Flobert NJIOKOU · UY1 Research Hub

BPA

Flobert NJIOKOU

Professeur

242Publ.

BPADép.

FSFaculté

Institution: Université de Yaoundé I
Faculté
Département
Email professionnel

Activité scientifique

Synthèse des publications

Période: 1992–2026
Accès ouvert: 134
Types: 3
Publ.: 242

Journal Article · 194
Other · 30
Preprint · 18

Mots-clés récurrents

biology
ecology
zoology

Profil chercheur

Biographie

Enseignant-chercheur à l’Université de Yaoundé I. Grade : Professeur.

Publications scientifiques

Publications

2026

2026Article de revue
Anthropophagy and Ecological Bridges: Blood-Meal Patterns of Invasive Aedes albopictus (Skuse, 1894) and Native Aedes aegypti Linnaeus, 1762 and Their Implications for Arbovirus Emergence in Central Africa
Armel N. Tedjou, Christophe R. Keumeni, Aurélie P. Yougang, Flobert Njiokou, Jo Lines, Sian E. Clarke et 2 autre(s)
Tropical Medicine and Infectious Disease
Aedes (Ae.) aegypti and Ae. albopictus are important vectors of arboviruses. Yet their blood-feeding pattern remains poorly characterised in Africa, including Cameroon. In this study, we characterised the blood-meal sources in both species collected from vegetation, household surroundings, and animal cages across four urban sites, one rural site, and a zoo-botanical garden where humans and animals in captivity are the main hosts. Overall, Aedes mosquitoes represented about half of 10,054 female mosquitoes collected, with Ae. albopictus strongly dominating Ae. aegypti among 5001 Aedes females, and only 5.95% of females visibly blood-fed. Sequencing a 748 base pairs (bp) fragment of the cytochrome oxidase I gene from 156 blood-fed abdomens yielded 126 high-confidence host assignments, of which 98.25% were humans, indicating a strong anthropophagic pattern in both species. Unpredictably, two Ae. albopictus individuals had fed on a baboon (Papio anubis) and a frugivorous bat (Pteropodidae), as confirmed by bio informatic analyses, highlighting the species’ opportunistic blood-feeding nature and providing preliminary molecular evidence consistent with a potential bridge-vector role in this setting. Despite the extreme anthropophagy of both species observed, results indicate that Ae. albopictus could also serve as a bridge vector enabling spillover of enzootic viruses to humans, including urbanised settings where wild animals are present. These findings emphasise the urgent need for enhanced arbovirus surveillance in Central Africa using a One Health approach.
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2026Article de revueAccès ouvert
Assessing the microsatellite diversity in Sodalis glossinidius harboured by Glossina palpalis palpalis (Diptera, Glossinidae) in Dodéo (Adamawa region, Cameroon)
Ginette KAME NGASSE, Oumarou Farikou, Tito MELACHIO TANEKOU, Anne Geiger, Flobert Njiokou
African Journal of Tropical Entomology Research
Control measures against tsetse flies, which are vectors of animal trypanosomosis, have drawbacks. Some of these issues include the toxicity of insecticides and the limited effectiveness of traps in eradicating tsetse flies. A new strategy to fight against this vector involves transforming one of its symbiotic bacteria through genetic engineering, which will render the tsetse resistant to establishing trypanosomes and thus prevent their transmission to vertebrate hosts. One of them, Sodalis glossinidius, a maternally transmitted secondary endosymbiont, is suspected of being involved in the vector competence of Glossina. To contribute to this major theme, the genetic diversity of Sodalis glossinidius was studied in tsetse flies in four villages of Dodéo in the Adamawa Region of Cameroon. Three species of tsetse flies were collected in the field using pyramidal traps: Glossina palpalis palpalis, G. morsitans submorsitans and G. fuscipes. We have only worked in Glossina palpalis palpalis, which represents 96% of the flies collected. Midguts were extracted, and S. glossinidius was identified by simple PCR-based methods and genotyped at four microsatellite loci. Of the three hundred and seventy (370) tsetse flies of the species G. palpalis palpalis analysed, 159 (42.9%) harboured S. glossinidius. The microsatellite loci studied revealed low polymorphism, i.e. 7 alleles and 4 multilocus haplotypes, with little genetic variability in S. glossinidius populations studied.S. glossinidius is known to enhance the vector competence of tsetse flies. Despite the low diversity observed in its populations, it remains crucial for analysing possibilities of using this tsetse symbiont to block trypanosome maturation through genetic engineering. Keywords: African Animal Trypanosomiasis, genotyping, Tsetse fly symbionts, Vector control.
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2026Article de revue
Molecular detection and maternal transmission of Microsporidia MB in the field-caught Anopheles coluzzii in Cameroon
Maurice Marcel Sandeu, Ghislaine Flore Tamko Mella, Claudine Grâce Maffo Tatsinkou, Ornella Possi, Carlos S. Djoko Tagne, Solange Meyin A. Ebong et 4 autre(s)
Scientific Reports
Recent discoveries of Microsporidia MB in Anopheles mosquitoes and its demonstrated capacity to block malaria transmission suggest that it could be a promising candidate for a symbiont-based malaria control strategy. However, the diversity of Microsporidia MB , particularly in major malaria vector such as An. coluzzii , remains unstudied in Cameroon. In this study, we investigated the prevalence and phylogenetic analysis of Microsporidia MB , along with its maternal transmission in natural populations of Anopheles mosquitoes in Cameroon. An entomological survey was conducted across four localities in Cameroon. PCR targeting the ribosomal RNA gene was used to detect the Microsporidia MB 18S sequence. Positive samples were validated by sequencing and phylogenetic analysis. Subsequently, the maternal transmission of Microsporidia MB was assessed by detecting its presence in F 1 mosquitoes derived from F 0 females that tested positive. Additionally, we examined the potential correlation between Microsporidia MB and P. falciparum . A total of 2559 mosquitoes, belonging to three species ( An. coluzzii , An. arabiensis , and An. gambiae ) were collected. Microsporidia MB infection was detected exclusively in An. coluzzii from Gounougou, with a prevalence of 1.13% (n = 29). Phylogenetic analysis showed that the Microsporidia MB strains detected in Cameroon were closely related to those found in Kenya. Evidence of vertical transmission was confirmed, with rates ranging from 50 to 100%, from F 0 parents to F 1 offspring, regardless of sex. Notably, none of the Microsporidia MB -positive mosquitoes carried P. falciparum . This study provides field-based evidence of Microsporidia MB presence in Anopheles mosquitoes in Cameroon. Further research should explore the stability of vertical transmission and the influence of this Microsporidia MB symbiont on Plasmodium development.
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2026Prépublication
Persistent Soil-Transmitted Helminthiasis Despite Long-Term Preventive Chemotherapy: Evaluation of Single-Dose Albendazole Effectiveness in Akonolinga, Cameroon
Antonia Foka Sindze, Laurentine Sumo, André Domché, Jean Bopda, Felix Priso Bile, Denis D. Ngara Bonguen et 6 autre(s)
Preprints.org
Preventive chemotherapy (PC), involving the periodic administration of anthelmintic drugs such as albendazole or mebendazole to at-risk populations, is the main strategy for controlling soil-transmitted helminth (STH) infections in endemic countries. This study assessed the efficacy of a single dose of albendazole against STH infections in the Akonolinga Health District, Centre Region, Cameroon, where STH prevalence remains high despite more than a decade of PC implementation. A community-based screening survey identified 131 individuals infected with at least one of the target species, Ascaris lumbricoides or Trichuris trichiura. All infected participants received a single dose of Albendazole. Three weeks after treatment, stool samples were collected and examined using the Kato–Katz technique to evaluate treatment efficacy. Cure rate (CR), defined as the proportion of participants who became egg-free, and egg reduction rate (ERR), reflecting the decrease in egg counts, were computed. For A. lumbricoides, the CR was 94.9% (95% CI: 87.7 - 98.0) and the ERR was 97.5%, while for T. trichiura, the CR and ERR were 26.0% (95% CI: 17.5 - 36.7) and 29.8%, respectively. Compared with WHO efficacy thresholds, Albendazole showed satisfactory effectiveness against A. lumbricoides but poor efficacy against T. trichiura. Species-specific treatment strategies are urgently needed to improve STH control and support elimination efforts.
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2026Article de revue
Risk of transmission of sleeping sickness in the four historical epicentre villages of the Bipindi focus, Cameroon
Guy R. Njitchouang, Jeanne C Sondi Dissake, Laurentine Sumo, André Domché, Alphonse Acho, Hugues C Nana Djeunga et 2 autre(s)
Transactions of the Royal Society of Tropical Medicine and Hygiene
BACKGROUND: Bipindi is a historic focus of human African trypanosomiasis (HAT). With the number of cases declining to near-elimination levels, understanding the current entomological risk is crucial to guiding elimination strategies. METHODS: Two entomological surveys in four historical sentinel villages used pyramidal traps to capture tsetse flies. Dissected midguts were analyzed by polymerase chain reaction (PCR) for trypanosome infection. Blood meal origins were identified using cytochrome B gene heteroduplex analysis. RESULTS: Glossina palpalis palpalis was accounted for 99.0% of 708 captured tsetse flies. Apparent density was significantly higher in the dry season (2.11) than in the rainy season (0.89) (P < .0001). Blood meal analysis revealed that these flies fed on pigs (25.0%), humans (16.7%), dogs (12.5%) and goats (8.3%). PCR-based analysis of 371 flies detected Trypanosoma congolense (16.4%), Trypanozoon spp. (8.1%) and Trypanosoma vivax (2.7%). No Trypanosoma brucei gambiense was found, suggesting no transmission risk, despite high vector competence. CONCLUSIONS: Although no evidence of T. b. gambiense transmission was found in this study, the presence of competent tsetse flies represents a potential danger that could jeopardize current control efforts, underscoring the need for sustained integrated surveillance and vector control to achieve elimination.
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2026Article de revueAccès ouvert
Targeted sequencing enhances detection of pangolin trafficking hotspots and dynamics of both domestic and global trade markets
Sean P. Heighton, Jérôme Murienne, Mukesh Thakur, Alain Didier Missoup, Wirdateti Wirdateti, Chabi Djagoun et 14 autre(s)
PLoS Biology
Pangolins have become emblematic of the global wildlife trade crisis due to intense trafficking for consumption and traditional medicine. Coupled with habitat loss, the illicit trade in pangolins has severely threatened wild populations. Genetic identification of distinct pangolin populations is an imperative step toward guiding effective and informed conservation management. These populations can serve as a reference for assigning seized individuals to their geographic origins, and thus tracing trafficking networks. However, pangolin population genetics studies have been hindered by limited sampling of geo-referenced individuals, largely due to the species' elusive nature. To address this, we developed a tailored gene-capture approach targeting 671 loci totaling 627 kb with high evolutionary and adaptive value across all eight pangolin species. We optimized the approach for low-quality DNA, including samples from museum collections and wildlife trade, such as bushmeat and scale seizures. We reassessed range-wide population delineations for the three most traded species, the white-bellied (Phataginus tricuspis), Sunda (Manis javanica), and Chinese (M. pentadactyla) pangolins, highlighting the need for biogeographically consistent lineage nomenclature and spatially aware analyses to support coherent conservation planning. The unprecedented geo-referenced DNA database for the three species yielded snapshot insights into pangolin trafficking hotspots and trade dynamics of both domestic markets and global trade seizures, the former providing novel insights into bushmeat trade. Domestic trade reflects local and occasional cross-border sourcing, averaging 454 km across the three species, while international trafficking seizures in mostly scales point to broader, regional procurement. However, common sourcing regions between the two trade market types indicate their interconnectivity, suggesting that local trade may contribute to international trade supply. Our study identified significant international trade hotspots for the white-bellied, Sunda, and Chinese pangolins, centered around southwestern Cameroon, southwestern Borneo Island, and Myanmar, respectively. Addressing geo-referenced sampling gaps and increasing local-to-global seizure data over time may offer deeper spatiotemporal insights into pangolin trade dynamics. Our study design may serve as a replicable model for enabling authorities and practitioners to implement intelligence-driven, geographically targeted interventions, by identifying the key regions most implicated in pangolin trafficking.
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2026Article de revueAccès ouvert
Xenomonitoring surveillance of schistosome transmission: implications for schistosomiasis elimination and zoonotic transmission awareness
Alvine C. Kengne Fokam, Etienne D. Bassock Bayiha, Steve Feudjio Soffack, David Woutouoba Ntieche, Balbine Mouatchoua, Tito T. Melachio Tanekou et 1 autre(s)
Frontiers in Tropical Diseases
Background In Cameroon, despite numerous mass screening and treatment campaigns against schistosomiasis, reinfection persists, mainly due to continued contact with infested water bodies. Consequently, the disease remains a significant threat to population health and socioeconomic development. In this study, we assessed the environmental risk of schistosomiasis transmission by screening intermediate hosts. This complementary approach helps identify active transmission sites at human–water contact points and may help interrupt parasite transmission through targeted control interventions. Methods We conducted a longitudinal study in Nkolbisson, a semi-rural area near Yaoundé, where mass drug administration campaigns have been implemented for more than a decade. Four human-water contact points were surveyed, and snails were collected and categorized by species. Infestation rates were determined using both parasitological techniques and molecular xenomonitoring with two primers. ETTS2/ETTS17 primers detected ribosomal DNA of Biomphalaria snails, Schistosoma species, and other trematodes, while SMF/R-F/SMF/R-R primers were specific to the Schistosoma mansoni 28S ribosomal region. Daily cercarial production was monitored in 34 infected Biomphalaria pfeifferi over eight days, and positive amplicons were sequenced and subjected to a nucleotide BLAST search for comparison with existing sequences. Results A total of 1,482 freshwater snails from four species were collected: Biomphalaria pfeifferi (361) , Lymnaea natalensis (465) , Physa acuta (348) , and Melanoides tuberculata (134). Five morphologically distinct cercarial types were identified. Parasitological infestation rates were 19.59% for B. pfeifferi and 7.94% for L. natalensis . Molecular xenomonitoring revealed significantly higher infestation rates for B. pfeifferi : 45.14% with ETTS primers and 23.07% with S. mansoni -specific SMF primers. Infected snails produced a mean of 3151.25± 2165 cercariae per snail over eight days, with some individuals releasing over 2500 cercariae daily. Sequencing analysis confirmed the identity of S. mansoni , showing 100% sequence similarity with reference strains. Conclusions The study identified active transmission foci where humans remain at high risk of S. mansoni infection and exposure to zoonotic trematodes despite years of mass chemotherapy. Molecular xenomonitoring proved to be more sensitive than traditional parasitological methods for detecting infected snails. It may consequently support targeted snail control strategies to complement mass drug administration for the sustainable elimination of schistosomiasis.
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2025

2025Article de revueAccès ouvert
Association of knockdown resistance mutations with pyrethroid resistance in Aedes aegypti, a major arbovirus vector in Cameroon
Christophe R. Keumeni, Aurélie P. Yougang, Flobert Njiokou, Siân E. Clarke, Jo Lines, Charles S. Wondji et 1 autre(s)
Parasites & Vectors
BACKGROUND: The development of insecticide resistance in Aedes mosquitoes has been reported in several African countries. However, information about the mechanisms involved remains scarce. This study aimed to address this issue by updating the resistance profile of A. aegypti and evaluating the role of known knockdown resistance (kdr) mutations in the observed phenotypic resistance in Ae. aegypti in Cameroon. METHODS: Larvae and pupae of Aedes were collected in 2022 in four sites in Cameroon and reared to adulthood. Adult mosquitoes were tested using World Health Organization (WHO) tube bioassays for pyrethroids, bendiocarb and fenitrothion, synergist assays with piperonyl butoxide (PBO) and WHO bottle tests for clothianidin following WHO recommendations. Dead and live mosquitoes after exposure to deltamethrin and permethrin insecticides were used for the genotyping of the F1534C, V1016I and V410L mutations, sequencing of fragments of the voltage-gated sodium channel (VGSC) gene and assessment their association with observed resistance. RESULTS: The analyses revealed that A. aegypti exhibited high resistance to all of the tested pyrethroids. Mortality rates ranged from 0% for alphacypermethrin 0.05% in Douala to 63.57% for deltamethrin 0.3% in Yaoundé. An increase in resistance was also observed for 0.1% bendiocarb, with mortality rates ranging from 50.54% in Douala to 68.31% in Garoua. Full susceptibility was observed with 1% fenitrothion. Partial or full recovery of mortality was reported following pre-exposure to a synergist. This suggests the involvement of cytochrome P450 genes in the observed resistance, although other mechanisms may also be involved. The F1534C, V1016I and V410L mutations were found in live and dead mosquitoes in Douala, Yaoundé and Bertoua. However, the V1016I and V410L mutations were more prevalent in alive mosquitoes than in dead ones, indicating an association between pyrethroid resistance and these mutations. After a 1 h exposure, clothianidin showed full susceptibility in samples from Bertoua, Douala and Garoua after 7 days of observation. In Yaoundé, probable resistance was observed with a mortality rate of 94.3%. CONCLUSIONS: These findings provide evidence that metabolic and kdr resistance are both involved in A. aegypti resistance to insecticides in Cameroon. This should be considered when implementing arbovirus vector control strategies and insecticide resistance management in the country.
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2024

2024Article de revue
Contrasting patterns of Asaia association with Plasmodium falciparum between field-collected Anopheles gambiae and Anopheles coluzzii from Cameroon
Claudine Grâce Tatsinkou Maffo, Maurice Marcel Sandeu, Micareme Tchoupo, Fleuriane Metissa Dondji Kamga, Leon M. J. Mugenzi, Flobert Njiokou et 2 autre(s)
Microbiology Spectrum
ABSTRACT The widespread prevalence of Asaia in mosquitoes makes it a potential candidate for paratrangenic control in Anopheles . To better understand whether this bacterium could be used for malaria control, we quantified Asaia in An. gambiae s.l populations in malaria endemic regions examining co-infection with Plasmodium falciparum . Adult Anopheles mosquitoes were collected across two different eco-geographical localities in Cameroon, during both the dry and wet seasons. DNA was extracted from whole individual mosquitoes, and real time-qPCR amplification of the 16S ribosomal RNA was used to quantify Asaia in both An. gambiae and An. coluzzii samples. We also detected and quantified P. falciparum infection in the same mosquitoes. The density of Asaia was successfully quantified in a total of 864 field mosquitoes, comprising of 439 An. gambiae from Bankeng and 424 An. coluzii collected from Gounougou. Interestingly, a higher prevalence of Asaia in An. gambiae (88.3%) compared to An. coluzzii (80.9%) was observed. Moreover, the density of Asaia in both species was significantly affected by seasonal changes in the two localities. Furthermore, a significant difference between the infection densities of Asaia and the Plasmodium infection status in the two species was recorded. However, no correlation was observed between the number of Asaia and P. falciparum infections. This study provides evidence that naturally occurring Asaia infection is not correlated to P. falciparum development within An. gambiae and An. coluzzii . Nevertheless, further studies incorporating experimental infections are required to better investigate the correlation between Anopheles mosquitoes, Asaia, and Plasmodium . IMPORTANCE The symbiont Asaia has emerged as a promising candidate for paratransgenic control of malaria, but further analysis of its biology and genetics across Africa is necessary. In this study, we investigated and quantified the influence of Asaia in naturally infected An. gambiae s.l . populations with the malaria parasite Plasmodium falciparum . Genomic DNA was extracted from whole individual mosquitoes collected from two localities, and Asaia was quantified using real-time qPCR by amplification of the 16S ribosomal RNA gene. We also detected and quantified Plasmodium falciparum infection in the same mosquitoes and established the correlation between Asaia and Plasmodium coinfection. This study provides evidence that naturally occurring Asaia infection is not correlated with P. falciparum development within An. gambiae and An. coluzzii mosquitoes.
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2023

2023PrépublicationAccès ouvert
A Chlorfenapyr-Based Net Interceptor® G2 Shows High Efficacy Against a Pyrethroid Resistant Anopheles funestus from Central Cameroon
Magellan Tchouakui, Riccado F. Thiomela, Elysée Nchoutpouen, Benjamin D. Menze, Cyrille Ndo, Dorothy Achu et 4 autre(s)
Research Square
Abstract Background The increasing reports of resistance to pyrethroid insecticides associated with reduced efficacy of pyrethroid-only interventions highlight the urgency of introducing new non-pyrethroid-only control tools. Here, we investigated the performance of PBO-pyrethroid (PermaNet 3.0 (P3.0)) and dual active ingredients (AI) nets (Interceptor G2 (IG2) containing pyrethroids and chlorfenapyr) and Royal Guard (RG)- containing pyrethoids and pyripoxyfen) against pyrethroid-resistant malaria vectors in Cameroon. Methods The efficacy of these tools was first evaluated on Anopheles gambiae and Anopheles funestus s.s using cone/tunnel assays in five sites across the country. In addition, experimental hut trials (EHT) were performed to evaluate the performance of these nets in semi-field conditions where An funestus predominate using unwashed and 20 times washed nets. Furthermore, pyrethroid-resistant markers were genotyped in dead vs alive, blood-fed vs unfed mosquitoes after exposure to these nets to evaluate the impact of known pyrethroid resistance markers on performance of the new nets. Results IG2 was the most effective net against wild pyrethroid -resistant An funestus followed by PermaNet 3.0. In EHT, this net induced up to 87.8% (95% CI 83– 92%) mortality and 55.6% (95% CI 48– 63%) after 20 washes whilst unwashed pyrethroid-only net (Royal sentry) killed just 18% (95% CI 13–23%) of host-seeking An. funestus . The unwashed P3.0 killed up to 54% (95% CI 44–63%) of field-resistant mosquitoes and 47% (95% CI 38– 57%) when washed 20 times. IG2 and P3.0 also provided better personal protection (blood feeding inhibition 66.2% and 92.8%) compared to pyrethroid-only net RS (8.4%) RG (77.84%). Interestingly, a negative association was found between kdrW and the chlorfenapyr-based net IG2 (χ2 = 138; P < 0.0001) with RR mosquitoes predominantly found in the dead Conclusions The high mortality recorded by Interceptor G2 against pyrethroid-resistant An. funestus in this study provides first field evidence of high efficacy against this major malaria vector in Cameroon. However the efficacy of this tools should be assessed in other locations and on other major malaria vectors across the country.
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2022

2022Article de revueAccès ouvert
&lt;i&gt;Anopheles leesoni&lt;/i&gt; Evans 1931, a Member of the &lt;i&gt;Anopheles funestus&lt;/i&gt; Group, Is a Potential Malaria Vector in Cameroon
Edmond Kopya, Cyrille Ndo, Landre Djamouko-Djonkam, Leslie Nkahe, Parfait Awono‐Ambene, Flobert Njiokou et 2 autre(s)
Advances in Entomology
Background: Understanding the biology of Anopheles malaria vector species is essential to planning effective and sustainable malaria control strategies in endemic countries. This study reported the implication of Anopheles leesoni in malaria transmission in Cameroon, Central Africa. Methods: Mosquitoes were collected in three localities from May 2015 to March 2018 using electric aspirators and Centers for Disease Control light traps (CDC-LT). Anopheles funestus sensu lato (s.l.) mosquitoes were identified as species using polymerase chain reaction assay (PCR). Furthermore, Plasmodium falciparum infection status was determined using the enzyme-linked immunosorbent assay (ELISA) method. Results: A total of 12,744 Anopheles mosquitoes were collected by electric aspirator (N = 4844) and CDC-LT (N = 7900). Anopheles funestus s.l. (86.95%) was the major species and the main malaria vector in rural savannah and rural forest sites followed by A. gambiae s.l. (13.05%) whereas in urban areas, A. gambiae s.l. was by far the most abundant representing 91.45% of Anopheles mosquitoes collected. Two members of the A. funestus group were identified among 1389 analysed by PCR: 1307 A. funestus sensu stricto (s.s.) (94.10%) and 82 A. leesoni (5.9%). Plasmodium falciparum infection rate was 21.04% in A. funestus s.s. For the first time, A. leesoni was found positive for P. falciparum (infection rate: 10.98%) in Cameroon. Conclusion: A very high P. falciparum infection rate was observed in this study in A. funestus s.s., highlighting its high implication in malaria transmission in Cameroon. Furthermore, the detection of P. falciparum infection in A. leesoni calls for more attention towards this neglected vector species.
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2021

2021Prépublication
A 6.5kb Intergenic Structural Variation Exacerbates Fitness Cost of P450- Metabolic Resistance in the Major African Malaria Vector Anopheles Funestus
Magellan Tchouakui, Leon M. J. Mugenzi, Murielle J. Wondji, Micareme Tchoupo, Flobert Njiokou, Charles S. Wondji
SSRN Electronic Journal
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2021Autre
Additional file 1 of Urban malaria in sub-Saharan Africa: dynamic of the vectorial system and the entomological inoculation rate
Patricia Doumbe-Belisse, Edmond Kopya, Carmène Sandra Ngadjeu, Nadège Sonhafouo-Chiana, Abdou Talipouo, Landre Djamouko-Djonkam et 4 autre(s)
Figshare
Additional file 1. Database of the entomological inoculation rate estimates reported in the 90 scientific publications selected for the review.
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2020

2020Article de revueAccès ouvert
Assessment of the Anophelinae blood seeking bionomic and pyrethroids resistance of local malaria vectors in the forest region of Southern Cameroon
Roland Bamou, Edmond Kopya, Landre Djamouko-Djonkam, Parfait Awono‐Ambene, Timoléon Tchuinkam, Flobert Njiokou et 1 autre(s)
Journal of Entomology and Zoology Studies
To assess the anophelinae blood seeking bionomic and susceptibility status to pyrethroids of local malaria vectors in the forest region of southern-Cameroon, entomological surveillance, detection of Plasmodium infection and susceptibility to permethrin and deltamethrine was done using specific protocol. Of a total of 2,091 mosquitoes collected, 543 (25.97%) belong to anophelinae species. Malaria vectors collected included An. gambiaes. L., An. moucheti, An. marshallii, An. ziemanni, An. paludis, An. coustani and An. nili. Anopheline trapped using WET varied from 1.31 anophelines/trap in Nyabessan to 2.87 anophelines/trap in Olama. The densities of mosquitoes collected using CDC-LT were 3.08 (indoor) and 4.18 (outdoor) mosquitoes/trap/night in Olama whereas they were 13.44 (indoor) and 7.84 (outdoor) mosquitoes/trap/night in Nyabessan. Of the 392 anophelines screened using ELISA, 2 (0.51%) were recorded infected by Plasmodium falciparum. Several species including An. gambiaesl, An. moucheti and An. nili were found resistant or highly tolerant to permethrin and/or deltamethrin. CDC-LT and WET are not sensitive tools for monitoring mosquito populations in the forest region. The study also suggested increase tolerance of several local anopheline species to pyrethroids. These information need further consideration while designing vector control interventions in theses settings.
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2019

2019Article de revueAccès ouvert
TRIM5α 136Q, CCR5 Promoter 59029G And CCR264I Alleles Impact The Progression Of HIV In Children And Adolescents
Béatrice Dambaya, Céline Nguefeu Nkenfou, Linda Mouafo Mekue, Georges Této, Marie Nicole Ngoufack, Georgia Ambada et 3 autre(s)
The Application of Clinical Genetics
Background: Children show various degrees of vulnerability regarding HIV infection and disease progression. This disparity presents challenges for the follow-up of infected children. Here we investigated reasons behind this variability focusing on some host-related HIV genes. Methods: We screened 570 Cameroonian children and adolescents, aged 1 to 19 years old. Among them, 137 were followed over 4 years, from 2010 to 2015. Upon signing a proxy consent, children and adolescents were classified according to their age, CD4 count, viral load and clinical symptoms as long-term non-progressors (LTNP), slow progressors (SP) and rapid progressors (RP). Their blood was collected every 6 months and used for biological and host genetic polymorphism analyses. Five genes were genotyped: Trim5α (R136Q), CCR5 promoter 59029G, CCR2-64I, SDF 3ʹA and CCR5-Δ32 . Exposed non-infected (HEU) and unexposed HIV negative children (HNEU) were recruited as control groups. Results: Among the 5 genes studied, the protective allele of Trim5α (R136Q) was present in all LTNP and in 72.34% and 2.56% of SP and RP, respectively (p<0.0001). The CCR5 promoter 59029G/G was also more present in LTNP and SP than in RP (p=0.02; p=0.04). The protective CCR2-64I homozygous genotype was almost absent in all groups, only the heterozygous genotype was present with a significant difference between RP vs SP (p=0.0001), and SP vs LTNP (p=0.0002). The CCR2-∆32 was completely absent either as homozygous or heterozygous genotype. It was a monomorphic allele. SDF 3ʹA was almost present as homozygous wild-type genotype in our study population and was associated neither to disease acquisition nor to disease progression. Conclusion: Among the 5 genes described in the study, Trim 5α (R136Q), CCR5 promoter 59029G and CCR2V64I alleles were associated to the progression of HIV infection in children and adolescents. Keywords: aids related genes, infected children, disease progression
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2018

2018Article de revueAccès ouvert
Biomphalaria camerunensis as a viable alternative intermediate host for Schistosoma mansoni in southern Cameroon
Alvine C. Kengne-Fokam, Hugues C. Nana-Djeunga, Mohamed Bagayan, Flobert Njiokou
Parasites & Vectors
BACKGROUND: Intestinal schistosomiasis due to Schistosoma mansoni was mapped in Cameroon in the 1990s and preventive chemotherapy launched since 2005. A situation analysis conducted in 2011 revealed an increase in schistosomiasis transmission, especially in the equatorial part of the country, despite the fact that Biomphalaria pfeifferi, the main intermediate host of this parasite, is now scarce in many foci. Biomphalaria camerunensis, restricted to the equatorial part of the country, is considered as a less suitable host for S. mansoni due to it resistance to the parasite, although exhibiting a better survival than B. pfeifferi. In a context where human migration is quite frequent as a consequence of terrorism, war in neighboring countries, as well as development of hydraulic projects, it seems appropriate to evaluate the current epidemiological role of B. camerunensis to estimate the risk of extension of S. mansoni distribution in Cameroon. To do this, the susceptibility of three B. pfeifferi and five B. camerunensis populations to a strain of S. mansoni was assessed. Juvenile snails (G1) of each population were infected with S. mansoni miracidia, and prepatent period, infection and survival rates of infected snails, as well as cercarial production were recorded and compared between snail species and populations. RESULTS: = 258.88, df = 1, P < 0.0001). All the three B. pfeifferi-infected populations were susceptible to S. mansoni. However, among the five B. camerunensis populations tested, four were susceptible to S. mansoni, with 21.9% as the highest infection rate. The prepatent period was, on average, shorter in B. pfeifferi than in B. camerunensis (P < 0.0001), but the cercarial production was significantly higher in B. camerunensis as compared to B. pfeifferi (P < 0.001). CONCLUSION: These findings indicate that B. camerunensis populations might substantially contribute to S. mansoni transmission and dissemination in Cameroon, their low susceptibility being compensated by their high cercariae production. More attention and surveillance towards this species are required to achieve intestinal schistosomiasis elimination in Cameroon.
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2017

2017Article de revueAccès ouvert
A polymorphism in the haptoglobin, haptoglobin related protein locus is associated with risk of human sleeping sickness within Cameroonian populations
Elvis Ofon, Harry Noyes, Julius Mulindwa, Hamidou Ilboudo, Martin Simuunza, Vincent Ebo’o et 7 autre(s)
PLoS neglected tropical diseases
BACKGROUND: Human African Trypanosomiasis (HAT) is a neglected disease targeted for elimination as a public health problem by 2020. Elimination requires a better understanding of the epidemiology and clinical evolution of HAT. In addition to the classical clinical evolution of HAT, asymptomatic carriers and spontaneous cure have been reported in West Africa. A genetic component to human susceptibility to HAT has been suggested to explain these newly observed responses to infection. In order to test for genetic associations with infection response, genetic polymorphism in 17 genes were tested (APOL1, IL1B, IL4, IL4R, IL6, IL8, IL12B, IL12RB1, IL10, TNFA, INFG, MIF, HLA-G, HLA-A, HP, HPR and CFH). METHODOLOGY: A case-control study was performed on 180 blood samples collected from 56 cases and 124 controls from Cameroon. DNA was extracted from blood samples. After quality control, 25 samples (24 controls and 1 case) were eliminated. The genotyping undertaken on 155 individuals including 55 cases and 100 controls were investigated at 96 loci (88 SNPs and 8 indels) located on 17 genes. Associations between these loci and HAT were estimated via a case-control association test. RESULTS: Analyses of 64 SNPs and 4 indels out of 96 identified in the selected genes reveal that the minor allele (T) of rs8062041 in haptoglobin (HP) appeared to be protective against HAT (p = 0.0002395, OR 0.359 (CI95 [0.204-0.6319])); indicating higher frequency in cases compared to controls. This minor allele with adjusted p value of 0.0163 is associated with a lower risk (protective effect) of developing sleeping sickness. CONCLUSION: The haptoglobin related protein HPR and HP are tightly linked and both are duplicated in some people and may lead to higher activity. This increased production could be responsible of the protection associated with rs8062041 even though this SNP is within HP.
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2016

2016Autre
Accession numbers of sequences used for comparison.
Solange Meyin A. Ebong, Elsa Petit, Philippe Le Gall (655439), Pingping Chen, Nico Nieser, Éric Guilbert et 6 autre(s)
INDIGO (University of Illinois at Chicago)
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2016Article de revue
Additional file 1: of Analysis of mating system, fecundity, hatching and survival rates in two Schistosoma mansoni intermediate hosts (Biomphalaria pfeifferi and Biomphalaria camerunensis) in Cameroon
Alvine C. Kengne-Fokam, Hugues C. Nana-Djeunga, FĂŠlicitĂŠ Djuikwo-Teukeng, Flobert Njiokou
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2015

2015Article de revue
Effect of sampling methods, effective population size and migration rate estimation in Glossina palpalis palpalis from Cameroon
Tanekou Tito Trésor Mélachio, Flobert Njiokou, Sophie Ravel, Gustave Simo, Philippe Solano, Thierry De Meeûs
Infection Genetics and Evolution
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2015Article de revueAccès ouvert
Mapping of Bancroftian Filariasis in Cameroon: Prospects for Elimination
Hugues C. Nana-Djeunga, Jules Brice Tchatchueng‐Mbougua, Jean Bopda, Stève Mbickmen-Tchana, Nathalie Elong-Kana, Etienne Nnomzo’o et 5 autre(s)
PLoS neglected tropical diseases
BACKGROUND: Lymphatic filariasis (LF) is one of the most debilitating neglected tropical diseases (NTDs). It still presents as an important public health problem in many countries in the tropics. In Cameroon, where many NTDs are endemic, only scant data describing the situation regarding LF epidemiology was available. The aim of this study was to describe the current situation regarding LF infection in Cameroon, and to map this infection and accurately delineate areas where mass drug administration (MDA) was required. METHODOLOGY: The endemicity status and distribution of LF was assessed in eight of the ten Regions of Cameroon by a rapid-format card test for detection of W. bancrofti antigen (immunochromatographic test, ICT). The baseline data required to monitor the effectiveness of MDA was collected by assessing microfilariaemia in nocturnal calibrated thick blood smears in sentinel sites selected in the health districts where ICT positivity rate was ≥ 1%. PRINCIPAL FINDINGS: Among the 120 health districts visited in the eight Regions during ICT survey, 106 (88.3%) were found to be endemic for LF (i.e. had ICT positivity rate ≥ 1%), with infection rate from 1.0% (95% CI: 0.2-5.5) to 20.0% (95% CI: 10-30). The overall infection rate during the night blood survey was 0.11% (95% CI: 0.08-0.16) in 11 health districts out of the 106 surveyed; the arithmetic mean for microfilaria density was 1.19 mf/ml (95% CI: 0.13-2.26) for the total population examined. CONCLUSION/SIGNIFICANCE: ICT card test results showed that LF was endemic in all the Regions and in about 90% of the health districts surveyed. All of these health districts qualified for MDA (i.e. ICT positivity rate ≥ 1%). Microfilariaemia data collected as part of this study provided the national program with baseline data (sentinel sites) necessary to measure the impact of MDA on the endemicity level and transmission of LF important for the 2020 deadline for global elimination.
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2014

2014Article de revue
Bushmeat genetics: setting up a reference framework for the DNA typing of A frican forest bushmeat
Philippe Gaubert, Flobert Njiokou, Ayodeji Olayemi, Paolo Pagani, Sylvain Dufour, Emmanuel Danquah et 6 autre(s)
Molecular Ecology Resources
The bushmeat trade in tropical Africa represents illegal, unsustainable off-takes of millions of tons of wild game - mostly mammals - per year. We sequenced four mitochondrial gene fragments (cyt b, COI, 12S, 16S) in >300 bushmeat items representing nine mammalian orders and 59 morphological species from five western and central African countries (Guinea, Ghana, Nigeria, Cameroon and Equatorial Guinea). Our objectives were to assess the efficiency of cross-species PCR amplification and to evaluate the usefulness of our multilocus approach for reliable bushmeat species identification. We provide a straightforward amplification protocol using a single 'universal' primer pair per gene that generally yielded >90% PCR success rates across orders and was robust to different types of meat preprocessing and DNA extraction protocols. For taxonomic identification, we set up a decision pipeline combining similarity- and tree-based approaches with an assessment of taxonomic expertise and coverage of the GENBANK database. Our multilocus approach permitted us to: (i) adjust for existing taxonomic gaps in GENBANK databases, (ii) assign to the species level 67% of the morphological species hypotheses and (iii) successfully identify samples with uncertain taxonomic attribution (preprocessed carcasses and cryptic lineages). High levels of genetic polymorphism across genes and taxa, together with the excellent resolution observed among species-level clusters (neighbour-joining trees and Klee diagrams) advocate the usefulness of our markers for bushmeat DNA typing. We formalize our DNA typing decision pipeline through an expert-curated query database - DNA BUSHMEAT - that shall permit the automated identification of African forest bushmeat items.
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2013

2013Article de revue
Antagonisms and synergisms between Schistosoma haematobium and soil transmitted helminths in southwest cameroon
Nkengazong Lucia, RM Ngoudjou Tchuente, Flobert Njiokou, Samuel Wanji, Félicité Flore Djuikwo-Teukeng, Peter Enyong et 1 autre(s)
Health sciences and disease
We show antagonisms and synergisms between Schistosoma haematobium , Ascaris lumbricoides, and Trichuris trichiura in co-infected hosts in southwest Cameroon. The mean intensity of each of the parasites varied according to whether the co-infecting parasite was S. haematobium , A. lumbricoides, or T. trichiura . Using immunological phenomena already described in the literature, we suggest reasons for these interactions between the parasites.
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2013Article de revueAccès ouvert
Dynamics of Onchocerca volvulus Microfilarial Densities after Ivermectin Treatment in an Ivermectin-naïve and a Multiply Treated Population from Cameroon
Sébastien D. S. Pion, Hugues C. Nana-Djeunga, Joseph Kamgno, Nicholas Tendongfor, Samuel Wanji, Flobert Njiokou et 2 autre(s)
PLoS neglected tropical diseases
BACKGROUND/OBJECTIVE: Ivermectin has been the keystone of onchocerciasis control for the last 25 years. Sub-optimal responses to the drug have been reported in Ghanaian communities under long-term treatment. We assessed, in two Cameroonian foci, whether the microfilaricidal and/or embryostatic effects of ivermectin on Onchocerca volvulus have been altered after several years of drug pressure. METHODS: We compared the dynamics of O. volvulus skin microfilarial densities after ivermectin treatment in two cohorts with contrasting exposure to this drug: one received repeated treatment for 13 years whereas the other had no history of large-scale treatments (referred to as controls). Microfilarial densities were assessed 15, 80 and 180 days after ivermectin in 122 multiply treated and 127 ivermectin-naïve individuals. Comparisons were adjusted for individual factors related to microfilarial density: age and number of nodules. FINDINGS: Two weeks post ivermectin, microfilarial density dropped equally (98% reduction) in the ivermectin-naïve and multiply treated groups. Between 15 and 180 days post ivermectin, the proportion of individuals with skin microfilariae doubled (from 30.8% to 67.8%) in controls and quadrupled (from 19.8% to 76.9%) in multiply treated individuals but the mean densities remained low in both sites. In fact, between 15 and 80 days, the repopulation rate was significantly higher in the multiply treated individuals than in the controls but no such difference was demonstrated when extending the follow-up to 180 days. The repopulation rate by microfilariae was associated with host factors: negatively with age and positively with the number of nodules. CONCLUSION: These observations may indicate that the worms from the multi-treated area recover mf productivity earlier but would be less productive than the worms from the ivermectin-naïve area between 80 and 180 days after ivermectin. Moreover, they do not support the operation of a strong cumulative effect of repeated treatments on the fecundity of female worms as previously described.
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2012

2012Autre
Etude de la structure génétique de différentes souches de Schistosoma haematobium (Digenea, Strigeatida) du Cameroun par des marqueurs microsatellites.
Félicité Flore Djuikwo-Teukeng, Rima Zein-Eddine, Alphonse Blondeau, Bertrand Courtioux, Flobert Njiokou, G. Dreyfuss
HAL (Le Centre pour la Communication Scientifique Directe)
International audience
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2012Article de revue
Genetic characterization of Trypanosoma brucei circulating in domestic animals of the Fontem sleeping sickness of Cameroon
Gustave Simo, Guy R. Njitchouang, Flobert Njiokou, G Cuny, Tazoacha Asonganyi
Microbes and Infection
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2011

2011Article de revue
Bacterial Diversity Associated with Populations of Glossina spp. from Cameroon and Distribution within the Campo Sleeping Sickness Focus
Anne Geiger, Marie‐Laure Fardeau, Flobert Njiokou, Manon Joseph, Tazoacha Asonganyi, Bernard Ollivier et 1 autre(s)
Microbial Ecology
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2011Article de revueAccès ouvert
Genetic Diversity and Population Structure of the Secondary Symbiont of Tsetse Flies, Sodalis glossinidius, in Sleeping Sickness Foci in Cameroon
Oumarou Farikou, Sophie Thévenon, Flobert Njiokou, François Allal, G Cuny, Anne Geiger
PLoS neglected tropical diseases
BACKGROUND: Previous studies have shown substantial differences in Sodalis glossinidius and trypanosome infection rates between Glossina palpalis palpalis populations from two Cameroonian foci of human African trypanosomiasis (HAT), Bipindi and Campo. We hypothesized that the geographical isolation of the two foci may have induced independent evolution in the two areas, resulting in the diversification of symbiont genotypes. METHODOLOGY/PRINCIPAL FINDINGS: To test this hypothesis, we investigated the symbiont genetic structure using the allelic size variation at four specific microsatellite loci. Classical analysis of molecular variance (AMOVA) and differentiation statistics revealed that most of the genetic diversity was observed among individuals within populations and frequent haplotypes were shared between populations. The structure of genetic diversity varied at different geographical scales, with almost no differentiation within the Campo HAT focus and a low but significant differentiation between the Campo and Bipindi HAT foci. CONCLUSIONS/SIGNIFICANCE: The data provided new information on the genetic diversity of the secondary symbiont population revealing mild structuring. Possible interactions between S. glossinidius subpopulations and Glossina species that could favor tsetse fly infections by a given trypanosome species should be further investigated.
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2010

2010Article de revue
A new transmission risk index for human African trypanosomiasis and its application in the identification of sites of high transmission of sleeping sickness in the Fontem focus of southwest Cameroon
Guy R. Njitchouang, Flobert Njiokou, Hugues C. Nana-Djeunga, Tazoacha Asonganyi, P. FEWOU-MOUNDIPA, G Cuny et 1 autre(s)
Medical and Veterinary Entomology
A new index for the risk for transmission of human African trypanosomiasis was developed from an earlier index by adding terms for the proportion of tsetse infected with Trypanosoma brucei gambiense group 1 and the contribution of animals to tsetse diet. The validity of the new index was then assessed in the Fontem focus of southwest Cameroon. Averages of 0.66 and 4.85 Glossina palpalis palpalis (Diptera: Glossinidae) were caught per trap/day at the end of one rainy season (November) and the start of the next (April), respectively. Of 1596 tsetse flies examined, 4.7% were positive for Trypanosoma brucei s.l. midgut infections and 0.6% for T. b. gambiense group 1. Among 184 bloodmeals identified, 55.1% were from pigs, 25.2% from humans, 17.6% from wild animals and 1.2% from goats. Of the meals taken from humans, 81.5% were taken at sites distant from pigsties. At the end of the rainy season, catches were low and similar between biotopes distant from and close to pigsties, but the risk for transmission was greatest at sites distant from the sties, suggesting that the presence of pigs reduced the risk to humans. At the beginning of the rainy season, catches of tsetse and risk for transmission were greatest close to the sties. In all seasons, there was a strong correlation between the old and new indices, suggesting that both can be used to estimate the level of transmission, but as the new index is the more comprehensive, it may be more accurate.
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2009

2009Autre
[Distribution and ecology of the Savannah human African trypanosomiasis vectors in disturbed forest zone in south Cameroon: about case in the Doumé forest].
Mbida Mbida Ja, Rémy Mimpfoundi, Flobert Njiokou, L. Manga, Claude Laveissière
PubMed
Vector control through trapping in the foci of humid forest areas is rather difficult because of the wide spreading of tsetse flies and transmission sites of human African trypanosomiasis. In fact, traps should be a priori set up everywhere to stop the transmission. The identification of the disease transmission sites enables efficient trapping through localisation of dangerous tsetse flies habitats needing vector control measures. The study of adult tsetse flies and teneral tsetse flies spatial distribution and human vector contacts was conducted in Doumb to determine the transmission of human African trypanosomiasis for efficient vector control. Glossina fuscipes fuscipes was the only tsetse fly captured with a very low apparent density of 0.13 tsetse flies per trap and per day. Furthermore, the disease transmission in the focus was not found uniform. In fact, human vector contacts are high in two villages (Paki and Mendin) located in the highly disturbed forest zones. These contacts occur in humid shallows where teneral tsetse flies were only captured around streams and forest galleries. The Doumé focus presents therefore characteristics of savannah focus where river banks and nearby biotopes are the main target sites for vector control campaigns.
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2009Article de revue
Influence of habitat and seasonal variation on wild mammal diversity and distribution with special reference to the Trypanosoma brucei gambiense host-reservoir in Bipindi (Cameroon)
Jacques Anselme Massussi, Champlain Djiéto‐Lordon, Flobert Njiokou, Claude Laveissière, J.D. van der Ploeg
Acta Tropica
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2004

2004Autre
[Dynamics of intestinal schistosomiasis in Cameroon: evolution of transmission in the mixed zone of Nkolmébanga, Lékié].
Flobert Njiokou, Yimta Tsemo Lc, Thomas Kuété, Same Ekobo A
PubMed
This study was undertaken to evaluate the current status of shistosomiasis in the Nkolmébanga region (Lékié) of Cameroon, previously determined to be a mixed zone harboring both Schistosoma mansoni and S. intercalatum. Study involved both malacology with collection and identification of freshwater snails in four waterpools and parasitology with collection and analysis of stools from schoolchildren. Five species of freshwater snails were identified including two that were intermediate host of Schistosomes, i.e., Biomphalaria pfeifferi and Bulinus forskalii. Only B. pfeifferi species collected from the Momboh and Mbonsoh Rivers shed Schistosoma cercaria. A total of 347 schoolchildren were enrolled but only 200 provided stools for parasitological testing. There were 93 boys and 107 girls. Parisitology demonstrated S. intercalatum eggs in the stools of no children. S. mansoni eggs were identified in the stools of 10 children for a prevalence of 5%. Parasitic load ranged from 24 to 1104 eggs per gram of stool. In this study both malacologic and parasitological findings suggested that S. mansoni persists in Nkolmébanga region but that S. intercalatum has disappeared probably as a result of deforestation and urbanization.
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2004Article de revue
[Experimental study of the compatibility between Schistosoma haematobium and two species of Bulinus in Cameroon].
Flobert Njiokou, E Teukeng, Bilong Bilong Cf, Thomas Njiné, Same Ekobo A
PubMed
A study on the compatibility between Schistosoma haematobium from three remote localities (Mourtourwa, Gounougou and Kékem) and four populations of Bulinus truncatus (Gounougou, Ngaoundéré, Bertoua and Kékem) and four populations of B. globosus (Mourtourwa, Ouroudoukoudje, Bafia and Yaoundé) was undertaken in order to estimate the risk of extension of urinary schistosomiasis in Cameroon. First generation of offspring from wild Bulinus was exposed to miracidia liberated by schistosome eggs extracted from patient urine. Between the 25th and the 60th day post-infestation the number of snails still alive, the number emitting cercariae and the prepatent period duration were noted. Results showed that all B. truncatus samples were susceptible to the three strains of parasite whereas only B. globosus of Mourtourwa and Ouroudoukoudje were susceptible to S. haematobium from Mourtourwa. The schistosome infection rate was then significantly higher in B. truncatus and the prepatent period significantly lower than in B. globosus. The compatibility characterised by a high infection rate and a low prepatent period was significantly better in homopatric couples than in allopatric combinations. The results suggested that B. truncatus might be potentially more implicated than B. globosus to the extension of the urinary bilharziasis in Cameroon.
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2002

2002Article de revue
Characterization of Trypanosoma brucei s.l. subspecies by isoenzymes in domestic pigs from the Fontem sleeping sickness focus of Cameroon
Stephenson W. Nkinin, Flobert Njiokou, Laurent Penchenier, Pascal Grébaut, Gustave Simo, Stéphane Herder
Acta Tropica
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2002Article de revueAccès ouvert
Identification of trypanosomes in wild animals from Southern Cameroon using the polymerase chain reaction (PCR)
Stéphane Herder, Gustave Simo, Stephenson W. Nkinin, Flobert Njiokou
Parasite
One possible explanation of the maintenance of many historical foci of sleeping sickness in Central Africa could be the existence of a wild animal reservoir. In this study, PCR was used to detect the different trypanosome species present in wild animal captured by hunters in the southern forest belt of Cameroon (Bipindi). Trypanosomes were also detected by a parasitological method (Quantitative buffy coat: QBC). Parasite could not be isolated in culture medium (Kit for in vitro isolation: KIVI). Specific primers of T. brucei s.l., T. congolense forest type, T. congolense savannah type, T. vivax, T. simiae and T. b. gambiense group 1 were used to identify parasites in the blood of 164 animals belonging to 24 different species including ungulates, rodents, pangolins, carnivores, reptiles and primates. Of the 24 studied species, eight were carrying T. b. gambiense group 1. Those parasites pathogenic to man were found in monkeys (Cercocebus torquatus and Cercopithecus nictitans), in ungulates (Cephalophus dorsalis and C. monticola), in carnivores (Nandinia binotata and Genetta servalina) and in rodents (Cricetomys gambianus and Atherurus africanus). 13 species (54%) were carrying T. brucei s.l. identified as non-gambiense group 1.
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2001

2001Autre
[Risk factors for human African trypanosomiasis in the Bipindi region of Cameroon].
Pascal Grébaut, Jean-Marie Bodo, A Assona, V Foumane Ngane, Flobert Njiokou, G Ollivier et 2 autre(s)
PubMed
In the course of two surveys carried out at the end of 1998 and beginning of 1999, sleeping sickness was diagnosed in a total of 43 people in the Bipindi region of Cameroon. This observation led us to investigate the mechanisms of transmission of human African trypanosomiasis in the epicentrer of the outbreak. A case-control study showed a particularly high risk of infection associated with hunting activities (Odds-Ratio: 2.87; CI 95%: 0.96-9.52). Interpretation of this finding in the light of local geographical features and current entomological data suggests that the higher risk in hunters is linked to the presence of a perennial vector population and absence of domestic pigs.
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2001Article de revueAccès ouvert
Evolutionary Relationships and Biogeography of Biomphalaria (Gastropoda: Planorbidae) with Implications Regarding Its Role as Host of the Human Bloodfluke, Schistosoma mansoni
Randall J. DeJong, Jess A. T. Morgan, W. Lobato Paraense, Jean-Pierre Pointier, Manuel Amarista, Patrick F. Ayeh‐Kumi et 23 autre(s)
Molecular Biology and Evolution
The wide geographic distribution of Schistosoma mansoni, a digenetic trematode and parasite of humans, is determined by the occurrence of its intermediate hosts, freshwater snails of the genus Biomphalaria (Preston 1910). We present phylogenetic analyses of 23 species of Biomphalaria, 16 Neotropical and seven African, including the most important schistosome hosts, using partial mitochondrial ribosomal 16S and complete nuclear ribosomal ITS1 and ITS2 nucleotide sequences. A dramatically better resolution was obtained by combining the data sets as opposed to analyzing each separately, indicating that there is additive congruent signal in each data set. Neotropical species are basal, and all African species are derived, suggesting an American origin for the genus. We confirm that a proto-Biomphalaria glabrata gave rise to all African species through a trans-Atlantic colonization of Africa. In addition, genetic distances among African species are smaller compared with those among Neotropical species, indicating a more recent origin. There are two species-rich clades, one African with B. glabrata as its base, and the other Neotropical. Within the African clade, a wide-ranging tropical savannah species, B. pfeifferi, and a Nilotic species complex, have both colonized Rift Valley lakes and produced endemic lacustrine forms. Within the Neotropical clade, two newly acquired natural hosts for S. mansoni (B. straminea and B. tenagophila) are not the closest relatives of each other, suggesting two separate acquisition events. Basal to these two species-rich clades are several Neotropical lineages with large genetic distances between them, indicating multiple lineages within the genus. Interesting patterns occur regarding schistosome susceptibility: (1) the most susceptible hosts belong to a single clade, comprising B. glabrata and the African species, (2) several susceptible Neotropical species are sister groups to apparently refractory species, and (3) some basal lineages are susceptible. These patterns suggest the existence of both inherent susceptibility and resistance, but also underscore the ability of S. mansoni to adapt to and acquire previously unsusceptible species as hosts. Biomphalaria schrammi appears to be distantly related to other Biomphalaria as well as to Helisoma, and may represent a separate or intermediate lineage.
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2000

2000Article de revueAccès ouvert
Cinétique de Trypanosoma brucei gambiense en culture sur milieux KIVI et Cunningham
T.L. Kohagne, Stephenson W. Nkinin, Pascal Grébaut, Flobert Njiokou, Laurent Penchenier
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2000Article de revue
The influence of self-fertilization and pairing on life-history traits in the freshwater snail Bulinus forskalii (Gastropoda, Planorbidae)
Flobert Njiokou, Jean Bosco Mouafo, Félicité Flore Djuikwo-Teukeng, Thomas Njiné, Albert Same Ekobo, Philippe Jarne
Acta Tropica
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1999

1999Autre
[The focus of human trypanosomiasis in Campo (Cameroon). History and endemic situation in 1998].
Laurent Penchenier, Pascal Grébaut, V. Ebo'o Eyenga, Jean-Marie Bodo, Flobert Njiokou, J J Binzouli et 4 autre(s)
PubMed
For the first time in the last thirteen years, the human sleeping sickness focus at Campo, spanning the Cameroon-Equatorial Guinea border areas, has been prospected. The screening was carried out simultaneously on both sides of the border. This focus has been known since the beginning of the century but, contrary to what took place in other well-known foci in bordering countries south of Cameroon, either in the 1920s or the 1980s--there has never been an epidemic outbreak in that area. Such an epidemiological situation makes this focus particularly interesting. Though still active, trypanosomiasis is not very manifest. According to passive screening carried out in recent years, the estimated prevalence ranges between 0.2 and 0.5%. For this screening, 5,255 persons were examined on the Cameroonian side of the focus (90.6% of the census population). The serological screenings were carried out with the CATT 1.3, which is the CATT generally used in screening, and with the latex CATT which associates LiTat 1.3, 1.5 and 1.6. The search for trypanosomes was made by testing the lymph nod juice in presence of adenopathy and in the blood by Quantitative Buffy Coat (QBC), the mini anion exchange centrifugation (mAEC), as well as the in vitro culture using the kit for in vitro isolation of trypanosomes (KIVI) for individuals suspected to be serologically positive. 16 patients were identified in Cameroon but none in Equatorial Guinea. The results show that the Campo focus is active only on the Cameroonian side, centred on the village of Ipono with a limited prevalence (0.3%). The persisting epidemic is most likely to be associated with the presence of pigs carrying the Trypanosoma brucei gambiense which was identified during the study in Ipono. The strain that we isolated was studied by isoenzyme electrophoresis on cellulose acetate. Its zymodeme is the same as that of the human strain isolated in Campo. With the collected epidemiological data, a concerted medical and entomological action could be planned within the limits of the village of Ipono to eradicate the disease. This action may be organised by the existing local health structures. During this study, the latex CATT proved to be more cost-effective than the CATT 1.3 since a similar result was reached requiring eight times less work at a lower cost. This remains to be confirmed in a hyperendemic focus.
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1997

1997Article de revue
The evolution of schistosomiasis at Loum, Cameroon: replacement of Schistosoma intercalatum by S. haematobium through introgressive hybridization
L.A. Tchuem Tchuenté, V. R. Southgate, Flobert Njiokou, Thomas Njiné, L Kouemeni, J. Jourdane
Transactions of the Royal Society of Tropical Medicine and Hygiene
L.A.Tchuem Tchuenté, V.R. Southgate, F. Njiokou, T. Njiné, L.E. Kouemeni, J. Jourdane; The evolution of schistosomiasis at Loum, Cameroon: replacement of S
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1994

1994Article de revueAccès ouvert
Population genetic structure of the schistosome-vector snail Bulinus globosus: examining the role of genetic drift, migration and human activities
Flobert Njiokou, Bernard Delay, Christian Bellec, Eliézer K. N’Goran, Grégoire Yapi Yapi, Philippe Jarne
Heredity
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1993

1993Article de revueAccès ouvert
Do self-fertilization and genetic drift promote a very low genetic variability in the allotetraploid Bulinus truncatus (Gastropoda: Planorbidae) populations?
Flobert Njiokou, Christian Bellec, Patrick Berrebi, Bernard Delay, Philippe Jarne
Genetics Research
Summary Bulinus truncatus , one of the intermediate hosts of the genus Schistosoma is an hermaphrodite freshwater snail species occupying a variety of environments over almost all Africa. These environments are subjected to large variations in water availability. B. truncatus is allotetraploid and its populations exhibit various frequencies of aphallic individuals (unable to reproduce as male). Both traits probably favour a reproduction by self-fertilization. Here we investigate the genetic structure of populations of B. truncatus of Niger and Ivory Coast using protein electrophoresis to analyse the influence of the environment and of both the last traits. To obtain an estimate of the true heterozygosity in this allotetraploid species, we analyse independently the two diploid loci at each tetraploid locus. Our study indicates (i) an extremely low intrapopulation polymorphism with most alleles fixed and the total absence of heterozygotes and (ii) low differentiation between populations. These results indicate high gene flow between populations. However, the existence of private alleles sometimes at high frequency, the low polymorphism and the lack of heterozygotes point to the role of both genetic drift and self-fertilization, the second amplifying the genetic consequences of the first.
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1992

1992Article de revue
COMPARATIVE FITNESS AND REPRODUCTIVE ISOLATION BETWEEN TWO BULINUS GLOBOSUS (GASTROPODA: PLANORBIDAE) POPULATIONS
Flobert Njiokou, Christian Bellec, Eliézer K. N’Goran, Grégoire Yapi Yapi, Bernard Delay, Philippe Jarne
Journal of Molluscan Studies
Bulinus globosus, an intermediate host of schisto-somes, is a self-fertile hermaphrodite species whose regular mating system is cross-fertilization. Fitness of selfing individuals originating from two geographically remote populations (Elevi, Ivory Coast; Daikaina, Niger) was scored. Individuals were then paired either with individuals from their own population, or with individuals from the other population. Electrophoretic analysis showed that pairing ‘female’ Elevi and ‘male’ Daikaina individuals results in only a low level of outcrossing, whereas the reverse pairings produced almost only outcrossed offspring. This could reflect unilateral partial isolation between the two populations. However, analysis of fitness values within and among groups of self-fertilizing and cross-fertilizing individuals, as well as electrophoretic data, suggest that selfing (or partial selfing) is the regular mating system in Elevi. Such experiments are relevant to the biological control of schistosiomasis by introducing resistant snails from allopatric populations, because they allow an assessment of the fate of introduced resistant genes.
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2025Article de revueAccès ouvert

Evaluation of two candidate molecules—TCTP and cecropin—on the establishment of Trypanosoma brucei gambiense into the gut of Glossina palpalis gambiensi s

François Sougal Ngambia Freitas, Linda De Vooght, Flobert Njiokou, Jan Van Den Abeele, Géraldine Bossard, Bernadette Tchicaya et 4 autre(s)

Insect Science

Trypanosomiasis, transmitted by tsetse flies (Glossina spp.), poses a significant health threat in 36 sub-Saharan African countries. Current control methods targeting tsetse flies, while effective, allow reinfestation. This study investigates paratransgenesis, a novel strategy to engineer symbiotic bacteria in tsetse flies, Sodalis glossinidius, to deliver anti-trypanosome compounds. Disrupting the trypanosome life cycle within the fly and reducing parasite transmission could offer a sustainable solution for trypanosomiasis control. In this context, we tested the effect of cecropin, reported to be lethal for Trypanosoma cruzi (Chagas disease) and TbgTCTP (Translationally Controlled Tumor Protein from Trypanosoma brucei gambiense), previously reported to modulate the growth of bacteria isolated from the fly microbiome, to delay the first peak of parasitemia and the death of trypanosome-infected mice. We have successfully cloned and transfected the genes encoding the two proteins into Sodalis strains. These Sodalis recombinant strains (recSodalisTbgTCTP and recSodaliscecropin) have been then microinjected into the L3 larval stage of Glossina palpalis gambiensis flies. The stability of the cloned genes was checked up to the 20th day after microinjection of recSodalis. The rate of fly emergence from untreated pupae was 95%; it was reduced by nearly 50% due to the mechanical injury caused by microinjection. It decreased to nearly 7% when larvae were injected with recSodalisTbgTCTP, which suggests TCTP could have a lethal impact to larvae development. When challenged with T. brucei gambiense, a slightly lower, but statistically non-significant, infection rate was recorded in flies harboring recSodaliscecropin compared to control flies. The effect of recSodalisTbgTCTP could not be measured due to the very low rate of fly emergence after corresponding treatment of the larvae. The results do not allow to conclude on the effect of cecropin or TCTP, delivered by para-transgenesis into the fly's gut, on the fly infection by the trypanosome. Nevertheless, the results are encouraging insofar as the technical approach works on the couple G. p. gambiensis/T. brucei gambiense. The next step will be to optimize the system and test other targets chosen among the ESPs (Excreted-Secreted Proteins) of the trypanosome secretum, or the differentially expressed genes associated with the sensitivity/resistance of the fly to trypanosome infection.