Background Chromosomal inversions are key drivers of local adaptation and ecological diversification in Anopheles gambiae, the principal malaria vector in sub-Saharan Africa. Among these, the 2La inversion is associated with tolerance to aridity, behavioural variation, and insecticide resistance. However, large-scale data on inversion frequency and ecological association remain scarce in Nigeria. This study investigated the spatial distribution of 2La inversion frequencies in An. gambiae and their relationship with ecological zones across the country. Methods A total of 1200 Anopheles mosquitoes were collected across 12 states representing Nigeria's major ecozones. 2La inversion karyotypes were determined by PCR, and allele frequencies were analysed in relation to ecological zones, latitude, and ecological gradients. Spatial mapping and statistical analyses were performed using R version 4.4. Results Morphological identification and species-specific PCR revealed 999 An. gambiae s.l., comprising An. gambiae s.s. (39.7%), An. coluzzii (51.5%), and An. arabiensis (8.7%). A total of 399 An. gambiae s.s. was karyotyped. From the An. gambiae s.s. population karyotyped, a distinct south-north cline in inversion frequency was observed. The 2La/2La homokaryotype predominated in arid northern ecozones (Sahelian and Sudan savannas), whereas 2La + /2La + was dominant in humid southern forests and mangrove regions.The heterokaryotype 2La/2La + occurred at moderate frequencies in transitional zones (Osun-Taraba corridor). Linear regression analyses confirmed significant correlations between inversion frequency and latitude (R2=0.68-0.73, P < 0.001). Generally, the allele frequencies from 2La karyotyping did not deviate significantly from Hardy-Weinberg equilibrium expectations (P > 0.05) except in Bayelsa and Kebbi States. Conclusion This study provides the first nationwide evidence linking 2La inversion polymorphism to ecological adaptation of An. gambiae in Nigeria. The inversion likely enhances vector survival across diverse habitats, contributing to spatial variation in malaria transmission.These findings have direct operational relevance for Nigeria's National Malaria Elimination Programme (NMEP), indicating that vector-control effectiveness may vary by ecological context. Integrating ecotype-and region-specific evidence into NMEP planning could improve intervention targeting. Continuous genomic surveillance will be essential to sustain malaria control gains.

BackgroundChromosomal inversions are important genetic mechanisms that facilitate local adaptation, ecological flexibility, and behavioural variation in mosquito populations. In Anopheles coluzzii, a dominant malaria vector in West Africa, the 2La inversion has been associated with desiccation tolerance, thermal resistance, and insecticide resistance. Despite Nigeria's ecological diversity and substantial malaria burden, the spatial distribution and clinal dynamics of 2La inversion polymorphism in An. coluzzii remain poorly characterized. This study investigated the distribution of 2La inversion karyotypes across major Nigerian ecozones and examined their association with climatic gradients.MethodsLarvae of Anopheles mosquitoes were sampled across 12 states representing Nigeria's southern, central, and northern ecological zones. Species identification was conducted morphologically and confirmed with PCR diagnostics. The 2La inversion was determined using established molecular assays, and allele frequencies were analyzed with respect to ecozone and climatic gradients. Spatial distribution maps and statistical analyses, including correlation and clinal trend assessment, were done in R version 4.4.ResultsA clear geographic structuring of 2La inversion polymorphism was observed in An. coluzzii populations. The 2La/2La homokaryotype was strongly predominant in the northern Sahelian and Sudan savanna ecozones, reflecting adaptation to hot and arid conditions. In contrast, the standard 2La+/2La+ arrangement was predominant in humid southern forest and mangrove regions. The heterokaryotype (2La/2La+) occurred at intermediate frequencies within the central transitional belt, where ecological gradients overlap. Karyotype frequencies exhibited a pronounced latitudinal cline, with heterozygosity peaking in central Nigeria. The spatial patterns indicate that climatic pressures, particularly aridity and humidity, might be a major determinant of inversion distribution in An. coluzzii from Nigeria.ConclusionThis study provides the first detailed nationwide characterization of 2La inversion polymorphism in An. coluzzii across Nigeria's ecological zones. The strong alignment between inversion frequency and eco-climatic gradients highlights the role of chromosomal rearrangements in promoting vector survival and ecological fitness. These adaptive patterns have significant implications for malaria control, as inversion-mediated adaptability may influence resting behaviour, insecticide response, and vector persistence under climate change. Integrating chromosomal inversion surveillance into entomological monitoring frameworks will be essential for designing ecologically tailored vector control strategies in Nigeria.

Malaria vector abundance has been linked to certain agricultural practices. This work examined the impact of the agricultural practice of irrigation on the composition and seasonal distribution of malaria vectors in agrarian communities of Kano state. Longitudinal data collection was done four times a year, corresponding to different transmission seasons from early rains to late rainy season, early dry season to late dry season. Indoor-biting adult mosquitoes were collected using standard pyrethrum spray collection (PSC) techniques. Female Anopheles mosquitoes collected from houses were morphologically identified to species level. Molecular characterisation of the members of the Anopheles gambiae complex was carried out using PCR technique. Two thousand four hundred fifty-two (2452) adult female Anopheles species were collected throughout the study period. The Large Irrigation (LIC) and Urban Irrigation Communities (UIC) had a higher mean abundance of female Anopheles mosquitoes across seasons. There was a significant difference in the mean adult mosquito catch across the season (F =113.49, p≤0.001) and across the three communities (F = 44.73; p ≤0.001). Anopheles gambiae sl. was the most encountered among the four species, with a mean abundance of 11.94±11.76, 5.39±7.45 and 2.58 ±3.41 for LIC, UIC and NIC, respectively. Molecular characterisation of An. gambiae s.l. by PCR showed the presence of three sibling species, An. coluzzi, An. gambiae ss and An. arabiensis. An. Coluzzi was significantly more abundant across the three communities during the wet and dry seasons. The predominance of this species has implications for malaria control. This study shows that irrigation is likely to influence mosquito breeding, thus exposing community members to a higher risk of being bitten by infected vectors. A review of the ecology of Anopheles species, especially in urban environments, is needed, considering the current abundance of malaria vectors in the urban community. Keywords: Seasonal, Abundance, Composition, Anopheles species, Irrigation, Urban

A retrospective scrutiny of dataset from a semi-longitudinal investigation reveals a dynamic interaction between seasons, vector population density and malaria prevalence. Indoor resting mosquitoes collected between the hours of 06:00 and 09:00 using Pyrethrum Spray Catch (PSC), were preserved dry over silica gel and used for morphological and molecular identification. Asymptomatic malaria prevalence was determined through Rapid Diagnostic Test (RDT), Microscopy test and PCR. A line list hospital attendance record was collated to explore the symptomatic malaria situation. Metrological data was collected from a weather station in the study community to see impact of some weather elements on the malaria situation. The four seasons under study shows a progressive increase in vector population density with increase in rainfall. A strong positive correlation exists between vector population and asymptomatic malaria prevalence [PCRtest-R2=0.439(43.9%); RDT+MicroT -R2=0.425(42.5%); RDT- R2=0.342(34.2%)]. Symptomatic malaria peaked during the dry season (12.54%) with lower vector density while onset of rains with higher vector density recorded the least (4.7%). Established here is a dynamic interaction between malaria vector population, prevalence and the environmental landscape; hence the imperative for an ecological input in the face of fluctuating climatic elements.

Malaria vector surveillance is required to determine disease transmission dynamics, vector insecticide susceptibility status, suitable control strategies and impact of control interventions. However, capacity and resources for vector surveillance and insecticide resistance monitoring is often inadequate in most countries at risk of vector-borne diseases. Collaborations and linkages between malaria control policy makers and existing research institutions generating vector surveillance research data are often weak, thereby hindering the availability of data for decision-making. A national vector surveillance programme, mobilizing all stakeholders towards quality data generation and policy making, is required for effective data-driven country-wide vector control. This paper provides an analysis and suggested future directions for such synergized national malaria vector surveillance and insecticide resistance monitoring system currently being implemented by all research and policy stakeholders in Nigeria. The harmonized national vector surveillance system described here can be used as a model for the development or improvement of such structures in other countries with high malaria transmission risks.

Enzymes mediated resistance development and their activities are well documented in Anopheles gambiae vectors. However, biological consequences of such resistance development in malaria vectors are obscure. The present study aims to determine the implications of such response in An. gambiae (Kisumu) population following exposure to a concentration of Permethrin selection pressure across multiple generations. Adult Kisumu mosquitoes exposed to 0.2 µg/ CDC bottle over generations were compared with unexposed control populations by way of resistance status, cost of fitness, and correlating metabolic enzymes. Data obtained were analysed using SPSS. Analysis of Variance was employed to determine statistical differences at 95%. Fecundity rates of the mosquito population dropped progressively over generations. With increase in activity of metabolic enzymes, resistance status of the mosquito population progressed significantly (P< 0.05) over generations with 5.0 µg (18.00±0.00; 72%) at f4 generation. Mosquito resistance development is therefore a disadvantage to malaria vectors as it reduces ovipository capability, and increases longevity of immature stages (life cycle) with filial generations.

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.

Countries like Nigeria have launched Malaria-Lymphatic Filariasis (Malaria-LF) co-intervention plans by targeting joint Anopheles and Culex mosquito human host-seeking behaviour with synergistic insecticide-based control tools. However, insecticide resistance currently threatens mosquito vector control. This study investigated separate and joint pyrethroid insecticide exposure response of Anopheles gambiae and Culex pipiens complex mosquitoes collected from mixed breeding sites in Ilorin, Nigeria. Adult Anopheles and Culex mosquitoes reared from larval collections were exposed in separate and joint insecticide susceptibility tests to permethrin, deltamethrin and alphacypermethrin using WHO kits. Mosquito molecular identifications and knock down resistance ( kdr ) mutation detection were carried out. Mosquito knockdown times (kdt), percentage knockdown, and mortality for the different mosquito and exposure types were compared. Both mosquitoes were resistant to all pyrethroid insecticides tested. Significantly higher deltamethrin Anopheles knockdown was recorded compared to Culex for the joint ( Anopheles 79–89%, Culex 44–50% P ≤ 0.011) and separate ( Anopheles 67–88%, Culex 46–47% P ≤ 0.048) exposures respectively. Time to 95% knock down were shorter by half during separate (2200.9 mins) than in joint (4513.9 mins) Anopheles and Culex mosquito exposures. Faster Anopheles (kdt 50 18.7–68.8) than Culex (kdt 50 22.1–98.8) knockdown was recorded in separate and joint insecticide exposures. Higher but not significantly different ( P ≥ 0.083) mosquito mortalities were recorded from separate ( Anopheles 43–77%, Culex 43–72%) than in joint exposures ( Anopheles 44–68%, Culex 41–69%). There were no significant ( P ≥ 0.072) differences between Anopheles 43–77% and Culex 41–72% mortalities for separate and joint exposures. Anopheles arabiensis (≥ 81.4%), An. gambiae (≥ 10.7%), An. coluzzii (0-1.8%) with different kdr frequencies (44–67%) and Cx. quinquefasciatus without kdr occurrence were identified. The speed of action and morbidity effects of the pyrethroid insecticides tested were lower during joint than in the separate mosquito exposures. Reduced pyrethroid speed of action and morbidity along with multiple mosquito resistance noted could threaten insecticide user-acceptability, performance perception and Malaria-LF co-intervention in the field.

Background: Anopheles gambiae mosquitoes are one of the best-known of the genus Anopheles because of their predominant role in transmitting the most dangerous malaria parasite species (to humans), Plasmodium falciparum. Unfortunately, An. gambiae mosquitoes have grown resistant to the most popular and widely used insecticides, particularly Permethrin, spreading across Africa. The current study sought to determine the lowest Permethrin concentrations that could be a selection pressure for metabolic resistance development in the renowned adult An. gambiae (Kisumu) mosquito population. Methods: Established, insectary-reared, and fully susceptible strains of Kisumu populations were reared, and exposed for mortality assay and Lowest Sub-lethal Concentrations (LSLCs) determination at the adult stage. Various exposure concentrations were achieved by slightly modifying the Centre for Disease Control (CDC) protocol. Adult Kisumu mosquitoes exposed to the same LSLC over generations were compared with unexposed control populations by way of resistance status and correlating levels of esterase, monooxygenase, and Glutathione-S -transferases (GST) metabolic enzymes. Information obtained was analysed using SPSS 16.0 and Analysis of Variance at P=0.05 with the aid of Graph-Pad prism 8. Results: The LSLCs of Permethrin with mortality rates not significantly (P> 0.05) different from control Kisumu strains (0.00) were 0.2μg (0.00) and 0.4μg (0.00) per CDC bottle, i.e., LSLC 1 and LSLC 2 respectively. The LSLC 1 exposure lasted five generations (f0-f4), during which resistance statuses were consistently below 1.00±0.82 (4.0%) after 1 hour. There was no significant difference (P>0.05) in the levels of esterase across generations, while monooxygenase and GST levels were significantly up-regulated (P<0.05) in subsequent generations of LSLC 1-treated mosquitoes. However, there was a consistent and progressive increase in GST level with advancing generations. Conclusion: It may be concluded that the P450 monooxygenase enzyme mechanism is a prelude to the overexpression of the GST enzyme. Hence, if the development of the GST resistance enzyme can be inhibited or stopped in An. gambiae mosquito vector populations, multiple resistance and cross-resistance mechanisms in malaria vectors could be effectively regulated.

The use of larval source management (LSM) in sub-Saharan Africa is limited, however, widespread report of insecticide resistance in adult mosquitoes has engendered renewed interest in LSM; especially larviciding. Hence, this study evaluated bioefficacy and residual efficacy of commercially available larvicides;Temephos, Spinosad, Bacillus thuringiensis var. isrealensis (Bti) and Bacillus thuringiensis var. israelensis/Bacillus sphaericus (Bti/Bs) on larvae of Anopheles gambiae s.l, Culex quinquefasciatus and Aedes aegypti in Lagos, Nigeria. Acute toxicity assay was used to determine LC95 and the LC95 was doubled to determine discriminating doses. Residual efficacy was assessed by exposing larvae to discriminating doses of larvicides in deionised water and in water collected from larval habitat for 28 days and 24 hr mortality post-introduction of larvae was checked for 2nd, 4th, 7th, 14th, 21st and 28th day. Probit analysis was used to estimate LC95 and residual efficacy at mortality ≥95%. T-Test was used to determine the level of significance (P<0.05) of the residual effect. Temephos (0.007mg/l) was the most toxic considering 24h LC95. The trend of LC95 (Temephos < Spinosad < Bti/Bs < Bti) in Anopheles gambiae s.l was the same for Culex quinquefasciatus and Aedes aegypti. Residual effect of Bti/Bs > Bti > Temephos > Spinosad on mosquito larvae from Lagos, Nigeria. The trend of residual efficacy is the same in both bioassays albeit reduced when larvicides were dissolved in water collected from larval habitats. Strong bioefficacy and better residual capacity of Bti/Bs make it a better larviciding agent against Anopheles gambiae s.l, Culex quinquefasciatus and Aedes aegypti in Lagos, Nigeria.

Entomological data gathering is essential for monitoring malaria vector disease risks and selection of appropriate interventions for the protection of exposed human populations. This study assessed the relative abundance, species composition, and sporozoite infection rates of indoor resting An. gambiae s.l. malaria vectors in six communities across 3 Local Government Areas in Kwara State, Nigeria. Total number of mosquitoes collected by Pyrethrum Spray Catch method over a period of eighth months were correlated with rainfall values in the area. Plasmodium falciparum sporozoite infection rates and sibling species identification of collected An. gambiae s.l. mosquito samples were determined by ELISA and PCR respectively. Results showed a positive correlation (r = 0.639, p = 0.08) between rainfall and numbers of Anopheles mosquitoes in the study areas. The overall composition of the An. gambiae s.l sibling species in the collected samples from all the six communities showed the predominance of An. gambiae s.s 298 (75.3%) compared to An. coluzzii 94(23.7%) and An. arabiensis 4(1.0%). However, the sporozoite infection rate of An. coluzzii (22.3%) was higher compared to An. gambiae s.s (12.8%) and An. arabiensis (0%). Mean numbers of An. gambiae s.l mosquitoes were significantly higher in Ilorin west LGA compared to Asa (F = 17.81, P < 0.001) and Ilorin East LGAs (F = 22.81, P < 0.001). Sporozoite rates of both An. gambiae s.s and An. coluzzii sibling species were higher in Ilorin West communities (Aiyede 21%, Ogundele 32%) compared to Asa (Idi Emi 11.1%, Lasoju 5.1%) and Ilorin East (Oke Oyi 2.4%, Ote-efan 0%) communities. Prevalence of sporozoite-infected An. gambiae s.s and An. coluzzii indoors highlight the need for effective insecticide treated bed-nets interventions to protect the residents from malaria risks. Higher numbers of An. coluzzii in the swampy rice marshed Ilorin West LGA communities require larval source management as an additional strategy for effective malaria vector control.

Background: Insecticide resistance in Anopheles gambiae s.l. is a major challenge for malaria vector control in Nigeria. Both target-site insensitivity and metabolic resistance have been im-plicated in resistance process, with the latter receiving little attention in Nigeria. Therefore, we investigated metabolic enzyme activities in Anopheles gambiae s.l populations resistant to Del-tamethrin and Diethyldichlorotriethylethane (DDT) in South-West Nigeria. Methods: Anopheles larvae were collected from Ibadan, Oyo and Badagry, Lagos. Adults were exposed to Deltamethrin and DDT using WHO method. Cohorts of populations were further exposed to Pyperonil Butoxide (PBO) and Deltamethrin. Insecticide-exposed and unexposed co-horts were examined for metabolic enzyme activities. Results were compared between exposed and unexposed samples ANOVA (P<0.05). Results: Mosquitoes were identified as An. gambiae (89%, Ibadan; 0%, Badagry) and An. coluzzii (11%, Ibadan; 100%, Badagry). The populations showed varied level of resistance to Deltamethrin (26%, Ibadan; 71%, Badagry) and DDT (2%, Ibadan; 44%, Badagry). Mortality to Deltamethrin in-creased from 26% to 64% (Ibadan) and 71% to 84% (Badagry) when populations were pre-exposed to PBO. Biochemical analysis revealed significant high levels (P<0.05) of cytochrome P450 and GST in exposed samples. Conclusions: Cytochrome P450 and GST are involved in Deltamethrin and DDT resistance in Anopheles gambiae s.l populations in South-West Nigeria.

The ability of malaria parasites to develop resistance to antimalarial drugs has made it necessary to continuously survey malaria parasite populations for resistance markers. Mutations in specific malaria parasite genes confer resistance to antimalarial drugs. The study compared mutations in Pfcrt and Pfmdr1 genes of P. falciparum from two ecologically different areas of Nigeria. Plasmodium falciparum dried blood spots collected from New Bussa (Northcentral Nigeria) and Ijede (Southwest Nigeria) were analysed by PCR-RFLP for Pfcrt, K76 T, Pfmdr1, N86Y and Y184F mutations. Pfmdr1 copy number was determined by quantitative-PCR. A total of 145 blood spots [Ijede = 55; New Bussa = 90 blood spots] were analysed, but Pfcrt gene was successfully amplified in 144 samples while Pfmdr1 was amplified in 132 samples. Overall, prevalence of mutant forms of Pfcrt 76 T,Pfmdr1 86Y and 184F were 74.3% (95% CI: 66.4-81.2%), 18.2% (95% CI: 12.0-25.8%) and 35.6% (95% CI: 27.5-44.4%). The frequency of Pfcrt 76 T was similar in both study sites [Ijede: 81.8% (95%CI: 69.1-90.9%); New Bussa: 69.7% (95%CI: 59.0-79.0), p = 0.105]. However, the frequencies of Pfmdr1 86Y and 184F were significantly higher in Ijede (28.3% and 62.3%) than in New Bussa (11.4% and 17.7%), respectively (P < 0.05). Eight parasite genotypes based on three codons of the two genes were identified. The most frequent genotype was TNY 53(40.5%) while the least was KYF 1 (0.8%). The most frequent genotype in Ijede and New Bussa were TNF 18(34.0%) and TNY 40 (51.3%) respectively. The frequency of wild strain KNF in Ijede and New Bussa were 3 (5.7%) and 18 (23.1%), respectively. The distribution of the genotypes differed significantly by location. The genotypes with more than two or more mutations were more in Ijede 32 (60.4%) than in New Bussa 16 (20.5%) (p < 0.001). Amplification of Pfmdr1 copy number was not observed in the two study sites. The prevalence of Pfcrt 76 T was similar in both locations while Pfmdr1 86Y and 184F differed in both locations. Single nucleotide polymorphisms in the three codons assessed were more in Ijede than in New Bussa.

Malaria is a leading public health challenge causing mortality and morbidity in sub-Saharan Africa. Prominent malaria vector control methods employed in sub-Saharan Africa include Long Lasting Insecticide Nets (LLINs) and Indoor Residual spraying (IRS). This study investigated knowledge, attitude and practices (KAP) of malaria vector control methods in Lagos, South-West Nigeria. Structured questionnaires were employed for the cross-sectional survey which was carried out between May and August 2018. Multi-stage sampling technique was used to select Lagos Mainland, Kosofe, and Ojo local government areas (LGAs). Five hundred and twenty questionnaires were used for the study. Data were analyzed for descriptive statistics, whereas chi(2) was used to determine influence of respondents' LGA, level of education and type of dwelling on respondents' attitude and practice. Respondents' LGAs have no significant impact on attitude and practice to malaria vector control methods. However, 'level of education' as well as 'type of dwelling structure' impacted significantly on some practices and attitude. Basically, IRS is the major tool employed in malaria vector control, but sometimes it is used in combination with other methods. A good number of residents also use LLINs. 'Choice of method' employed is mainly based on the effectiveness of method. General perception about LLINs and IRS is that they are effective, cheap and safer. Considering the widespread use of IRS and LLINs for malaria vector control in Lagos, implementation of malaria control programs should consider KAP to these two strategies.

Chromosomal inversion 2La play a vital role in local adaptation of the malaria vector Anopheles. This polymorphic inversion, linked with ecological and behavioural plasticity, ensures adaptation of these species and continued transmission of the malaria parasite. However, the adaptive significance of this inversion in several Anopheles populations is still not well understood. Here, we determined the frequencies of polymorphic inversion 2La in natural populations of Anopheles coluzzii, the second major malaria vector in Southwest Nigeria, and its association with ecotypes. Anopheles larvae were collected from eleven localities across the mangrove/forest and forest/savannah ecozones of Southwest Nigeria. Adults were identified morphologically and with Polymerase Chain Reaction (PCR). Chromosomal inversion frequencies were determined by PCR. Relationship between genotype frequencies and ecotypes was determined using linear regression analysis and chi square. A total of 333 Anopheles coluzzii were scored for inversion 2La karyotypes. Frequencies of the 2La/2La homokaryotype increased progressively Northwards (F = 10.9; p = 0.01; R2=0.54) corresponding to a significant decline in the frequencies of 2L+a/2L+a (linear regression: F = 7.03; p = 0.03; R2=0.44), an indication of association with ecotypes. The heterokaryotype (2L+a/2La) however, showed high frequencies across ecotypes (F = 0.15; p = 0.71; R2=0.02). There was no significant deviation of the karyotype frequencies from Hardy-Weinberg estimates, an indication of a possible heterozygous advantage.

Studies profiling community and zonal malaria entomological risk indices are required to identify high risk areas where targeted control resources are most needed or likely to have the greatest impact on reducing risk of malaria infection. This study presents a first report on malaria vector risk indices in two vegetation zones within Adamawa state, Nigeria. Endophilic mosquitoes were collected for one year in selected communities in the Guinea and Sudan savanna zones within the State. Plasmodium falciparum Sporozoite and human blood meal ELISA assays were carried out on the female Anopheles mosquitoes collected. Sibling species composition of the An. gambiae complex were determined using PCR assays. Mean numbers of mosquitoes in the Guinea savanna communities were significantly (t = 7.73, DF = 11, p < 0.001) higher than the Sudan. Man-biting rates (F = 2.76, p = 0.13) of Anopheles mosquitoes were higher in the Guinea but not significantly different from Sudan savanna. Sporozoite rates of mosquitoes within the Guinea savanna were 2.7 times higher than the Sudan. The predominant Anopheles coluzzii species encountered in the state had higher overall human blood indices (0.63) and sporozoite rates (6.9%) compared to An. gambiae (0.39, 1.9%) and An. arabiensis (0.58, 2.3%) respectively. Overall annual human blood indices (0.59) of mosquitoes in Adamawa were lower compared to reports from other States. Prevalence and higher transmission risks indices of endophilic An. coluzzii mosquitoes reveal the need for LLIN and management of relatively permanent An. coluzzii breeding sites in the State. Widespread cattle rearing lifestyle and lower human blood indices of mosquitoes in the study area suggest the need to investigate cattle blood indices of the mosquitoes in the state. Higher entomological risk indices in the Guinea Savanna zone provide baseline information for prioritization of malaria vector control supplies within the State.

Demographic and health surveys provide household level data on population dynamics and health-related issues. Findings from a well characterized community can be used by relevant stakeholders to plan appropriate and acceptable health interventions for the benefit of the citizens. This project aimed to characterize Ijede community in Ikorodu LGA of Lagos State, Nigeria in preparation for a more appropriate Demographic and Health Surveillance System (DHSS) in the community. The study carried out a cross-sectional study in Ijede community in Lagos State. Buildings and structures in the community were mapped, a census of the community taken, socio-demographic details of household heads obtained, availability of water, sanitation and hygiene, and other facilities assessed. Descriptive statistics were used for analysis of data. The population of the community was 8,208 persons in 2,171 households with a male-female ratio of 1:1. About half of the populations (47.4%) were aged less than 20 years. Majority of household heads were males (72.4%), aged 40-59 years (43.0%), retail traders (25.8%), and married (68.8%). Multifarious tenement buildings constituted majority of buildings. The major source of water supply is the borehole (59.6%) and the water is not purified in 60.0% of cases. The flush toilet constitutes majority of toilet facilities but 15.4% are still uncovered pit latrines. Ijede community has been characterized, with a population of 8,208 and key demographic parameters obtained, thus providing required baseline for the establishment of a DHSS in this community. Key words: Mapping, demographic, surveillance, health, population.

Insecticide treated nets (ITNs) have been the major tool in halving malaria's burden since 2000, but pyrethroid insecticide resistance threatens their ongoing effectiveness. In 2017, the WHO concluded that long-lasting ITNs (LLINs) with a synergist, piperonyl butoxide (PBO), provided additional public health benefit over conventional (pyrethroid-only) LLINs alone in areas of moderate insecticide resistance and endorsed them as a new class of vector control products. We performed an economic appraisal of PBO nets compared with conventional LLINs in 2019 US$ from prevention and health systems perspectives (including treatment cost offsets). We used data from a pragmatic randomized 2012-2014 trial in Nigeria with epidemiological outcomes in an area with confirmed pyrethroid resistance. Each village had 50 months of epidemiologic data, analyzed by village by month, using negative binomial regression. Compared with LLINs, although adding $0.90 per net delivered, PBO nets reduced symptomatic malaria cases by 33.4% (95% CI 10.2-50.6%). From a prevention perspective, the incremental cost-effectiveness ratio was $11 (95% CI $8-$37) per disability-adjusted life year averted. From the health systems perspective, PBO nets were significantly cost-saving relative to conventional LLINs. The benefit-cost analysis found that the added economic benefits of PBO nets over LLINs were $201 (95% CI $61-$304) for every $1 in incremental costs. Growing pyrethroid resistance is likely to strengthen the economic value of PBO nets over LLINs. Beyond their contribution to reducing malaria, PBO nets deliver outstanding economic returns for a small additional cost above conventional LLINs in locations with insecticide resistance.