Larval habitats and susceptibility of malaria vectors to insecticides in semi-urban and rural localities of the Coast-Cameroon region: preliminary data

Le choix d’une stratégie appropriée de lutte anti-paludique dans un faciès éco-climatique donné requiert une bonne connaissance de l’écologie des vecteurs, notamment la distribution spatiale et la productivité des gîtes larvaires, et de leur niveau de sensibilité aux insecticides. La présente étude cartographie, caractérise les gîtes de ponte des moustiques et évalue la susceptibilité aux insecticides des vecteurs de paludisme à Banya II et Bodiman, deux localités l’une sub-urbaine et l’autre rurale, de la région du littoral camerounais. Les enquêtes sur le terrain ont été menées en mai 2015. Les gîtes de moustiques ont été géo-réferencés. Pour chaque gîte, les larves ont été prélevées puis élevées et les paramètres physico-chimiques mesurés in situ. La sensibilité des vecteurs au Dichlorodiphényltrichloroéthane (DDT), à la Deltaméthrine et à la Perméthrine a été évaluée sur les anophèles issus de l’élevage des larves. Une diversité de gîtes a été identifiée dans les sites d’étude (mares, cours d’eau, caniveaux, pneus, emballages-plastiques, récipients de réserve d’eau, récipients abandonnés, trous de papayer, trous de bambou). Cependant, Anopheles gambiae s.l., l’espèce la plus abondante à Banya II a été plus fréquente dans les mares, alors que Culex poicilipes, l’espèce la plus abondante à Bodiman a été majoritairement collectée dans des récipients abandonnés. Les deux catégories de gîtes avaient respectivement une conductivité électrique de 167,5 [16,9-305] et 170,43 [11,6-461] µs/cm ; une salinité de 90,5 [23,5-157] et 94,6[15-240] g/l ; un total de solides dissous (TDS) de 119,6 [20,6-215] et 123,3 [7,8-354] ppm. Les trois insecticides testés ont induit des taux de mortalité inférieurs à 85 % pour la souche Banya II d’A. gambiae s.l. et supérieurs à 98 % pour la souche Bodiman d’A. nili. Les présentes informations devraient être prises en compte pour une meilleure orientation des stratégies de lutte si l’on veut contrôler efficacement les vecteurs dans les localités d’étude.Choosing an appropriate strategy for mosquito control in an eco-climatic facies requires knowledge of vector ecology, including the spatial distribution and productivity of larval habitats and their level of susceptibility to insecticides. This study maps, characterizes the mosquito breeding sites and evaluates the susceptibility to insecticides of malaria vectors to Banya II and Bodiman, two semi-urban and rural areas of the coastal region of Cameroon. The field surveys were conducted in May 2015. The mosquito breeding sites were geo-referenced. For each breeding site, larvae were collected then reared and physico-chemical parameters measured in situ. The susceptibility of vectors to dichlorodiphenyltrichloroethane (DDT), deltamethrin and permethrin was evaluated on the anopheline obtained from larva rearing. A variety of breeding sites has been identified in the study sites (ponds, rivers, ditches, tires, plastic wrap, water storage containers, abandoned containers, papaya holes, bamboo holes). However, Anopheles gambiae s.l, the most abundant species in Banya II was more common in the pools, while Culex poicilipes, the most abundant species in Bodiman was mainly collected in abandoned containers. The two categories of breeding sites had respectively electrical conductivity of 167.5 [16.9-305] and 170.43 [11.6-461] µs/cm, salinity of 90.5 [23.5-157] and 94.63[15-240] g/l and total dissolved solids of 119.6 [20.6-215] and 123.3 [7.8-354] ppm. Insecticides tests revealed mortality rates below 85 % for the Banya II Strain of A. gambiae s.l. and over 98 % for the Bodiman strain of A. nili. These informations should be taken into account for a better orientation of control strategies in order to control effectively the vectors in the study localities

Contribution to the sustainable management of the Wouri watershed by a study of the distribution of its culicidian fauna (Littoral-Cameroon)

Une étude comparative entre la diversité et la productivité culicidiennes du fleuve Wouri et celles de sa rive a été menée pour évaluer la possibilité de préserver le cours d’eau d’un ""larviciding"" qui affecterait les ressources halieutiques lors des campagnes anti-larvaires. Les stations d’étude sur le fleuve Wouri et les gîtes larvaires de sa rive ont été cartographiés, leur productivité culicidienne ainsi que leurs paramètres physico-chimiques mesurés. Les moustiques échantillonnés ont été identifiés morphologiquement et ceux du complexe Anopheles gambiae par la biologie moléculaire. Huit types de gîtes larvaires ont été répertoriés sur la rive avec une fréquence plus élevée des gîtes artificiels dont la productivité culicidienne était significativement plus élevée que celle des gîtes naturels. Les communautés culicidiennes du fleuve Wouri et de sa rive présentaient une similarité spécifique. Cependant 93 % de l’ensemble des moustiques échantillonnés et 94 % des vecteurs du paludisme identifiés provenaient de la rive. La préservation du fleuve Wouri pourrait être envisagée lors des campagnes de ""larviciding"" compte tenu de sa productivité culicidienne, de son importance écologique et socio-économique.A comparative study of the culicidian diversity and productivity of the Wouri River and its shoreline has been carried out to evaluate the possibility of preserving the water course from a ""larviciding"" which will affect fishery resources during anti-larval campaigns. The study stations on the Wouri River and the larval breeding sites on its bank have been mapped, their culicidian productivity as well as their physico-chemical parameters measured. The sampled mosquitoes were identified morphologically and those of the Anopheles gambiae complex by molecular biology. Eight types of breeding sites were recorded on the bank with a higher frequency of artificial lodges with significantly higher culicidian productivity than natural deposits. The culicidian communities of the Wouri River and its shore had a specific similarity. However, 93 % of all mosquitoes sampled and 94 % of the malaria vectors identified came from the shoreline. The preservation of the Wouri River could be envisaged during the ""larviciding"" campaigns in view of its culicidian productivity, its ecological and socio-economic importance

Bendiocarb and Malathion Resistance in Two Major Malaria Vector Populations in Cameroon Is Associated with High Frequency of the G119S Mutation (Ace-1) and Overexpression of Detoxification Genes

The spread of pyrethroid resistance in malaria vectors is a major threat affecting the performance of current control measures. However, there is still not enough information on the resistance profile of mosquitoes to carbamates and organophosphates which could be used as alternatives. The present study assessed the resistance profile of Anopheles gambiae s.l. to bendiocarb and malathion, at the phenotypic and molecular levels, in different eco-epidemiological settings in Cameroon. Anopheles gambiae s.l. mosquitoes were collected from four eco-epidemiological settings across the country and their susceptibility level to bendiocarb and malathion was determined using WHO tubes bioassays. The ace-1 target site G119S mutation was screened by PCR. Reverse Transcription quantitative PCR 3-plex TaqMan assays were used to quantify the level of expression of eight genes associated with metabolic resistance. Resistance to malathion and/or bendiocarb was recorded in all study sites except in mosquitoes collected in Kaélé and Njombé. The Ace-1 (G119S) mutation was detected in high frequencies (>40%) in Kékem and Santchou. Both An. gambiae and An. coluzzii were detected carrying this mutation. The cytochrome P450s gene Cyp6p3 associated with carbamate resistance and the glutathione S-transferase gene Gste2 associated with organophosphate resistance were found to be overexpressed. Genes associated with pyrethroid (Cyp6m2, Cyp9k1, Cyp6p3) and organochlorine (Gste2, Cyp6z1, Cyp6m2) and cuticle resistance (Cyp4g16) were also overexpressed. The rapid spread of resistance to organophosphates and carbamates could seriously compromise future control strategies based on IRS. It is therefore becoming important to assess the magnitude of bendiocarb and malathion resistance countrywide

Patterns of anopheline feeding/resting behaviour and Plasmodium infections in North Cameroon, 2011-2014: implications for malaria control.

BACKGROUND: Effective malaria control relies on evidence-based interventions. Anopheline behaviour and Plasmodium infections were investigated in North Cameroon, following long-lasting insecticidal net (LLIN) distribution in 2010. METHODS: During four consecutive years from 2011 to 2014, adult mosquitoes were collected indoors, outdoors and in exit traps across 38 locations in the Garoua, Pitoa and Mayo-Oulo health districts. Anophelines were morphologically and molecularly identified, then analysed for blood meal origins and Plasmodium falciparum circumsporozoite protein (Pf-CSP). Blood from children under 5 years-old using LLINs was examined for Plasmodium infections. RESULTS: Overall, 9376 anophelines belonging to 14 species/sibling species were recorded. Anopheles gambiae (s.l.) [An. arabiensis (73.3%), An. coluzzii (17.6%) and An. gambiae (s.s.) (9.1%)] was predominant (72%), followed by An. funestus (s.l.) (20.5%) and An. rufipes (6.5%). The recorded blood meals were mainly from humans (28%), cattle (15.6%) and sheep (11.6%) or mixed (45%). Pf-CSP rates were higher indoors (3.2-5.4%) versus outdoors (0.8-2.0%), and increased yearly (χ2 < 18, df = 10, P < 0.03). Malaria prevalence in children under 5 years-old, in households using LLINs was 30% (924/3088). CONCLUSIONS: The present study revealed the variability of malaria vector resting and feeding behaviour, and the persistence of Plasmodium infections regardless the use of LLINs. Supplementary interventions to LLINs are therefore needed to sustain malaria prevention in North Cameroon

Habitats larvaires et sensibilité des vecteurs du paludisme aux insecticides dans des localités (semi-urbaine et rurale) de la région du littoral camerounais : données préliminaires

Larval habitats and susceptibility of malaria vectors to insecticides in semi-urban and rural localities of the Coast-Cameroon region : preliminary data. Choosing an appropriate strategy for mosquito control in an eco-climatic facies requires knowledge of vector ecology, including the spatial distribution and productivity of larval habitats and their level of susceptibility to insecticides. This study maps, characterizes the mosquito breeding sites and evaluates the susceptibility to insecticides of malaria vectors to Banya II and Bodiman, two semi-urban and rural areas of the coastal region of Cameroon. The field surveys were conducted in May 2015. The mosquito breeding sites were geo-referenced. For each breeding site, larvae were collected then reared and physico-chemical parameters measured in situ. The susceptibility of vectors to dichlorodiphenyltrichloroethane (DDT), deltamethrin and permethrin was evaluated on the anopheline obtained from larva rearing. A variety of breeding sites has been identified in the study sites (ponds, rivers, ditches, tires, plastic wrap, water storage containers, abandoned containers, papaya holes, bamboo holes). However, Anopheles gambiae s. l, the most abundant species in Banya II was more common in the pools, while Culex poicilipes, the most abundant species in Bodiman was mainly collected in abandoned containers. The two categories of breeding sites had respectively electrical conductivity of 167.5 [16.9-305] and 170.43 [11.6-461] μs/cm, salinity of 90.5 [23.5-157] and 94.63[15-240] g/l and total dissolved solids of 119.6 [20.6-215] and 123.3 [7.8-354] ppm. Insecticides tests revealed mortality rates below 85 % for the Banya II Strain of A. gambiae s. l. and over 98 % for the Bodiman strain of A. nili. These informations should be taken into account for a better orientation of control strategies in order to control effectively the vectors in the study localities.Le choix d’une stratégie appropriée de lutte anti-paludique dans un faciès éco-climatique donné requiert une bonne connaissance de l’écologie des vecteurs, notamment la distribution spatiale et la productivité des gîtes larvaires, et de leur niveau de sensibilité aux insecticides. La présente étude cartographie, caractérise les gîtes de ponte des moustiques et évalue la susceptibilité aux insecticides des vecteurs de paludisme à Banya II et Bodiman, deux localités l’une sub-urbaine et l’autre rurale, de la région du littoral camerounais. Les enquêtes sur le terrain ont été menées en mai 2015. Les gîtes de moustiques ont été géo-réferencés. Pour chaque gîte, les larves ont été prélevées puis élevées et les paramètres physico-chimiques mesurés in situ. La sensibilité des vecteurs au Dichlorodiphényltrichloroéthane (DDT), à la Deltaméthrine et à la Perméthrine a été évaluée sur les anophèles issus de l’élevage des larves. Une diversité de gîtes a été identifiée dans les sites d’étude (mares, cours d’eau, caniveaux, pneus, emballages-plastiques, récipients de réserve d’eau, récipients abandonnés, trous de papayer, trous de bambou). Cependant, Anopheles gambiae s. l., l’espèce la plus abondante à Banya II a été plus fréquente dans les mares, alors que Culex poicilipes, l’espèce la plus abondante à Bodiman a été majoritairement collectée dans des récipients abandonnés. Les deux catégories de gîtes avaient respectivement une conductivité électrique de 167,5 [16,9-305] et 170,43 [11,6-461] μs/cm ; une salinité de 90,5 [23,5-157] et 94,6 [15-240] g/l ; un total de solides dissous (TDS) de 119,6 [20,6-215] et 123,3 [7,8-354] ppm. Les trois insecticides testés ont induit des taux de mortalité inférieurs à 85 % pour la souche Banya II d’A. gambiae s. l. et supérieurs à 98 % pour la souche Bodiman d’A. nili. Les présentes informations devraient être prises en compte pour une meilleure orientation des stratégies de lutte si l’on veut contrôler efficacement les vecteurs dans les localités d’étude.Ntonga Akono Patrick, Mbida Mbida Arthur, Awono Ambene Parfait, Youmbi Enga Lyonnais, Abdel Kayoum Yomon, Kekeunou Sévilor. Habitats larvaires et sensibilité des vecteurs du paludisme aux insecticides dans des localités (semi-urbaine et rurale) de la région du littoral camerounais : données préliminaires. In: Revue d'Écologie (La Terre et La Vie), tome 73, n°2, 2018. pp. 132-141

Contribution à la gestion durable du bassin versant du Wouri par une étude de la répartition de sa faune culicidienne (Littoral-Cameroun)

Contribution to the sustainable management of the Wouri watershed by a study of the distribution of its culicidian fauna (Littoral-Cameroon). A comparative study of the culicidian diversity and productivity of the Wouri River and its shoreline has been carried out to evaluate the possibility of preserving the water course from a "larviciding" which will affect fishery resources during anti-larval campaigns. The study stations on the Wouri River and the larval breeding sites on its bank have been mapped, their culicidian productivity as well as their physico-chemical parameters measured. The sampled mosquitoes were identified morphologically and those of the Anopheles gambiae complex by molecular biology. Eight types of breeding sites were recorded on the bank with a higher frequency of artificial lodges with significantly higher culicidian productivity than natural deposits. The culicidian communities of the Wouri River and its shore had a specific similarity. However, 93 % of all mosquitoes sampled and 94 % of the malaria vectors identified came from the shoreline. The preservation of the Wouri River could be envisaged during the "larviciding" campaigns in view of its culicidian productivity, its ecological and socio-economic importance.Une étude comparative entre la diversité et la productivité culicidiennes du fleuve Wouri et celles de sa rive a été menée pour évaluer la possibilité de préserver le cours d’eau d’un "larviciding" qui affecterait les ressources halieutiques lors des campagnes anti-larvaires. Les stations d’étude sur le fleuve Wouri et les gîtes larvaires de sa rive ont été cartographiés, leur productivité culicidienne ainsi que leurs paramètres physico-chimiques mesurés. Les moustiques échantillonnés ont été identifiés morphologiquement et ceux du complexe Anopheles gambiae par la biologie moléculaire. Huit types de gîtes larvaires ont été répertoriés sur la rive avec une fréquence plus élevée des gîtes artificiels dont la productivité culicidienne était significativement plus élevée que celle des gîtes naturels. Les communautés culicidiennes du fleuve Wouri et de sa rive présentaient une similarité spécifique. Cependant 93 % de l’ensemble des moustiques échantillonnés et 94 % des vecteurs du paludisme identifiés provenaient de la rive. La préservation du fleuve Wouri pourrait être envisagée lors des campagnes de "larviciding" compte tenu de sa productivité culicidienne, de son importance écologique et socio-économique.Mbida Mbida Arthur, Ntonga Akono Patrick, Awono Ambene Parfait, Simo Wopo Hermann, Talipouo Abdou, Tchoffo Fobasso Romeo, Dongmo Alain, Lehman Gustave, Mimpfoundi Remy. Contribution à la gestion durable du bassin versant du Wouri par une étude de la répartition de sa faune culicidienne (Littoral-Cameroun). In: Revue d'Écologie (La Terre et La Vie), tome 73, n°4, 2018. pp. 550-558

Impact of vegetable crop agriculture on anopheline agressivity and malaria transmission in urban and less urbanized settings of the South region of Cameroon

Abstract Background The use of inland valley swamps for vegetable crop agriculture contributes to food security in urban and less urbanized settings in Africa. The impact of this agriculture on aggressive mosquitoes’ diversity and malaria transmission in central Africa is poorly documented. This study is aimed at assessing the impact of vegetable crop agriculture on these entomological parameters in urban and less urbanized settings of the forest area, south of Cameroon. Methods The human bait technique was used for the capture of aggressive mosquitoes from January to December 2012. For three consecutive days each month, captures were performed on volunteers in hydro-agricultural and river bank sites of Akonolinga and Yaoundé. Physico-chemical characteristics of mosquito breeding sites were recorded. Molecular alongside morpho-taxonomic techniques were used for the identification of mosquito species; ELISA test was used to reveal Plasmodium falciparum infected mosquitoes through the detection of CSP. Mosquito diversity, aggressivity and malaria transmission in sites and settings were determined and compared. Results Biting rates were higher in hydro-agricultural sites of less urbanized and urban settings (31.8 b/p/n and 28.6 b/p/n respectively) than in river banks sites (6.83 b/p/n and 3.64 b/p/n respectively; p < 0.0001). Physico-chemical parameters of breeding sites were not fundamentally different. Five anopheline species were identified; An. gambiae, An. funestus s.s., An. moucheti s.s., An. hancocki and An. nili s.s. In hydro-agricultural sites 2 species were captured in the urban setting versus 4 in the less urbanized setting, meanwhile in river bank sites, 3 species were captured in the urban setting versus 4 species in the less urbanized setting. An. nili s.s. was found in river banks only. An. hancocki was not found to insure Plasmodium falciparum Welch transmission. EIR in hydro-agricultural sites varied from 1.86 ib/p/n (urban area) to 2.13 ib/p/n (less urbanized area) with higher rates in April/May and August. Overall, EIR was higher in less urbanized areas (p < 0.0001) but the difference was nullified with the practice of vegetable crop agriculture (p = 0.2). Conclusion These results highlight the need for specific preventive measures that take into account the ecological peculiarities related to vegetable crop agriculture on hydro-agricultural lands, in order to protect inhabitants from malaria

Pyrethroid Resistance Situation across Different Eco-Epidemiological Settings in Cameroon

Rapid emergence and spread of pyrethroid resistance in Anopheles gambiae populations is among the main factors affecting malaria vector control in Cameroon, but there is still not enough data on the exact pyrethroid resistance status across Cameroon. The present study assessed pyrethroid resistance profile in different eco-epidemiological settings in Cameroon. Susceptibility bioassay tests were performed with F0 An. gambiae females aged three to five days. Mosquito susceptibility to both permethrin and deltamethrin was assessed. Species of the An. gambiae s.l. complex were identified using molecular diagnostic tools. Target site mutations conferring resistance were detected using Taqman assays. Quantitative reverse transcription-real-time PCR (qRT-PCR) 3-plex TaqMan&reg; assays were used for the quantification of detoxification genes implicated in pyrethroid resistance. An. gambiae, An. coluzzii and An. arabiensis were identified in the different settings. An. gambiae was dominant in Santchou, K&eacute;kem, B&eacute;labo, Bertoua and Njomb&eacute;, while An. coluzzii was abundant in Tibati and Ka&eacute;l&eacute;. High frequencies of the kdr L1014F allele ranging from 43% to 100% were recorded in almost all sites. The L1014S kdr allele was detected at low frequency (4.10&ndash;10%) only in mosquito populations from Njomb&eacute; and Tibati. The N1575Y mutation was recorded in Ka&eacute;l&eacute;, Santchou, Tibati and Bertoua with a frequency varying from 2.10% to 11.70%. Six Cytochrome P450 genes (Cyp6p3, Cyp6m2, Cyp9k1, Cyp6p4, Cyp6z1, and Cyp4g16) were found to be overexpressed in at least one population. Analysis of cuticular hydrocarbon lipids indicated a significant increase in CHC content in mosquito populations from Ka&eacute;l&eacute; and Njomb&eacute; compared to K&eacute;kem, B&eacute;labo and Bertoua populations. The study indicated high pyrethroid resistance across different ecological settings in Cameroon with different profile of resistance across the country. The present situation calls for further actions in order to mitigate the impact of insecticide resistance on vector control measures