Mosquito Breeding Habitats Research Articles

Characterization of Anopheles mosquito breeding habitats for malaria vector control in Mazowe and Shamva districts, Zimbabwe.

Area-specific identification and studies of Anopheles breeding habitat diversity, distribution, and productivity in different seasons are important in designing and advancing effective malaria vector control according to the local context and needs. This study identified and characterized Anopheles breeding habitats for targeted control of malaria vectors in Mazowe and Shamva districts. Repeated cross-sectional surveys were conducted in Mazowe and Shamva districts between April and December 2023. Habitat productivity and physicochemical parameters were measured. Anopheles larvae were collected, reared to adults, and identified using morphological keys. SPSS software was used for data analysis. One-way ANOVA, Fisher's exact, Pearson's correlation, and simple linear regression tests were conducted. Seven different types of Anopheles breeding habitats were identified from 56 sites. The highest mean density of larvae was recorded in stream edge pools during the post-rainfall period. Anophelespretoriensis (67.4%), An. gambiae s.l. (23.1%), An. rufipes (9.2%) and An. coustani (0.38%) were breeding in the study area. Anopheles pretoriensis bred in all habitat types, An. coustani in swamps only while An. gambiae s.l. and An. rufipes preferred stream edge pools, roadside pools, and hoof prints. There was a significant positive correlation between larval density and dissolved oxygen (r = 0.535; p < 0.001) and conductivity (r = 0.288; p = 0.032). Size, origin, and type of breeding habitat were positive indicators for different Anopheles species in the study area. Potential malaria vector breeding habitats should be targeted for larval control under the current malaria control and elimination phases in the two districts.

Larval habitat diversity, physicochemical characterization and their effect on the density of larval malaria vectors in the city of Accra, Ghana.

Malaria is more prevalent in rural areas due to fewer mosquito breeding habitats in urban settings. However, urban factors such as irrigated farming, open sewers, and discarded containers create mosquito breeding sites. This study investigates the diversity and distribution of larval habitats and the impact of physicochemical characteristics on the presence and density of Anopheles gambiae s.l. larvae in Accra, Ghana. Larval surveys and collections were conducted at fifteen locations in Accra, divided into five categories: Irrigated Urban Farming (IUF), Lower Socioeconomic Status (LS), Middle Socioeconomic Status (MS), High Socioeconomic Status (HS), and Peri-urban (PU) areas. Physicochemical parameters were measured, and species identification was performed using morphological and molecular methods. A total of 727 breeding habitats were identified, with 65.34% (475/727) positive for Anopheles larvae. Drainage ditches were the most common habitat type (48.21%, 229/475). The highest abundance of An. gambiae s.l. was found in IUF sites (6,244/22,919), especially during the rainy season (77.01%, 17,650/22,919; R2 = 3.46, P = 0.000). Polluted habitats, including household effluents, had higher ammonium levels (3.4 mg/L NH -N) compared to unpolluted ones (1.3 mg/L NH -N). Other distinguishing parameters included dissolved oxygen (34% vs 52.9%), conductivity (5106 μS/cm vs 2049 μS/cm), and total dissolved solids (3181 mg/L vs 1255 mg/L). The predominant malaria vector was An. coluzzii(54.4%, 368/677). Additionally, the invasive An. stephensi, previously unreported in Ghana, was detected. Malaria vectors breed in diverse and often polluted urban habitats, with high larval densities in urban agricultural areas. The detection of the invasive An. Stephensi highlights the need for continuous monitoring and vector control strategies in urban settings.

Identifying villages and breeding habitats for dengue transmission in Thailand: insights from long-term larval surveys

BackgroundIn Thailand, the Department of Disease Control (DDC) regularly performs visual larval surveys throughout the country to monitor dengue fever outbreaks. Since 2016, the DDC switched from a paper-based to a digital-based larval survey process. The significant amount of larval survey data collected digitally presents a valuable opportunity to precisely identify the villages and breeding habitats that are vulnerable to dengue transmission.MethodsThe study used digitally collected larval survey data from 2017 to 2019. It employed larval indices to evaluate the risk of dengue transmission in villages based on seasonal, regional, and categorical perspectives. Furthermore, the study comprehensively scrutinized each container category by employing different measures to determine its breeding preference ratio.ResultsThe result showed that villages with a very high-risk of dengue transmission were present year-round in all regions, with the highest proportion during the rainy season. The Southern region had more high-risk villages during the winter season due to rainfall. Slums and residential communities were more vulnerable to dengue than commercial areas. All container categories could potentially serve as breeding habitats for dengue-carrying mosquitoes, with abandoned containers being the most significant breeding sites.ConclusionsThe risk of dengue transmission was present year-round throughout Thailand. This underscores the importance of community and government initiatives, along with sustained public awareness campaigns and active community engagement, to efficiently and permanently eradicate mosquito breeding habitats. It should be noted that larval indices may not strongly correlate with dengue cases, as indicated by the preliminary analysis. However, they offer valuable insights into potential breeding sites for targeted preventive measures.

Physico-chemical characteristics of breeding habitats in relation to larval density and relative abundance of Aedes mosquitoes from Siliguri sub-division, West Bengal, India

Aim: Characterization of physico-chemical parameters of Aedes mosquito breeding habitats from dengue-endemic Siliguri sub-divisional area and correlation of larval density with the habitat characteristics. Methodology: Natural and artificial water-holding containers found in four blocks, namely- Naxalbari, Matigara, Khoribari and Phansidewa of Siliguri sub-divisional area were surveyed for the collection of Aedes mosquito larvae. Water parameters such as pH, temperature, electric conductance (EC), total dissolved solid (TDS), chloride, salinity, total hardness (TH) and dissolved oxygen (DO) were measured and the larval density (LD) indices and relative abundance for Aedes spp., were calculated. Results: Out of 40 habitats, larvae of Aedes spp. were found in 20 habitats (50%). Ae. albopictus was found as the pre-dominant species (81.24%) in all the positive breeding habitats. Three habitat characteristics, like chloride (r= -0.959; p= 0.041), salinity (r= -0.958; p= 0.041)and TH (r= -0.961; p= 0.039) showed significant negative association with larval densityin the study. Whereas the remaining parameters, like-pH, temperature, EC, TDS, were positively correlated and DO showed a negative correlation with larval density. Although none of the later correlations were statistically significant. The larval density of Aedes spp. (mean ± SD) was lowest in Khoribari (27.66 ± 21.55) and highest in Phansidewa block (128.33 ± 187.26). Interpretation: Pre-dominance of Ae. albopictus reiterates its importance as a principal dengue vectorin rural, peri- or sub-urban area of the sub-division. Utilizing the obtained data, the efficacy of oviposition traps can be enhanced for locale-specific vector surveillance and development of novel techniques that may deter larval growth, development and survival in an area. Key words: Aedes mosquitoes, Dengue, Larval density, Mosquito-borne viral diseases, Siliguri

The Influence of Population Behavior and Settlement Environment on the Incidence of Filariasis in Sigi Regency, Central Sulawesi, Indonesia

Introduction: A health issue is filariasis including in Sigi Regency, brought on by filarial worms and spread by mosquito bites. Filariasis is a parasitic infection that threatens about one-third or 1.3 billion of the world’s population in 83 countries that are vulnerable to filariasis. This research intends to examine the impact of behaviour and environment on the occurrence of filariasis in the Sigi Regency. Methods: The study used an observational analytic method with a case control approach, involving 114 people from 13 villages in Sigi Regency, of whom 38 were cases and 76 were controls. The control group is people who live in the same environment as the case group. The data collection methods were a survey and an environmental assessment. Results and Discussions: The logistic regression analysis revealed that the most influential factors for the occurrence of filariasis in endemic regions in Sigi Regency were mosquito breeding sites with Odds Rasio (OR) value =8.57 (2.43-34.33), p-value = &lt;0.001, existence of animal pens with OR value=5.16 (1.15-29.44), p-value = 0.044, and not using anti-mosquito medication with OR value = 6.06 (1.54-27.56), p-value = 0.013. Conclusion: The breeding habitats of disease-transmitting mosquitoes, the presence of animal pens and the habit of not using anti-mosquito medication are the dominant risk factors related to the occurrence of filariasis in endemic regions in the Sigi Regency.

Species composition of larval mosquitoes (Diptera: Culicidae) in bamboo stumps in mid-western Nepal

ABSTRACT Bamboo stumps serve as important phytotelmata in which mosquitoes breed. The physiochemical parameters of water in the bamboo stumps influence the species composition and larval abundance of mosquito species. Bamboo stumps were scanned in monsoon season of 2022 by adopting a larval survey method in mid-western Nepal. Supplementary data such as water volume, temperature and pH were also recorded. The linear relationship between different physiochemical parameters with mosquito larval population and larval abundance of different mosquito species was analysed in RStudio-1.0.44 and Past software version 4.07. Altogether, 120 larval mosquitoes belonging to 7 species and 3 genera were recorded from 26 bamboo stumps. The larval abundance of immature mosquito shows positive correlation with water temperature, pH and volume of the water. The coexistence of larvae of dengue vectors (Aedes aegypti and Aedes albopictus) and vector of Lymphatic Filariasis (Culex quinquefasciatus) as well the coexistence of different larval mosquito species were recorded. This established bamboo stumps as important mosquito breeding habitats including vector species in mid-western Nepal.

Seasonal Diversity in Mosquito Larval Ecology and Its Public Health Implications in Urban Slums of Lagos, Nigeria.

Mosquito-borne diseases (MBDs) are major public health burdens in tropical nations, including Nigeria. This study assessed mosquito larval species composition, abundance, and abiotic factors influencing mosquito breeding in slum communities of Lagos with the goal of informing MBD control measures. Three slum communities-Bariga, Makoko, and Ajegunle-were selected along with the nonslum community of Ikeja, which served as a control site. Larval sampling was done using the standard dipping technique between December 2021 and July 2022 across the dry and wet seasons. Mosquito larvae were raised to adults and identified using morphological keys and molecular assays. A total of 57,753 immature mosquitoes were collected from all study sites, with a significantly (P < 0.05) greater abundance in the dry season than the wet season. The majority (98.1%) of the mosquitoes collected belonged to Culex pipiens s.l., the only species found during the dry season in almost all locations. In the wet season, species identified from all sites combined were Anopheles gambiae ss., Anopheles arabiensis, Aedes aegypti, Aedes albopictus, Cx. pipiens s.l., and Lutzia tigripes, with Ajegunle having the greatest species diversity (H = 0.593). Among physicochemical parameters measured, only water temperature had a significant positive correlation (r = 0.934, P = 0.020) with larval densities in Ajegunle only. Permanent mosquito-breeding habitats had significantly greater larval densities than temporary habitats within the slum communities. These findings could inform the development of integrated vector control strategies that address the different species of mosquitoes in the fight against MBDs in urban slums.

Ecological and physicochemical characteristics of tree holes as mosquito breeding habitats: A systematic review

Ecological and physicochemical characteristics of tree holes as mosquito breeding habitats: A systematic review

Evaluation of Insect Growth Regulators (IGRs) as biological pesticides for control of Aedes aegypti mosquitoes

Background &amp; objectives: Insect growth regulators (IGRs) are biological hormone analogue or mimics used as pesticides to inhibit the growth of larva during their molting and skin shedding. This study aimed to test the effect of IGRs on the eggs hatching and post-hatching inhibition of Aedes mosquitoes and understanding its effect in the mosquito breeding habitats for reduction in adult emergence. Methods: Experiments on the evaluation of three insect growth regulators (IGRs) for the control of different stages of Aedes aegypti was carried out during 2020-21. Each experiment consisted of four treatments viz., Pyriproxyfen, Novaluron, and Larvicol at 1.0 ppm and distilled water as a control. All experiments were carried out in completely randomized design (CRD) except eggs which were carried out in factorial design each with three replications. Results: All tested IGRs performed better in affecting eggs, larval and pupal stages of Ae. aegypti. Highest eggs hatching inhibition (80%) of fresh eggs occurred in Pyriproxyfen followed by Novaluron (66%) and lowest in Larvicol (62%). Eggs hatch inhibition of embryonated eggs was lower than fresh eggs. Pyriproxyfen caused 69%, Novaluron 59% and Larvicol 39% eggs hatch inhibition of embryonated eggs. Both Pyriproxyfen and Novaluron performed better in causing 98–100% larval mortality followed by Larvicol (39%). Larval development to pupal stage was completely prevented by both Pyriproxyfen and Novaluron. Although Larvicol resulted in lowest eggs hatch and larval inhibition but prevented pupae to emerge as adults. Results further showed 70–89% mortality of 3rd instar larvae of Ae. aegypti when exposed to Pyriproxyfen and Novaluron solutions after 30 days storage at lab. temperature (27±2°C), RH 70±5. Interpretation &amp; conclusion: None of the IGRs was more effective at the pupal stage but showed carry-on activity of growth inhibition and mortality of the successive stages of development when used against eggs stages. Therefore, we recommend early application of IGRs at mosquito habitats during the beginning and onset of the season when very early stages of mosquitoes are available in the field.

Determinants of Aedes mosquito larval ecology in a heterogeneous urban environment- a longitudinal study in Bengaluru, India.

Aedes-borne disease risk is associated with contemporary urbanization practices where city developing structures function as a catalyst for creating mosquito breeding habitats. We lack better understanding on how the links between landscape ecology and urban geography contribute to the prevalence and abundance of mosquito and pathogen spread. An outdoor longitudinal study in Bengaluru (Karnataka, India) was conducted between February 2021 and June 2022 to examine the effects of macrohabitat types on the diversity and distribution of larval habitats, mosquito species composition, and body size to quantify the risk of dengue outbreak in the landscape context. A total of 8,717 container breeding sites were inspected, of these 1,316 were wet breeding habitats. A total of 1,619 mosquito larvae representing 16 species from six macrohabitats and nine microhabitats were collected. Aedes aegypti and Aedes albopictus were the dominant species and significantly higher in artificial habitats than in natural habitats. Breeding preference ratio for Aedes species was high in grinding stones and storage containers. The Aedes infestation indices were higher than the WHO threshold and showed significant linear increase from Barren habitat to High density areas. We found Ae. albopictus breeding in sympatry with Ae. aegypti had shorter wing length. A large proportion of larval habitats were man-made artificial containers. Landscape ecology drives mosquito diversity and abundance even at a small spatial scale which could be affecting the localized outbreaks. Our findings showed that sampling strategies for mosquito surveillance must include urban environments with non-residential locations and dengue transmission reduction programmes should focus on 'neighbourhood surveillance' as well to prevent and control the rising threat of Aedes-borne diseases.

Diversity and species composition of microbiota associated with dengue mosquito breeding habitats: A cross-sectional study from selected areas in Udapalatha MOH division, Sri Lanka

Objective: To determine the diversity of microbiota associated with different breeding habitats of dengue vector mosquitoes Aedes (Ae.) aegypti. and Ae. albopictus and to identify any parasitic, epibiont, pathogenic, competitive or predatory species. Methods: Sampling was performed from a variety of breeding habitats using dipping, pipetting and siphoning techniques. Microbiota in water samples were preserved using Rose Bengal solution and Lugol's iodine, and were identified. Live samples of microbiota were kept under laboratory conditions to observe any pathogenic or parasitic microbiota interacting with larvae. Results: A total of eleven microbiota species (Canthocamptus staphylinus, Canthocamptus microstaphylinus, Parastenocaris brevipes, Lepadella ovalis, Lepadella patella, Rotatoria rotatoria, Rotatoria macrura, Asplanchna brightwelli, Trichocerca rattus, Euglena variabilis, and Flagilaria capucina) belonging to four (4) phyla (Arthropoda, Rotifera, Euglenozoa, and Ochrophyta) and 8 microbiota species belonged to four phyla (Arthropoda, Rotifera, Euglenozoa, and Ochrophyta) were identified from Ae. aegypti and Ae. albopictus breeding habitats respectively. There was a higher percentage (54.54%) of larval habitats positive for the secondary vector Ae. albopictus than through the primary vector Ae. aegypti in the Gampola urban area indicating higher possibility of transmitting the dengue virus through the secondary vector. However, no pathogenic or parasitic ciliates on mosquito larvae were encountered in the present study. Those findings may be due to sampling maingly from temporary container-type breeding habitats. Conclusions: The relative distribution of microbiota associated with mosquito species differed significantly among Ae. aegypti and Ae. albopictus. The overall findings of this study could help in implementing novel eco-friendly vector-control strategies in the study area.

The 2022 dengue outbreak in Bangladesh: hypotheses for the late resurgence of cases and fatalities.

Bangladesh reported the highest number of annual deaths (n = 281) related to dengue virus infection in 2022 since the virus reappeared in the country in 2000. Earlier studies showed that >92% of the annual cases occurred between the months of August and September. The 2022 outbreak is characterized by late onset of dengue cases with unusually higher deaths in colder months, that is, October-December. Here we present possible hypotheses and explanations for this late resurgence of dengue cases. First, in 2022, the rainfall started late in the season. Compared to the monthly average rainfall for September and October between 2003 and 2021, there was 137 mm of additional monthly rainfall recorded in September and October 2022. Furthermore, the year 2022 was relatively warmer with a 0.71°C increased temperature than the mean annual temperature of the past 20 yr. Second, a new dengue virus serotype, DENV-4, had recently reintroduced/reappeared in 2022 and become the dominant serotype in the country for a large naïve population. Third, the post-pandemic return of normalcy after 2 yr of nonpharmaceutical social measures facilitates extra mosquito breeding habitats, especially in construction sites. Community engagement and regular monitoring and destruction of Aedes mosquitoes' habitats should be prioritized to control dengue virus outbreaks in Bangladesh.

Increased malaria incidence following irrigation practices in the Endorheic Rift Valley Basin of Sidama Region, Ethiopia.

Water resource development practice such as irrigation is key to ensuring economic growth and food security in developing countries. However, unintended public health problems such as malaria linked to such development projects have been a concern. This study aimed to determine the impact of irrigation on malaria incidence and vector mosquito abundance in southern Ethiopia. Eight years' malaria morbidity data were extracted from the medical registers of health facilities in both irrigated and non-irrigated settings. Additionally, adult and larval malaria vector surveys were carried out in both irrigated and non-irrigated villages. The trend of malaria incidence, case distribution across age and sex, seasonality, parasite species proportion, and mosquito density were analyzed and compared between irrigated and non-irrigated villages. The result showed that annual mean malaria incidence was 6.3 higher in the irrigated (95% CI: 0.7-33.6) than in the non-irrigated villages (95% CI: 1.2-20.6). Although a remarkable declining trend in malaria incidence was observed for four successive years (2013-2017), a significant resurgence between 2018 and 2020 was noted following the introduction of irrigation schemes. The densities of adult Anopheles mosquitoes were 15-fold higher in the irrigated compared to non-irrigated villages. Of the total potential mosquito-breeding habitats surveyed, the majority (93%) were from irrigated villages. Higher malaria incidence, adult Anopheles density, and mosquito-breeding habitat were recorded in the irrigated villages compared to non-irrigated villages. These observations have important implications for the effectiveness of existing malaria interventions. Environmental management could help reduce the breeding of malaria vector mosquitoes around irrigation schemes.

Digitally managed larviciding as a cost-effective intervention for urban malaria: operational lessons from a pilot in São Tomé and Príncipe guided by the Zzapp system

BackgroundOnce a mainstay of malaria elimination operations, larval source management (LSM)—namely, the treatment of mosquito breeding habitats–has been marginalized in Africa in favour of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). However, the development of new technologies, and mosquitoes' growing resistance to insecticides used in LLINs and IRS raise renewed interest in LSM.MethodsA digitally managed larviciding (DML) operation in three of the seven districts of São Tomé and Príncipe (STP) was launched by the Ministry of Health (MOH) and ZzappMalaria LTD. The operation was guided by the Zzapp system, consisting of a designated GPS-based mobile application and an online dashboard, which facilitates the detection, sampling and treatment of mosquito breeding sites. During the operation, quality assurance (QA) procedures and field management methods were developed and implemented.Results12,788 water bodies were located and treated a total of 128,864 times. The reduction impact on mosquito population and on malaria incidence was 74.90% and 52.5%, respectively. The overall cost per person protected (PPP) was US$ 0.86. The cost varied between areas: US$ 0.44 PPP in the urban area, and US$ 1.41 PPP in the rural area. The main cost drivers were labour, transportation and larvicide material.ConclusionDML can yield highly cost-effective results, especially in urban areas. Digital tools facilitate standardization of operations, implementation of QA procedures and monitoring of fieldworkers’ performance. Digitally generated spatial data also have the potential to assist integrated vector management (IVM) operations. A randomized controlled trial (RCT) with a larger sample is needed to further substantiate findings.

Observation and Simulation of Mosquito Breeding Site Water Temperature for Malaria Transmission at Kaita Local Governmet Township of Katsina State, Nigeria

Studies showed that transmission of malaria is influenced by environmental factors such as temperature. This work is aimed at finding the impact of mosquito's breeding site water temperature on mosquito's larva development time. An artificial mosquito's breeding habitat was created. The water temperature of the habitat was measured at an hourly interval, then it is averaged into daily time scale. Weather variables of the experimental site were inpu into the the energy balance model to simulate the breeding habit water temperature. The mosquito's larva development time was then predicted by inputting both the observed water and simulated water temperature into the vector borne disease community model (VECTRI) .The daily maximum, and minimum observed water temperatures were 27.9°C, 32.6°C and 21.7°C, respectively. The daily mean, maximum, and minimum simulated water temperatures were 29.8°C, 35.6°C, and 23.5°C respectively. These temperatures are within the temperature range that supports mosquito’s larva development. Mosquito's larva development was predicted using the VECTRI model. According to this study larva development reached completion in 7.1 days using the observed water temperature, 6.03 days using the simulated water temperature and 8.01days using the observed air temperature. This energy balance model is an improved water temperature scheme over the assumption that air temperature is equal to air temperature. This work shows the importance of water temperature and the value of degree day required for emergence of an adult mosquito in the simulation of aquatic stage development. Both the observed water and simulated water temperatures are higher than the on observed air temperature, thus air temperature cannot be used as the water temperature in the simulation of the mosquito’s larva development time. The finding of the work can be used as source toward mosquito's larval control through water temperature. It is however clear from the finding that could be as result of temperature due to shorter time predicted for mosquito's larval development.

Combined effect of physico-chemical and microbial quality of breeding habitat water on oviposition of malarial vector Anopheles subpictus.

Mosquitoes prefer diverse water bodies for egg laying and larval survival. Present study was performed with an objective to characterize physico-chemical properties and microbial profiling of breeding habitat water bodies of Anopheles subpictus mosquitoes. A field survey was accomplished to check the presence of An. subpictus larvae to record per dip larval density in various breeding habitats throughout the year. Physico-chemical and bacteriological properties in relation to mosquito oviposition were assessed. Dissolved oxygen content, pH and alkalinity were found to have major impacts and ponderosity on the prevalence of An. subpictus larvae. Larval density showed significant positive correlation with dissolved oxygen content of water and significant negative correlation with pH and alkalinity of habitat water. Comparatively higher population (cfu/mL) of Bacillus spp. competent with starch hydrolyzing and nitrate reducing properties were recorded all the breeding habitat water bodies of An. subpictus. Higher amplitude of anopheline larvae was portrayed during monsoon and post-monsoon season in clear water with an inclining trend to high dissolved oxygen content and neutral pH. B. cereus, B. megaterium, B. subtilis and B. tequilensis prevalent in all habitat water bodies were marked as oviposition attractants of gravid An. subpictus mosquitoes. Microbial population played key roles in the modulation of physico-chemical parameters of habitat water with a view to enhance its acceptability by gravid mosquitoes in relation to their oviposition. Better understanding of the interactions along with the control of oviposition attractant bacterial strains from mosquito breeding habitats might contribute to the vector management programme.

Knowledge, practices and perceptions of communities during a malaria larviciding randomized trial in the city of Yaoundé, Cameroon

Urban malaria is becoming a major public health concern in major cities in Cameroon. To improve malaria vector control, a pilot larviciding trial was conducted to assess its impact on mosquito density and malaria transmission intensity in Yaoundé. The present study investigated perceptions and practices of communities on malaria control during the larviciding trial implemented in Yaoundé. Quantitative and qualitative data were collected in non-intervention and intervention areas. Quantitative data were collected during three cross-sectional surveys using a structured pre-tested questionnaire while qualitative data were obtained through interviews. A total of 26 in-depth interviews and eight focus group discussions with community members were performed. A binary logistic regression model was used to assess the perception of the community on larviciding impact on some malaria or bed nets use indicators. People living in intervention areas were 2.64 times more likely to know the mode of malaria transmission (95% CI: 1.82-3.84; p<0.001) and 1.3 time more likely to know mosquito breeding habitats (95% CI: 1.06-1.56; p = 0.009) compared to those living in non-intervention areas. In intervention areas, interviewee opinions on larviciding were generally good i.e. most interviewees reported having noticed a reduction in mosquito nuisance and malaria cases following larviciding implementation; whereas in non-intervention areas no report of reduction of mosquito nuisance was recorded. LLINs were regularly used by the population despite the implementation of larviciding treatments. There was high interest in larviciding program and demand for continuation, even if this needs the community involvement. The larviciding program in the city of Yaoundé did not negatively affected community members' behaviour and practices concerning the use of treated nets. The study indicated the acceptance of larviciding program by the population. This positive environment could favour the implementation of future antilarval control activities in the city of Yaoundé.

Evaluation of machine learning approaches for surface water monitoring using Sentinel-1 data

The monitoring of mosquito breeding habitats requires the production of surface water maps on a regular basis and at a high-resolution using mapping algorithms. To map surface water, several machine learning (ML) algorithms were evaluated, taking advantage of frequently available synthetic aperture radar imagery from the Sentinel-1 mission with a 10-m spatial resolution and a large dataset of field observations of the water state (inundated/dry) in rice paddies and wetlands. One-class support vector machine, one-class self-organizing map, and multilayer perceptron with automatic relevance determination (MLP-ARD) algorithms were trained and assessed to examine their accuracy in detecting surface water. Results show the robustness of the MLP-ARD algorithm, which provides an overall accuracy of 0.974 for a single date and 0.892 for a 5-month study period from May to September. The accuracy of water detection was found to be mainly affected by the presence of dense and high vegetation in inundated fields and the presence of floating vegetation or algae.

Susceptibility status of the malaria vector, Anopheles arabiensis to insecticides used in vector-borne diseases control in areas with heterogeneous sources of pollutants in South-East Tanzania

In malaria-endemic countries, monitoring of insecticide resistance in malaria vectors in areas contaminated with different sources of pollutants is still lacking. This study investigated insecticide resistance and its mechanisms in Anopheles arabiensis across four villages in Southeast Tanzania. Mosquitoes were collected from breeding habitats and tested against permethrin, deltamethrin, lambda-cyhalothrin, pirimiphos-methyl, and bendiocarb. Mechanisms of resistance [P450s enzymes and knockdown resistance (kdr)] were investigated. Comparison of mosquito mortality between sites was performed through one-way analysis of variance (ANOVA) and Tukey–Kramer tests. Anopheles arabiensis was highly resistant to pyrethroid and fully susceptible to bendiocarb and pirimiphos-methyl with mortality ranges of 29%−57%; 37%−65%; 34%−53%; 98%−100%; and 100% in permethrin, deltamethrin, lambda-cyhalothrin, pirimiphos-methyl, and bendiocarb respectively. Anopheles arabiensis mortality, particularly, in permethrin and deltamethrin was significantly higher in less polluted areas (Mofu and Namwawala) p < 0.001 as compared to areas with agrochemicals (Minepa) and domestic pollutants (Ifakara town) (p < 0.01). Moreover, significant involvement of P450s enzymes in pyrethroid resistance was observed while kdr mutations were not detected. The present study shows that pollution of mosquito breeding habitats might accelerate insecticide resistance which could impede the control of malaria vectors.

Water quality assessment in mosquito breeding habitats based on dissolved organic matter and chlorophyll measurements by laser-induced fluorescence spectroscopy.

Rapid urbanization and its associated pollution can affect water quality in mosquito breeding habitats and, as a result, the ecology and control of mosquito vectors. To understand the effects of pollution on mosquito vectors, an accurate assessment of water quality in breeding habitats is needed. Presently, water quality assessment of mosquito breeding habitats is usually based on the measurement of individual physicochemical parameters. However, several parameters are sometimes difficult to interpret or may not give a clear picture of the overall water quality of the breeding habitats, especially when the pollutants are in complex mixtures. This study employed the use of Laser-Induced Fluorescence (LIF) spectroscopy to assess water quality in breeding habitats of Anopheles, Aedes, and Culex mosquitoes in urban areas in Cape Coast, Ghana. The LIF spectra, using a 445-nm diode laser, were measured from field-collected water samples in the laboratory. The LIF spectra showed the presence of dissolved organic matter (DOM) and chlorophyll in the breeding habitats. The DOM and chlorophyll fluorescence signals were normalised by the Raman vibrational signals to determine water quality in each habitat. The overall water quality was better in Aedes breeding habitats than in Anopheles and Culex breeding habitats. The poor water quality in Anopheles and Culex breeding habitats was due to the presence of high fulvic acid and chlorophyll content, which often reflect pollutants from anthropogenic sources. Anopheles and Aedes habitats were made up of mainly An. coluzzii and Ae. aegypti respectively while Culex species were identified to genus level. The results add up to the growing concern about the breeding of Anopheles in polluted habitats. The study demonstrated for the first time the ability of LIF spectroscopy to assess water quality in mosquito breeding habitats.