- Cameroon
Francis Zeukeng
Yaounde I, Biochemistry, Department Member
- IITA, Molecular Biology, Department Memberadd
- I am a molecular epidemiologist with a background in Biochemistry. I have worked in the molecular biology of infectio... moreI am a molecular epidemiologist with a background in Biochemistry. I have worked in the molecular biology of infectious diseases since 2012 and I have developed a keen interest in the use of genomics and bioinformatics tools to study the agents that cause emerging and neglected tropical diseases. I believe that better knowledge of microbial genomes, their evolution, and virulence could contribute to the elimination of infectious diseases. I have a BSc and MSc in Biochemistry from the University of Yaoundé 1 in Cameroon, a Ph.D. in Molecular Epidemiology from the same University, and I currently serve as a postdoctoral fellow at Noguchi Memorial Institute for Medical Research in Ghana.edit
Research Interests: Genomics and Grassroots
Rabies is a neglected enzootic disease which represents a serious public health problem. In Cameroon, efforts to prevent human deaths caused by rabies are often thwarted by the lack of community awareness. The community knowledge, as well... more
Rabies is a neglected enzootic disease which represents a serious public health problem. In Cameroon, efforts to prevent human deaths caused by rabies are often thwarted by the lack of community awareness. The community knowledge, as well as attitudes and perception on rabies, is therefore important for both prevention of human deaths and control in animals. A cross-sectional study was carried out to evaluate the level of community knowledge as well as the role of open garbage dumps (OGDs) in the epidemiology of human rabies. Overall 420 heads of household were interviewed in the Biyem-Assi health district of Yaoundé. OGDs were identified through a systematic check, and household wastes they contained were characterized. Although 66.9% of respondents have knowledge on stray dogs, only 35% of respondents knew the role of OGDs in the increase of stray dog population. Overall OGDs consisted of fermentable wastes. Nutrition places for stray dogs were wild garbage dumps (68.1%), markets ...
Research Interests:
Research Interests:
Background Malaria remains endemic in Cameroon, with heterogeneous transmission related to eco-climatic variations, vector diversity and spatial distribution. The intensification of malaria prevention and control through the free... more
Background Malaria remains endemic in Cameroon, with heterogeneous transmission related to eco-climatic variations, vector diversity and spatial distribution. The intensification of malaria prevention and control through the free distribution of insecticide-treated nets in recent years may have altered the composition, geographic distribution and natural infection rate of Anopheles species, with implications for malaria transmission dynamics. The present study seeks to assess the vectorial diversity, dynamics and infectivity across different seasons and altitudes in relationship to parasite prevalence around the slopes of Mount Cameroon, southwestern region. Method Mosquitoes were sampled (indoors and outdoors) in 11 eco-epidemiological settings at low (18–197 m), intermediate (371–584 m) and high (740–1067 m) altitude by nightly human landing catches. The mosquitoes were identified morphologically and Anopheles gambiae sibling species identified by PCR. Parity status was ascertaine...
Research Interests:
BackgroundMalaria remains one of the main causes of morbidity and mortality in Cameroon. To inform vector control intervention decision making, malaria vector surveillance was conducted monthly from October 2018 to September 2020 in five... more
BackgroundMalaria remains one of the main causes of morbidity and mortality in Cameroon. To inform vector control intervention decision making, malaria vector surveillance was conducted monthly from October 2018 to September 2020 in five selected sentinel sites (Gounougou and Simatou in the North, Bonabéri, Mangoum and Nyabessang in the South).MethodsHuman landing catches (HLCs), U.S. Centers for Disease Control and Prevention (CDC) light traps, and pyrethrum spray catches (PSCs) were used to assess vector density and species composition, human biting rate (HBR), endophagic index, indoor resting density (IRD), parity, sporozoite infection rates, entomological inoculation rate (EIR), and Anopheles vectorial capacity. ResultsA total of 139,322 Anopheles mosquitoes from 21 species were collected across all sites and methods. Out of the 21 species, eleven were implicated in malaria transmission including An. gambiae s.l., An. funestus s.l., An. nili, An. moucheti, An. paludis, An. demei...
Research Interests:
Background Cameroon is considering the implementation of indoor residual spraying (IRS) as a complementary measure to control malaria in the context of high pyrethroid resistance in major malaria vectors. Non-pyrethroid insecticide... more
Background Cameroon is considering the implementation of indoor residual spraying (IRS) as a complementary measure to control malaria in the context of high pyrethroid resistance in major malaria vectors. Non-pyrethroid insecticide classes such as organophosphates and carbamates may be utilized in IRS due to widespread pyrethroid resistance. However, the success of this strategy depends on good knowledge of the resistance status of malaria vectors to carbamates and organophosphates. Here, we assessed the susceptibility profile of Anopheles gambiae sensu lato with respect to carbamates and organophosphate and the distribution of the molecular mechanism underlying resistance to these insecticides. Methods Anopheles gambiae s.l. mosquitoes were collected from nine settings across the country and bio-assayed with bendiocarb, propoxur and pirimiphos-methyl. The Ace-1 target-site G119S mutation was genotyped using a TaqMan assay. To investigate the polymorphism in the Ace-1 gene, a region...
Research Interests:
Additional file 1. Sequence alignment of the Ace-1 gene at the G119S point mutation in live and dead An. gambiae mosquitoes 24 h after exposure to carbamate.
Additional file 2. Number of An. gambiae s.l. mosquitoes identified among those alive and dead after exposure to insecticides.
Additional file 1. Distribution of sampled water bodies within the study sites in Akonolinga health district.
Additional file 2. Distribution of MU-positivity per sampled locality and sample type.
Research Interests:
Introduction: Insecticide treated net remains a tool of choice for malaria prevention in Cameroon. However, data suggests that its use by the population, especially vulnerable groups remains low. Moreover, there is a paucity of... more
Introduction: Insecticide treated net remains a tool of choice for malaria prevention in Cameroon. However, data suggests that its use by the population, especially vulnerable groups remains low. Moreover, there is a paucity of information about factors influencing its use. We sought out to identify factors associated with net use in Mfou health district, prior to distribution of long lasting insecticides treated nets (LLINs) in households. Methods: A two-stage cluster random sampling was conducted in 4 health areas with an average of 13 villages each. A total of 541 households were selected and heads interviewed using a structured household questionnaire. Data collected were entered into a database and multivariate
Research Interests:
Agricultural practices play a major role in the selection of insecticide resistance in field populations of Anopheles mosquitoes. Here, we investigated the possible links between agricultural practice and the resistance to pyrethroid... more
Agricultural practices play a major role in the selection of insecticide resistance in field populations of Anopheles mosquitoes. Here, we investigated the possible links between agricultural practice and the resistance to pyrethroid insecticides in the major malaria vector Anopheles gambiae s.l in the city of Yaounde in Cameroon. Entomological surveys were conducted in the peri-urban and urban areas of Yaounde. KAP surveys on agricultural practice and the use of pesticides in vegetable farms were conducted in all farms and the susceptibility status of female Fo An. gambiae s.l progeny to permethrin (type I pyrethroid) and deltamethrin (type II pyrethroid) was assessed using the WHO tubes bioassay protocol. The resistance mechanisms were assessed using synergist and kdr-genotyping assays. Our findings revealed that the application of pesticide active molecules is a common practice in vegetable farms across Yaounde. This phenomenon has increased the development of resistance to pyret...
Research Interests:
1Laboratory of Zoology, Higher Teacher Training College, University of Yaoundé I, P.O.Box 47, Yaoundé, Cameroon. 2Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O.Box 288, Yaoundé, Cameroon.... more
1Laboratory of Zoology, Higher Teacher Training College, University of Yaoundé I, P.O.Box 47, Yaoundé, Cameroon. 2Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O.Box 288, Yaoundé, Cameroon. 3Department of animal Biology, Faculty of Science, University of Yaoundé I, P.O Box 812, Cameroon. 4Department of Biochemistry, Faculty of Science, University of Yaoundé I, P.O.Box. 812, Yaoundé, Cameroon.
Research Interests:
We investigated the impact of the kdr genotypes on the survival rate of mosquitoes exposed to insecticides in the main malaria vectors Anopheles coluzzii and An. gambiae s.s.. The genotype-phenotype interaction was investigated following... more
We investigated the impact of the kdr genotypes on the survival rate of mosquitoes exposed to insecticides in the main malaria vectors Anopheles coluzzii and An. gambiae s.s.. The genotype-phenotype interaction was investigated following two experimental designs; the first one consisted to determine the survival rate of well-characterized adult mosquito strains sharing different kdr genotypes but same genetic background to various insecticides, whereas the second one consisted to expose wild mosquitoes to the same insecticides. Two to five days old adult females were exposed to DDT (4%), deltamethrin (0.05%), and permethrin (0.75%) following WHO protocols. Alive and dead specimens were kept separately to screen the kdr mutations 1014F. The correlation between the kdr genotype and the survival rate to insecticides was investigated in An. coluzzii and An. gambiae s.s. using a logistic regression model. In the laboratory strains, after exposure to DDT and permethrin, the survival rate ...
Research Interests:
Background: The water used for irrigation contains measurable quantities of dissolved substances which, when accumulated in the soil and crops, have serious consequences on the environment and human health. This cross-sectional and... more
Background: The water used for irrigation contains measurable quantities of dissolved substances which, when accumulated in the soil and crops, have serious consequences on the environment and human health. This cross-sectional and descriptive study was carried out on the Nkolondom vegetables production site in order to assess the health risks related to water used for irrigation and thus, improve on the quality of vegetables and the health of consumers. Methods: Thirty structured questionnaires were administered to vegetable producers. Water used for irrigation and the main vegetables produced were carefully collected to determine the degree of contamination in toxic heavy metals (Pb, Cd, As, Cu) and in microbes or fecal and total coliforms. A new advanced and sensitive approach, the Metalyser Pro HM3000 helped us to quantify the heavy metals. Results: Vegetable growing in Nkolondom is a basic activity which is characterised using traditional watering cans for irrigation, the non-u...
Research Interests:
1 Laboratory of Zoology, Higher Teacher Training College, University of Yaoundé I, P.O. Box 47, Yaoundé, Cameroon. 2 Laboratory of Hydrobiology and Environment, Department of animal Biology, Faculty of Science, University of Yaoundé I,... more
1 Laboratory of Zoology, Higher Teacher Training College, University of Yaoundé I, P.O. Box 47, Yaoundé, Cameroon. 2 Laboratory of Hydrobiology and Environment, Department of animal Biology, Faculty of Science, University of Yaoundé I, P.O Box 812, Cameroon. 3 Department of Biochemistry, Faculty of Science, University of Yaoundé I, P.O.Box. 812, Yaoundé, Cameroon. 4 Laboratory of Microbiology, Faculty of Science, University of Yaoundé I, P.O.Box 812, Yaoundé, Cameroon.
Research Interests:
Francis ZEUKING , Rousseau DJOUAKA, Jude BIGOGA , Razack ADEOTI, Manuele TAMO, Wilfred F. MBACHAM, Anthony ABLORDEY 1 AgroEcoHealth Platform, International Institute of Tropical Agriculture (IITA), 08 P.O.Box 0932, Tri-Postal Cotonou,... more
Francis ZEUKING , Rousseau DJOUAKA, Jude BIGOGA , Razack ADEOTI, Manuele TAMO, Wilfred F. MBACHAM, Anthony ABLORDEY 1 AgroEcoHealth Platform, International Institute of Tropical Agriculture (IITA), 08 P.O.Box 0932, Tri-Postal Cotonou, Cotonou, Bénin. 2 Faculty of Science, Department of Biochemistry, University of Yaoundé I, P.O.Box., 812, Yaoundé, Cameroon. 3 Department of Bacteriology, Noguchi Memorial Institute for Medical Research, University of Ghana, P.O.Box., 581, Legon, Accra, Ghana.
Research Interests:
Background The long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) are major malaria vector control strategies in Mali. The success of control strategies depends on a better understanding of the status... more
Background The long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) are major malaria vector control strategies in Mali. The success of control strategies depends on a better understanding of the status of malaria vectors with respect to the insecticides used. In this study we evaluate the level of resistance of Anopheles gambiae (sensu lato) to bendiocarb and the molecular mechanism that underlies it. Methods Larvae of An. gambiae (s.l.) were collected from breeding habitats encountered in the three study sites and bioassayed with bendiocarb. The ace-1 target site substitution G119S was genotyped using a TaqMan assay. Results The three species of the An. gambiae complex in Mali, i.e. An. arabiensis, An. coluzzii and An. gambiae (s.s.) were found in sympatry in the three surveyed localities with different frequencies. We observed a resistance and suspicious resistance of the three species to bendiocarb with a mortality rate ranging from 37% to 86%...
Research Interests:
Background: The insecticide susceptibility status ofAnopheles funestus,one of the main malaria vectors in the Afrotropical regions, remains under-studied due to the difficulty of working with this mosquito species. Collecting their... more
Background: The insecticide susceptibility status ofAnopheles funestus,one of the main malaria vectors in the Afrotropical regions, remains under-studied due to the difficulty of working with this mosquito species. Collecting their larvae in natural breeding sites, rearing and maintaining them in normal laboratory conditions have been a difficult task. Forced-egg laying technique has been a very good tool to generate eggs from adult mosquitoes collected from the wild but rearing these eggs to obtain satisfying portion as adults has always been the problem. In this study, we optimized the development of mosquito species larvae under standard laboratory conditions for desired production of adult mosquitoes that can be useful for insecticide susceptibility tests.Methods: A forced-egg laying technique was used to obtain eggs from gravid femaleAnopheles funestuscollected from Kpome locality in Benin. Eggs were reared in three different water samples (water from the borehole,and two mine...
Research Interests:
Background:To optimize the success of insecticide-based malaria control intervention, knowledge of the distribution ofAnopheles gambiaespecies and insecticide resistance mechanisms is necessary. This paper reported an updated data on... more
Background:To optimize the success of insecticide-based malaria control intervention, knowledge of the distribution ofAnopheles gambiaespecies and insecticide resistance mechanisms is necessary. This paper reported an updated data on pyrethroids/DDT resistance in theAn. gambiae s.lpopulation from Togo. Methods:From December 2013 to April 2015, females of indoor-restingAn. gambiae s.lwere captured in three locations belonging to three different ecological zones. Resistance to DDT, permethrin and deltamethrin was screened in F1 progeny of collected mosquitoes using WHO susceptibility tests. The identification of species ofAn. gambiaecomplex and the detection ofkdrandace.1Rallele were carried out using DNA-based molecular techniques.Results:An. gambiaefrom Kovié and Nangbéto were highly resistant to DDT and permethrin with mortalities rate ranging from 0.83% to 1.58% for DDT and zero to 8.54% for permethrin. Mosquitoes collected in Nangbéto displayed 81.53% mortality with deltamethrin....
Research Interests:
Lambda-cyhalothrin (λ-cyhalothrin) is the most commonly used pyrethroid insecticide for vegetable farming in Benin. This insecticide is misused and overused by farmers, and hence may pose health hazards to consumers. We monitored... more
Lambda-cyhalothrin (λ-cyhalothrin) is the most commonly used pyrethroid insecticide for vegetable farming in Benin. This insecticide is misused and overused by farmers, and hence may pose health hazards to consumers. We monitored λ-cyhalothrin residues in lettuce and cabbage from farms at the market gates in Cotonou and Parakou using high performance liquid chromatography (HPLC) analysis techniques. These residues were also monitored on samples directly from farms (on-farm sampling) for 14 days post-treatment. Potential factors such as photolysis and hydrolysis involved in λ-cyhalothrin degradation were also screened. Results revealed that the level of λ-cyhalothrin residue concentrations in lettuce from Houeyiho decreased from 4.2 mg/kg on Day 1 to about 0.2 mg/kg on Day 7. On Day 9, analyzed lettuces were all λ-cyhalothrin free. In contrast, even 14 days after treatment of cabbage from Bawera (Parakou), we still recorded the presence of λ-cyhalothrin residues in analyzed samples. ...
Research Interests:
The environmental pathogen, Mycobacterium ulcerans (MU) can infect both humans and animals and cause Buruli ulcer (BU) disease. However, its mode(s) of transmission from the colonized environment to human/animal hosts remain unclear. In... more
The environmental pathogen, Mycobacterium ulcerans (MU) can infect both humans and animals and cause Buruli ulcer (BU) disease. However, its mode(s) of transmission from the colonized environment to human/animal hosts remain unclear. In Australia, MU can infect both wildlife and domestic mammals. Till date, BU-like lesions have only been reported in wildlife in Africa. This warrants a thorough assessment of possible MU in domestic animals in Africa. Here, we screened roaming domesticated animals that share the human microhabitat in two different BU endemic sites, Sedje-Denou in Benin and Akonolinga in Cameroon, for MU lesions. We screened roaming mammals and birds across 3 endemic villages of Sedje-Denou in Southern Benin and 6 endemic villages of Akonolinga in Cameroon. After approval from relevant authorities, specimens (wound swabs and tissue fragments) were collected from animals with open or active lesion and systematically screened to detect the presence of MU though the diagn...
Research Interests:
Background.Buruli ulcer (BU) continues to be a serious public health threat in wet tropical regions and the mode of transmission of its etiological agent,Mycobacterium ulcerans(MU), remains poorly understood. In this study, mosquito... more
Background.Buruli ulcer (BU) continues to be a serious public health threat in wet tropical regions and the mode of transmission of its etiological agent,Mycobacterium ulcerans(MU), remains poorly understood. In this study, mosquito species collected in endemic villages in Benin were screened for the presence ofMU. In addition, the ability of mosquitoes larvae to pick upMUfrom their environment and remain colonized through the larval developmental stages to the adult stage was investigated.Methods.7,218 adults and larvae mosquitoes were sampled from endemic and nonendemic villages and screened forMUDNA targets (IS2404,IS2606, and KR-B) using qPCR.Results. MUwas not detected in any of the field collected samples. Additional studies of artificially infected larvae ofAnopheles kisumuwithMUstrains revealed that mosquitoes larvae are able to ingest and hostMUduring L1, L2, L3, and L4 developmental stages. However, we noticed an absence of these bacteria at both pupae and adult stages, ce...
Research Interests:
Research Interests:
Seumen Tiogang CH, Zeukeng F, Bigoga J, Tchinda Matong VH, Zofou D, 1 1Molecular Parasitology and Diseases Vectors research Laboratory, The Biotechnology Center, University of Yaounde I 2 2Institute of Medical Research and Medicinal Plant... more
Seumen Tiogang CH, Zeukeng F, Bigoga J, Tchinda Matong VH, Zofou D, 1 1Molecular Parasitology and Diseases Vectors research Laboratory, The Biotechnology Center, University of Yaounde I 2 2Institute of Medical Research and Medicinal Plant Studies (IMPM), The Medical Research Centre 3 Department of Biochemistry, Faculty of Science, University of Yaounde I 4 Department of Biochemistry and Molecular Biology, University of Buea
Research Interests:
Helicoverpa armigera is an indigenous species in Africa and has been reported in the destruction of several crops in Benin. Management of H. armigera pest is mainly focused on the use of synthetic pyrethroids, which may contribute to... more
Helicoverpa armigera is an indigenous species in Africa and has been reported in the destruction of several crops in Benin. Management of H. armigera pest is mainly focused on the use of synthetic pyrethroids, which may contribute to resistance selection. This study aimed to screen the susceptibility pattern of field populations of H. armigera to deltamethrin in Benin. Relevant information on the type of pesticides used by farmers were gathered through surveys. Collected samples of Helicoverpa (F0) were reared to F1. F0 were subjected to morphological speciation followed by a confirmation using restriction fragment length polymorphism coupled with a polymerase chain reaction (RFLP-PCR). F1 (larvae) were used for insecticide susceptibility with deltamethrin alone and in the presence of the P450 inhibitor Piperonyl Butoxide (PBO). Deltamethrin and lambda-cyhalothrin were the most used pyrethroids in tomato and cotton farms respectively. All field-sampled Helicoverpa were found to be H...
Research Interests:
Background Insecticide-based vector control is responsible for reducing malaria mortality and morbidity. Its success depends on a better knowledge of the vector, its distribution, and resistance status to the insecticides used. In this... more
Background Insecticide-based vector control is responsible for reducing malaria mortality and morbidity. Its success depends on a better knowledge of the vector, its distribution, and resistance status to the insecticides used. In this paper, we assessed Anopheles gambiae sensu lato (A gambiae s.l.) population resistance to pyrethroids in different ecological settings. Methods The World Health Organization standard bioassay test was used to assess F0A gambiae s.l. susceptibility to pyrethroids. Biochemical Synergist assays were conducted with piperonyl butoxide (PBO), S,S,S-tributyl phosphotritioate, and diethyl maleate. L1014F, L1014S, and N1575Y knockdown resistance (kdr) mutations were investigated using TaqMan genotyping. Results Anopheles gambiae sensu lato was composed of Anopheles arabienisis, Anopheles coluzzii, and A gambiae in all study sites. Anopheles gambiae sensu lato showed a strong phenotypic resistance to deltamethrin and permethrin in all sites (13% to 41% mortalit...
Research Interests:
Background Genotyping is a powerful tool for investigating outbreaks of infectious diseases and it can provide useful information such as identifying the source and route of transmission, and circulating strains involved in the outbreak.... more
Background Genotyping is a powerful tool for investigating outbreaks of infectious diseases and it can provide useful information such as identifying the source and route of transmission, and circulating strains involved in the outbreak. Genotyping techniques based on variable number of tandem repeats (VNTR) are instrumental in detecting heterogeneity in Mycobacterium ulcerans (MU) and also for discriminating MU from other mycobacteria species. Here, we describe and map the distribution of MU genotypes in Buruli ulcer (BU) endemic communities of the Nyong valley in Cameroon. We also tested the hypothesis of whether the suspected animal reservoirs of BU that share the human microhabitat are shedding contaminated fecal matters and saliva into their surrounding environments. Methods Environmental samples from suspected MU-risk factors and lesion swabs from human patients were sampled in BU-endemic communities and tested for the presence of MU by qPCR targeting three independent sequenc...
Research Interests:
Malaria endemicity in Cameroon greatly varies according to ecological environment. In such conditions, parasitaemia, which is associated with fever, may not always suffice to define an episode of clinical malaria. The evaluation of... more
Malaria endemicity in Cameroon greatly varies according to ecological environment. In such conditions, parasitaemia, which is associated with fever, may not always suffice to define an episode of clinical malaria. The evaluation of malaria control intervention strategies mostly consists of identifying cases of clinical malaria and is crucial to promote better diagnosis for accurate measurement of the impact of the intervention. We sought out to define and quantify clinical malaria cases in children from three health districts in the Northern region of Cameroon. A cohort study of 6,195 children aged between 6 and 120 months was carried out during the raining season (July to October) between 2013 and 2014. Differential diagnosis of clinical malaria was performed using the parasite density and axillary temperature. At recruitment, patients with malaria-related symptoms (fever [axillary temperature ≥ 37.5°C], chills, severe malaise, headache, or vomiting) and a malaria positive blood sm...
Research Interests:
Background: Insecticides resistance in Anopheles mosquitoes limits Long-Lasting Insecticidal Nets (LLIN) used for malaria control in Africa, especially Benin. This study aimed to evaluate the bio-efficacy of current LLINs in an area where... more
Background: Insecticides resistance in Anopheles mosquitoes limits Long-Lasting Insecticidal Nets (LLIN) used for malaria control in Africa, especially Benin. This study aimed to evaluate the bio-efficacy of current LLINs in an area where An. funestus s.l. and An. gambiae have developed multi-resistance to insecticides, and to assess in experimental huts the performance of a mixed combination of pyrethroids and piperonyl butoxide (PBO) treated nets on these resistant mosquitoes. Methods: The study was conducted at Kpomè, Southern Benin. The bio-efficacy of LLINs against An. funestus and An. gambiae was assessed using the World Health Organization (WHO) cone and tunnel tests. A released/recapture experiment following WHO procedures was conducted to compare the efficacy of conventional LLINs treated with pyrethroids only and LLINs with combinations of pyrethroids and PBO. Prior to huts trials, we confirmed the level of insecticide and PBO residues in tested nets using high performance...
Insecticides resistance in mosquitoes limits
Research Interests:
Background
Research Interests:
Overcoming the phenomenon of insecticides resistance in malaria vectors in Sub-Saharan tropics remains a great challenge to stop the burden of malaria disease. We tested the efficacy of Zingiber officinale as an alternative insecticide to... more
Overcoming the phenomenon of insecticides resistance in malaria vectors in Sub-Saharan tropics remains a great challenge to stop the burden of malaria disease. We tested the efficacy of Zingiber officinale as an alternative insecticide to synthetic pesticides and as a vector control tool against Anopheles coluzzii, the main malaria vector in Cameroon. The biotoxicity of Z. officinale essential oil on aquatic stages of An. coluzzii was assessed using WHO guidelines, and the essential oil active compounds were identified using Gas Chromatography coupling Mass Spectrometry (GC-MS). The essential oil of Z. officinale revealed an ovicidal and larvicidal property against developmental stages of An. coluzzii. A median inhibitory concentration (IC50) of 17.81 ppm was obtained for eggs hatching potentials, while LC50 of 12.20, 12.12, 12.77 and 13.67 were obtained after exposure to first, second, third and fourth instars larvae respectively. All larval stages exhibited similar and full susceptibility to Z. officinale essential oil at 25 ppm. Overall, the essential oil extraction yield was 0.301% and 26 compounds were identified from their retention indices and mass spectra. Hydrocarbon monoterpenes (24.52%), oxygenated monoterpenes (44.93%) and hydrocarbon sesquiterpenes (30.54%) constituted the major classes of the essential oil. β-curcumene (15.24%), geranial (15.16%), camphene (13.79%), neral (11.88%) and α-zingiberene (6.18%) were the most abundant oil compounds. In summary, Z. officinale essential oil revealed important ovicidal and larvicidal properties and stands as a promising tool to manage the phenomenon of insecticides resistant vectors in malaria endemic regions.
Research Interests:
Background: The water used for irrigation contains measurable quantities of dissolved substances which, when accumulated in the soil and crops, have serious consequences on the environment and human health. This cross-sectional and... more
Background: The water used for irrigation contains measurable quantities of dissolved substances which, when accumulated in the soil and crops, have serious consequences on the environment and human health. This cross-sectional and descriptive study was carried out on the Nkolondom vegetables production site in order to assess the health risks related to water used for irrigation and thus, improve on the quality of vegetables and the health of consumers. Methods: Thirty structured questionnaires were administered to vegetable producers. Water used for irrigation and the main vegetables produced were carefully collected to determine the degree of contamination in toxic heavy metals (Pb, Cd, As, Cu) and in microbes or fecal and total coliforms. A new advanced and sensitive approach, the Metalyser Pro HM3000 helped us to quantify the heavy metals. Results: Vegetable growing in Nkolondom is a basic activity which is characterised using traditional watering cans for irrigation, the non-use of personal protective equipment and the excessive use of inputs and pesticides. Irrigation is done with water from the river et the main crops produced there are lettuce and celery. The irrigation water as well as the vegetables that were analysed contained non-toxic doses of heavy metals which varied as follows: Cu> Pb> As> Cd. The mean concentrations in fecal coliforms found were not toxic in the water used for irrigation (100 UFC/100 ml) and toxic in the vegetables (2,67 104 UFC/100 g). Vegetables grown in Nkolondom are thus dangerous for consumption and could cause many health issues to vegetable producers.
Research Interests:
The anopheline resistance to synthetic pesticides has led to the use of plant biocides as alternative biological and natural control strategies. The red variety of Capsicum annuum (Solanaceae), locally used to fight against insects was... more
The anopheline resistance to synthetic pesticides has led to the use of plant biocides as alternative biological and natural control strategies. The red variety of Capsicum annuum (Solanaceae), locally used to fight against insects was tested in this study for its insecticidal effect against aquatic stages of Anopheles gambiae s.l. mosquitoes. Fresh ripe fruits were crushed, and essential oil was extracted by hydro distillation in Clevenger-type apparatus. Seven working concentrations (0, 10, 20, 30, 40, 50, and 100 ppm) were tested against eggs, larval and pupal stages of An. Gambiae s.l. Overall, the hatching rates were low and decreased with the oil concentrations with median inhibitory concentration (IC 50) of 13.735 ppm after 24 h exposure to C. annuum fresh fruits essential oil. This oil revealed high larvicidal effect against third instars larvae (L3) of An. Gambiae s.l. with median lethal concentration (LC 50) of 26.181 ppm and 19.643 ppm, respectively after 30 min and 1 h exposure. A pupicidal effect was also observed against pupal stages of An. Gambiae s.l. with LC 50 of 27.303 ppm and 20.939 ppm, respectively after 30 min and 1 h exposure. Overall, this study revealed and confirmed the biological potentials of C. annuum fresh fruits essential oil as a safe tool to fight against eggs, larvae and pupal stages of An. Gambiae s.l. in areas where this insect is known as vector borne disease implicated in the transmission of malaria.
Research Interests:
The insecticide susceptibility status of one of the Background: Anopheles funestus, main malaria vectors in the Afrotropical regions, remains under-studied due to the difficulty of working with this mosquito species. Collecting their... more
The insecticide susceptibility status of one of the Background: Anopheles funestus, main malaria vectors in the Afrotropical regions, remains under-studied due to the difficulty of working with this mosquito species. Collecting their larvae in natural breeding sites, rearing and maintaining them in normal laboratory conditions have been a difficult task. Forced-egg laying technique has been a very good tool to generate eggs from adult mosquitoes collected from the wild but rearing these eggs to obtain satisfying portion as adults has always been the problem. In this study, we optimized the development of mosquito species larvae under standard laboratory conditions for desired production of adult mosquitoes that can be useful for insecticide susceptibility tests. A forced-egg laying technique was used to obtain eggs from gravid female Methods: collected from Kpome locality in Benin. Eggs were reared in three Anopheles funestus different water samples (water from the borehole,and two mineral water namely FIFA and Possotômè) and larvae were fed with TetraMin baby fish food. The physico-chemical parameters of the waters were investigated prior to use for egg incubation. In contrast to mineral water that had no contamination, the borehole water Results: source was contaminated with lead (2.5mg/L) and nitrate (118.8mg/L). Egg hatching rates ranged as 91.9 ± 4.4%, 89.1 ± 2.5% and 87.9 ± 2.6% in FIFA, Possotômè and borehole water respectively. High emergence of larvae to adult mosquitoes was recorded as in FIFA (74.3%) and Possotômè(79.5%) water. No adult mosquito was obtained from larvae reared in borehole water. This study gave insight on the water sources that could be good for Conclusions: rearing to mass produce in the laboratory. More analysis with other local An. funestus mineral water sources in our environments could be considered in the future, hopefully giving better outputs.
Background. Buruli ulcer (BU) continues to be a serious public health threat in wet tropical regions and the mode of transmission of its etiological agent, Mycobacterium ulcerans (MU), remains poorly understood. In this study, mosquito... more
Background. Buruli ulcer (BU) continues to be a serious public health threat in wet tropical regions and the mode of transmission of its etiological agent, Mycobacterium ulcerans (MU), remains poorly understood. In this study, mosquito species collected in endemic villages in Benin were screened for the presence of MU. In addition, the ability of mosquitoes larvae to pick up MU from their environment and remain colonized through the larval developmental stages to the adult stage was investigated. Methods. 7,218 adults and larvae mosquitoes were sampled from endemic and nonendemic villages and screened for MU DNA targets (IS2404, IS2606, and KR-B) using qPCR. Results. MU was not detected in any of the field collected samples. Additional studies of artificially infected larvae of Anopheles kisumu with MU strains revealed that mosquitoes larvae are able to ingest and host MU during L1, L2, L3, and L4 developmental stages. However, we noticed an absence of these bacteria at both pupae and adult stages, certainly revealing the low ability of infected or colonized mosquitoes to vertically transmit MU to their offspring. Conclusion. The overall findings highlight the low implication of mosquitoes as biological vectors in the transmission cycle of MU from the risk environments to humans.
Research Interests:
We investigated the impact of the kdr genotypes on the survival rate of mosquitoes exposed to insecticides in the main malaria vectors Anopheles coluzzii and An. gambiae s.s.. The genotype-phenotype interaction was investigated following... more
We investigated the impact of the kdr genotypes on the survival rate of mosquitoes exposed to insecticides in the main malaria vectors Anopheles coluzzii and An. gambiae s.s.. The genotype-phenotype interaction was investigated following two experimental designs; the first one consisted to determine the survival rate of well-characterized adult mosquito strains sharing different kdr genotypes but same genetic background to various insecticides, whereas the second one consisted to expose wild mosquitoes to the same insecticides. Two to five days old adult females were exposed to DDT (4%), deltamethrin (0.05%), and permethrin (0.75%) following WHO protocols. Alive and dead specimens were kept separately to screen the kdr mutations 1014F. The correlation between the kdr genotype and the survival rate to insecticides was investigated in An. coluzzii and An. gambiae s.s. using a logistic regression model. In the laboratory strains, after exposure to DDT and permethrin, the survival rate was significantly higher in F/F individuals comparing to L/F and L/L individuals (p<0.05). A perfect correlation was observed between the survival rate and the
Research Interests:
Water used for irrigation always contains measurable quantities of dissolved substances that may accumulate in the soil with serious consequences on human health and the environment. A descriptive study was carried out on market gardeners... more
Water used for irrigation always contains measurable quantities of dissolved substances that may accumulate in the soil with serious consequences on human health and the environment. A descriptive study was carried out on market gardeners in Cotonou and Parakou in Benin and Yaoundé in Cameroon to assess the presence of coliforms and heavy metals contamination in water used for irrigation and their fresh produces on the farm fields. Ninety structured questionnaires were administered on farmers to get information on market gardening practices (water sources used for irrigation, watering systems and cultivated fresh produces), consumption of fresh produces, and human health risks. Waters used for irrigation and vegetables were carefully collected to assess the heavy metals contamination (Pb, Cd, As, Cu) and faecal coliforms using the new advanced Metalyser Pro HM3000 and the membrane filtration methods respectively. Heavy metals concentrations which are below the WHO threshold limits in both irrigation water sources and fresh produces ranged as Cu>Pb>As>Cd from the study sites in Cameroon and Benin. The average concentrations of faecal coliforms found in both irrigation water sources and their fresh produces were harmful when compared to WHO threshold limits. The study site of Baouèra in Benin had the highest level of harmful contaminants in irrigation water sources (F = 18.78; P = 0,003) and the corresponding fresh produces (F = 5.16; P = 0.049). The results also revealed that the health risks awareness of these contaminants might impact the consumption of fresh produces in market gardeners in Baouèra. Regular monitoring for safe market gardening practices is strongly recommended in order to break down the harmful levels of contaminants found in consumed fresh produces.