Spatial distribution and ecological niche modeling of geographical spread of Anopheles gambiae complex in Nigeria using real time data.

The need for evidence-based data, to inform policy decisions on malaria vector control interventions in Nigeria, necessitated the establishment of mosquito surveillance sites in a few States in Nigeria. In order to make evidence-based-decisions, predictive studies using available data becomes imperative. We therefore predict the distribution of the major members of the Anopheles gambiae s.l. in Nigeria. Immature stages of Anopheles were collected from 72 study locations which span throughout the year 2020 resulted in the identification of over 60,000 Anopheline mosquitoes. Of these, 716 breeding sites were identified with the presence of one or more vector species from the An. gambiae complex and were subsequently used for modelling the potential geographical distribution of these important malaria vectors. Maximum Entropy (MaxEnt) distribution modeling was used to predict their potentially suitable vector habitats across Nigeria. A total of 23 environmental variables (19 bioclimatic and four topographic) were used in the model resulting in maps of the potential geographical distribution of three dominant vector species under current climatic conditions. Members of the An. gambiae complex dominated the collections (98%) with Anopheles stephensi, Anopheles coustani, Anopheles funestus, Anopheles moucheti, Anopheles nilli also present. An almost equal distribution of the two efficient vectors of malaria, An. gambiae and Anopheles coluzzii, were observed across the 12 states included in the survey. Anopheles gambiae and Anopheles coluzzii had almost equal, well distributed habitat suitability patterns with the latter having a slight range expansion. However, the central part of Nigeria (Abuja) and some highly elevated areas (Jos) in the savannah appear not suitable for the proliferation of these species. The most suitable habitat for Anopheles arabiensis was mainly in the South-west and North-east. The results of this study provide a baseline allowing decision makers to monitor the distribution of these species and establish a management plan for future national mosquito surveillance and control programs in Nigeria.

Low frequency of knockdown resistance mutation (L1014F) and the efficacy of PBO synergist in multiple insecticide-resistant populations of Anopheles gambiae in Ikorodu, Lagos State, Nigeria.

Objective: We evaluated the susceptibility status of Anopheles gambiae in two communities of Ikorodu, Lagos, Nigeria to DDT, deltamethrin, lambda cyhalothrin and bendiocarb. Methods: Anopheles immature stages were collected from their habitats in the surveyed community and allowed to emerge before exposure adult females to discriminating doses of WHO insecticides including DDT, deltamethrin, lambda cyhalothrin, bendiocarb and malathion. PBO synergistic bioassay was conducted for insecticides where the mosquito samples showed resistance. PCR assay was used for the detection of kdr mutation in the mosquitoes. Results: Resistance to DDT (40% and 86%) and lambda cyhalothrin (75% and 84%) in Oke-Ota and Majidun respectively. Suspected resistance to deltamethrin (94.9%) and bendiocarb (93.5%) was recorded in Oke-Ota community and the mosquitoes were susceptible to malathion in both communities. KDR mutation (L1014F) from resistance samples from both locations though with a low frequency that significantly departs from Hardy-Weinberg's probability (P> 0.01). PBO synergized bioassay was able to increase knockdown, percentage mortality and restore full susceptibility to deltamethrin and bendiocarb. Conclusion: Results from this study indicates that the metabolic resistance mechanism is highly implicated in the resistance to different classes of insecticide in Ikorodu and this should be taken into consideration when implementing vector control activities in this area.

Geospatial distribution and predictive modeling of onchocerciasis in Ogun State, Nigeria.

Onchocerciasis caused by infection with Onchocerca volvulus is a disease of public health importance and is highly associated with disability. As Nigeria is aiming at eliminating onchocerciasis by 2030, there is a need to develop newer tools to map disease prevalence and identify environmental factors driving disease prevalence, even in places that have not been previously targeted for preventive chemotherapy. This study produced predictive risk-maps of onchocerciasis in Ogun State. Georeferenced onchocerciasis infection data obtained from a cross-sectional survey at 32 locations between March and July 2015 together with remotely-sensed environmental data were analyzed using Ecological Niche Models (ENM). A total of 107 field occurrence points for O. volvulus infection were recorded. A total of 43 positive occurrence points were used for modelling. ENMs were used to estimate the current geographic distribution of O. volvulus in Ogun State. Maximum Entropy distribution modeling (MaxEnt) was used for predicting the potential suitable habitats, using a portion of the occurrence records. A total of 19 environmental variables were used to model the potential geographical distribution area under current climatic conditions. Empirical prevalence of 9.3% was recorded in this study. The geospatial distribution of infection revealed that all communities in Odeda Local Government Area (a peri-urban LGA) showed remarkably high prevalence compared with other LGAs. The predicted high-risk areas (probability > 0.8) of O. volvulus infection were all parts of Odeda, Abeokuta South, and Abeokuta North, southern part of Imeko-Afon, a large part of Yewa North, some parts of Ewekoro and Obafemi-Owode LGAs. The estimated prevalence for these regions were >60% (between 61% and 100%). As predicted, O. volvulus occurrence showed a positive association with variables reflecting precipitation in Ogun State. Our predictive risk-maps has provided useful information for the elimination of onchocerciais, by identifying priority areas for delivery of intervention in Ogun State, Nigeria.

Acute and subacute oral toxicity characterization and safety assessment of COVID organics® (Madagascar's Anti-COVID Herbal Tea) in animal models.

Introduction: Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2. No drug has been generally approved as safe and effective for the treatment of COVID-19. Several therapeutic agents such as COVID Organics® (CVO) have been explored as treatment options. CVO is an herbal tea composed of 62% of Artemisia annua and 38% of other plants. There is presently no existing scientific report and data on the safety and efficacy of CVO herbal drug. Thus, acute and subacute toxicity studies were undertaken to evaluate the safety and toxicity of CVO on short- and long-term usage in animal models. Materials and Methods: Phytochemical and nutritional compositions of CVO were determined using standard methods. Acute oral toxicity was investigated using female Swiss albino mice (three per group). While subacute oral toxicity was done using female and male Swiss albino rats (five per group). The animals were administered 2000 mg/kg, 5000 mg/kg, therapeutic dose; 5500 mg/kg and supratherapeutic dose; 11,000 mg/kg of CVO herbal product. The control group received water ad libitum. The oral toxicity studies were done in accordance with Organization for Economic Corporation and Development guidelines. The experimental protocol was approved by the Institutional Animal Care and Use Committee, Nigerian Institute of Medical Research (Ethics No. IRB/17/043). Results: CVO is rich in antioxidants: flavonoids (10.3%), tannins (29.1%), and phenolics (434.4 mg). It contains proteins (33.8%), carbohydrates (34.5%), fat (6.8%), and fiber (0.5%). In the acute toxicity study, no mortality was recorded in all the treated and untreated groups. The lethal dose of CVO is >5000 mg/kg body weight. The hematological, biochemical, lipid profile, and histologic parameters were all normal at therapeutic doses when compared to the control group. Conclusion: The acute and subacute oral toxicity studies revealed that CVO is not toxic. The specific organ toxicity evaluations also indicated that CVO has no toxic effects on blood parameters and vital organs structure and function at therapeutic dose. Thus, CVO is safe for short- and long-term usage. We recommend that CVO should be subjected to efficacy studies to investigate whether it is effective for COVID-19 treatment as claimed by the manufacturer.

Résumé Introduction: La maladie à coronavirus 2019 (COVID-19) est une maladie infectieuse causée par le coronavirus 2 du syndrome respiratoire aigu sévère. Aucun ne médicamenta été généralement approuvé comme étant sûr et efficace pour le traitement du COVID-19. Plusieurs agents thérapeutiques comme le COVID Organics® (CVO) ont été explorées comme options de traitement. CVO est une tisane composée à 62% d'Artemisia annua et à 38% d'autres plantes. Il y a actuellement il n'existe aucun rapport scientifique ni aucune donnée sur l'innocuité et l'efficacité du médicament à base de plantes CVO. Ainsi, des études de toxicité aiguë et subaiguë ont été entreprises évaluer la sécurité et la toxicité du CVO sur une utilisation à court et à long terme dans des modèles animaux. Matériels et méthodes: phytochimiques et les compositions nutritionnelles du CVO ont été déterminées à l'aide de méthodes standard. La toxicité orale aiguë a été étudiée chez des femmes albinos suisses souris (trois par groupe). La toxicité orale subaiguë a été réalisée sur des rats albinos suisses femelles et mâles (cinq par groupe). Les animaux étaient administrés 2 000 mg/kg, 5 000 mg/kg, 5 500 mg/kg (dose thérapeutique) et 11 000 mg/kg (dose suprathérapeutique) de produit à base de plantes CVO. Le le groupe témoin a reçu de l'eau à volonté. Les études de toxicité orale ont été réalisées conformément à l'Organisation pour la société économique et Directives de développement. Le protocole expérimental a été approuvé par le Comité institutionnel de protection et d'utilisation des animaux de l'Institut nigérian de Recherche médicale (Éthique n° IRB/17/043). Résultats: Le CVO est riche en antioxydants : flavonoïdes (10,3 %), tanins (29,1 %) et phénoliques (434,4 mg). Il contient des protéines (33,8 %), des glucides (34,5 %), des lipides (6,8 %) et des fibres (0,5 %). Dans l'étude de toxicité aiguë, aucune mortalité n'a été enregistrée chez tous les groupes traités et non traités. La dose mortelle de CVO est > 5 000 mg/kg de poids corporel. Le profil hématologique, biochimique, lipidique et les paramètres histologiques étaient tous normaux aux doses thérapeutiques par rapport au groupe témoin. Conclusion: Les conséquences orales aiguës et subaiguës des études de toxicité ont révélé que le CVO n'est pas toxique. Les évaluations de la toxicité spécifique pour certains organes ont également indiqué que le CVO n'a aucun effet toxique sur le sang. Paramètres et structure et fonction des organes vitaux à dose thérapeutique. Ainsi, CVO est sans danger pour une utilisation à court et à long terme. Nous recommandons que Le CVO doit être soumis à des études d'efficacité pour déterminer s'il est efficace pour le traitement du COVID-19, comme le prétend le fabricant. Mots-clés: Maladie à coronavirus 2019, plantes médicinales, histopathologie, produits phytochimiques, analyses immédiates, évaluation de la toxicité.

Acute and subacute oral toxicity characterization and safety assessment of COVID organics® (Madagascar's Anti­COVID Herbal Tea) in animal models

Introduction: Coronavirus disease 2019 (COVID 19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2. No drug has been generally approved as safe and effective for the treatment of COVID 19. Several therapeutic agents such as COVID Organics® (CVO) have been explored as treatment options. CVO is an herbal tea composed of 62% of Artemisia annua and 38% of other plants. There is presently no existing scientific report and data on the safety and efficacy of CVO herbal drug. Thus, acute and subacute toxicity studies were undertaken to evaluate the safety and toxicity of CVO on short and long term usage in animal models. Materials and Methods: Phytochemical and nutritional compositions of CVO were determined using standard methods. Acute oral toxicity was investigated using female Swiss albino mice (three per group). While subacute oral toxicity was done using female and male Swiss albino rats (five per group). The animals were administered 2000 mg/kg, 5000 mg/kg, therapeutic dose; 5500 mg/kg and supratherapeutic dose; 11,000 mg/kg of CVO herbal product. The control group received water ad libitum. The oral toxicity studies were done in accordance with Organization for Economic Corporation and Development guidelines. The experimental protocol was approved by the Institutional Animal Care and Use Committee, Nigerian Institute of Medical Research (Ethics No. IRB/17/043). Results: CVO is rich in antioxidants: flavonoids(10.3%), tannins(29.1%), and phenolics(434.4 mg). It contains proteins (33.8%), carbohydrates (34.5%), fat (6.8%), and fiber (0.5%). In the acute toxicity study, no mortality was recorded in all the treated and untreated groups. The lethal dose of CVO is >5000 mg/kg body weight. The hematological, biochemical, lipid profile, and histologic parameters were all normal at therapeutic doses when compared to the control group. Conclusion: The acute and subacute oral toxicity studies revealed that CVO is not toxic. The specific organ toxicity evaluations also indicated that CVO has no toxic effects on blood parameters and vital organs structure and function at therapeutic dose. Thus, CVO is safe for short and long term usage. We recommend that CVO should be subjected to efficacy studies to investigate whether it is effective for COVID 19 treatment as claimed by the manufacturer.

Detection and Co-occurrence of kdr (F1534C and S989P) Mutations in Multiple Insecticides Resistant Aedes aegypti (Diptera: Culicidae) in Nigeria.

The outbreak of yellow fever virus transmitted by Aedes aegypti has been of major concern in Nigeria, this mosquito also transmits several other arboviruses globally. The control of many vectors of mosquito-borne diseases relies heavily on the use of insecticides. Therefore, constant monitoring of insecticide resistance status and associated mechanisms is crucial within the local mosquito population. Here, we determined the resistance profile of adult Ae. aegypti from Majidun and Oke Ota communities, Ikorodu Local Government Area of Lagos State, Nigeria to different classes of insecticides using WHO procedures. The resistant phenotypes of Ae. aegypti were screened for the presence of kdr mutations F1534C, S989P, and V1016G, which have been implicated in insecticide resistance in yellow fever vectors. A high level of resistance to DDT and pyrethroids was recorded in Ae. aegypti in this study, although possible resistance to deltamethrin, one of the pyrethroids was reported in one of the locations. Resistance to bendiocarb was recorded in the Majidun community while Ae. aegypti in both locations were susceptible to malathion. The presence of F1534C mutation associated with DDT and deltamethrin resistance in Ae. aegypti population, and the presence of S989P mutation were detected singly and in co-occurrence with F1534C for the first time in Africa, while V1016G mutation was not detected in this study. The role of these mutations in resistance phenotype expressed in Ae. aegypti in larger populations needs to be established.

Towards improvement in malaria policy implementation in Nigeria: a qualitative study on factors influencing the translation of malaria policies to practice.

BACKGROUND: Malaria is a severe health issue in Nigeria, particularly for pregnant women and children <5 y of age, despite all malaria control programs. From the standpoint of major stakeholders in Nigeria, this study explored both promoting and limiting factors affecting the implementation of malaria policy. METHODS: From March to June 2019, in-depth interviews were conducted with 16 key respondents. Key informants such as malaria researchers, policy advisers and program managers were identified using purposive and snowballing sampling strategies. Interviews were performed in English, recorded, transcribed and analysed using QSR NVivo 11. RESULTS: Some of the variables increasing the implementation of malaria policies in Nigeria, according to respondents, were political will, access to funds from donors, and staff commitment. Insufficient planning, lack of commitment, poor finance, manpower shortages, and a lack of synergy between academics and policymakers, on the other hand, were recognized as important barriers to the malaria policy implementation process by respondents. CONCLUSIONS: Implementation gaps may result from a lack of capability for the policy implementation process and a lack of support for policy objectives. The difficulties in implementing malaria policy in Nigeria were highlighted in this study, and relevant recommendations were made.

Design and methods for a quasi-experimental pilot study to evaluate the impact of dual active ingredient insecticide-treated nets on malaria burden in five regions in sub-Saharan Africa.

BACKGROUND: Vector control tools have contributed significantly to a reduction in malaria burden since 2000, primarily through insecticidal-treated bed nets (ITNs) and indoor residual spraying. In the face of increasing insecticide resistance in key malaria vector species, global progress in malaria control has stalled. Innovative tools, such as dual active ingredient (dual-AI) ITNs that are effective at killing insecticide-resistant mosquitoes have recently been introduced. However, large-scale uptake has been slow for several reasons, including higher costs and limited evidence on their incremental effectiveness and cost-effectiveness. The present report describes the design of several observational studies aimed to determine the effectiveness and cost-effectiveness of dual-AI ITNs, compared to standard pyrethroid-only ITNs, at reducing malaria transmission across a variety of transmission settings. METHODS: Observational pilot studies are ongoing in Burkina Faso, Mozambique, Nigeria, and Rwanda, leveraging dual-AI ITN rollouts nested within the 2019 and 2020 mass distribution campaigns in each country. Enhanced surveillance occurring in select study districts include annual cross-sectional surveys during peak transmission seasons, monthly entomological surveillance, passive case detection using routine health facility surveillance systems, and studies on human behaviour and ITN use patterns. Data will compare changes in malaria transmission and disease burden in districts receiving dual-AI ITNs to similar districts receiving standard pyrethroid-only ITNs over three years. The costs of net distribution will be calculated using the provider perspective including financial and economic costs, and a cost-effectiveness analysis will assess incremental cost-effectiveness ratios for Interceptor® G2, Royal Guard®, and piperonyl butoxide ITNs in comparison to standard pyrethroid-only ITNs, based on incidence rate ratios calculated from routine data. CONCLUSIONS: Evidence of the effectiveness and cost-effectiveness of the dual-AI ITNs from these pilot studies will complement evidence from two contemporary cluster randomized control trials, one in Benin and one in Tanzania, to provide key information to malaria control programmes, policymakers, and donors to help guide decision-making and planning for local malaria control and elimination strategies. Understanding the breadth of contexts where these dual-AI ITNs are most effective and collecting robust information on factors influencing comparative effectiveness could improve uptake and availability and help maximize their impact.

Factors Affecting Willingness to Use Indoor Residual Spraying Among Pregnant Women Attending Antenatal Care in Hyperendemic State of West Africa: A Random Survey.

This study assessed the perception of pregnant women on indoor residual spraying (IRS), documented acceptability, and factors that significantly dictate willingness to use IRS among the pregnant women attending antenatal clinic in Ibadan Nigeria. A structured questionnaire was used to obtain relevant information from 500 pregnant women. Descriptive and principal component analysis (PCA) were done at 5% level of significance. Majority of the pregnant women had between good and fair knowledge of IRS. Less than 70% of the respondents were willing to allow IRS in their homes. Our PCA revealed that major factors responsible for acceptance and willingness to use IRS were associated with perceived benefits, advantages, and disadvantages of IRS rather than overall knowledge of IRS among the respondents. The analysis revealed that these factors were responsible for at least 80% of the reasons for a pregnant woman to willingly accept IRS or not. The factors that positively influenced willingness to use IRS include its benefit in controlling mosquitoes and other insects, reducing malaria incidence, and prolonged effects of IRS which is an added advantage over continuous purchase of aerosols. One major factor that may negatively affect the acceptance of IRS is the fact that you may have to pack out of the house and wait for more than 3 d before entering. This current study has identified some specific factors that seem to promote and/or reduce willingness to accept IRS as a malaria control intervention among pregnant women in South Western Nigeria.

Knowledge, attitudes and perception of communities on mosquitoes and its control practices in Lagos State, Nigeria.

INTRODUCTION: evidence-based mosquito control strategy is important for efficient and effective delivery of mosquito control interventions. This is hinged on effective community participation and thorough understanding of the Knowledge Attitude and Practices (KAPs) to achieve desired result. Such community dynamics are often understudied. We designed this study to assess the perception of four local communities on aspects of mosquito behavior, prevention and control in Lagos State, Nigeria. METHODS: a cross-sectional survey was carried out using pretested semi-structured questionnaires to assess socio-demographic factors and KAPs in Kosofe, Alimosho, Ibeju-Lekki and Badagry Local Government Areas of Lagos State, Nigeria. Data analysis was carried out using IBM SPSS version 23. RESULTS: a total of 746 questionnaires were analyzed. Socio-demographic profile of the sampled population reveals that majority of the study population (73.1%) was between 18 and 40 years which constitute 49% males and 51% females. The knowledge of mosquito as a disease vector was high among the respondents which correlates with their level of education (P<0.05). The use of insecticide aerosols and Insecticides Treated Nets (ITNs) are the main control measures employed for mosquito control by respondents. Cost, convenience of usage and awareness majorly influenced the type of control measures that respondents adopt. Reasons such as not being easy to setup, skin irritation and the filling of being caged are reasons why some individuals do not use ITNs. Indoors, 32.4% of the respondents indicate the use of dichlorvos (DDVP) for household control of mosquitoes. CONCLUSION: the knowledge of mosquito control is high among middle aged individuals in Lagos State. Insecticide aerosols and ITNs are two major mosquito control methods used with DDVP insecticides frequently used indoors. This can inform the design of appropriate control methods in Lagos State.

Pyrethroids resistance intensity and resistance mechanisms in Anopheles gambiae from malaria vector surveillance sites in Nigeria.

Anopheles gambiae, An. coluzzii and An. arabiensis are the three major vectors of malaria in Nigeria. These mosquitoes have developed resistance to different insecticides. Insecticides resistance intensity assay was recently introduced to provide insight into the potential operational significance of insecticide resistance. Here, we present data on pyrethroids resistance intensity and resistance mechanisms from six vector surveillance sites (Lagos, Ogun, Edo, Anambra, Kwara and Niger) in Nigeria. Adult Anopheles reared from larval collections were tested using WHO insecticides susceptibility protocol with 1x concentration of permethrin and deltamethrin followed with intensity assays with 5x and 10x concentrations of both insecticides. Synergistic and biochemical assays were carried out and underlying resistance mechanisms determined following standard protocols. Anopheles gambiae constituted >50% samples tested in five sites. Permethrin and deltamethrin resistance was observed at all the sites. The Kdt50 varied from 15 minutes (CI = 13.6-17.2) in deltamethrin to 42.1 minutes (CI = 39.4-44.1) in permethrin. For both insecticides, Kdt95 was >30 minutes with 25% to 87% post exposure mortality at the different sites. The West Africa knock down resistance (kdr-w) mechanism was found at each site. Resistant An. gambiae from Lagos, Ogun and Niger synergized prior to permethrin or deltamethrin exposure showed significant mortality (89-100%) compared to unsynergized mosquitoes (Lagos, p = 0.031; Ogun, p = 0.025; Niger, p = 0.018). Biochemical analyses revealed significant increased levels of P450 enzymes in resistant Anopheles gambiae from Lagos (p = 0.038); Ogun (p = 0.042) and Niger (p = 0.028) in addition to GST in Lagos (p = 0.028) and Ogun (p = 0.033). Overall, the results revealed high pyrethroid resistance associated with increased activities of metabolic enzymes (P450 + GST) in An. gambiae and An. coluzzii from Lagos and Ogun. The presence of kdr + P450 conferred moderate resistance whereas low resistance was the case where kdr was the sole resistance mechanism. Findings thus suggests that elevated levels of cytochrome P450 enzymes together with GST were responsible for high or severe pyrethroid resistance.

Impact of PermaNet 3.0 on entomological indices in an area of pyrethroid resistant Anopheles gambiae in south-western Nigeria.

BACKGROUND: PermaNet® 3.0 is an insecticide synergist-combination long-lasting insecticidal net designed to have increased efficacy against malaria vectors with metabolic resistance, even when combined with kdr. The current study reports on the impact of this improved tool on entomological indices in an area with pyrethroid-resistant malaria vectors in Nigeria. METHODS: Baseline entomological indices across eight villages in Remo North LGA of Ogun State provided the basis for selection of three villages (Ilara, Irolu and Ijesa) for comparing the efficacy of PermaNet® 3.0 (PN3.0), PermaNet® 2.0 (PN2.0) and untreated polyester nets as a control (UTC). In each case, nets were distributed to cover all sleeping spaces and were evaluated for insecticidal activity on a 3-monthly basis. Collection of mosquitoes was conducted monthly via window traps and indoor resting catches. The arithmetic means of mosquito catches per house, entomological inoculation rates before and during the intervention were compared as well as three other outcome parameters: the mean mosquito blood feeding rate, mean mortality and mean parity rates. RESULTS: Anopheles gambiae s.l. was the main malaria vector in the three villages, accounting for >98% of the Anopheles population and found in appreciable numbers for 6-7 months. Deltamethrin, permethrin and lambdacyhalothrin resistance were confirmed at Ilara, Irolu and Ijesa. The kdr mutation was the sole resistance mechanism at Ilara, whereas kdr plus P450-based metabolic mechanisms were detected at Irolu and Ijesa. Bioassays repeated on domestically used PN 2.0 and PN 3.0 showed persistent optimal (100%) bio-efficacy for both net types after the 3rd, 6th, 9th and 12th month following net distribution. The use of PN 3.0 significantly reduced mosquito densities with a 'mass killing' effect inside houses. Households with PN 3.0 also showed reduced blood feeding as well as lower mosquito parity and sporozoite rates compared to the PN 2.0 and the UTC villages. A significant reduction in the entomological inoculation rate was detected in both the PN 2.0 village (75%) and PN 3.0 village (97%) post LLIN-distribution and not in the UTC village. CONCLUSION: The study confirms the efficacy of PN 3.0 in reducing malaria transmission compared to pyrethroid-only LLINs in the presence of malaria vectors with P450-based metabolic- resistance mechanisms.

The development of insecticide-treated durable wall lining for malaria control: insights from rural and urban populations in Angola and Nigeria.

BACKGROUND: Durable lining (DL) is a deltamethrin-impregnated polyethylene material, which is designed to cover domestic walls that would normally be sprayed with residual insecticide. The operational success of DL as a long-lasting insecticidal substrate will be dependent on a high level of user acceptability as households must maintain correctly installed linings on their walls for several years. Preliminary trials were undertaken to identify a material to develop into a marketable wall lining and to assess its level of acceptability among rural and urban populations. METHODS: In Angola (n=60), prototype DL and insecticide-treated plastic sheeting (ITPS) were installed on urban house walls and ceilings, respectively, and acceptability was compared to indoor residual spraying (IRS) (n=20) using a knowledge, attitude and practice (KAP) questionnaire. In Nigeria (n=178), three materials (prototype DL, ITPS and insecticide-treated wall netting) were distributed among rural and urban households. User opinions were gathered from focus group discussions, in-depth interviews and KAP questionnaires. RESULTS: In Angola, after two weeks, the majority of participants (98%) expressed satisfaction with the products and identified the killing of insects as the materials' principal benefits (73%). After one year, despite a loss of almost 50% of households to refugee repatriation, all 32 remaining households still asserted that they had liked the DL/ITPS in their homes and given the choice of intervention preferred DL/ITPS to IRS (94%) or insecticide-treated nets (78%). In Nigeria, a dichotomy between rural and urban respondents emerged. Rural participants favoured wall adornments and accepted wall linings because of their perceived decorative value and entomological efficacy. By contrast, urban households preferred minimal wall decoration and rejected the materials based upon objections to their aesthetics and installation feasibility. CONCLUSIONS: The high level of acceptability among rural inhabitants in Nigeria identifies these communities as the ideal target consumer group for durable wall linings. The poorer compliance among urban participants suggests that wall linings would not be readily adopted or sustained in these regions. If DL is as well received by other rural populations it could overcome some of the logistical constraints associated with spray campaigns and has the potential to become a long-lasting alternative to IRS in malaria endemic areas.

Evidence of carbamate resistance in urban populations of Anopheles gambiae s.s. mosquitoes resistant to DDT and deltamethrin insecticides in Lagos, South-Western Nigeria.

BACKGROUND: Resistance monitoring is essential in ensuring the success of insecticide based vector control programmes. This study was carried out to assess the susceptibility status of urban populations of Anopheles gambiae to carbamate insecticide being considered for vector control in mosquito populations previously reported to be resistant to DDT and permethrin. METHODS: Two - three day old adult female Anopheles mosquitoes reared from larval collections in 11 study sites from Local Government Areas of Lagos were exposed to test papers impregnated with DDT 4%, deltamethrin 0.05% and propoxur 0.1% insecticides. Additional tests were carried out to determine the susceptibility status of the Anopheles gambiae population to bendiocarb insecticide. Members of the A. gambiae complex, the molecular forms, were identified by PCR assays. The involvement of metabolic enzymes in carbamate resistance was assessed using Piperonyl butoxide (PBO) synergist assays. The presence of kdr-w/e and ace-1R point mutations responsible for DDT-pyrethroid and carbamate resistance mechanisms was also investigated by PCR. RESULTS: Propoxur resistance was found in 10 out of the 11 study sites. Resistance to three classes of insecticides was observed in five urban localities. Mortality rates in mosquitoes exposed to deltamethrin and propoxur did not show any significant difference (P > 0.05) but was significantly higher (P < 0.05) in populations exposed to DDT. All mosquitoes tested were identified as A. gambiae s.s (M form). The kdr -w point mutation at allelic frequencies between 45%-77% was identified as one of the resistant mechanisms responsible for DDT and pyrethroid resistance. Ace-1R point mutation was absent in the carbamate resistant population. However, the possible involvement of metabolic resistance was confirmed by synergistic assays conducted. CONCLUSION: Evidence of carbamate resistance in A. gambiae populations already harbouring resistance to DDT and permethrin is a clear indication that calls for the implementation of insecticide resistance management strategies to combat the multiple resistance identified.

The importance of considering community-level effects when selecting insecticidal malaria vector products.

BACKGROUND: Insecticide treatment of nets, curtains or walls and ceilings of houses represent the primary means for malaria prevention worldwide. Direct personal protection of individuals and households arises from deterrent and insecticidal activities which divert or kill mosquitoes before they can feed. However, at high coverage, community-level reductions of mosquito density and survival prevent more transmission exposure than the personal protection acquired by using a net or living in a sprayed house. METHODS: A process-explicit simulation of malaria transmission was applied to results of 4 recent Phase II experimental hut trials comparing a new mosaic long-lasting insecticidal net (LLIN) which combines deltamethrin and piperonyl butoxide with another LLIN product by the same manufacturer relying on deltamethrin alone. RESULTS: Direct estimates of mean personal protection against insecticide-resistant vectors in Vietnam, Cameroon, Burkina Faso and Benin revealed no clear advantage for combination LLINs over deltamethrin-only LLINs (P = 0.973) unless both types of nets were extensively washed (Relative mean entomologic inoculation rate (EIR) ± standard error of the mean (SEM) for users of combination nets compared to users of deltamethrin only nets = 0.853 ± 0.056, P = 0.008). However, simulations of impact at high coverage (80% use) predicted consistently better impact for the combination net across all four sites (Relative mean EIR ± SEM in communities with combination nets, compared with those using deltamethrin only nets = 0.613 ± 0.076, P < 0.001), regardless of whether the nets were washed or not (P = 0.467). Nevertheless, the degree of advantage obtained with the combination varied substantially between sites and their associated resistant vector populations. CONCLUSION: Process-explicit simulations of community-level protection, parameterized using locally-relevant experimental hut studies, should be explicitly considered when choosing vector control products for large-scale epidemiological trials or public health programme procurement, particularly as growing insecticide resistance necessitates the use of multiple active ingredients.