The sticky resting box, a new tool for studying resting behaviour of Afrotropical malaria vectors

Background: Monitoring densities of adult mosquito populations is a major challenge in efforts to evaluate the epidemiology of mosquito-borne diseases, and their response to vector control interventions. In the case of malaria, collection of outdoor-resting Anophelines is rarely incorporated into surveillance and control, partially due to the lack of standardized collection tools. Such an approach, however, is increasingly important to investigate possible changes in mosquito behaviour in response to the scale up of Insecticide Treated Nets and Indoor Residual Spraying. In this study we evaluated the Sticky Resting Box (SRB) - i.e. a sticky variant of previously investigated mosquito Resting Box, which allows passive collection of mosquitoes entering the box – and compared its performance against traditional methods for indoor and outdoor resting mosquito sampling.<p></p> Methods: Daily collections were carried out in two neighbouring villages of Burkina Faso during rainy season 2011 and dry season 2012 by SRB located indoors and outdoors, and by Back-Pack aspiration inside houses (BP) and in ad hoc built outdoor pit-shelters (PIT).<p></p> Results: Overall, almost 20,000 Culicidae specimens belonging to 16 species were collected and morphologically identified. Malaria vectors included Anopheles coluzzii (53%), An. arabiensis (12%), An. gambiae s.s. (2.0%) and An. funestus (4.5%). The diversity of species collected in the two villages was similar for SRB and PIT collections outdoors, and significantly higher for SRB than for BP indoors. The population dynamics of An. gambiae s.l. mosquitoes, as obtained by SRB-collections was significantly correlated with those obtained by the traditional methods. The predicted mean estimates of An. gambiae s.l. specimens/sampling-unit/night-of-collections was 6- and 5-times lower for SRB than for BP indoors and PIT outdoors, respectively.<p></p> Conclusions: Overall, the daily performance of SRB in terms of number of malaria vectors/trap was lower than that of traditionally used approaches for in- and outdoor collections. However, unlike these methods, SRB could be set up to collect mosquitoes passively over at least a week. This makes SRB a promising tool for passively monitoring anopheline resting populations, with data presented here providing guidance for how to set up SRB-based collections to acquire information comparable to those obtained with other methods.<p></p&gt

Challenges and opportunities associated with the introduction of next generation long lasting insecticidal nets for malaria control: a case study from Burkina Faso.

BACKGROUND Reductions in malaria incidence in Africa can largely be attributed to increases in malaria vector control activities; predominately the use of long lasting insecticidal nets (LLINs). With insecticide resistance affecting an increasing number of malaria endemic countries and threatening the effectiveness of conventional LLINs, there is an increasing urgency to implement alternative tools that control these resistant populations. The aim of this study was to identify potential challenges and opportunities for accelerating access to next generation LLINs in Burkina Faso, a country with areas of high levels of insecticide resistance. METHODS An analytical framework was used to guide the selection of interviewees, data collection and analysis. Semi structured interviews were carried out with key informants in April 2014 in Burkina Faso. Interviews were conducted in French and English, audio recorded, transcribed and entered into NVivo10 for data management and analysis. Data were coded according to the framework themes and then analysed to provide a description of the key points and explain patterns in the data. RESULTS Interviewees reported that the policy architecture in Burkina Faso is characterised by a strong framework of actors that contribute to policymaking and strong national research capacity which indirectly contributes to national policy change via collaboration with internationally led research. Financing significantly impacts the potential adoption, availability and affordability of next generation LLINs. This confers significant power on international donors that fund vector control. National decisions around which LLINs to procure were restricted to quantity and delivery dates; the potential to tackle insecticide resistance was not part of the decision-making process. Furthermore, at the time of the study there was no World Health Organisation (WHO) guidance on where and when next generation LLINs might positively impact on malaria transmission, severely limiting their adoption, availability and affordability. CONCLUSIONS This study shows that access to next generation LLINs was severely compromised by the lack of global guidance. In a country like Burkina Faso where WHO recommendations are relatively quickly adopted, a clear WHO recommendation and adequate financing will be key to accelerate access to next generation LLINs. Key Words: Malaria, Next generation long lasting insecticidal nets, LLINs, PBO nets, Policy Analysis, Vector Control, Burkina Faso

Biological activities of four essential oils against Anopheles gambiae in Burkina Faso and their in vitro inhibition of acetylcholinesterase

The control of malaria is still a challenge partly due to mosquito’s resistance to current available insecticides. The aim of this work was to evaluate the ovicidal, larvicidal and repellent activities of Lantana camara, Hyptis suaveolens, Hyptis spicigera and Ocimum canum essential oils against  Anopheles gambiae s.l.  according to the World Health Organization standard method. The in vitro acetylcholinesterase inhibition activity of these oils was also evaluated. The repellent effect using the method of “separated arms” was evaluated. Lantana camara oil was more effective on both eggs and larvae. The LD50 and LD90 values observed in this oil solution were respectively 53.59 and 170.89 ppm on eggs whereas LD50 and LD90 were 61 and 125 ppm respectively on larvae. All oils exhibited repellent activities against adult mosquitoes. The most effective repellent was the oil of Hyptis suaveolens with a 50% efficacy dose value of 67 ppm. The highest  cetylcholinesterase inhibitory activity was observed with O. canum and H. suaveolens essential oils which IC50 was 0.21 and 0.55 μg/ml respectively. Results suggest that these essential oils have a potential for vector control and can be considered as a source of natural and ecofriendly substances for malaria vector control.Keywords: Anopheles gambiae s.l., malaria, essential oil, acetylcholinesterase, insecticidal activity

Distance sampling for epidemiology: an interactive tool for estimating under-reporting of cases from clinic data

Background: Distance sampling methods are widely used in ecology to estimate and map the abundance of animal and plant populations from spatial survey data. The key underlying concept in distance sampling is the detection function, the probability of detecting the occurrence of an event as a function of its distance from the observer, as well as other covariates that may influence detection. In epidemiology, the burden and distribution of infectious disease is often inferred from cases that are reported at clinics and hospitals. In areas with few public health facilities and low accessibility, the probability of detecting a case is also a function of the distance between an infected person and the “observer” (e.g. a health centre). While the problem of distance-related under-reporting is acknowledged in public health; there are few quantitative methods for assessing and correcting for this bias when mapping disease incidence. Here, we develop a modified version of distance sampling for prediction of infectious disease incidence by relaxing some of the framework’s fundamental assumptions. We illustrate the utility of this approach using as our example malaria distribution in rural Burkina Faso, where there is a large population at risk but relatively low accessibility of health facilities. Results: The modified distance-sampling framework was used to predict the probability of reporting malaria infection at 8 rural clinics, based on road-travel distances from villages. The rate at which reporting probability dropped with distance varied between clinics, depending on road and clinic positions. The probability of case detection was estimated as 0.3–1 in the immediate vicinity of the clinic, dropping to 0.1–0.6 at a travel distance of 10 km, and effectively zero at distances > 30–40 km. Conclusions: To enhance the method’s strategic impact, we provide an interactive mapping tool (as a self-contained R Shiny app) that can be used by non-specialists to interrogate model outputs and visualize how the overall probability of under-reporting and the catchment area of each clinic is influenced by changing the number and spatial allocation of health centres

Effective population size of Anopheles funestus chromosomal forms in Burkina Faso

BACKGROUND: As Anopheles funestus is one of the principal Afro-tropical malaria vectors, a more complete understanding of its population structure is desirable. In West and Central Africa, An. funestus population structure is complicated by the coexistence of two assortatively mating chromosomal forms. Effective population size (N(e)) is a key parameter in understanding patterns and levels of intraspecific variation, as it reflects the role of genetic drift. Here, N(e )was estimated from both chromosomal forms, Kiribina and Folonzo, in Burkina Faso. METHODS: Short-term N(e )was estimated by evaluating variation at 16 microsatellite loci across temporal samples collected annually from 2000–2002. Estimates were based on standardized variance in allele frequencies or a maximum likelihood method. Long-term N(e )was estimated from genetic diversity estimates using mtDNA sequences and microsatellites. RESULTS: For both forms, short-term and long-term N(e )estimates were on the order of 10(3 )and 10(5), respectively. Long-term N(e )estimates were larger when based on loci from chromosome 3R (both inside and outside of inversions) than loci outside of this arm. CONCLUSION: N(e )values indicate that An. funestus is not subject to seasonal bottlenecks. Though not statistically different because of large and overlapping confidence intervals, short-term N(e )estimates were consistently smaller for Kiribina than Folonzo, possibly due to exploitation of different breeding sites: permanent for Folonzo and intermittent for Kiribina. The higher long-term N(e )estimates on 3R, the arm carrying the two inversions mainly responsible for defining the chromosomal forms, give natural selection broader scope and merit further study

When a discriminating dose assay is not enough: measuring the intensity of insecticide resistance in malaria vectors

Background Guidelines from the World Health Organization for monitoring insecticide resistance in disease vectors recommend exposing insects to a predetermined discriminating dose of insecticide and recording the percentage mortality in the population. This standardized methodology has been widely adopted for malaria vectors and has provided valuable data on the spread and prevalence of resistance. However, understanding the potential impact of this resistance on malaria control requires a more quantitative measure of the strength or intensity of this resistance. Methods Bioassays were adapted to quantify the level of resistance to permethrin in laboratory colonies and field populations of Anopheles gambiae sensu lato. WHO susceptibility tube assays were used to produce data on mortality versus exposure time and CDC bottle bioassays were used to generate dose response data sets. A modified version of the CDC bottle bioassay, known as the Resistance Intensity Rapid Diagnostic Test (I-RDT), was also used to measure the knockdown and mortality after exposure to different multipliers of the diagnostic dose. Finally cone bioassays were used to assess mortality after exposure to insecticide treated nets. Results The time response assays were simple to perform but not suitable for highly resistant populations. After initial problems with stability of insecticide and bottle washing were resolved, the CDC bottle bioassay provided a reproducible, quantitative measure of resistance but there were challenges performing this under field conditions. The I-RDT was simple to perform and interpret although the end point selected (immediate knockdown versus 24 h mortality) could dramatically affect the interpretation of the data. The utility of the cone bioassays was dependent on net type and thus appropriate controls are needed to interpret the operational significance of these data sets. Conclusions Incorporating quantitative measures of resistance strength, and utilizing bioassays with field doses of insecticides, will help interpret the possible impact of resistance on vector control activities. Each method tested had different benefits and challenges and agreement on a common methodology would be beneficial so that data are generated in a standardized format. This type of quantitative data are an important prerequisite to linking resistance strength to epidemiological outcomes

Seasonal distribution of Anopheles funestus chromosomal forms from Burkina Faso

Abstract Background Previous studies of Anopheles funestus chromosomal inversion polymorphisms in Burkina Faso showed large departures from Hardy-Weinberg equilibrium and linkage disequilibrium among inversions located on different chromosomes, implying the existence of two taxonomic units ("chromosomal forms") with limited genetic flow. One chromosomal form, named Folonzo, is highly polymorphic for alternative rearrangements of 3R a, 3R b, 2R a, and 3L a; the other, Kiribina, is predominantly characterized by the standard arrangement of these inversions. To investigate the temporal distribution of these chromosomal forms, further collections were carried out in two villages near Ouagadougou where they are found in sympatry. Methods Chromosomal karyotypes were determined from indoor-resting, half-gravid females sampled within and across six breeding seasons, from December 1998 to April 2007. Results As expected, the pattern of chromosomal polymorphism in An. funestus was consistent with assortatively mating Folonzo and Kiribina forms. When samples were assigned to each chromosomal form, their relative abundance varied within successive breeding seasons in a repeating pattern of temporal variability. Relative abundance of the Folonzo form was correlated with climatic variables related to temperature and rainfall. Conclusion The relative abundance of Folonzo and Kiribina forms of An. funestus likely reflects different larval ecologies that are linked to varying climatic conditions. Further analysis of the bionomics of these vectors is recommended in light of its relevance to vector control.http://deepblue.lib.umich.edu/bitstream/2027.42/112459/1/12936_2009_Article_987.pd

The issue is not 'compliance': exploring exposure to malaria vector bites through social dynamics in Burkina Faso

Credited with averting almost 68% of new cases between 2000 and 2015, insecticide-treated bednets (ITNs) are one of the most efficacious malaria-prevention tools. Their effectiveness, however, depends on if and how they are used, making 'compliance' (and the social factors affecting it) a key area of interest for research on malaria transmission. This article situates the notion of compliance with 'bednet use' within everyday practices in an area of south-west Burkina Faso with high malaria transmission. By drawing on ethnographic fieldwork conducted between 2017 and 2018, it critically describes the precarious micro-environments that foreground bednet use-from gender and age to the means of (re)production of social and labour conditions-and assesses the bednets' effectiveness and community uptake. Bednet use stems from concrete, ordinary dynamics that interweave only apparently at the margins of the time individuals most need to be protected by a net. This work conceptualises 'compliance' beyond binary indicators of intervention uptake and locates 'use' as the result of contingent assemblages

Valorisation territoriale du street art : le cas de la commune d’Abobo (Côte-d’Ivoire)

Le street art ou l’art urbain est un mouvement artistique contemporain qui regroupe toutes les formes d’art réalisées dans les rues et espaces publics. En Côte d’Ivoire, depuis l’année 2000, le street art est entré dans les mœurs des jeunes. Au fil des années, l’art urbain se repend jusqu’atteindre des gouvernants et s’institutionnalise avec l’implication de la commune d’Abobo. À l’origine, le street art donnait une image précaire aux espaces publics. Dans sa phase d’institutionnalisation, il contribue de façon périodique à la valorisation du territoire communal. De ces constats, se dégage le problème d’appropriation illégale d’espaces publics à travers des formes d’art. L’étude vise à révéler les logiques qui sous-tendent l’institutionnalisation du street art dans la commune d’Abobo. Il résulte de cette étude, la construction d’une citoyenneté et des trajectoires de politisation par le canal de l’art urbain.Street art or urban art is a contemporary artistic movement which brings together all forms of art achieved in streets and public spaces. Since 2000, street art has become young people’s customs in Côte d’Ivoire. Over years, urban art is spreading to reach governments and becomes institutionalized with the implication of the commune of Abobo. Originally, street art gave public spaces a precarious image. It periodically contributes to the valuation of communal territory in its institutionalization phase. From these remarks, it results the problem of illegal appropriation of public spaces through the forms of art. The study aims at revealing the logics which underlie street art institutionalization in the commune of Abobo. This work results in the construction of a citizenship and politicization trajectories through the channel of urban art