Green cities and vector-borne diseases: emerging concerns and opportunities.

Aligned with the Sustainable Development Goals, nature-based solutions such as urban greening e.g. public gardens, urban forests, parks and street trees, which aim to protect, sustainably manage or restore an ecosystem, have emerged as a promising tool for improving the health and well-being of an ever-increasing urban population. While urban greening efforts have undeniable benefits for human health and the biological communities inhabiting these green zones, disease vector populations may also be affected, possibly promoting greater pathogen transmission and the emergence of infectious diseases such as dengue, West Nile fever, malaria, leishmaniosis and tick-borne diseases. Evidence for the impact of urban green areas on vector-borne disease (VBD) transmission is scarce. Furthermore, because of vast disparities between cities, variation in green landscapes and differing scales of observation, findings are often contradictory; this calls for careful assessment of how urban greening affects VBD risk. Improved understanding of the effect of urban greening on VBDs would support planning, monitoring and management of green spaces in cities to sustainably mitigate VBD risks for surrounding urban populations.

Entomological drivers of uneven malaria transmission in urban lowland areas in Bouaké, Côte d'Ivoire.

BACKGROUND: The use of urban lowlands for agriculture contributes to the food security of city- dwellers, but promotes malaria transmission. The objective of the study was to characterize the entomological drivers of malaria transmission in two lowlands (N'Gattakro and Odiennekourani) in the city of Bouaké, Côte d'Ivoire. METHODS: The human landing catch technique was used to capture mosquitoes in houses located at the edge of two lowlands in Bouaké from February to December 2019. Cultivated surfaces were calculated monthly in both lowlands for each crop type (rice and market gardening) using images acquired by a drone. The different mosquito species were identified morphologically and by PCR analysis for the Anopheles gambiae complex. Anopheles infection by Plasmodium parasites was assessed by quantitative PCR. Mosquito diversity, biting behaviour and rhythmicity, and malaria transmission were determined in each lowland and compared. RESULTS: Anopheles gambiae sensu lato (s.l.) was predominant in N'Gattakro and Culex quinquefasciatus in Odiennekourani. Four Anopheles species were identified: An. gambiae s.l. and Anopheles funestus s.l. in both lowlands, Anopheles pharoensis in N'Gattakro, and Anopheles ziemanni in Odiennekourani. Within the An. gambiae complex, three species were caught: An. gambiae sensu stricto (s.s.), Anopheles coluzzii, and Anopheles arabiensis for the first time in Côte d'Ivoire (30.1%, 69.9% and 0% in N'Gattakro, and 45.1%, 52.6% and 2.4% in Odiennekourani, respectively). Anopheles gambiae s.l. species exhibited a significant exophagic behaviour in N'Gattakro (77.1% of outdoor bites versus 52.2% in Odiennekourani). In N'Gattakro, 12.6% of captures occurred before bedtime (09.00 pm) and after waking up (05.00 am), 15.1% in Odiennekourani. The mean human biting rate was higher in N'Gattakro than in Odiennekourani (61.6 versus 15.5 bites per person per night). Overall, Anopheles infection rate was 0.68%, with 0.539 and 0.029 infected bites per person per night in N'Gattakro and Odiennekourani, respectively. CONCLUSION: The risk of malaria in urban agricultural lowland areas is uneven. The role of agricultural developments and irrigation patterns in the production of larval habitat should be explored. The exophagic behaviour of Anopheles vectors raises the question of the residual transmission that needs to be assessed to implement appropriate control strategies.

Qualitative study on the use and maintenance of long-lasting insecticidal nets (LLINs) in Bouaké (Côte d'Ivoire), 17 months after the last mass distribution campaign.

BACKGROUND: The use of long-lasting insecticide-treated nets (LLINs) is one of the main malaria prevention method promoted by the World Health Organization (WHO) in Côte d'Ivoire. LLIN-coverage has reached 95% since 2015 and nearly 16 million LLINs were distributed in 2017. Despite these efforts, malaria incidence at the national level remains high (120‰ in 2012 to 164‰ in 2017) although this could be partly explained by increased screening efforts. This study aimed at determining what preventative measures were used against mosquito bites, as well as LLIN maintenance practices used by the inhabitants of the city of Bouaké, capital city of the Gbêkê region with a malaria incidence of 257‰ in 2017. METHODS: A descriptive qualitative investigation took place in Bouaké, in four neighbourhoods that were selected through purposive sampling based on their social composition. Data were collected using an interview guide based on convenience sampling. RESULTS: The results of the study reveal that LLINs are the most reported used malaria prevention measure (66.4%). Environmental health (28.8%) came second in their declarations, smoke coils (23.5%) third and aerosol cans (18.8%) last. The percentage of respondents who answered that they had slept under an LLIN the previous night was 53%. 57.7% reported that they wash their LLINs, 12.1% that they do not wash them, and 4% that they replace dirty LLINs with new ones. The LLINs washing methods described by the respondents did not comply with the WHO recommendations and there was no mention of LLINs repairs. CONCLUSION: Despite mass distributions of LLINs in Côte d'Ivoire, this key malaria control tool remains under-used by the population. Regarding LLIN maintenance, more than half of the population reports that they wash their nets while not complying with recommended practices or repairing them.

First detection of the malaria vector Anopheles arabiensis in Côte d'Ivoire: urbanization in question.

BACKGROUND: Previous studies have revealed high malaria transmission in Bouaké, Côte d'Ivoire. The sociopolitical crisis in the country and the resulting environmental changes have raised the need to update existing knowledge on mosquito vector species and malaria transmission. METHODS: Adult mosquitoes were caught using the human landing catch (HLC) sampling method in Bouaké. They were collected in six districts representative of the diversity in urban landscapes. Sampling points were selected along the water network crossing the city and monitored from 2020 to 2021 to detect the presence of anopheline larvae. PCR techniques were used to ascertain the species of the Anopheles gambiae complex, Plasmodium falciparum sporozoite infection in a subset of Anopheles vectors, and insecticide resistance mechanisms in Anopheles arabiensis only. RESULTS: A total of 4599 Anopheles mosquitoes were collected and then identified. Anopheles gambiae sensu lato (s.l.) made up the majority of the whole collection (99%) while Anopheles funestus (0.7%), Anopheles ziemanni (0.2%), Anopheles pharoensis (0.2%) represented the remaining proportion of collection. Among the Anopheles gambiae complex, three species were identified namely An. gambiae sensu stricto (45.9%), Anopheles coluzzii (52.2%), and Anopheles arabiensis (1.9%). The first two species had already been collected in Bouaké, however this is the first time that An. arabiensis is reported in Côte d'Ivoire. Anopheles arabiensis was also collected during the larval surveys in a similar proportion (1.1%) in the same areas as the adults. CONCLUSIONS: This study detected the presence of An. arabiensis for the first time in Côte d'Ivoire. This species was found quite far from its usual geographic area and its expansion could be linked to the urbanization process. Although no An. arabiensis was found to be infected by Plasmodium sp., its role in malaria transmission in Bouaké has to be explored, particularly since its exophagic behaviour raises the issue of control measures and the use of insecticide-impregnated nets. The spread of this species in Côte d'Ivoire should be assessed through further research in additional towns in the country.

Seasonal variation and intra urban heterogeneity of the entomological risk of transmission of dengue and yellow fever in Abidjan, Côte d'Ivoire.

Dengue and yellow fever are prevalent in Côte d'Ivoire and Aedes (Stegomyia) aegypti (Linnaeus), (Diptera: Culicidae), is known as the main vector. We aimed to assess seasonal variation and spatial heterogeneity in the transmission of both arbovirus diseases in Abidjan. Entomological surveys targeting larvae of A. aegypti, were carried out between November 2015 and August 2016 covering the four climatic seasons including a cohort of 100 houses randomly selected in three neighbourhoods. A. aegypti was the predominant species (96.6%) of mosquitoes resulting from the rearing of harvested larvae, and the only vector of dengue and yellow fever recorded during the study period. The highest proportion of water storage containers (45.5%) which represented the major breeding sites infested by the larvae of A. aegypti, was observed in Anoumabo. The house indices >5% and/or Breteau indices >20 recorded in each neighbourhood, during the different climatic seasons, indicated that there was, a high and permanent, heterogeneity in the transmission risk of dengue and yellow fever between the three neighbourhoods. In terms of transmission risk, Anoumabo was the neighbourhood with the highest risk compared to the two others, then, particular attention should be paid to this site in terms of surveillance by vector control programme in Abidjan.

Malaria vectors diversity, insecticide resistance and transmission during the rainy season in peri-urban villages of south-western Burkina Faso.

BACKGROUND: This study reports an updated description on malaria vector diversity, behaviour, insecticide resistance and malaria transmission in the Diébougou and Dano peri-urban areas, Burkina Faso. METHODS: Mosquitoes were caught monthly using CDC light traps and pyrethrum spray catches. Mosquitoes were identified using morphological taxonomic keys. PCR techniques were used to identify the species of the Anopheles gambiae complex and insecticide resistance mechanisms in a subset of Anopheles vectors. The Plasmodium sporozoite infection status and origins of blood meals of female mosquitoes were determined by ELISA methods. Larvae were collected, breed in the insectary and tested for phenotypic resistance against four insecticides using WHO bioassays. RESULTS: This study contributed to update the entomological data in two peri-urban areas of Southwest Burkina Faso. Anopheles populations were mostly anthropophilic and endophilic in both areas and exhibit high susceptibility to an organophosphate insecticide. This offers an alternative for the control of these pyrethroid-resistant populations. These data might help the National Malaria Control Programme for decision-making about vector control planning and resistance management. CONCLUSIONS: This study contributed to update the entomological data in two peri-urban areas of Southwest Burkina Faso. Anopheles populations were mostly anthropophilic and endophilic in both areas and exhibit high susceptibility to an organophosphate insecticide. This offers an alternative for the control of these pyrethroid-resistant populations. These data might help the National Malaria Control Programme for decision-making about vector control planning and resistance management.

Efficacy and risk of harms of repeat ivermectin mass drug administrations for control of malaria (RIMDAMAL): a cluster-randomised trial.

BACKGROUND: Ivermectin is widely used in mass drug administrations for controlling neglected parasitic diseases, and can be lethal to malaria vectors that bite treated humans. Therefore, it could be a new tool to reduce plasmodium transmission. We tested the hypothesis that frequently repeated mass administrations of ivermectin to village residents would reduce clinical malaria episodes in children and would be well tolerated with minimal harms. METHODS: We invited villages (clusters) in Burkina Faso to participate in a single-blind (outcomes assessor), parallel-assignment, two-arm, cluster-randomised trial over the 2015 rainy season. Villages were assigned (1:1) by random draw to either the intervention group or the control group. In both groups, all eligible participants who consented to the treatment and were at least 90 cm in height received single oral doses of ivermectin (150-200 µg/kg) and albendazole (400 mg), and those in the intervention group received five further doses of ivermectin alone at 3-week intervals thereafter over the 18-week treatment phase. The primary outcome was cumulative incidence of uncomplicated malaria episodes over 18 weeks (analysed on a cluster intention-to-treat basis) in an active case detection cohort of children aged 5 years or younger living in the study villages. This trial is registered with ClinicalTrials.gov, number NCT02509481. FINDINGS: Eight villages agreed to participate, and four were randomly assigned to each group. 2712 participants (1333 [49%] males and 1379 [51%] females; median age 15 years [IQR 6-34]), including 590 children aged 5 years or younger, provided consent and were enrolled between May 22 and July 20, 2015 (except for 77 participants enrolled after these dates because of unavailability before the first mass drug administration, travel into the village during the trial, or birth), with 1447 enrolled into the intervention group and 1265 into the control group. 330 (23%) participants in the intervention group and 233 (18%) in the control group met the exclusion criteria for mass drug administration. Most children in the active case detection cohort were not treated because of height restrictions. 14 (4%) children in the intervention group and 10 (4%) in the control group were lost to follow-up. Cumulative malaria incidence was reduced in the intervention group (648 episodes among 327 children; estimated mean 2·00 episodes per child) compared with the control group (647 episodes among 263 children; 2·49 episodes per child; risk difference -0·49 [95% CI -0·79 to -0·21], p=0·0009, adjusted for sex and clustering). The risk of adverse events among all participants did not differ between groups (45 events [3%] among 1447 participants in the intervention group vs 24 events [2%] among 1265 in the control group; risk ratio 1·63 [1·01 to 2·67]; risk difference 1·21 [0·04 to 2·38], p=0·060), and no adverse reactions were reported. INTERPRETATION: Frequently repeated mass administrations of ivermectin during the malaria transmission season can reduce malaria episodes among children without significantly increasing harms in the populace. FUNDING: Bill & Melinda Gates Foundation.

Spatial Assessment of Contact Between Humans and Anopheles and Aedes Mosquitoes in a Medium-Sized African Urban Setting, Using Salivary Antibody-Based Biomarkers.

BACKGROUND: Anarchic and poorly controlled urbanization led to an increased risk of mosquito-borne diseases (MBD) in many African cities. Here, we evaluate the spatial heterogeneity of human exposure to malaria and arboviral disease vectors in an urban area of northern Senegal, using antibody-based biomarkers of exposure to Anopheles and Aedes mosquito bites. METHODS: A cross-sectional study was undertaken during the rainy season of 2014 in 4 neighborhoods of Saint-Louis, a city in northern Senegal. Among children aged 6-59 months in each neighborhood, the dried blood spot technique was used to evaluate immunoglobulin G (IgG) responses to both gSG6-P1 (Anopheles) and Nterm-34-kDa (Aedes) salivary peptides as validated biomarkers of respective mosquito bite exposure. RESULTS: IgG response levels to gSG6-P1 and Nterm-34-kDa salivary peptides varied significantly between the 4 neighborhoods (P < .0001). The level of exposure to Aedes bites also varied according to household access to sanitation services (P = .027), whereas that of exposure to Anopheles bites varied according to insecticide-treated bed net use (P = .006). In addition, spatial clusters of high contact between humans and mosquitoes were identified inside 3 neighborhoods. CONCLUSIONS: Antibody-based biomarkers of exposure to Anopheles and Aedes mosquito bites could be helpful tools for evaluating the heterogeneity of exposure to malaria and arboviral disease vectors by national control programs.

Evaluation of Effectiveness of a Community-Based Intervention for Control of Dengue Virus Vector, Ouagadougou, Burkina Faso.

We evaluated the effectiveness of a community-based intervention for dengue vector control in Ouagadougou, the capital city of Burkina Faso. Households in the intervention (n = 287) and control (n = 289) neighborhoods were randomly sampled and the outcomes collected before the intervention (October 2015) and after the intervention (October 2016). The intervention reduced residents' exposure to dengue vector bites (vector saliva biomarker difference -0.08 [95% CI -0.11 to -0.04]). The pupae index declined in the intervention neighborhood (from 162.14 to 99.03) and increased in the control neighborhood (from 218.72 to 255.67). Residents in the intervention neighborhood were less likely to associate dengue with malaria (risk ratio 0.70 [95% CI 0.58-0.84]) and had increased knowledge about dengue symptoms (risk ratio 1.44 [95% CI 1.22-1.69]). Our study showed that well-planned, evidence/community-based interventions that control exposure to dengue vectors are feasible and effective in urban settings in Africa that have limited resources.

Targeted application of an organophosphate-based paint applied on windows and doors against Anopheles coluzzii resistant to pyrethroids under real life conditions in Vallée du Kou, Burkina Faso (West Africa).

BACKGROUND: A novel strategy applying an organophosphate-based insecticide paint on doors and windows in combination with long-lasting insecticide-treated nets (LLINs) was tested for the control of pyrethroid-resistant malaria vectors in a village setting in Vallée du Kou, a rice-growing area west of Burkina Faso. METHODS: Insecticide Paint Inesfly 5A IGR™, comprised of two organophosphates and an insect growth regulator, was applied to doors and windows and tested in combination with pyrethroid-treated LLINs. The killing effect was monitored for 5 months by early morning collections of anophelines and other culicids. The residual efficacy was evaluated monthly by WHO bioassays using Anopheles gambiae 'Kisumu' and local populations of Anopheles coluzzii resistant to pyrethroids. The spatial mortality efficacy (SME) at distances of 1 m was also assessed against pyrethroid-susceptible and -resistant malaria vectors. The frequency of L1014F kdr and Ace-1 R G119S mutations was, respectively, reported throughout the study. The Insecticide Paint Inesfly 5A IGR had been tested in past studies yielding a long-term mortality rate of 80% over 12 months against An. coluzzii, the local pyrethroid-resistant malaria vector. The purpose of the present study is to test if treating smaller, targeted surfaces (e.g. doors and windows) was also efficient in killing malaria vectors. RESULTS: Treating windows and doors alone yielded a killing efficacy of 100% for 1 month against An. coluzzii resistant to pyrethroids, but efficacy reduced quickly afterwards. Likewise, WHO cone bioassays yielded mortalities of 80-100% for 2 months but declined to 90 and 40% 2 and 3 months after treatment, respectively. Mosquitoes exposed to insecticide paint-treated surfaces at distances of 1 m, yielded mortality rates of about 90-80% against local pyrethroids-resistant An. coluzzii during the first 2 months, but decreased to 30% afterwards. Anopheles coluzzii was reported to be exclusively the local malaria vector and resistant to pyrethroids with high L1014 kdr frequency. CONCLUSION: The combination of insecticide paint on doors and windows with LLINs yielded high mortality rates in the short term against wild pyrethroid-resistant malaria vector populations. A high SME was observed against laboratory strains of pyrethroid-resistant malaria vectors placed for 30 min at 1 m from the treated/control walls. The application of the insecticide paint on doors and windows led to high but short-lasting mortality rates. The strategy may be an option in a context where low cost, rapid responses need to be implemented in areas where malaria vectors are resistant to pyrethroids.

Does mosquito mass-rearing produce an inferior mosquito?

BACKGROUND: The success of the sterile insect technique depends, among other things, on continuous releases of sexually competitive sterile males within the target area. Several factors (including high rearing density and physical manipulation, such as larvae and pupae separation) can influence the quality of males produced in mass-rearing facilities. The different steps in mass production in the laboratory may modify the behaviour of mosquitoes, directly or through loss of natural characters as a result of adaptation to lab rearing, and lead to the competitiveness of sterile male being reduced. In the present study, the objective was to evaluate the effect of mass-rearing conditions on sterile male sexual competitiveness in semi-field cages compared to routine small scale laboratory rearing methods. METHODS: Anopheles arabiensis immature stages were reared both on a large scale using a rack and tray system developed by the FAO/IAEA (MRS), and on a small scale using standard laboratory rearing trays (SRS). Mosquito life history traits such as pupation rate, emergence rate, adult size as well as the effect of irradiation on adult longevity were evaluated. Moreover, 5-6 day old mosquitoes were released into field cages and left for two nights to mate and the mating competitiveness between sterile mass-reared males and fertile males reared on a small scale when competing for small scale reared virgin females was investigated. Resulting fertility in a treatment ratio of 1:1:1 (100 irradiated males: 100 non-irradiated males: 100 virgin females) was compared to control cages with 0:100:100 (non-irradiated control) and 100:0:100 (irradiated control). RESULTS: No significant differences in life history parameters were observed between rearing methods. The competitiveness index of mass reared males (0.58) was similar to males reared on a small scale (0.59). A residual fertility rate of 20% was observed in the irradiated control (100:0:100), measured as the percentage of eggs collected from the cages which developed to adulthood. No significant difference was observed (t = 0.2896, df = 4, P = 0.7865) between the rearing treatments (MRS and SRS) in the fertility rate, a measure of mating competitiveness. CONCLUSIONS: The results showed that the FAO/IAEA mass-rearing process did not affect mosquito life history parameters or the mating competitiveness of males.

Development of a spatial sampling protocol using GIS to measure health disparities in Bobo-Dioulasso, Burkina Faso, a medium-sized African city.

BACKGROUND: Many cities in developing countries experience an unplanned and rapid growth. Several studies have shown that the irregular urbanization and equipment of cities produce different health risks and uneven exposure to specific diseases. Consequently, health surveys within cities should be carried out at the micro-local scale and sampling methods should try to capture this urban diversity. METHODS: This article describes the methodology used to develop a multi-stage sampling protocol to select a population for a demographic survey that investigates health disparities in the medium-sized city of Bobo-Dioulasso, Burkina Faso. It is based on the characterization of Bobo-Dioulasso city typology by taking into account the city heterogeneity, as determined by analysis of the built environment and of the distribution of urban infrastructures, such as healthcare structures or even water fountains, by photo-interpretation of aerial photographs and satellite images. Principal component analysis and hierarchical ascendant classification were then used to generate the city typology. RESULTS: Five groups of spaces with specific profiles were identified according to a set of variables which could be considered as proxy indicators of health status. Within these five groups, four sub-spaces were randomly selected for the study. We were then able to survey 1045 households in all the selected sub-spaces. The pertinence of this approach is discussed regarding to classical sampling as random walk method for example. CONCLUSION: This urban space typology allowed to select a population living in areas representative of the uneven urbanization process, and to characterize its health status in regards to several indicators (nutritional status, communicable and non-communicable diseases, and anaemia). Although this method should be validated and compared with more established methods, it appears as an alternative in developing countries where geographic and population data are scarce.

Human IgG antibody response to Aedes aegypti Nterm-34 kDa salivary peptide as an indicator to identify areas at high risk for dengue transmission: a retrospective study in urban settings of Vientiane city, Lao PDR.

OBJECTIVE: Using human IgG antibody response to the Aedes Nterm-34 kDa salivary peptide as an indicator of human exposure to Aedes bites in surveying exposed populations from areas at risk of dengue virus (DENV) transmission in urban settings of Vientiane city, Lao PDR. METHODS: Enzyme-linked immunosorbent assay tests were performed to measure the IgG response to Nterm-34 kDa peptide in blood samples collected within a flavivirus seroprevalence survey carried out in 2006 including 3558 randomly selected individuals. The level of IgG response to the Nterm-34 kDa peptide in individuals was analysed in relation to the level of urbanisation of the individual's residence, areas that presented significant differences in the prevalence of recent DENV infection. RESULTS: No differences were observed in the anti-Nterm-34 kDa IgG level between DENV-positive and DENV-negative individuals. However, the level of specific IgG response was higher among individuals living in slightly urbanised neighbourhoods than among those in more highly urbanised areas (P < 0.0001). Interestingly, a similar pattern had already been observed concerning the prevalence of recent DENV infection in the same populations. CONCLUSION: The results of this retrospective study indicate that the evaluation of human IgG response to the Aedes Nterm-34 kDa salivary peptide could be a useful indicator to identify places with risk of dengue virus transmission in urban endemic areas.

Assessment of Culicidae collection methods for xenomonitoring lymphatic filariasis in malaria co-infection context in Burkina Faso.

BACKGROUND: Entomological surveillance of lymphatic filariasis and malaria infections play an important role in the decision-making of national programs to control, or eliminate these both diseases. In areas where both diseases prevalence is low, a large number of mosquitoes need to be sampled to determine vectors infection rate. To do this, efficient mosquito collection methods must be used. This study is part in this framework, to assess appropriate mosquito collection methods for lymphatic filariasis xenomonitoring in a coexistence context with malaria in Burkina Faso. METHODOLOGY/PRINCIPAL FINDINGS: Mosquito collections were performed between August and September 2018 in four villages (Koulpissi, Seiga, and Péribgan, Saptan), distributed in East and South-West health regions of Burkina Faso. Different collection methods were used: Human Landing Catches (HLC) executed indoor and outdoor, Window Exit-Trap, Double Net Trap (DNT) and Pyrethrum Spray Catches (PSC). Molecular analyses were performed to identify Anopheles gambiae s.l. sibling species and to detect Wuchereria bancrofti and Plasmodium falciparum infection in Anopheles mosquitoes. A total of 3 322 mosquitoes were collected among this, Anopheles gambiae s.l. was the vector caught in largest proportion (63.82%). An. gambiae s.l. sibling species molecular characterization showed that An. gambiae was the dominant specie in all villages. The Human Landing Catches (indoor and outdoor) collected the highest proportion of mosquitoes (between 61.5% and 82.79%). For the sampling vectors infected to W. bancrofti or P. falciparum, PSC, HLC and Window Exit-Trap were found the most effective collection methods. CONCLUSIONS/SIGNIFICANCE: This study revealed that HLC indoor and outdoor remained the most effective collection method. Likewise, the results showed the probability to use Window Exit-Trap and PSC collection methods to sample Anopheles infected.

Spatiotemporal analysis of malaria incidence in Côte d'Ivoire from 2015 to 2019.

BACKGROUND: The collection of malaria cases over time allows the identification of areas with the highest incidence. Our objective was to characterize the spatial distribution of malaria in Côte d'Ivoire from 2015 to 2019 at the health district level. METHODS: Data on the number of reported malaria cases confirmed by rapid diagnostic test (RDT) in the general population, the number of patients attending medical consultations and the total population by health district and year were collected from the National Malaria Control Program in Côte d'Ivoire. Crude and adjusted incidence rates were estimated for each health district and year. Adjusted incidence rates were used to perform global (Moran's index) and local indicators of spatial autocorrelation (LISA) analyses. RESULTS: Between 2015 and 2019, mean crude incidence rates increased from 155.5‰ to 229.8‰. We observed significant heterogeneity in malaria incidence rates across the study period and within a given year. The overall Moran index showed spatial autocorrelation for every year analysed except 2017. The LISA analysis showed that the health districts with high incidence rates were concentrated in the western zone of Côte d'Ivoire. CONCLUSIONS: The use of spatial analyses to identify the areas with the highest malaria incidence rates is a relevant approach to optimize control measures in targeted areas.

Urban Green Spaces and Vector-Borne Disease Risk in Africa: The Case of an Unclean Forested Park in Libreville (Gabon, Central Africa).

In Africa, vector-borne diseases are a major public health issue, especially in cities. Urban greening is increasingly considered to promote inhabitants' well-being. However, the impact of urban green spaces on vector risk remains poorly investigated, particularly urban forests in poor hygienic conditions. Therefore, using larval sampling and human landing catches, this study investigated the mosquito diversity and the vector risk in a forest patch and its inhabited surroundings in Libreville, Gabon, central Africa. Among the 104 water containers explored, 94 (90.4%) were artificial (gutters, used tires, plastic bottles) and 10 (9.6%) were natural (puddles, streams, tree holes). In total, 770 mosquitoes belonging to 14 species were collected from such water containers (73.1% outside the forested area). The mosquito community was dominated by Aedes albopictus (33.5%), Culex quinquefasciatus (30.4%), and Lutzia tigripes (16.5%). Although mosquito diversity was almost double outside compared to inside the forest (Shannon diversity index: 1.3 vs. 0.7, respectively), the species relative abundance (Morisita-Horn index = 0.7) was similar. Ae. albopictus (86.1%) was the most aggressive species, putting people at risk of Aedes-borne viruses. This study highlights the importance of waste pollution in urban forested ecosystems as a potential driver of mosquito-borne diseases.

The ecological significance of arthropod vectors of plant, animal, and human pathogens.

Vector management is a cornerstone in the fight against vector-borne pathogens. However, the impact on ecosystem functioning of reducing or eliminating arthropod vector populations remains poorly understood. Vectors are members of complex ecological communities, and recent studies suggest that their population suppression alters food web dynamics (bottom-up and top-down trophic cascades), inter- and intraspecific competition, and plant pollination. Other possible overlooked roles are also proposed. In this review, with examples from vectors of plant, animal, and human pathogens, we highlight that, although the ecological roles of most vector species might be redundant with other non-vector species, changes in vector abundance alter biotic interactions and, thus, are unlikely to be neutral in terms of ecosystem functioning.

Serological and molecular detection of Leishmania species in dog peripheral blood from Bobo-Dioulasso city, a confirmation of canine leishmaniasis enzootic area for Burkina Faso.

Canine leishmaniasis is increasingly reported worldwide and represent a threat to both animal and human health. In a previous pilot study conducted in Bobo-Dioulasso, the second town of Burkina Faso, we reported five cases of canine leishmaniasis. With the perspective of a One Health action plan, and in the context of increasing urbanization, this study aimed to provide new information on Leishmania spp in dogs in this city. A cross-sectional survey was carried out from May to August 2018 in six districts of the city in order to record clinical and biological data from domestic dogs randomly selected per district. Blood samples were collected into EDTA tubes (4-5 mL), treated and stored at -20 °C until further analyses. The infection status of the dogs was performed by serological tests using plasma, and real time-PCR (RT-PCR) to detect Leishmania parasites using buffy coats. Nested PCR was used for typing the Leishmania species in dogs which were found to be RT-PCR positive. A total of 147 dogs were examined clinically and sampled for blood collection, including 53.7% females and 46.3% of males with a median age of 3 years. The seroincidence of Leishmania parasites within this dog population was 4.76% (95% CI:2.26-9.72). The incidence of Leishmania was 10.88% (95% CI: 6.73-17.11) by RT-PCR which was significantly more sensitive (p = 0,047) and a fair concordance was observed between both tests (Kappa = 0.39, p < 0.001). The characterization of Leishmania species revealed that L. major was circulating in this domestic dog population. Our results confirmed the persistence of zoonotic circulation of Leishmania parasites such as L. major currently in Bobo-Dioulasso city and highlight the need for targeted interventions in order to control transmission of leishmaniasis in this region.

Spatial Heterogeneity and Seasonal Distribution of Aedes (Stegomyia) aegypti (L) in Abidjan, Côte d'Ivoire.

Although the urban areas of Abidjan, Côte d'Ivoire have faced recurrent outbreaks of Aedes-borne arboviruses, the seasonal dynamics of local populations of the key vector Aedes aegypti remained still underexplored for an effective vector control. The current study thus assessed the seasonal dynamics and the spatial distribution of Ae. aegypti in three neighborhoods of Abidjan city. Aedes eggs were collected using ovitraps in three different neighborhoods (Anoumambo, Bromakoté, and Petit-Bassam) during the four climatic seasons of Abidjan. Aedes egg samples were immersed into distilled water, and emerged larvae were reared until the adult stage for species morphological identification. Spatial autocorrelation was measured with the Moran's Index, and areas with high egg abundance were identified. In total, 3837 eggs were collected providing 1882 adult mosquitoes in the 3 neighborhoods. All the specimens belonged to only one Aedes species, Ae. aegypti. The average of 15.89 eggs per ovitrap, 13.67 eggs per ovitrap, and 19.87 eggs per ovitrap were obtained in Anoumambo, Bromakoté, and Petit-Bassam, respectively, with no statistical difference between the three sites. A higher abundance of Ae. aegypti was observed during the long rainy season and the short dry season. The Moran analysis showed a clustered distribution of Ae. aegypti eggs during the long rainy season in the three sites and a random spatial distribution during the short dry season. Ovitraps with high number of eggs were aggregated in the peripheral part (near to the lagoon) of Anoumambo and Petit-Bassam in central Bromakoté and extending along the railway during the long rainy season. This study revealed a heterogeneous potential risk of transmission of arbovirus according to neighborhood. It provided data to better understand Ae. aegypti ecology to select appropriate periods and places for Aedes vector control actions and surveillance of arboviruses in Abidjan.

Diversity in anopheline larval habitats and adult composition during the dry and wet seasons in Ouagadougou (Burkina Faso).

BACKGROUND: Several cases of malaria are frequently recorded during the dry period in Ouagadougou town (Burkina Faso). This has led to the design of a series of studies focusing on both parasitological and entomological investigations intended to provide relevant health data on the risk of local malaria transmission according to the way of urbanisation. METHODS: A cross-sectional entomological survey was carried out in various districts of Ouagadougou in April and October 2006. Adult malaria vectors were collected using CDC traps and indoor insecticide spraying performed in four houses during four consecutive days/nights. Intensive larval sampling was also done in available water ponds throughout the study sites. RESULTS: In April, the anopheline breeding sites consisted only of semi-permanent or permanent swamps located mainly in the two peripheral districts. Despite the presence of anopheline larvae in these breeding sites, less than five Anopheles gambiae s.l. adults were caught by CDC traps and indoor insecticide spraying. In October, additionally to the permanent breeding sites reported in April, some rainfall swamps were also found positive to anophelines. The number of adults' mosquitoes was higher than that collected in April (2 vs 159 in October). Out of 115 larvae of An. gambiae s.l. analysed by PCR in April, 59.1% (68/115) were identified as Anopheles arabiensis, 39.1% (45/115) as An. gambiae M while the S form represented less than 2%. Overall 120 larvae and 86 females were identified by PCR in October as An. gambiae M form (51%) and An. arabiensis (42.2%). The S form represented only 6.8%. The global sporozoite rate recorded was high (6.8%) and did not differ between the districts except in the central district where no positive mosquito was detected. CONCLUSION: Although only few adults' mosquitoes were actively caught during the driest month, malaria vectors persisted all year long that increases the risk of urban malaria transmission. The distribution of breeding sites and especially the occurrence of malaria vectors were more abundant in the periphery, which is more like that of a rural settlement. The evolution of malaria prevalence and the factors sustaining the risk of transmission in Ouagadougou as well in many African cities during the dry season are discussed.