Physico-chemical characterization of Anopheles gambiae s.l. breeding sites and kdr mutations in urban areas of Cotonou and Natitingou, Benin.

BACKGROUND: This study aimed to investigate the relationship between the physicochemical characteristics of An. gambiae s.s. and An. coluzzii breeding sites, the susceptibility profiles to commonly used insecticides in public health, and the underlying insecticide resistance mechanisms. METHODS: Anopheles breeding sites surveys were conducted in Cotonou and Natitingou in September 2020, January and August 2021. Physicochemical properties and bacterial loads were determined in individual breeding sites. The WHO susceptibility assays were carried out using the female of the emerging adult mosquitoes. Anopheles species were identified through PCR techniques. Kdr L1014F/S, N1575Y and G119S mutations were investigated using TaqMan genotyping assays. RESULTS: Molecular analysis showed that all mosquitoes analyzed in Cotonou were Anopheles coluzzii, while those of Natitingou were Anopheles gambiae s.s. Fecal coliforms were identified as playing a role in this distribution through their significant influence on the presence of An. coluzzii larvae. WHO susceptibility assay indicated a high level of resistance to deltamethrin in the two cities. The resistance levels to deltamethrin were higher in Cotonou (X2 = 31.689; DF = 1; P < 0.0001). There was a suspected resistance to bendiocarb in Cotonou, whereas the mosquito population in Natitingou was resistant. The kdr L1014F mutation was highly observed in both mosquito populations (frequence: 86-91%), while the Ace-1 mutation was found in a small proportion of mosquitoes. In Cotonou, salinity was the only recorded physicochemical parameter that significantly correlated with the resistance of Anopheles mosquitoes to deltamethrin (P < 0.05). In Natitingou, significant correlations were observed between the allelic frequencies of the kdr L1014F mutation and pH, conductivity, and TDS. CONCLUSION: These results indicate a high level of pyrethroid resistance in the anopheles populations of both Cotonou and Natitingou. Moreover, this study report the involvement of abiotic factors influencing Anopheles susceptibility profile.

["Farmer Field School", a participatory educational approach for improving the fight against malaria vectors in irrigated rice-growing areas in Benin]. / « Champ-École Paysan ¼, une approche pédagogique participative pour l'amélioration de la lutte contre les vecteurs du paludisme en zone de riziculture irriguée au Bénin.

Background & rationale: Malaria is a major health problem in Benin where it is the main cause of morbidity and mortality, particularly among children under 5 and pregnant women. Although the vast majority of malaria cases occurs in rural and agricultural areas and are often associated with development projects, very few interventions target the agro-ecosystem. In Benin, irrigated rice growing is expanding to meet the increasing demand of the population. However, continuous flooding and tillage systems induce the development and proliferation of malaria and other diseases vectors. Intermittent flooding of rice plots and minimal tillage can reduce significantly the proliferation of mosquitoes including Anopheles in rice fields. However, the dissemination and implementation of these agricultural practices require community-wide action for greater effectiveness. As part of strengthening the capacity of farming communities in the fight against malaria vectors, the "Farmer Field School" appears to be an innovative approach. This learning by doing method promotes interactions between groups of producers to disseminate proven technologies. This study aims to disseminate among rice producers the agricultural practices of intermittent flooding and minimal tillage, likely to reduce the proliferation of malaria vectors in the rice fields. Materials & methods: This study was carried out in the rice-growing perimeter of Malanville, Benin (11° 52' 5" North, 3° 22' 59" East) which covers an area of 516 hectares. Farmer Field Schools were set up after a basic survey at producer level. This survey was carried out through in-depth interview, focus group discussions and direct field observation with producers. Focus groups discussions and interviews made it possible to understand the perception of rice farmers on the link between rice production and the transmission of malaria. In order to disseminate new agricultural practices such as intermittent flooding and minimal tillage among producers, twelve plots have been set up. Farmer Field Schools were monitored weekly with rice producers accompanied by a facilitator and a medical entomologist (learning facilitator or moderator) helping the farmers with the collection and identification of mosquito larvae. According to the different stages of rice development (transplanting, tillering, maturation), the mosquito larvae were collected in the test and control plots from 10 a.m. to 2 p.m. by the dipping method. Then the water in the test compartments (intermittent flooding) was emptied. A cycle of 7 days of flooding and 2 days of drying was carried out for intermittent flooding. Mosquito larvae were identified morphologically using the identification key and Anopheles genus larvae were isolated in plastic cups. The impacts of intermittent flooding and minimum tillage in reducing breeding sites and larval densities were established by determining and comparing the larval densities of mosquitoes and of Anopheles between the test and control plots. Results: Direct observations in the field allowed to identify three tillage systems, which include the use of tiller (28%), plow (66%) and hoe (6%) on the rice field. Continuous flooding was the only irrigation system used by farmers. The water used for irrigation comes either from boreholes installed individually or from the Niger River. The volume of water used varies with the seasons, the size of the farms and the variety of rice grown. Farmers observe that the nuisance of mosquitoes increases during the rice production period with an outbreak of malaria cases, especially among children, which leads to crowds in health centers. The preventive measures against malaria among farmers are the use of impregnated mosquito nets distributed free of charge by the national program against malaria, and of insecticide bombs or spirals. Considering the development stages of the rice, the larval densities varied according to the treatments. Overall, minimal tillage applied to intermittent flooding significantly reduced the density of mosquito larvae of all species. The reduction rates were 10.5, 5.4 and 2.5 during transplanting, tillering and maturation, respectively. Considering only the Anopheles larvae, minimal tillage applied to intermittent flooding reduced their density by 16, 5.5 and 4 respectively during transplanting, tillering and maturation. Discussion/conclusion: The rice-growing area of Malanville has many favorable conditions for rice production, including the presence of water supply sources such as the Niger River located near the rice field and numerous boreholes. The availability of water pockets for mosquito breeding during irrigation appeared to contribute to the extension of malaria transmission. The present study showed that the intermittent flooding coupled with minimal tillage could reduce the proliferation of malaria vectors. The results suggested that with technical support to farmers through the "Farmer Field School", the malaria incidence could be reduced in the farming community.

Attitudes and prevention towards malaria in the context of COVID-19 pandemic in urban community in Benin, West Africa.

BACKGROUND: The COVID-19 pandemic and its damages have severely impacted the global healthcare system even in countries with the best systems. In sub-Saharan Africa (SSA), it could worsen the malaria situation in endemic countries such as Benin. This study was conducted to describe the potential effects of the pandemic on urban dwellers attitudes, prevention and treatment against malaria in four major cities of Benin. METHODS: A cross-sectional questionnaire survey was conducted in Cotonou, Bohicon, Parakou and Natitingou, four urban cities of Benin. A total of 800 randomly selected households were interviewed. The questionnaire consisted of four parts: sociodemographic characteristics, knowledge, attitude, and practice. Descriptive statistics and binomial logistic regression analysis were used in the statistical analysis. RESULTS: More than 90% of the participants interviewed had a good level of knowledge about the transmission and prevention of malaria in the cities surveyed. In contrast, low proportions of participants reported visiting health-care facilities when they suspected malaria. Compared to the proportions observed at Parakou and Natitingou, the low proportion of participants was statistically significant at Cotonou (Parakou: X2 = 31.345, df = 1, P < 0.0001; Natitingou: X2 = 17.471, df = 1, P < 0.0001). Among the reasons for not seeking care, these related to COVID-19 were the most mentioned. Moreover, the good education level of the participants was one of the factors associated with the non-use of healthcare facilities due to over-knowledgeable about Covid-19, which might have increased the fear to go to the health facilities. Finally, high proportions of self-medication practice were mentioned with high use of malaria drugs to treat both malaria and to protect against COVID-19. CONCLUSIONS: The data show a negative impact of COVID-19 on visits to healthcare facilities for malarial treatment and malaria drugs usage by the population. It is, therefore, necessary to rebuild malaria programmes by integrating measures adapted to health crises such as the COVID-19 pandemic.

Diversity of larval habitats of Anopheles mosquitoes in urban areas of Benin and influence of their physicochemical and bacteriological characteristics on larval density.

BACKGROUND: The implementation of anti-larval strategies in the fight against malaria vectors requires fundamental knowledge of their oviposition sites. The aim of this study was to assess the spatial and temporal distribution of Anopheles breeding sites as well as the influence of abiotic and biotic factors on the proliferation of larvae in urban and non-urban areas of Benin. METHODS: Sampling of Anopheles larvae was carried out during the rainy and dry seasons in urbanized and non-urbanized areas of the cities of Cotonou, Bohicon, Parakou, and Natitingou in Benin. The Anopheles larval breeding sites were georeferenced and characterized by their nature, type, physicochemical (pH, temperature, dissolved oxygen, conductivity, turbidity, salinity) and biological attributes (larval density and coliform density). RESULTS: A total of 198 positive breeding sites for Anopheles larvae were identified, comprising 163 (82.3%) in the rainy season and 35 (17.7%) in the dry season. Out of these larval habitats, 61.9% were located in urbanized areas, and were predominantly puddles. Principal component analysis revealed a high positive correlation of larval density with temperature and dissolved oxygen, and with salinity in the coastal zone. In addition, cross-sectional analysis of the microbiological results with larval density showed a significant negative correlation between larval productivity and faecal coliform load. CONCLUSIONS: This study indicated the presence of multiple larval habitats of Anopheles in the urban areas which were created through human activities, and associations between larval density and intrinsic factors of the habitats such as temperature, dissolved oxygen and faecal coliform load. This type of information may be useful for the implementation of appropriate control strategies in urban areas, including regulation of the human activities that lead to the creation of breeding sites, proper environmental management and targeted larvicidal use.