Background In Alibori and Donga, two departments of high malaria incidence of Northern Benin, pir... more Background In Alibori and Donga, two departments of high malaria incidence of Northern Benin, pirimiphos-methyl, mixture deltamethrin + clothianidin, as well as clothianidin were used at large scale for IRS. The present study aimed to assess the residual efficacy of these products. Methods Immatures of Anopheles gambiae sensu lato (s.l.) collected in the communes of Kandi and Gogounou (Department of Alibori), Djougou and Copargo (Department of Donga) were reared until adulthood. Females aged 2–5 days were used for susceptibility tube tests following the WHO protocol. The tests were conducted with deltamethrin (0.05%), bendiocarb (0.1%), pirimiphos-methyl (0.25%) and clothianidin (2% weight per volume). For cone tests performed on cement and mud walls, the An. gambiae Kisumu susceptible strain was used. After the quality control of the IRS performed 1-week post-campaign, the evaluation of the residual activity of the different tested insecticides/mixture of insecticides was conducted...
The efficacy of a vector control tool in reducing mosquito biting is crucial for its acceptabilit... more The efficacy of a vector control tool in reducing mosquito biting is crucial for its acceptability. The present study compared the vector density of Culex spp. And Mansonia spp. across clusters, which received two dual-active ingredient (a.i.) long-lasting insecticidal nets (LLINs) and a standard pyrethroid-only LLIN, and assessed the seasonality of these mosquito genera. A total of 85,723 Culex spp. and 144,025 Mansonia spp. were caught over the study period. The density of Culex and Mansonia was reduced in all three arms over the study period. There was no evidence of a significant reduction in the indoor or outdoor density of Culex spp. in either dual-a.i. LLIN arm as compared to the standard pyrethroid-only net arm. A similar trend was observed with Mansonia spp. A high density of Culex spp. was found both in rainy and dry seasons, while for Mansonia spp., this was mainly observed during the rainy season. These results suggest that the novel insecticides in the dual-a.i. LLINs d...
The main objective of the present study is to assess the preferences in terms of vertebrate hosts... more The main objective of the present study is to assess the preferences in terms of vertebrate hosts of Anopheles coluzzii, the main malaria vector in the pastoral area of Malanville, Benin, where rice cultivation and livestock are the main source of income for the populations. Adult mosquitoes were collected through pyrethrum spray catch, and human landing catch in two communes in Benin: Malanville, a pastoral area, and Porto-Novo, a nonpastoral area. Molecular species identification was performed through PCR within the Anopheles gambiae complex. Blood meal origin and P. falciparum sporozoite infection were determined using ELISA blood meal and circumsporozoite protein tests, respectively. Overall, 97% of females of An. gambiae s.l. were An. coluzzii, with biting behavior more pronounced outdoors in the pastoral area. In Malanville, the main vertebrate hosts on which females An. coluzzii blood fed were goats (44%), humans (24.29%), bovines (22%), and pigs (1.4%). Our results also show...
Agricultural production activities usually occur in Benin with the use of a huge amount of insect... more Agricultural production activities usually occur in Benin with the use of a huge amount of insecticides including pyrethroids for pest control. It is therefore important to regularly monitor pyrethroid resistance intensity in Anopheles gambiae s.l., the main malaria vector. This study was conducted in cereal, cotton, rice growing, and urban market gardening areas throughout the country in 2018 and 2019. Females An. gambiae s.l. field-collected as larvae were exposed to deltamethrin 1 × (0.05%), 2 × (0.1%), 5 × (0.25%), and 10 × (0.5%) and permethrin 1 × (0.75%), 2 × (1.5%), 5 × (3.75%), and 10 × (7.5%). Synergist assays were also performed using World Health Organization articles combining piperonyl butoxide (PBO) (4%) + deltamethrin 1 × and, PBO (4%) + Permethrin 1 × . Molecular species and L1014F kdr mutation were identified using PCR. Expression of metabolic enzymes was also assessed through biochemical tests. After exposure to permethrin and deltamethrin 10 × , An. gambiae s.l. displayed mortality rates <98%. Synergist assays induced significantly higher mortality rates than pyrethroids alone (p < 0.05). An. gambiae s.l. complex was composed of An. gambiae s.s., Anopheles coluzzii, and Anopheles arabiensis, with mean frequency of the L1014F kdr mutation >75%. Overexpression of nonspecific α and β esterases was observed in the cereal, cotton, and urban market gardening areas, while an overexpression of mixed function oxidases was observed in the cotton and rice growing areas. Overall, An. gambiae s.l. showed high resistance intensity to both deltamethrin and permethrin. The synergist and biochemical tests performed suggest that PBO long-lasting insecticidal nets may provide a greater control of pyrethroid-resistant mosquitoes.
Background The selection and the spread of insecticide resistance in malaria vectors to the main ... more Background The selection and the spread of insecticide resistance in malaria vectors to the main classes of insecticides used in vector control tools are a major and ongoing challenge to malaria vector control programmes. This study aimed to determine the intensity of vector resistance to insecticides in three regions of Benin with different agro-ecological characteristics. Methods Larvae of Anopheles gambiae sensu lato (s.l.) were collected from September to November 2017 in different larval sites in three northern Benin communes: Parakou, Kandi and Malanville. Two to five-day-old, non-blood-fed, female mosquitoes were exposed to papers impregnated with deltamethrin, permethrin and bendiocarb at dosages of 1 × the diagnostic dose, 5 × and 10 × to determine the intensity of resistance in these vectors. Molecular frequencies of the kdr L1014F and ace-1R G119S insecticide resistance mutations and levels of detoxification enzymes were determined for mosquitoes sampled at each study sit...
Objectives: Urban malaria is on the rise in Cotonou due to rapid urbanization and development act... more Objectives: Urban malaria is on the rise in Cotonou due to rapid urbanization and development activities. However, malaria transmission depends on several factors. Hydrology is a key factor that influences the presence of suitable habitats for the development of Anopheles larvae, thereby affecting survival of the malaria vector. For a long time, clean water bodies were thought to be the favorite Anopheles gambiae s.l. breeding sites. Nowadays, Anopheles gambiae s.l. is found in polluted waters, which used to be only favorable for the development of Culex quinquefaciatus. The current study was designed to assess both the water quality of Anopheles breeding sites and the ability of Anopheles larvae to develop in polluted water bodies. Methods: Larvae were collected in four districts in the city of Cotonou. All open water bodies were considered as potential breeding sites and investigated. Most of the breeding sites were shallow, exposed to sunlight and contained different qualities of...
Monitoring vector resistance to insecticides is a major component of resistance management. Adult... more Monitoring vector resistance to insecticides is a major component of resistance management. Adults of Anopheles gambiae s.l. from larvae collected at thirteen sites were tested with papers impregnated with bendiocarb, permethrin; deltamethrin; pirimiphos-methyl and induced bottles of insecticide including bendiocarb; deltamethrin, permethrin and pirimiphos-methyl. Molecular analyses were performed and detoxification enzyme levels were determined for each study site. This study revealed a generalized distribution of resistance of An. gambiae s.l. to pyrethroids (permethrin and deltamethrin) and a clear resistance to carbamates (bendiocarb) especially in the northern region of the country. This vector is still susceptible to organophosphates, especially pirimiphos-methyl, but resistance is a dynamic phenomenon and it would be necessary to monitor the susceptibility of these anopheles to pyrimiphos-methyl and to find alternative vector control methods to slow down the spread of resista...
Background Insecticide resistance is threatening the effectiveness of efforts to control malaria ... more Background Insecticide resistance is threatening the effectiveness of efforts to control malaria vectors in Benin. This study explores the levels and mechanisms of insecticide resistance in An. gambiae s.l. to pyrethroids. Methods Larvae were collected from August 2017 to July 2018 in five communes in southern Benin (Adjohoun, Allada, Bohicon, Cotonou, and Porto-Novo) representing diverse ecological regions, and were reared in Benin’s insectary. Two- to five-day-old female mosquitoes from each district were exposed to multiple doses of deltamethrin and permethrin (1×, 2×, 5×, and 10×) using the WHO insecticide resistance intensity bioassay. The effect of pre-exposure to the synergist, piperonyl butoxide (PBO), was also tested at different pyrethroid doses. Molecular allele frequencies of kdr (1014F) and ace-1R (119S) insecticide resistance mutations and levels of detoxification enzymes were determined for mosquitoes sampled from each study area. Results An. gambiae s.l. were resista...
Background Changes in the natural habitats of insect groups are determined the genetic polymorphi... more Background Changes in the natural habitats of insect groups are determined the genetic polymorphisms between individuals. The objective of this study was to establish the genetic structure of the Anopheles coluzzii populations in four localities of Benin. Methods Insecticide surveys and larval sampling were conducted on 4 study localities, including Cotonou, Ketou, Zagnanado, and Sô-Ava. Molecular characterizations were performed on the Anopheles mosquitoes collected with the allelic and genotypic frequencies of kdr gene determined. The multiple comparison Chi square test for proportions was performed with R version 3.3.3. Next, the observed heterozygosity, expected heterozygosity, and indices of fixation, and genetic differentiation were estimated. Finally, the Hardy–Weinberg equilibrium (EHW) was determined to assess whether panmixia exists in the different populations of mosquitoes of the agroecological zones under study. Results Carbamates, pyrethroids, organophosphorus and orga...
Background: Climate variability influence the diversity and abundance of malaria vectors and ther... more Background: Climate variability influence the diversity and abundance of malaria vectors and thereby on malaria transmission dynamics. Examine its effect on Anopheles parameters involved in transmission may predict the potential malaria hotspot as a right target for its control intervention strategies. Here, we investigated the influence of meteorological parameters on the aggressiveness and infectivity of Anopheles in two health districts zones where IRS has been extended in Northern Benin. Methods: Mosquito collections were carried out using human landing catches to evaluate rates of aggression and infectivity in twelve villages. Concomitantly, meteorological data from synoptic stations of Benin and neighbouring countries were collected in 2016-2017. Results: The spatial distribution of infective bites of An. gambiae is characterized by an intense aggression in the rural villages of the study area. Analysis of variances showed significant HBR difference according to the period but...
Background In May 2019, a confirmed dengue fever case was detected at the local hospital of Abome... more Background In May 2019, a confirmed dengue fever case was detected at the local hospital of Abomey-Calavi Commune in southern Benin. In Benin, there remains a dearth of literature concerning the distribution and biology of Aedes aegypti, the principal vector of dengue fever. This study was initiated by the Ministry of Health to partially fill this gap. The findings allowed us to assess the arboviral transmission risk incurred by the population of Abomey-Calavi to support programmatic decision-making. Methods Entomological assessments were conducted in 5% of the houses, meaning 314 houses selected from 11 boroughs in Abomey-Calavi Centre district and 9 villages in Hêvié district. The surveyed breeding sites were water containers located in (domestic) and around (peri-domestic) the dwellings. When a container was positive (housing larvae), a portion of the immature population was sampled with a larval dipper and poured into labeled jars. Immatures were then reared to adulthood at the ...
Background In Alibori and Donga, two departments of high malaria incidence of Northern Benin, pir... more Background In Alibori and Donga, two departments of high malaria incidence of Northern Benin, pirimiphos-methyl, mixture deltamethrin + clothianidin, as well as clothianidin were used at large scale for IRS. The present study aimed to assess the residual efficacy of these products. Methods Immatures of Anopheles gambiae sensu lato (s.l.) collected in the communes of Kandi and Gogounou (Department of Alibori), Djougou and Copargo (Department of Donga) were reared until adulthood. Females aged 2–5 days were used for susceptibility tube tests following the WHO protocol. The tests were conducted with deltamethrin (0.05%), bendiocarb (0.1%), pirimiphos-methyl (0.25%) and clothianidin (2% weight per volume). For cone tests performed on cement and mud walls, the An. gambiae Kisumu susceptible strain was used. After the quality control of the IRS performed 1-week post-campaign, the evaluation of the residual activity of the different tested insecticides/mixture of insecticides was conducted...
The efficacy of a vector control tool in reducing mosquito biting is crucial for its acceptabilit... more The efficacy of a vector control tool in reducing mosquito biting is crucial for its acceptability. The present study compared the vector density of Culex spp. And Mansonia spp. across clusters, which received two dual-active ingredient (a.i.) long-lasting insecticidal nets (LLINs) and a standard pyrethroid-only LLIN, and assessed the seasonality of these mosquito genera. A total of 85,723 Culex spp. and 144,025 Mansonia spp. were caught over the study period. The density of Culex and Mansonia was reduced in all three arms over the study period. There was no evidence of a significant reduction in the indoor or outdoor density of Culex spp. in either dual-a.i. LLIN arm as compared to the standard pyrethroid-only net arm. A similar trend was observed with Mansonia spp. A high density of Culex spp. was found both in rainy and dry seasons, while for Mansonia spp., this was mainly observed during the rainy season. These results suggest that the novel insecticides in the dual-a.i. LLINs d...
The main objective of the present study is to assess the preferences in terms of vertebrate hosts... more The main objective of the present study is to assess the preferences in terms of vertebrate hosts of Anopheles coluzzii, the main malaria vector in the pastoral area of Malanville, Benin, where rice cultivation and livestock are the main source of income for the populations. Adult mosquitoes were collected through pyrethrum spray catch, and human landing catch in two communes in Benin: Malanville, a pastoral area, and Porto-Novo, a nonpastoral area. Molecular species identification was performed through PCR within the Anopheles gambiae complex. Blood meal origin and P. falciparum sporozoite infection were determined using ELISA blood meal and circumsporozoite protein tests, respectively. Overall, 97% of females of An. gambiae s.l. were An. coluzzii, with biting behavior more pronounced outdoors in the pastoral area. In Malanville, the main vertebrate hosts on which females An. coluzzii blood fed were goats (44%), humans (24.29%), bovines (22%), and pigs (1.4%). Our results also show...
Agricultural production activities usually occur in Benin with the use of a huge amount of insect... more Agricultural production activities usually occur in Benin with the use of a huge amount of insecticides including pyrethroids for pest control. It is therefore important to regularly monitor pyrethroid resistance intensity in Anopheles gambiae s.l., the main malaria vector. This study was conducted in cereal, cotton, rice growing, and urban market gardening areas throughout the country in 2018 and 2019. Females An. gambiae s.l. field-collected as larvae were exposed to deltamethrin 1 × (0.05%), 2 × (0.1%), 5 × (0.25%), and 10 × (0.5%) and permethrin 1 × (0.75%), 2 × (1.5%), 5 × (3.75%), and 10 × (7.5%). Synergist assays were also performed using World Health Organization articles combining piperonyl butoxide (PBO) (4%) + deltamethrin 1 × and, PBO (4%) + Permethrin 1 × . Molecular species and L1014F kdr mutation were identified using PCR. Expression of metabolic enzymes was also assessed through biochemical tests. After exposure to permethrin and deltamethrin 10 × , An. gambiae s.l. displayed mortality rates <98%. Synergist assays induced significantly higher mortality rates than pyrethroids alone (p < 0.05). An. gambiae s.l. complex was composed of An. gambiae s.s., Anopheles coluzzii, and Anopheles arabiensis, with mean frequency of the L1014F kdr mutation >75%. Overexpression of nonspecific α and β esterases was observed in the cereal, cotton, and urban market gardening areas, while an overexpression of mixed function oxidases was observed in the cotton and rice growing areas. Overall, An. gambiae s.l. showed high resistance intensity to both deltamethrin and permethrin. The synergist and biochemical tests performed suggest that PBO long-lasting insecticidal nets may provide a greater control of pyrethroid-resistant mosquitoes.
Background The selection and the spread of insecticide resistance in malaria vectors to the main ... more Background The selection and the spread of insecticide resistance in malaria vectors to the main classes of insecticides used in vector control tools are a major and ongoing challenge to malaria vector control programmes. This study aimed to determine the intensity of vector resistance to insecticides in three regions of Benin with different agro-ecological characteristics. Methods Larvae of Anopheles gambiae sensu lato (s.l.) were collected from September to November 2017 in different larval sites in three northern Benin communes: Parakou, Kandi and Malanville. Two to five-day-old, non-blood-fed, female mosquitoes were exposed to papers impregnated with deltamethrin, permethrin and bendiocarb at dosages of 1 × the diagnostic dose, 5 × and 10 × to determine the intensity of resistance in these vectors. Molecular frequencies of the kdr L1014F and ace-1R G119S insecticide resistance mutations and levels of detoxification enzymes were determined for mosquitoes sampled at each study sit...
Objectives: Urban malaria is on the rise in Cotonou due to rapid urbanization and development act... more Objectives: Urban malaria is on the rise in Cotonou due to rapid urbanization and development activities. However, malaria transmission depends on several factors. Hydrology is a key factor that influences the presence of suitable habitats for the development of Anopheles larvae, thereby affecting survival of the malaria vector. For a long time, clean water bodies were thought to be the favorite Anopheles gambiae s.l. breeding sites. Nowadays, Anopheles gambiae s.l. is found in polluted waters, which used to be only favorable for the development of Culex quinquefaciatus. The current study was designed to assess both the water quality of Anopheles breeding sites and the ability of Anopheles larvae to develop in polluted water bodies. Methods: Larvae were collected in four districts in the city of Cotonou. All open water bodies were considered as potential breeding sites and investigated. Most of the breeding sites were shallow, exposed to sunlight and contained different qualities of...
Monitoring vector resistance to insecticides is a major component of resistance management. Adult... more Monitoring vector resistance to insecticides is a major component of resistance management. Adults of Anopheles gambiae s.l. from larvae collected at thirteen sites were tested with papers impregnated with bendiocarb, permethrin; deltamethrin; pirimiphos-methyl and induced bottles of insecticide including bendiocarb; deltamethrin, permethrin and pirimiphos-methyl. Molecular analyses were performed and detoxification enzyme levels were determined for each study site. This study revealed a generalized distribution of resistance of An. gambiae s.l. to pyrethroids (permethrin and deltamethrin) and a clear resistance to carbamates (bendiocarb) especially in the northern region of the country. This vector is still susceptible to organophosphates, especially pirimiphos-methyl, but resistance is a dynamic phenomenon and it would be necessary to monitor the susceptibility of these anopheles to pyrimiphos-methyl and to find alternative vector control methods to slow down the spread of resista...
Background Insecticide resistance is threatening the effectiveness of efforts to control malaria ... more Background Insecticide resistance is threatening the effectiveness of efforts to control malaria vectors in Benin. This study explores the levels and mechanisms of insecticide resistance in An. gambiae s.l. to pyrethroids. Methods Larvae were collected from August 2017 to July 2018 in five communes in southern Benin (Adjohoun, Allada, Bohicon, Cotonou, and Porto-Novo) representing diverse ecological regions, and were reared in Benin’s insectary. Two- to five-day-old female mosquitoes from each district were exposed to multiple doses of deltamethrin and permethrin (1×, 2×, 5×, and 10×) using the WHO insecticide resistance intensity bioassay. The effect of pre-exposure to the synergist, piperonyl butoxide (PBO), was also tested at different pyrethroid doses. Molecular allele frequencies of kdr (1014F) and ace-1R (119S) insecticide resistance mutations and levels of detoxification enzymes were determined for mosquitoes sampled from each study area. Results An. gambiae s.l. were resista...
Background Changes in the natural habitats of insect groups are determined the genetic polymorphi... more Background Changes in the natural habitats of insect groups are determined the genetic polymorphisms between individuals. The objective of this study was to establish the genetic structure of the Anopheles coluzzii populations in four localities of Benin. Methods Insecticide surveys and larval sampling were conducted on 4 study localities, including Cotonou, Ketou, Zagnanado, and Sô-Ava. Molecular characterizations were performed on the Anopheles mosquitoes collected with the allelic and genotypic frequencies of kdr gene determined. The multiple comparison Chi square test for proportions was performed with R version 3.3.3. Next, the observed heterozygosity, expected heterozygosity, and indices of fixation, and genetic differentiation were estimated. Finally, the Hardy–Weinberg equilibrium (EHW) was determined to assess whether panmixia exists in the different populations of mosquitoes of the agroecological zones under study. Results Carbamates, pyrethroids, organophosphorus and orga...
Background: Climate variability influence the diversity and abundance of malaria vectors and ther... more Background: Climate variability influence the diversity and abundance of malaria vectors and thereby on malaria transmission dynamics. Examine its effect on Anopheles parameters involved in transmission may predict the potential malaria hotspot as a right target for its control intervention strategies. Here, we investigated the influence of meteorological parameters on the aggressiveness and infectivity of Anopheles in two health districts zones where IRS has been extended in Northern Benin. Methods: Mosquito collections were carried out using human landing catches to evaluate rates of aggression and infectivity in twelve villages. Concomitantly, meteorological data from synoptic stations of Benin and neighbouring countries were collected in 2016-2017. Results: The spatial distribution of infective bites of An. gambiae is characterized by an intense aggression in the rural villages of the study area. Analysis of variances showed significant HBR difference according to the period but...
Background In May 2019, a confirmed dengue fever case was detected at the local hospital of Abome... more Background In May 2019, a confirmed dengue fever case was detected at the local hospital of Abomey-Calavi Commune in southern Benin. In Benin, there remains a dearth of literature concerning the distribution and biology of Aedes aegypti, the principal vector of dengue fever. This study was initiated by the Ministry of Health to partially fill this gap. The findings allowed us to assess the arboviral transmission risk incurred by the population of Abomey-Calavi to support programmatic decision-making. Methods Entomological assessments were conducted in 5% of the houses, meaning 314 houses selected from 11 boroughs in Abomey-Calavi Centre district and 9 villages in Hêvié district. The surveyed breeding sites were water containers located in (domestic) and around (peri-domestic) the dwellings. When a container was positive (housing larvae), a portion of the immature population was sampled with a larval dipper and poured into labeled jars. Immatures were then reared to adulthood at the ...
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