The recent decline in the burden of malaria in Côte d’Ivoire is largely attributable to the use of long-lasting insecticidal nets (LIN). However, this progress is threatened by insecticide resistance, behavioral changes in Anopheles gambiae populations, and residual malaria transmission, necessitating the need for additional tools. Therefore, the aim of this study was to evaluate the effectiveness of combined use of LLIN and Bacillus thuringiensis (Bti) and compare it with LLIN.
The study was conducted from March 2019 to February 2020 across two study arms (LLIN + Bti arm and LLIN only arm) in the Korhogo health region in northern Côte d’Ivoire. In the LLIN + Bti group, Anopheles larval habitats were treated with Bti every two weeks in addition to LLIN. Larval and adult mosquitoes were collected and morphologically identified to genus and species using standard methods. Member Ann. The Gambian complex was determined using polymerase chain reaction technology. Infection with Plasmodium An. The incidence of malaria in Gambia and the local population was also assessed.
Overall, Anopheles spp. Larval density was lower in the LLIN + Bti group compared to the LLIN alone group 0.61 [95% CI 0.41–0.81] larvae/dive (l/dive) 3.97 [95% CI 3.56–4 .38] l/dive (RR = 6.50; 95% CI 5.81–7.29 P < 0.001). Overall bite speed of An. The incidence of S. gambiae bites was 0.59 [95% CI 0.43–0.75] per person/night in the LLIN + Bti alone group, compared with 2.97 [95% CI 2.02–3. 93] bites per person/night in the LLIN-only group (P < 0.001). Anopheles gambiae sl is primarily identified as the Anopheles mosquito. Anopheles gambiae (ss) (95.1%; n = 293), followed by Anopheles gambiae (4.9%; n = 15). The human blood index in the study area was 80.5% (n = 389). The EIR for the LLIN + Bti group was 1.36 infected bites per person per year (ib/p/y), whereas the EIR for the LLIN only group was 47.71 ib/p/y. The incidence of malaria decreased sharply from 291.8‰ (n = 765) to 111.4‰ (n = 292) in the LLIN + Bti group (P < 0.001).
The combination of LLIN and Bti significantly reduced the incidence of malaria. The combination of LLIN and Bti may be a promising integrated approach for effective control of An. The Gambia is free of malaria.
Despite progress in malaria control over the past few decades, the burden of malaria remains a major problem in sub-Saharan Africa [1]. The World Health Organization (WHO) recently reported that there were 249 million malaria cases and an estimated 608,000 malaria-related deaths worldwide in 2023 [2]. The WHO African Region accounts for 95% of the world’s malaria cases and 96% of malaria deaths, with pregnant women and children under 5 years of age most affected [2, 3].
Long lasting insecticidal nets (LLIN) and indoor residual spraying (IRS) have played a key role in reducing the burden of malaria in Africa [4]. The expansion of these malaria vector control tools resulted in a 37% reduction in malaria incidence and a 60% reduction in mortality between 2000 and 2015 [5]. However, trends observed since 2015 have stalled alarmingly or even accelerated, with malaria deaths remaining unacceptably high, especially in sub-Saharan Africa [3]. Several studies have identified the emergence and spread of resistance among the major malaria vector Anopheles to insecticides used in public health as a barrier to the future effectiveness of LLIN and IRS [6,7,8]. In addition, changes in vector biting behavior outdoors and earlier at night are responsible for residual malaria transmission and are a growing concern [ 9 , 10 ]. Limitations of LLIN and IRS in controlling the vectors responsible for residual transmission are a major limitation of current malaria elimination efforts [11]. In addition, the persistence of malaria is explained by climatic conditions and human activities, which contribute to the creation of larval habitat [12].
Larval source management (LSM) is a breeding site-based approach to vector control that aims to reduce the number of breeding sites and the number of mosquito larvae and pupae contained within them [13]. LSM has been recommended by several studies as an additional integrated strategy for malaria vector control [14, 15]. In fact, the effectiveness of LSM provides a dual benefit against the bites of malaria vector species both indoors and outdoors [4]. In addition, vector control with larvicide-based LSMs such as Bacillus thuringiensis israelensis (Bti) can expand the range of malaria control options. Historically, LSM has played a key role in the successful control of malaria in the United States, Brazil, Egypt, Algeria, Libya, Morocco, Tunisia and Zambia [16,17,18]. Although LSM has played an important role in integrated pest management in some countries that have eradicated malaria, LSM has not been widely integrated into malaria vector control policies and practices in Africa and is used only in vector control programs in some sub-Saharan countries. countries [14,15,16,17,18,19]. One reason for this is the widespread belief that breeding sites are too numerous and difficult to find, making LSM very expensive to implement [4, 5, 6, 7, 8, 9, 10, 11, 13, 14]. Therefore, the World Health Organization has recommended for decades that resources mobilized for malaria vector control should focus on LLIN and IRS [ 20 , 21 ]. It was not until 2012 that the World Health Organization recommended the integration of LSM, particularly Bti interventions, as a complement to LLIN and IRS in certain settings in sub-Saharan Africa [20]. Since WHO made this recommendation, several pilot studies have been conducted on the feasibility, effectiveness and cost of biolarvicides in sub-Saharan Africa, demonstrating the effectiveness of LSM in reducing Anopheles mosquito densities and malaria transmission efficiency in terms of [22, 23]. . , 24].
Côte d’Ivoire is among the 15 countries with the highest malaria burden in the world [25]. The prevalence of malaria in Côte d’Ivoire represents 3.0% of the global malaria burden, with estimated incidence and number of cases ranging from 300 to over 500 per 1000 inhabitants [25]. Despite the long dry season from November to May, malaria spreads throughout the year in the northern savanna region of the country [26]. Malaria transmission in this region is associated with the presence of large numbers of asymptomatic carriers of Plasmodium falciparum [27]. In this region, the most common malaria vector is Anopheles gambiae (SL). Local security. Anopheles gambiae mosquitoes are primarily composed of Anopheles gambiae (SS), which is highly resistant to insecticides and therefore poses a high risk of residual malaria transmission [26]. The use of LLIN may have limited impact on reducing malaria transmission due to insecticide resistance of local vectors and therefore remains an area of major concern. Pilot studies using Bti or LLIN have shown effectiveness in reducing mosquito vector densities in northern Côte d’Ivoire. However, no previous studies have assessed the effect of repeated applications of Bti combined with LLIN on malaria transmission and malaria incidence in this region. Therefore, this study aimed to evaluate the effect of the combined use of LLIN and Bti on malaria transmission by comparing the LLIN + Bti group with the LLIN alone group in four villages in the northern region of Côte d’Ivoire. It was hypothesized that implementing a Bti-based LSM on top of LLIN would add value by further reducing malaria mosquito densities compared to LLIN alone. This integrated approach, targeting immature Anopheles mosquitoes carrying Bti and adult Anopheles mosquitoes carrying LLIN, could be critical to reducing malaria transmission in areas of high malaria endemicity, such as villages in northern Côte d’Ivoire. Therefore, the results of this study may help decide whether to include LSM in national malaria vector control programs (NMCPs) in endemic sub-Saharan countries.
The present study was carried out in four villages of the department of Napieldougou (also known as Napier) in the Korhogo sanitary zone in northern Côte d’Ivoire (Fig. 1). Villages under study: Kakologo (9° 14′ 2″ N, 5° 35′ 22″ E), Kolekakha (9° 17′ 24″ N, 5° 31′ 00″ E .), Lofinekaha (9° 17′ 31″). ) 5° 36′ 24″ N) and Nambatiurkaha (9° 18′ 36″ N, 5° 31′ 22″ E). The population of Napierledougou in 2021 was estimated to be 31,000 inhabitants, and the province consists of 53 villages with two health centers [28]. In Napyeledougou province, where malaria is the leading cause of medical visits, hospitalization and mortality, only LLIN is used to control Anopheles vectors [29]. All four villages in both study groups are served by the same health center, whose clinical records of malaria cases were reviewed in this study.
Map of Côte d’Ivoire showing the study area. (Map source and software: GADM data and ArcMap 10.6.1. LLIN long-lasting insecticidal net, Bti Bacillus thuringiensis israelensis
Malaria prevalence among the Napier Health Center target population reached 82.0% (2038 cases) (pre-Bti data). In all four villages, households use only PermaNet® 2.0 LLIN, distributed by the Ivorian NMCP in 2017, with >80% coverage [25, 26, 27, 28, 30]. The villages belong to the Korhogo region, which serves as a lookout point for the Ivory Coast National Military Council and is accessible all year round. Each of the four villages has at least 100 households and approximately the same population, and according to the health registry (a working document of the Ivorian Ministry of Health), several cases of malaria are reported each year. Malaria is primarily caused by Plasmodium falciparum (P. falciparum) and is transmitted to humans by Plasmodium. gambiae is also transmitted by Anopheles and Anopheles nili mosquitoes in the region [28]. Local complex An. gambiae consists primarily of Anopheles mosquitoes. gambiae ss has a high frequency of kdr mutations (frequency range: 90.70–100%) and a moderate frequency of ace-1 alleles (frequency range: 55.56–95%) [29].
Average annual rainfall and temperature range from 1200 to 1400 mm and 21 to 35 °C respectively, and relative humidity (RH) is estimated at 58%. This study area has a Sudanese-type climate with a 6-month dry season (November to April) and a 6-month wet season (May to October). The region is experiencing some of the effects of climate change, such as loss of vegetation and a longer dry season, characterized by the drying up of water bodies (lowlands, rice paddies, ponds, puddles) that can serve as habitat for Anopheles mosquito larvae. Mosquitoes[26].
The study was conducted in the LLIN + Bti group, represented by the villages of Kakologo and Nambatiurkaha, and in the LLIN only group, represented by the villages of Kolekaha and Lofinekaha. During the period of this study, people in all of these villages were using only PermaNet® 2.0 LLIN.
The effectiveness of LLIN (PermaNet 2.0) in combination with Bti against Anopheles mosquitoes and malaria transmission was evaluated in a randomized controlled trial (RCT) with two study arms: the LLIN + Bti group (treatment group) and the LLIN alone group (control group). The LLIN + Bti sleeves are represented by Kakologo and Nambatiourkaha, while Kolékaha and Lofinékaha were designed as LLIN-only shoulders. In all four villages, local residents are using LLIN PermaNet® 2.0 received from the Ivory Coast NMCP in 2017. It is assumed that the conditions for using PermaNet® 2.0 are the same in different villages because they received the network in the same way. . In the LLIN + Bti group, Anopheles larval habitats were treated with Bti every two weeks in addition to the LLIN already used by the population. Larval habitats within villages and within a 2 km radius from the center of each village were treated in accordance with the recommendations of the World Health Organization and the NMCP of Côte d’Ivoire [31]. In contrast, the LLIN-only group did not receive larvicidal Bti treatment during the study period.
A water-dispersible granular form of Bti (Vectobac WG, 37.4% wt; lot number 88–916-PG; 3000 International Toxicity Units IU/mg; Valent BioScience Corp, USA) was used at a dose of 0.5 mg/L. . Use a 16L backpack sprayer and a fiberglass spray gun with handle and adjustable nozzle with a flow rate of 52 ml per second (3.1 L/min). To prepare a nebulizer containing 10 L of water, the amount of Bti diluted in suspension is 0.5 mg/L × 10 L = 5 mg. For example, for an area with a design water flow of 10 L, using a 10 L sprayer to treat a volume of water, the amount of Bti that needs to be diluted is 0.5 mg/L × 20 L = 10 mg. 10 mg Bti was measured in the field using an electronic scale. Using a spatula, prepare a slurry by mixing this amount of Bti in a 10 L graduated bucket. This dose was selected after field trials of the effectiveness of Bti against various instars of Anopheles spp. and Culex spp. in natural conditions in an area different, but similar to the area of modern research [32]. The rate of application of the larvicide suspension and the duration of application for each breeding site were calculated based on the estimated volume of water at the breeding site [33]. Apply Bti using a calibrated hand sprayer. Nebulizers are calibrated and tested during individual exercises and in different areas to ensure the correct amount of Bti is delivered.
To find the best time to treat larval breeding sites, the team identified window spraying. The spray window is the period during which a product is applied to achieve optimal effectiveness: in this study, the spray window ranged from 12 hours to 2 weeks, depending on Bti persistence. Apparently, the uptake of Bti by larvae at the breeding site requires a period of time from 7:00 to 18:00. In this way, periods of heavy rain can be avoided when rain means stopping spraying and restarting the next day if the weather cooperates. Spraying dates and exact dates and times depend on observed weather conditions. To calibrate backpack sprayers for the desired Bti application rate, each technician is trained to visually inspect and set the sprayer nozzle and maintain pressure. Calibration is completed by verifying that the correct amount of Bti treatment is applied evenly per unit area. Treat the larvae habitat every two weeks. Larvicidal activities are carried out with the support of four experienced and well-trained specialists. Larvicidal activities and participants are supervised by experienced supervisors. Larvicidal treatment began in March 2019 during the dry season. In fact, a previous study showed that the dry season is the most suitable period for larvicidal intervention due to the stability of breeding sites and the decline in their abundance [27]. Controlling larvae during the dry season is expected to prevent the attraction of mosquitoes during the wet season. Two (02) kilograms of Bti costing US$99.29 allows the study group receiving treatment to cover all areas. In the LLIN+Bti group, larvicidal intervention lasted a full year, from March 2019 to February 2020. A total of 22 cases of larvicidal treatment occurred in the LLIN + Bti group.
Potential side effects (such as itching, dizziness or runny nose) were monitored through individual surveys of Bti biolarvicide nebulizers and household residents participating in the LIN + Bti group.
A household survey was conducted among 400 households (200 households per study group) to estimate the percentage of LLIN use among the population. When surveying households, a quantitative questionnaire method is used. The prevalence of LLIN use was divided into three age groups: 15 years. The questionnaire was completed and explained in the local Senoufo language to the head of the household or another adult over 18 years of age.
The minimum size of the surveyed household was calculated using the formula described by Vaughan and Morrow [34].
n is the sample size, e is the margin of error, t is the safety factor derived from the confidence level, and p is the proportion of the population’s parents with the given attribute. Each element of the fraction has a consistent value, so (t) = 1.96; The minimum household size in this situation in the survey was 384 households.
Prior to the current experiment, different habitat types for Anopheles larvae in the LLIN+Bti and LLIN groups were identified, sampled, described, georeferenced and labeled. Use a tape measure to measure the size of the nesting colony. Mosquito larval densities were then assessed monthly for 12 months at 30 randomly selected breeding sites per village, for a total of 60 breeding sites per study group. There were 12 larval samplings per study area, corresponding to 22 Bti treatments. The purpose of selecting these 30 breeding sites per village was to capture a sufficient number of larval collection sites across villages and study units to minimize bias. Larvae were collected by dipping with a 60 ml spoon [35]. Due to the fact that some nurseries are very small and shallow, it is necessary to use a small bucket other than the standard WHO bucket (350 ml). A total of 5, 10 or 20 dives were made from nesting sites with a circumference of 10 m, respectively. Morphological identification of collected larvae (e.g. Anopheles, Culex and Aedes) was carried out directly in the field [36]. The collected larvae were divided into two categories based on developmental stage: early instar larvae (stages 1 and 2) and late instar larvae (stages 3 and 4) [37]. Larvae were counted by genera and at each developmental stage. After counting, mosquito larvae are reintroduced to their breeding areas and replenished to their original volume with source water supplemented with rainwater.
A breeding site was considered positive if at least one larva or pupa of any mosquito species was present. Larval density was determined by dividing the number of larvae of the same genus by the number of dives.
Each study lasted for two consecutive days, and every two months, adult mosquitoes were collected from 10 households randomly selected from each village. Throughout the study, each research team conducted sample surveys of 20 households on three consecutive days. Mosquitoes were captured using standard window traps (WT) and pyrethrum spray traps (PSC) [38, 39]. At first, all the houses in each village were numbered. Four houses in each village were then randomly selected as collection points for adult mosquitoes. In each randomly selected house, mosquitoes were collected from the main bedroom. The selected bedrooms have doors and windows and were occupied the night before. Bedrooms remain closed before starting work and during mosquito collection to prevent mosquitoes from flying out of the room. A WT was installed in each window of each bedroom as a mosquito sampling point. The next day, mosquitoes that entered the workplace from the bedrooms were collected between 06:00 and 08:00 am. Collect mosquitoes from your work area using a mouthpiece and store them in a disposable paper cup covered with a raw piece. Mosquito net. Mosquitoes resting in the same bedroom were captured immediately after WT collection using pyrethroid-based PSC. After spreading white sheets on the bedroom floor, close the doors and windows and spray insecticide (active ingredients: 0.25% transfluthrin + 0.20% permethrin). About 10 to 15 minutes after spraying, remove the bedspread from the treated bedroom, use tweezers to pick up any mosquitoes that have landed on the white sheets, and store them in a Petri dish filled with water-soaked cotton wool. The number of people who spent the night in the selected bedrooms was also recorded. Collected mosquitoes are quickly transferred to an on-site laboratory for further processing.
In the laboratory, all collected mosquitoes were morphologically identified to genus and species [36]. Anna’s ovaries. gambiae SL using a binocular dissecting microscope with a drop of distilled water placed on a glass slide [35]. Parity status was assessed to separate multiparous women from nulliparous women based on ovarian and tracheal morphology, as well as to determine the fertility rate and physiological age [35].
The relative index is determined by testing the source of freshly collected blood meal. gambiae by enzyme-linked immunosorbent assay (ELISA) using blood from humans, livestock (cattle, sheep, goats) and chicken hosts [40]. Entomological infestation (EIR) was calculated using An. Estimates of SL women in The Gambia [41] Additionally, An. Infection with Plasmodium gambiae was determined by analyzing the head and chest of multiparous females using the circumsporozoite antigen ELISA (CSP ELISA) method [40]. Finally, there are the members of Ann. gambiae was identified by analyzing its legs, wings and abdomen using polymerase chain reaction (PCR) techniques [34].
Clinical data on malaria were obtained from the clinical consultation registry of Napyeledugou Health Centre, which covers all four villages included in this study (i.e. Kakologo, Kolekaha, Lofinekaha and Nambatiurkaha). The registry review focused on records from March 2018 to February 2019 and from March 2019 to February 2020. Clinical data from March 2018 to February 2019 represents baseline or pre-Bti intervention data, whereas clinical data from March 2019 to February 2020 represents pre-Bti intervention data. Data after Bti intervention. Clinical information, age and village of each patient in the LLIN+Bti and LLIN study groups were collected in the health registry. For each patient, information such as village origin, age, diagnosis, and pathology were recorded. In the cases reviewed in this study, malaria was confirmed by rapid diagnostic test (RDT) and/or malaria microscopy after administration of artemisinin-based combination therapy (ACT) by a health care provider. Malaria cases were divided into three age groups (i.e. 15 years). The annual incidence of malaria per 1000 inhabitants was estimated by dividing the prevalence of malaria per 1000 inhabitants by the village population.
Data collected in this study were double-entered into a Microsoft Excel database and then imported into the open source software R [42] version 3.6.3 for statistical analysis. The ggplot2 package is used to draw plots. Generalized linear models using Poisson regression were used to compare larval density and mean number of mosquito bites per person per night between study groups. Relevance ratio (RR) measurements were used to compare mean larval densities and bite rates of Culex and Anopheles mosquitoes. Gambia SL was placed between the two study groups using the LLIN + Bti group as the baseline. Effect sizes were expressed as odds ratios and 95% confidence intervals (95% CI). The ratio (RR) of the Poisson test was used to compare the proportions and incidence rates of malaria before and after the Bti intervention in each study group. The significance level used was 5%.
The study protocol was approved by the National Research Ethics Committee of the Ministry of Health and Public Health of Côte d’Ivoire (N/Ref: 001//MSHP/CNESVS-kp), as well as by the regional health district and the administration of Korhogo. Before collecting mosquito larvae and adults, signed informed consent was obtained from household survey participants, owners, and/or occupants. Family and clinical data are anonymous and confidential and are available only to designated investigators.
A total of 1198 nesting sites were visited. Of these nest sites surveyed in the study area, 52.5% (n = 629) belonged to the LLIN + Bti group and 47.5% (n = 569) to the LLIN only group (RR = 1.10 [95% CI 0 .98–1.24], P = 0.088). In general, local larval habitats were classified into 12 types, among which the largest proportion of larval habitats were rice fields (24.5%, n=294), followed by storm drainage (21.0%, n=252) and pottery ( 8.3). %, n = 99), river bank (8.2%, n = 100), puddle (7.2%, n = 86), puddle (7.0%, n = 84), village water pump (6.8 %, n = 81), Hoof prints (4.8%, n = 58), swamps (4.0%, n = 48), pitchers (5.2%, n = 62), ponds (1.9% , n = 23) and wells (0.9%, n = 11). ) .
Overall, a total of 47,274 mosquito larvae were collected from the study area, with a proportion of 14.4% (n = 6,796) in the LLIN + Bti group compared to 85.6% (n = 40,478) in the LLIN alone group ( (RR = 5.96) [95% CI 5.80–6.11], P ≤ 0.001). These larvae consist of three genera of mosquitoes, the predominant species being Anopheles. (48.7%, n = 23,041), followed by Culex spp. (35.0%, n = 16,562) and Aedes spp. (4.9%, n = 2340). Pupae comprised 11.3% of immature flies (n = 5344).
Overall average density of Anopheles spp. larvae. In this study, the number of larvae per scoop was 0.61 [95% CI 0.41–0.81] L/dip in the LLIN + Bti group and 3.97 [95% CI 3.56–4.38] L /dive in group LLIN only (optional). file 1: Figure S1). Average density of Anopheles spp. The LLIN alone group was 6.5 times higher than the LLIN + Bti group (HR = 6.49; 95% CI 5.80–7.27; P < 0.001). No Anopheles mosquitoes were detected during treatment. Larvae were collected in the LLIN + Bti group starting in January, corresponding to the twentieth Bti treatment. In the LLIN + Bti group, there was a significant decrease in early and late stage larval density.
Before the start of Bti treatment (March), the mean density of early instar Anopheles mosquitoes was estimated to be 1.28 [95% CI 0.22–2.35] L/dive in the LLIN + Bti group and 1.37 [95% CI 0.36– 2.36] l/dive in the LLIN + Bti group. l/dip. /dip only the LLIN arm (Fig. 2A). After application of the Bti treatment, the mean density of early Anopheles mosquitoes in the LLIN + Bti group generally gradually decreased from 0.90 [95% CI 0.19–1.61] to 0.10 [95% CI – 0.03–0.18] l/dip. Early instar Anopheles larval densities remained low in the LLIN + Bti group. In the LLIN-only group, fluctuations in the abundance of Anopheles spp. Early instar larvae were observed with mean densities ranging from 0.23 [95% CI 0.07–0.54] L/dive to 2.37 [95% CI 1.77–2.98] L/dive. Overall, the mean density of early Anopheles larvae in the LLIN-only group was statistically higher at 1.90 [95% CI 1.70–2.10] L/dive, while the mean density of early Anopheles larvae in group LLIN was 0.38 [95% CI 0.28–0.47]) l/dip. + Bti group (RR = 5.04; 95% CI 4.36–5.85; P < 0.001).
Changes in the average density of Anopheles larvae. Early (A) and late instar (B) mosquito nets in a study group from March 2019 to February 2020 in the Napier region, northern Côte d’Ivoire. LLIN: long-lasting insecticidal net Bti: Bacillus thuringiensis, Israel TRT: treatment;
Average density of Anopheles spp. larvae. late age in the LLIN + Bti group. Pre-treatment Bti density was 2.98 [95% CI 0.26–5.60] L/dip, whereas the density in the LLIN-alone group was 1.46 [95% CI 0.26–2.65] l/day After Bti application, the density of late-instar Anopheles larvae in the LLIN + Bti group decreased from 0.22 [95% CI 0.04–0.40] to 0.03 [95% CI 0.00–0.06] L/dip ( Fig. 2B). In the LLIN-only group, the density of late Anopheles larvae increased from 0.35 [95% CI - 0.15-0.76] to 2.77 [95% CI 1.13-4.40] l/dive with some variations in larval density depending on sampling date. The mean density of late-instar Anopheles larvae in the LLIN-only group was 2.07 [95% CI 1.84–2.29] L/dive, nine times higher than 0.23 [95% CI 0.11–0. 36] l/immersion in LLIN. + Bti group (RR = 8.80; 95% CI 7.40–10.57; P < 0.001).
Average density of Culex spp. Values were 0.33 [95% CI 0.21–0.45] L/dip in the LLIN + Bti group and 2.67 [95% CI 2.23–3.10] L/dip in the LLIN only group (additional file 2: Figure S2). Average density of Culex spp. The LLIN alone group was significantly higher than the LLIN + Bti group (HR = 8.00; 95% CI 6.90–9.34; P < 0.001).
Average density of the genus Culex Culex spp. Before treatment, Bti l/dip was 1.26 [95% CI 0.10–2.42] l/dip in the LLIN + Bti group and 1.28 [95% CI 0.37–2.36] in the only group LLIN (Fig. 3A). After application of the Bti treatment, densities of early Culex larvae decreased from 0.07 [95% CI - 0.001–0.] to 0.25 [95% CI 0.006–0.51] L/dip. No Culex larvae were collected from larval habitats treated with Bti beginning in December. Density of early Culex larvae was reduced to 0.21 [95% CI 0.14–0.28] L/dip in the LLIN + Bti group, but was higher in the LLIN only group at 1.30 [95% CI 1.10– 1.50] l/immersion. drop/d. The density of early Culex larvae in the LLIN alone group was 6 times higher than in the LLIN + Bti group (RR = 6.17; 95% CI 5.11–7.52; P < 0.001).
Changes in the average density of Culex spp. larvae. Early life (A) and early life (B) trials in a study group from March 2019 to February 2020 in the Napier region, northern Côte d’Ivoire. Long lasting insecticidal net LLIN, Bti Bacillus thuringiensis Israel, Trt treatment
Before Bti treatment, the mean density of late instar Culex larvae in the LLIN + Bti group and the LLIN group was 0.97 [95% CI 0.09–1.85] and 1.60 [95% CI – 0.16–3.37] l/immersion accordingly (Fig. 3B) ). Mean density of late-instar Culex species after initiation of Bti treatment. The density in the LLIN + Bti group gradually decreased and was lower than that in the LLIN only group, which remained very high. The mean density of late instar Culex larvae was 0.12 [95% CI 0.07–0.15] L/dive in the LLIN + Bti group and 1.36 [95% CI 1.11–1.61] L/dive in group only LLIN. The mean density of late-instar Culex larvae was significantly higher in the LLIN-only group than in the LLIN + Bti group (RR = 11.19; 95% CI 8.83–14.43; P < 0.001).
Before Bti treatment, the mean density of pupae per ladybug was 0.59 [95% CI 0.24–0.94] in the LLIN + Bti group and 0.38 [95% CI 0.13–0.63] in the LLIN only (Fig. 4). Overall pupal density was 0.10 [95% CI 0.06–0.14] in the LLIN + Bti group and 0.84 [95% CI 0.75–0.92] in the LLIN alone group. Bti treatment significantly reduced the mean pupal density in the LLIN + Bti group compared with the LLIN alone group (OR = 8.30; 95% CI 6.37–11.02; P < 0.001). In the LLIN + Bti group, no pupae were collected after November.
Changes in the average density of pupae. The study was conducted from March 2019 to February 2020 in the Napier region in northern Côte d’Ivoire. Long lasting insecticidal net LLIN, Bti Bacillus thuringiensis Israel, Trt treatment
A total of 3456 adult mosquitoes were collected from the study area. Mosquitoes belong to 17 species of 5 genera (Anopheles, Culex, Aedes, Eretmapodites) (Table 1). In malaria vectors An. gambiae sl was the most abundant species with a proportion of 74.9% (n = 2587), followed by An. gambiae sl. funestus (2.5%, n = 86) and An null (0.7%, n = 24). Anna’s wealth. gambiae sl in the LLIN + Bti group (10.9%, n = 375) was lower than in the LLIN alone group (64%, n = 2212). No peace. nli individuals were grouped with LLIN only. However, An. gambiae and An. funestus were present in both the LLIN + Bti group and the LLIN alone group.
In studies starting before Bti application at the breeding site (3 months), the overall mean number of nocturnal mosquitoes per person (b/p/n) in the LLIN + Bti group was estimated to be 0.83 [95% CI 0.50–1.17 ], whereas in the LLIN + Bti group it was 0.72 in the LLIN only group [95% CI 0.41–1.02] (Fig. 5). In the LLIN + Bti group, Culex mosquito damage decreased and remained low despite a peak of 1.95 [95% CI 1.35–2.54] bpp in September after the 12th Bti application. However, in the LLIN-only group, the mean mosquito bite rate gradually increased before peaking in September at 11.33 [95% CI 7.15–15.50] bp/n. The overall incidence of mosquito bites was significantly lower in the LLIN + Bti group compared with the LLIN alone group at any time point during the study (HR = 3.66; 95% CI 3.01–4.49; P < 0.001).
Bite rates of mosquito fauna in the study area of the Napier region in northern Côte d’Ivoire from March 2019 to February 2020 LLIN Long lasting insecticidal net, Bti Bacillus thuringiensis Israel, Trt treatment, bites b/p/night/human/night
Anopheles gambiae is the most common malaria vector in the study area. Bite speed of An. At baseline, Gambian women had b/p/n values of 0.64 [95% CI 0.27–1.00] in the LLIN + Bti group and 0.74 [95% CI 0.30–1.17] in the group only LLIN (Fig. 6). During the Bti intervention period, the highest biting activity was observed in September, corresponding to the twelfth course of Bti treatment, with a peak of 1.46 [95% CI 0.87–2.05] b/p/n in the LLIN + Bti group and a peak of 9 .65 [95% CI 0.87–2.05] w/n 5.23–14.07] LLIN group only. Overall bite speed of An. The infection rate in The Gambia was significantly lower in the LLIN + Bti group (0.59 [95% CI 0.43–0.75] b/p/n) than in the LLIN alone group (2.97 [95% CI 2, 02–3.93] b/p/no). (RR = 3.66; 95% CI 3.01–4.49; P < 0.001).
Anna’s bite speed. gambiae sl, research unit in the Napier region, northern Cote d’Ivoire, from March 2019 to February 2020 LLIN insecticide-treated long-lasting bed net, Bti Bacillus thuringiensis Israel, Trt treatment, bites b/p/night/ person/night
Total 646 amps. The Gambia is dismembered. Overall, the percentage of local security. Parity rates in The Gambia were generally >70% throughout the study period, with the exception of July, when only the LLIN group was used (Additional file 3: Figure S3). However, the average fertility rate in the study area was 74.5% (n = 481). In the LLIN+Bti group, the parity rate remained at a high level, above 80%, with the exception of September, when the parity rate fell to 77.5%. However, variations in mean fertility rates were observed in the LLIN-only group, with the lowest estimated mean fertility rate being 64.5%.
From 389 Ann. A study of individual blood units from The Gambia found that 80.5% (n = 313) were of human origin, 6.2% (n = 24) of women consumed mixed blood (human and domestic) and 5.1% (n = 20) consumed blood. feed from livestock (cattle, sheep and goats) and 8.2% (n = 32) of samples analyzed were negative for blood meal. In the LLIN + Bti group, the proportion of women receiving human blood was 25.7% (n = 100) compared to 54.8% (n = 213) in the LLIN only group (Additional file 5: Table S5).
Total 308 amps. P. gambiae was tested to identify members of the species complex and P. falciparum infection (Additional file 4: Table S4). Two “related species” coexist in the study area, namely An. gambiae ss (95.1%, n = 293) and An. coluzzii (4.9%, n = 15). Anopheles gambiae ss were significantly lower in the LLIN + Bti group than in the LLIN alone group (66.2%, n = 204) (RR = 2.29 [95% CI 1.78–2.97], P < 0.001) . A similar proportion of Anopheles mosquitoes were found in the LLIN + Bti group (3.6%, n = 11) and the LLIN only group (1.3%, n = 4) (RR = 2.75 [95% CI 0.81–11 .84], P = .118). Prevalence of Plasmodium falciparum infection among An. SL in Gambia was 11.4% (n = 35). Plasmodium falciparum infection rates. The infection rate in The Gambia was significantly lower in the LLIN + Bti group (2.9%, n = 9) than in the LLIN alone group (8.4%, n = 26) (RR = 2.89 [95% CI 1. 31–7.01], P = 0.006). ). Compared to Anopheles mosquitoes, Anopheles gambiae mosquitoes had the highest proportion of Plasmodium infection at 94.3% (n=32). coluzzii only 5.7% (n = 5) (RR = 6.4 [95% CI 2.47–21.04], P < 0.001).
A total of 2,435 people from 400 households were surveyed. The average density is 6.1 people per household. The rate of LLIN ownership among households was 85% (n = 340), compared with 15% (n = 60) for households without LLIN (RR = 5.67 [95% CI 4.29–7.59], P < 0.001) ( Additional file 5: Table S5). . LLIN use was 40.7% (n = 990) in the LLIN + Bti group compared with 36.2% (n = 882) in the LLIN alone group (RR = 1.12 [95% CI 1.02–1.23 ], P = 0.013). The average overall net utilization rate in the study area was 38.4% (n = 1842). The proportion of children under five years of age using the Internet was similar in both study groups, with net usage rates of 41.2% (n = 195) in the LLIN + Bti group and 43.2% (n = 186) in group only LLIN. (HR = 1.05 [95% CI 0.85–1.29], P = 0.682). Among children aged 5 to 15 years, there was no difference in net use rates between 36.3% (n = 250) in the LLIN + Bti group and 36.9% (n = 250) in the LLIN only group (RR = 1. 02 [95% CI 1.02–1.23], P = 0.894). However, those over 15 years of age used bed nets 42.7% (n = 554) less often in the LLIN + Bti group than 33.4% (n = 439) in the LLIN only group (RR = 1.26 [95% CI 1.11–1.43], P <0.001).
A total of 2,484 clinical cases were recorded at Napier Health Center between March 2018 and February 2020. The prevalence of clinical malaria in the general population was 82.0% of all cases of clinical pathology (n = 2038). The annual local incidence rates of malaria in this study area were 479.8‰ and 297.5‰ before and after Bti treatment (Table 2).
Post time: Jul-01-2024