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Item does not contain fulltext, Larval source management (LSM) programs for control of malaria vectors are often vertically organized, while there is much potential for involving local communities in program implementation. To address this, we evaluated the entomological impact of community-based application of Bacillus thuringiensis var. israelensis (Bti) in a rice irrigation scheme in Ruhuha, Rwanda. A non-randomized trial with control compared a Bti implementation program that was supervised by the project team (ES) with a program that was led and carried out by local rice farming communities (CB). One other area served as a control to assess mosquito populations without Bti application. Entomological surveys were carried out every two weeks and assessed the presence and abundance of the larval, pupal, and adult stages of Anopheles mosquitoes. In ES, the per round reduction in Anopheles larval habitats was estimated at 49%. This reduction was less in CB (28%) and control (22%) although the per round reduction in CB was still significantly higher than in control. Pupal production was almost completely prevented from round 5 (out of 10) onwards in both CB (average habitat occupancy 0.43%) and ES intervention arms (average habitat occupancy 0.27%), whereas pupal occupancy rates were on average 12.8% from round 5 onwards in the control. Emergence of adult mosquitoes from rice fields was thus prevented although this was not directly noticeable in adult An. gambiae populations in houses nearby the rice fields. Together with our earlier work on the willingness to financially contribute to the LSM program and the high perceived safety and acceptance of the Bti product, the current study demonstrates that, in an environment with limited resources, communities could become more engaged in LSM program implementation and contribute directly to malaria vector control in their environment.

Background: Current standard interventions are not universally sufficient for malaria elimination. The effects of community-based house improvement (HI) and larval source management (LSM) as supplementary interventions to the Malawi National Malaria Control Programme (NMCP) interventions were assessed in the context of an intensive community engagement programme. Methods: The study was a two-by-two factorial, cluster-randomized controlled trial in Malawi. Village clusters were randomly assigned to four arms: a control arm; HI; LSM; and HI + LSM. Malawi NMCP interventions and community engagement were used in all arms. Household-level, cross-sectional surveys were conducted on a rolling, 2-monthly basis to measure parasitological and entomological outcomes over 3 years, beginning with one baseline year. The primary outcome was the entomological inoculation rate (EIR). Secondary outcomes included mosquito density, Plasmodium falciparum prevalence, and haemoglobin levels. All outcomes were assessed based on intention to treat, and comparisons between trial arms were conducted at both cluster and household level. Results: Eighteen clusters derived from 53 villages with 4558 households and 20,013 people were randomly assigned to the four trial arms. The mean nightly EIR fell from 0.010 infectious bites per person (95% CI 0.006–0.015) in the baseline year to 0.001 (0.000, 0.003) in the last year of the trial. Over the full trial period, the EIR did not differ between the four trial arms (p = 0.33). Similar results were observed for the other outcomes: mosquito density and P. falciparum prevalence decreased over 3 years of sampling, while haemoglobin levels increased; and there were minimal differences between the trial arms during the trial period. Conclusions: In the context of high insecticide-treated bed net use, neither community-based HI, LSM, nor HI + LSM contributed to further reductions in malaria transmission or prevalence beyond the reductions observed over two

The sheep tick, Ixodes ricinus, transmits many pathogens to humans and animals, posing serious health concerns and economic losses. There is an increasing interest in if and how microorganisms affect the fitness and physiology, and possibly, the vectorial capacity of ticks.Little is known about the members, other than the pathogens, of the microbial community of I. ricinus: Specifically, who they are, what they do, and how they are acquired and propagated in ticks. The research presented in this thesis focused on describing the microbiome of I. ricinus and aimed to elucidate how it is generated. Therefore, I studied the bacterial communities of the different life stages of ticks from several geographical locations, which display different vertebrate communities and climatic conditions.I first showed that most ticks have a limited microbiome, which was surprising given that ticks are blood-sucking arthropods. The bacterial communities of ticks were strongly associated with geographical origin rather than the tick life stage, and differences in their Rickettsia abundance mostly determined the clusters.The most prominent tick symbionts were Rickettsia, Rickettsiella spp., Midichloria and Spiroplasma, all of which turned out to be vertically-transmitted. The distribution of symbionts was investigated in ~17,000 questing nymphs from 19 locations around the Netherlands. Their prevalences in ticks differed between the regions in which the symbionts occurred in different proportions. Therefore, I speculate that selective pressures on a regional scale determine infection rates of some heritable symbionts in I. ricinus.In a follow-up study, I studied whether the underlying microbiome of a tick could affect the acquisition of zoonotic pathogens and how a blood meal and pathogens might contribute to the overall change in the bacterial community. In the study, tick bacterial communities clustered poorly by pathogen infection status but better by geographic regions. As the presen

The urgency to develop new tools for malaria control to supplement existing ones (namely long-lasting insecticide-treated bed nets (LLINs) and indoor residual spraying (IRS), has been fuelled by the recent stagnation in control of malaria, especially in sub-Saharan Africa. This slow-down in control, and resurgence in some areas, has been attributed to increasing insecticide resistance in major malaria vectors and changes in mosquito populations from predominately endophilic and anthropophilic to exophilic and opportunistic feeders. The rising importance of outdoor-biting malaria vectors in maintaining residual malaria transmission has warranted the development of control tools that target these species. Due to the mainly indoor protection conferred by LLINs and IRS, development of new control tactics is required to target mosquito populations that bite and rest predominately outdoors. Tools previously developed to target malaria mosquitoes when used singly were experimentally combined towards synergizing their protective efficacy outdoors. Spatial repellents have received renewed interest due to their ability to prevent host-vector contact. Spatial repellents can be used to limit contact with outdoor-biting mosquitoes and in many cases, are also effective against mosquitoes which have been shown to be insecticide resistant. When used in combination with odour-baited traps, spatial repellents present opportunities for mosquito control through the use of a proposed ‘push-pull’ strategy in controlling outdoor-biting mosquitoes. This strategy could be effective in residual transmission settings.In order to understand the dynamics that a push-pull mosquito control strategy would involve, a number of research questions were studied; 1) Does the inclusion of an optimally-performing spatial repellent in an eave fabric reduce outdoor-biting rates of malaria vectors? 2) Does the addition of an optimised odour-baited trap to the spatial repellent improve on any protection conf

Mosquito-borne diseases are among the most serious infectious diseases in the world caused by parasites and pathogens. The African mosquito Anopheles gambiae transmits malaria parasites as well as filarial worms. The mosquitoes feed on humans inside and outside houses, which complicates control strategies. Current control strategies focus mostly on reducing contact with host-seeking mosquitoes through the use of long-lasting insecticide-impregnated nets (LLINs) and indoor residual spraying (IRS). Despite the fact that these tools have lowered the burden of malaria in many parts of the world, transmission is sustained by vectors that bite outdoors. This thesis proposes a new strategy for malaria vector control to be added to existing control tools. It goes beyond blood-feeding processes and it targets all mosquitoes which are feeding indoors and outdoors. The proposed strategy is based on manipulation of oviposition behaviour using chemical cues that mimic olfactory cues emitted by breeding sites. Mosquitoes are attracted to lay their eggs on selected water bodies with specific biotic and abiotic factors. Organic chemical cues, emitted by these sites, are presumed to act as infochemicals enabling these mosquitoes to find suitable breeding sites. Identification of the odours that mediate the site-seeking behaviour of mosquitoes can lead to the development of novel intervention methods for mosquito-borne disease control.My study marked an important progress in the development of mosquito surveillance and control strategies using infochemicals by: (1) generating knowledge on the biology and ecology of immature stages of Anopheles mosquitoes in the study area, (2) providing evidence that mosquitoes select breeding sites preferentially and lay eggs on suitable sites while avoiding unsuitable ones, (3) identifying and characterizing volatile organic chemicals that mediate oviposition behaviour in mosquitoes, (4) generating evidence that oviposition infochemicals can be use

Current trends in the fight against malaria suggest that further progress will be difficult with  the use of insecticide-based control measures alone. Without major reductions in the burden of malaria registered in the past few years, the use of additional interventions with synergistic effects on the current standard measures is required. Currently, interest in employing Larval Source Management (LSM) as a complementary tool is growing as it has shown to significantly reduce larval densities and consequently adult populations in settings where it has been applied along other interventions. LSM is commonly executed via 1) habitat modification, which includes physical transformation of a larval habitat through draining, filling and land levelling and 2) larviciding, commonly using an endotoxin-producing bacterial larvicide, Bacillus thuringiensis var. israelensis (Bti). Knowledge on the ecology of anopheline larval habitats is therefore important as it informs where LSM should be targeted. Also, knowledge about community acceptance and participation in LSM is important as it affects the scalability and future sustainability of the intervention. The study described in this thesis focused on the potential of community-led LSM in Malawi. Chapter 2 describes the habitat ecology of malaria vectors in the Majete area, southern Malawi. In this area, anopheline larvae develop in habitats with little silt, surrounded by bare-grounds and occupied by culicine larvae. I conclude that larval control should be directed towards such anopheline-productive habitats which sustain malaria transmission. In Chapter 3, I investigated whether application of Bti induces discrimination of treated sites by gravid females seeking oviposition sites. I found that treatment of the sites with the bacterial larvicide does not repel ovipositing females from laying eggs in such sites. This finding implies that the female mosquitoes did not detect the presence of the larvicide in aquatic sites. I

Rwanda made tremendous achievements in reducing malaria morbidity and mortality through the scale up of vector control interventions including long lasting insecticide nets (LLINs) and indoor residual spraying (IRS) from 2005 up to 2011. However, malaria remains a major public health concern in the country. With the resurgence of malaria since 2012, improving vector control is urgent. Inadequate financial resources and ecological changes which increase the risk of malaria transmission are among factors that have caused this upsurge. Hence, malaria resurgence has hindered to sustain the progress made in malaria reduction and control.Entomological surveillance is one of the most important strategies for malaria prevention and control being undertaken in Rwanda. Although, mosquito monitoring programmes are established in 12 sentinel sites, maps of malaria risk for the whole country is needed. In this way available resources for malaria control can be deployed in an efficient way. However, there are significant costs associated with the expansion of the mosquito monitoring programmes. The implementation of a citizen science programme for (malaria) mosquito surveillance has the potential to overcome these limitations.In this thesis biological, environmental and institutional factors have been described as contributors to the malaria resurgence in Rwanda. citizen science approach as a new and alternative strategy to contribute to the improvement of malaria mosquito surveillance in low resource settings for the vector control surveillance system in Rwanda are presented. The implementation of a sustainable citizen science programme for malaria vector surveillance requires the participation of citizens. Prior the implementation of citizen science, entomological and household surveys conducted in the studied areas demonstrate that mosquito abundance and species composition of malaria vectors collected using Centers for Disease Control and Prevention (CDC) light traps inside h

Vector-borne diseases often originate from wildlife and can spill over into the human population. One of the most important determinants of vector-borne disease transmission is the host preference of mosquitoes. Mosquitoes with a specialised host preference are guided by body odours to find their hosts in addition to carbon dioxide. Little is known about the role of mosquito host preference in the spillover of pathogenic agents from humans towards animals and vice versa. In the Republic of Congo, the attraction of mosquitoes to primate host odours was determined, as well as their possible role as malaria vectors, using odour-baited traps mimicking the potential hosts of mosquitoes. Most of the mosquito species caught showed a generalistic host preference. Anopheles obscurus was the most abundant Anopheles mosquito, with a generalistic host preference observed from the olfactory response and the detection of various Plasmodium parasites. Interestingly, Culex decens showed a much higher attraction towards chimpanzee odours than to human or cow odours. Human Plasmodium parasites were observed in both human and chimpanzee blood, although not in the Anopheles mosquitoes that were collected. Understanding the role of mosquito host preference for cross-species parasite transmission provides information that will help to determine the risk of spillover of vector-borne diseases.

Culicoides species from the Obsoletus group are important vectors of bluetongue and Schmallenberg virus. This group consists of several species that cannot easily be identified using morphological characteristics. Therefore, limited information is available about their distribution and habitat preferences. In this study, we aimed to elucidate the species composition of the Obsoletus group in three habitat types at climatically different latitudes across Europe. Traps were placed in three habitat types in three countries at different latitudes. After DNA extraction, biting midges were identified using PCR and gel electrophoresis. Extraction of DNA using Chelex proved to be a cost and time efficient method for species identification. A latitudinal effect on the relative abundance of species from the Obsoletus group was found. Species composition was unique for most country-habitat combinations. The majority of biting midges were either C. obsoletus s.s. or C. scoticus, and both species were found at all latitudes and habitats. Their wide distribution and their high abundance at livestock farms make these species likely candidates for rapid farm-to-farm transmission of pathogens throughout Europe. Our results emphasize the need to differentiate Obsoletus group species to better understand their ecology and contribution to pathogen transmission., Funding Agencies|Italian Ministry of Education, University and Research (MIUR) [Prin 2012 protocol 2012T85B3R]; Svenska Forskningsradet Formas; Linkoping University; Ministerie van Economische Zaken [1300018161]

Assessing the biting behaviour of malaria vectors plays an integral role in understanding the dynamics of malaria transmission in a region. Biting times and preference for biting indoors or outdoors varies among mosquito species and across regions. These behaviours may also change over time in response to vector control measures such as long-lasting insecticidal nets (LLINs). Data on these parameters can provide the sites and times at which different interventions would be effective for vector control. This study assessed the biting patterns of malaria vectors in Chikwawa district, southern Malawi. The study was conducted during the dry and wet seasons in 2016 and 2017, respectively. In each season, mosquitoes were collected indoors and outdoors for 24 nights in six houses per night using the human landing catch. Volunteers were organized into six teams of two individuals, whereby three teams collected mosquitoes indoors and the other three collected mosquitoes outdoors each night, and the teams were rotated among twelve houses. All data were analyzed using Poisson log-linear models. The most abundant species were Anopheles gambiae sensu lato (primarily An. arabiensis) and An. funestus s.l. (exclusively An. funestus s.s.). During the dry season, the biting activity of An. gambiaes.l. was constant outdoors across the categorized hours (18:00 h to 08:45 h), but highest in the late evening hours (21:00 h to 23:45 h) during the wet season. The biting activity of An. funestus s.l. was highest in the late evening hours (21:00 h to 23:45 h) during the dry season and in the late night hours (03:00 h to 05:45 h) during the wet season. Whereas the number of An. funestuss.l. biting was constant (P = 0.662) in both seasons, that of An. gambiaes.l. was higher during the wet season than in the dry season (P = 0.001). Anopheles gambiae s.l. was more likely to bite outdoors than indoors in both seasons. During the wet season, An. funestus s.l. was more likely to bite indoors than o

Most malaria control interventions are designed to target the life cycle of the malaria vector or the malaria parasite with the purpose to interrupt malaria transmission. However, the interruption of malaria transmission and eventual elimination of the disease remain one of the hardest challenges in malaria control, particularly in countries with low income-economies. Based on lessons from past malaria control strategies, and the promising results from insecticide treated nets (ITNs), long-lasting insecticide treated nets (LLINs) and new insecticides for indoor residual spraying (IRS), the global public health community was mobilized to aim for malaria elimination. Thus, the outcomes obtained on malaria reduction encouraged some countries, including Rwanda, to move forward to a malaria elimination phase. At the same time, malaria endemic countries have been encouraged to adopt the concept of integrated vector management (IVM) and, consequently, to rationalize the usage of limited resources. This approach intends to transform the existing vertical system of vector control by making it more evidence-based, and by enhancing the participation of decentralized communities. For the current thesis, the concept of IVM, with an emphasis on empowerment of the local community, was implemented for malaria control in Rwanda. The goal was to investigate the feasibility of malaria elimination in Rwanda and evaluate potential hindrances in rolling out IVM. Key questions therefore were: (1) what are the key entomological and environmental determinants which characterize malaria transmission in Rwanda? (2) what are the behavioral characteristics of vector populations over time and space in response to existing vector control interventions? and (3) will community based know-how and larval source management interventions next to the National Malaria Control Programme (NMCP) policy on LLINs, IRS and case management, achieve and sustain malaria control and contribute to elimination? The

Current methods of malaria vector control implemented by national control programmes rely mainly on the use of insecticides. These include the use of long-lasting insecticide treated nets (LLINs) and indoor residual spraying (IRS). The success of LLINs and IRS is underpinned by the protection from infectious mosquito bites provided to individuals and the reduction in mosquito population size caused by sufficient contact of mosquitoes with the insecticide in the nets or on the walls of the houses. The high degree of endophily (resting indoors) and endophagy (feeding indoors) exhibited by the dominant African malaria vectors has been, therefore, a key component of that success. However, in recent years in some regions, the biting behaviour of the African malaria vectors, both indoors and outdoors and during a wider range of times than previously recognized, has been reported. This has an implication on malaria control because individuals are at risk of receiving infectious bites from vectors that are biting either outdoors or indoors at times when people are not protected by the primary control tools. Additionally, resistance of mosquitoes to these insecticides exacerbates the risk for malaria transmission. Therefore, understanding the degree of endophagy/exophagy of the vectors, when or where humans are exposed to mosquito bites, entry points for malaria vectors into houses and biological factors enhancing malaria transmission in a region is important. The collective information from studying these natural behavioural aspects of mosquitoes will help in designing interventions that protect individuals from infective mosquito bites, thereby reducing malaria transmission and disease burden. The research described in this thesis focused on the biting behaviour of malaria vectors in and around houses in southern Malawi. Chapter 2 provides an overview of the biting times of malaria vectors in Africa, both historically and currently. Our literature search showed that the bi

The availability of data on distribution and density of mosquito vectors of disease is needed to understand the risk of mosquito-borne diseases. In case of an outbreak of a newly introduced mosquito-borne pathogen of medical or veterinary importance, such information is required in order to decide on a contingency and eventual control plan. In the recent decade, several exotic mosquito species have become established in European countries and they have rapidly expanded their distribution. The rationale for the present study was the increasingly frequent reporting of invasive mosquito species (IMS) in the Netherlands, some of which are known vectors of infectious diseases, as well as the lack of detailed knowledge on the spatio-temporal distribution of the indigenous mosquito fauna. The aim was therefore to develop methodologies for acquiring accurate information on the actual and potential distribution of indigenous and exotic mosquito species in the Netherlands, and to evaluate the surveillance and control methodologies applied after IMS findings. To establish a baseline for the spatio-temporal distribution of the indigenous mosquito fauna present in the Netherlands, a survey was conducted at the start of the study. Cross-sectional mosquito field surveys were carried out over a period of four years (2010-2013). These surveys provided occurrence maps for 26 indigenous species. One invasive mosquito species, Aedes japonicus, was discovered using this strategy. Furthermore, data on seasonality of the species, biodiversity and habitat preferences were also provided. Using the collected data on occurrence and abundance, a special study using random forest models was done to investigate the potential spatial distribution and population density of Anopheles plumbeus, a native nuisance mosquito species. I found a high environmental suitability and abundance of this species in the south-eastern provinces, mostly associated with abandoned pig farm buildings, and reports of b

Mosquitoes infected with malaria parasites have demonstrated altered behaviour that may increase the probability of parasite transmission. Here, we examine the responses of the olfactory system in Plasmodium falciparum infected Anopheles gambiae, Plasmodium berghei infected Anopheles stephensi, and P. berghei infected An. gambiae. Infected and uninfected mosquitoes showed differential responses to compounds in human odour using electroantennography coupled with gas chromatography (GC-EAG), with 16 peaks triggering responses only in malaria-infected mosquitoes (at oocyst, sporozoite or both stages). A selection of key compounds were examined with EAG, and responses showed differences in the detection thresholds of infected and uninfected mosquitoes to compounds including lactic acid, tetradecanoic acid and benzothiazole, suggesting that the changes in sensitivity may be the reason for differential attraction and biting at the oocyst and sporozoite stages. Importantly, the different cross-species comparisons showed varying sensitivities to compounds, with P. falciparum infected An. gambiae differing from P. berghei infected An. stephensi, and P. berghei infected An. gambiae more similar to the P. berghei infected An. stephensi. These differences in sensitivity may reflect long-standing evolutionary relationships between specific Plasmodium and Anopheles species combinations. This highlights the importance of examining different species interactions in depth to fully understand the impact of malaria infection on mosquito olfactory behaviour.

Culicoides species from the Obsoletus group are important vectors of bluetongue and Schmallenberg virus. This group consists of several species that cannot easily be identified using morphological characteristics. Therefore, limited information is available about their distribution and habitat preferences. In this study, we aimed to elucidate the species composition of the Obsoletus group in three habitat types at climatically different latitudes across Europe. Traps were placed in three habitat types in three countries at different latitudes. After DNA extraction, biting midges were identified using PCR and gel electrophoresis. Extraction of DNA using Chelex proved to be a cost and time efficient method for species identification. A latitudinal effect on the relative abundance of species from the Obsoletus group was found. Species composition was unique for most country-habitat combinations. The majority of biting midges were either C. obsoletus s.s. or C. scoticus, and both species were found at all latitudes and habitats. Their wide distribution and their high abundance at livestock farms make these species likely candidates for rapid farm-to-farm transmission of pathogens throughout Europe. Our results emphasize the need to differentiate Obsoletus group species to better understand their ecology and contribution to pathogen transmission.

Female mosquitoes can transmit pathogens to their host during blood feeding and are an important vector of human diseases such as dengue, chikungunya, filariasis and malaria. After 15 years of decline in the number of fatal malaria cases, this decline came to a halt in 2016. Growing resistance against drugs and insecticides pose a serious threat for future human health. This thesis focuses on the behaviour of host-seeking malaria mosquitoes by analysing their flight paths during their approach to different host cues. Fundamental knowledge on the role of selected host cues was acquired. In addition, studies to support successful implementation of vector control interventions were performed in both wind-tunnel settings and the semi-field in Kenya. My research demonstrates that automated tracking systems can strengthen behavioural-ecological studies on disease vectors, in addition to conventional bio-assays such as olfactometers, by providing detailed information on the approach behaviour of mosquitoes to different targets. The attraction towards the host-sensory cue CO2 was investigated in an olfactometer bioassay. Trap catches of female Anopheles gambiae s.s. were enhanced by separation of the CO2 source from the source of human skin emanations. Close-range deterrent effects of CO2 were overcome by the simultaneous presence of skin emanations. Flight path analysis of mosquitoes in a wind tunnel, showed that exposure to human odour resulted in prolonged and highly convoluted flight tracks. The combination of odour with heat was crucial to induce landings of host-seeking mosquitoes. A semi-field study in Kenya revealed that house-entering mosquitoes approached the eave of a house in a wide angle to the house at eave level, where the proportion that entered uninterruptedly (23%) spent just a few seconds around the eave area. The presence of insecticide-treated nets inside a house did not repel mosquitoes as measured by the number of house entries. At close range, in a w

Background The outbreaks of bluetongue and Schmallenberg disease in Europe have increased efforts to understand the ecology of Culicoides biting midges and their role in pathogen transmission. However, most studies have focused on a specific habitat, region, or country. To facilitate wider comparisons, and to obtain a better understanding of the spread of disease through Europe, the present study focused on monitoring biting midge species diversity in three different habitat types and three countries across Europe. Methods Biting midges were trapped using Onderstepoort Veterinary Institute light traps at a total of 27 locations in Sweden, the Netherlands and Italy, comprising farm, peri-urban and wetland habitats. From July 2014 to June 2015 all locations were sampled monthly, except for during the winter months. Trapped midges were counted and identified morphologically. Indices on species richness, evenness and diversity were calculated. Community compositions were analysed using non-metric multidimensional scaling (NMDS) techniques. Results A total of 50,085 female midges were trapped during 442 collection nights. More than 88% of these belonged to the Obsoletus group. The highest midge diversity was found in Sweden, while species richness was highest in the Netherlands, and most specimens were trapped in Italy. For habitats within countries, diversity of the trapped midges was lowest for farms in all countries. Differences in biting midge species communities were more distinct across the three countries than the three habitat types. Conclusions A core midge community could be identified, in which the Obsoletus group was the most abundant. Variations in vector communities across countries imply different patterns of disease spread throughout Europe. How specific species and their associated communities affect disease risk is still unclear. Our results emphasize the importance of midge diversity data at community level, how this differs across large geographic ran