviour

Background: Eave tubes are a type of housing modification that provide a novel way of delivering insecticides to mosquitoes as they attempt to enter the house. The current study reports on a series of semi-field studies aimed at improving the understanding of how eave tubes might impact mosquito mortality and behaviour. Methods: Experiments were conducted using West African style experimental huts at a field site in M'be, Côte d'Ivoire. Huts were modified in various ways to determine: (i) whether mosquitoes in this field setting naturally recruit to eave tubes; (ii) whether eave tubes can reduce house entry even in the absence of screening; (iii) whether mosquitoes suffer mortality if they attempt to exit a house via treated eave tubes; and, (iv) whether screening and eave tubes might deflect mosquitoes into neighbouring houses without the intervention. Results: Ninety percent more mosquitoes (Anopheles gambiae sensu lato, and other species) entered huts through open eaves tubes compared to window slits. The addition of insecticide-treated eave tubes reduced mosquito entry by 60%, even when windows remained open. Those mosquitoes that managed to enter the huts exhibited a 64% reduction in blood feeding and a tendency for increased mortality, suggesting contact with insecticide-treated inserts prior to hut entry. When An. gambiae mosquitoes were deliberately introduced into huts with treated eave tubes, there was evidence of six times increase in overnight mortality, suggesting mosquitoes can contact treated eave tube inserts when trying to exit the hut. There was no evidence for deflection of mosquitoes from huts with screening, or screening plus eave tubes, to adjacent unmodified huts. Conclusions: Eave tubes are a potentially effective way to target Anopheles mosquitoes with insecticides. That treated eave tubes can reduce mosquito entry even when windows are open is a potentially important result as it suggests that eave tubes might not need to be combined with household screening to have an impact on malaria transmission. The absence of deflection is also a potentially important result as coverage of eave tubes and/or screening is unlikely to be 100% and it is important that households that do not have the technology are not disadvantaged by those that do

Semi-field evaluation of the cumulative effects of a "lethal House Lure" on malaria mosquito mortality

Background: There is growing interest in the potential to modify houses to target mosquitoes with insecticides or repellents as they search for human hosts. One version of this 'Lethal House Lure' approach is the In2Care® EaveTube, which consists of a section of polyvinyl chloride (PVC) pipe fitted into a closed eave, with an insert comprising electrostatic netting treated with insecticide powder placed inside the tube. Preliminary evidence suggests that when combined with screening of doors and windows, there is a reduction in entry of mosquitoes and an increase in mortality. However, the rate of overnight mortality remains unclear. The current study used a field enclosure built around experimental huts to investigate the mortality of cohorts of mosquitoes over multiple nights. Methods: Anopheles gambiae sensu lato mosquitoes were collected from the field as larvae and reared through to adult. Three-to-five days old adult females were released inside an enclosure housing two modified West African style experimental huts at a field site in M'be, Côte d'Ivoire. Huts were either equipped with insecticide-treated tubes at eave height and had closed windows (treatment) or had open windows and open tubes (controls). The number of host-seeking mosquitoes entering the huts and cumulative mortality were monitored over 2 or 4 days. Results: Very few (0-0.4%) mosquitoes were able to enter huts fitted with insecticide-treated tubes and closed windows. In contrast, mosquitoes continually entered the control huts, with a cumulative mean of 50-80% over 2 to 4 days. Baseline mortality with control huts was approximately 2-4% per day, but the addition of insecticide-treated tubes increased mortality to around 25% per day. Overall cumulative mortality was estimated to be up to 87% over 4 days when huts were fitted with tubes. Conclusion: Only 20-25% of mosquitoes contacted insecticide-treated tubes or entered control huts in a given night. However, mosquitoes continue to host search over sequential nights, and this can lead to high cumulative mortality over 2 to 4 days. This mortality should contribute to community-level reduction in transmission assuming sufficient coverage of the intervention

Distribution du zooplancton en relation avec les caractéristiques environnementales de quatre rivières côtières du Sud-est de la Côte d’Ivoire (Afrique de l’ouest)

Objectifs: Cette étude vise à déterminer la distribution spatio temporelle du zooplancton en relation avec les caractéristiques environnementales dans quatre rivières côtières du Sud-est de la Côte d’Ivoire.Méthode et résultats: Le zooplancton a été échantillonné mensuellement de mars 2012 à février 2013 à l’aide d’un filet à plancton de 64 Gm de vide de maille. Au total 28 taxons ont été observés (15 Rotifères, 6 Copépodes, 4 Cladocères et 3 autres organismes). Les Rotifères constituent le groupe dominant avec 67% de l’abondance totale. Rotaria sp. est le taxon le plus abondant (52%). Globalement, la richesse taxonomique et l’abondance les plus faibles ont été enregistrées dans les rivières recevant les effluents d’unité agroindustrielles de palmier à huile (Ehania, Boulo1). Les résultats de l’analyse de redondance (RDA) montrent que les variables Influençant fortement la diversité taxonomique et l’abondance sont la vitesse du courant, la conductivité, la température, le taux de fermeture de la canopée et la proportion des débris végétaux.Conclusion et application: Cette étude à permis de déterminer l’influence des variables environnementales sur la distribution du zooplancton dans 4 rivières côtières du Sud-est de la Côte d’Ivoire et confirme la possibilité d’utiliser Rotaria sp. comme indicateur de pollution.Mots clés: Zooplancton, diversité, abondance, effluents industrielsEnglish Title: Distribution of zooplankton in relation with environmental characteristics of four coastal rivers in South-Eastern Côte d’Ivoire (West Africa)English AbstractObjectives: This study aims to determine the distribution of zooplankton in relation with environmental variables in four coastal rivers in South East Côte d’Ivoire.Method and results: Zooplankton samples were collected monthly from March 2012 to February 2013 in six sampling sites with a cylindro-conical net of 64-Gm mesh-size. 28 taxa of zooplankton belonging to Rotifera (15 taxa), Copepoda (6 taxa), Cladoceran (4 taxa) and others zooplankton (3) were identified. Rotifers constituted the most abundant group (67%). Rotaria sp. was the most abundant taxa (52% of total abundance). Overall, taxa diversity and abundance were lower in rivers receiving palm oil mill effluents in their catchment area. The ReDundancy Analysis (RDA) performed showed that environmental variables such as current velocity, conductivity, water temperature, canopy closure and vegetal debris occurrence influence strongly diversity and abundance of zooplankton.Conclusion and application: This study allowed to identify environmental factors, which influence the distribution of zooplankton taxa and show the possibility to use Rotaria sp. as pollution indicator.Keywords: Zooplankton, diversity, abundance, industrial effluent

Mapping insecticide resistance in Anopheles gambiae (s.l.) from Côte d’Ivoire

Abstract Background Insecticide resistance in malaria vectors is an increasing threat to vector control tools currently deployed in endemic countries. Resistance management must be an integral part of National Malaria Control Programmes’ (NMCPs) next strategic plans to alleviate the risk of control failure. This obviously will require a clear database on insecticide resistance to support the development of such a plan. The present work gathers original data on insecticide resistance between 2009 and 2015 across Côte d’Ivoire in West Africa. Methods Two approaches were adopted to build or update the resistance data in the country. Resistance monitoring was conducted between 2013 and 2015 in 35 sentinel sites across the country using the WHO standard procedure of susceptibility test on adult mosquitoes. Four insecticide families (pyrethroids, organochlorides, carbamates and organophosphates) were tested. In addition to this survey, we also reviewed the literature to assemble existing data on resistance between 2009 and 2015. Results High resistance levels to pyrethroids, organochlorides and carbamates were widespread in all study sites whereas some Anopheles populations remained susceptible to organophosphates. Three resistance mechanisms were identified, involving high allelic frequencies of kdr L1014F mutation (range = 0.46–1), relatively low frequencies of ace-1 R (below 0.5) and elevated activity of insecticide detoxifying enzymes, mainly mixed function oxidases (MFO), esterase and glutathione S-transferase (GST) in almost all study sites. Conclusion This detailed map of resistance highlights the urgent need to develop new vector control tools to complement current long-lasting insecticidal nets (LLINs) although it is yet unclear whether these resistance mechanisms will impact malaria transmission control. Researchers, industry, WHO and stakeholders must urgently join forces to develop alternative tools. By then, NMCPs must strive to develop effective tactics or plans to manage resistance keeping in mind country-specific context and feasibility

Selection for immune evasion in SARS-CoV-2 revealed by high-resolution epitope mapping and sequence analysis

Summary: Here, we exploit a deep serological profiling strategy coupled with an integrated, computational framework for the analysis of SARS-CoV-2 humoral immune responses. Applying a high-density peptide array (HDPA) spanning the entire proteomes of SARS-CoV-2 and endemic human coronaviruses allowed identification of B cell epitopes and relate them to their evolutionary and structural properties. We identify hotspots of pre-existing immunity and identify cross-reactive epitopes that contribute to increasing the overall humoral immune response to SARS-CoV-2. Using a public dataset of over 38,000 viral genomes from the early phase of the pandemic, capturing both inter- and within-host genetic viral diversity, we determined the evolutionary profile of epitopes and the differences across proteins, waves, and SARS-CoV-2 variants. Lastly, we show that mutations in spike and nucleocapsid epitopes are under stronger selection between than within patients, suggesting that most of the selective pressure for immune evasion occurs upon transmission between hosts