Abraham FOMENA · UY1 Research Hub

BPA

Abraham FOMENA

Professeur

74Publ.

BPADép.

FSFaculté

Institution: Université de Yaoundé I
Faculté
Département
Email professionnel

Activité scientifique

Synthèse des publications

Période: 1986–2026
Accès ouvert: 27
Types: 3
Publ.: 74

Journal Article · 62
Other · 9
Preprint · 3

Mots-clés récurrents

biology
ecology
myxozoan parasites in aquatic species

Profil chercheur

Biographie

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

Publications scientifiques

Publications

2026

2026Article de revue
Chemical Composition and Binary Combination Effect of Citrus sinensis (Rutaceae) and Callistemon rigidus (Myrtaceae) Essential Oils Against the Malarial Vector Anopheles gambiae s.l. (Diptera: Culicidae)
Lame Younoussa, Farida Lacmago Longmou, Kary Mallam Oumarou, Mamat Amina, Katamssadan Haman Tofel, Aurelie Dadji Foko et 3 autre(s)
International Journal of Zoology
Mosquito vector elimination using botanicals is recommended nowadays because they are biodegradable and less harmful to humans and nontarget organisms. In this context, binary combinations of Citrus sinensis and Callistemon rigidus essential oils were assayed against the larvae and adults of Anopheles gambiae in the laboratory. Essential oil combinations were emulsified with Tween‐80, and concentrations of 200, 100, 50, and 25 mg/L were prepared in 100 mL with tap water. In each concentration test solution or control, 25 fourth‐instar larvae of An. gambiae were transferred, and larval mortality was recorded after 24h. Adulticidal test was conducted using CDC bottles coated with the essential oil combination at concentrations of 100, 50, 25, and 12.5 mg/L. The knockdown effect was recorded every 10 min until 1h, and adult mortality of An. gambiae adults was registered after 24 h. GC/MS analysis revealed limonene (90.07%) and 1,8‐cineole (63.30%) as the major compounds in Ci. sinensis and Ca. rigidus essential oils, respectively. Among the combinations, the mixture Cs75% + Cr25% (LC 50 = 10.70 mg/L) was the most potent, presenting a synergistic action against An. gambiae larvae. On mosquito adults, the essential oil of Ca. rigidus tested alone caused more knockdown against An. gambiae adults (knockdown concentration 50% [KdC 50 ] = 1.88 mg/L) in short time (knockdown time 50% [KdT 50 ] = 1.99 min) than the combination products. After 24 h postexposure, all the combinations presented synergistic action, and the combination Cs50% + Cr50% (LC 50 = 1.38 mg/L) was the most effective against An. gambiae adults. Thus, combinations Cs75% + Cr25%, Cr100%, and Cs50% + Cr50% could be the new phyto‐insecticide candidates to control An. gambiae larvae and adults.
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2026Autre
Description of Heteracris lecoqi Yetchom-Fondjo & Kekeunou sp. nov. and Heteracris hannai Wandji & Kekeunou sp. nov. and redescription of Heteracris guineensis (Krauss, 1890) (Orthoptera: Acrididae) with comments on its ecology in the Southern part of Cameroon
Alain Christel Wandji, Jeanne Agrippine Yetchom Fondjo, Sévilor Kekeunou, Martin Kenne, Alain Didier Missoup, Maurice Tindo et 5 autre(s)
The Catalogue of Life
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2026Autre
Description of Heteracris lecoqi Yetchom-Fondjo & Kekeunou sp. nov. and Heteracris hannai Wandji & Kekeunou sp. nov. and redescription of Heteracris guineensis (Krauss, 1890) (Orthoptera: Acrididae) with comments on its ecology in the Southern part of Cameroon
Alain Christel Wandji, Jeanne Agrippine Yetchom Fondjo, Sévilor Kekeunou, Martin Kenné, Alain Didier Missoup, Maurice Tindo et 5 autre(s)
The Catalogue of Life
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2026Article de revue
Larval ecology of Aedes spp. mosquitoes and arbovirus transmission risk in four mid-sized cities of southern Cameroon
Bertille Carine Djapoum Theno, Gisele Aurelie Foko Dadji, Francis Zeukeng, Borel Djiappi-Tchamen, Nelly Armanda Kala-Chouakeu, Roland Bamou et 8 autre(s)
Current Research in Parasitology and Vector-Borne Diseases
Vector-based surveillance is crucial for monitoring arboviral diseases such as dengue, chikungunya, yellow fever, and Zika. In Cameroon, data on the distribution and bionomics of Aedes species in medium-sized cities within the equatorial forest region are limited. This study assessed the distribution, larval habitats, and bionomics of immature Aedes spp. stages across four mid-sized cities of southern Cameroon. Larval surveys were conducted from March 2022 to March 2023 in Bertoua, Kribi, Sangmelima, and Abong-Mbang during rainy and dry seasons. Water-holding containers were inspected using the dipping method, and collected larvae and pupae were reared to adults for morphological identification. Entomological indices were used to estimate arboviral transmission risk, and species co-occurrence in larval habitats was recorded. A generalized linear model was used to compare abundance and distribution among sites, seasons, and breeding site. From 758 larval habitats inspected (214 in Bertoua, 213 in Sangmelima, 184 in Kribi, 147 in Abong-Mbang), 3820 mosquitoes belonging to four genera and 11 species were emerged. Aedes spp. mosquitoes were the most abundant ( n = 2903), with Aedes albopictus and Aedes aegypti as dominant species that often co-occurred. Seasonal variation in the abundance of all mosquito genera was significant, with peak Aedes spp. abundance in the rainy season ( n = 2359; 81.3%). Tires were the most common larval habitats, mostly located within 10 m of human dwellings. Kribi and Bertoua exhibited the highest container, house, and Breteau indices, suggesting high potential risk. The study supports the need for regular vector-based surveillance to control arboviral disease in Cameroon. Such studies could also provide critical information for strengthening integrated vector management.
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2025

2025Article de revue
A low-cost house eave screening technique complements insecticide-treated nets in reducing indoor human exposure to the bites of anopheles mosquitoes in a malaria endemic area of south forested Cameroon: results from a pilot study
Rosine Danale Metitsi Tesongang, Emmanuel Elanga-Ndille, Glwadys Cheteug Nguetsa, Herman Parfait Awono-Ambene, Abraham Fomena, Raymond Tabue et 1 autre(s)
Experimental Parasitology
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2025Article de revue
Characterization of Henneguya kadeyensis sp. nov. (Myxosporea: Myxobolidae) infecting Distichodus mossambicus from Kadey River, Cameroon
Guy Benoît Lekeufack-Folefack, Nelly Ornelle Onana Ateba, Stéphane Fadanka Wapouo, Gloria Berinyuy-Tata, Abraham Fomena
Diseases of Aquatic Organisms
African freshwaters are inhabited by many endemic fishes. However, little is known about the associated myxozoan diversity. The present paper describes a new parasite species of Henneguya Thélohan, 1892 infecting Distichodus mossambicus Peters, 1852, an endemic freshwater fish species commonly found in the Congo Basin. Fish were collected from the Kadey River at Mindourou, a village in the East Region of Cameroon. To study the new Henneguya species, morphological analysis using light microscopy was combined with a phylogenetic analysis of small subunit ribosomal DNA (SSU rDNA) using maximum likelihood and Bayesian inference methods. White and elongated plasmodia were found in the gill lamellae. The myxospore body was 11.5 ± 0.2 (mean ± SD) (range: 10.4-12.7) µm long, 3.3 ± 0.1 (2.7-3.9) µm wide, and 2.3 ± 0.1 (1.9-2.9) µm thick. The caudal appendages were 22.1 ± 0.4 (20.1-25.9) µm long and the total length of the new species was 29.7 ± 0.3 (27.5-32.3) µm. The 2 pyriform polar capsules were of the same size, 3.7 ± 0.1 (3.2-4.2) µm long and 1.0 ± 0.03 (0.9-1.2) µm wide. Phylogeny of the SSU rDNA showed the new Henneguya species within a subclade composed exclusively of unidentified Myxobolidae infecting African Citharinoidei fish. Further work characterizing myxozoan species using both morphological, molecular, and phylogenetic data is required to better understand myxozoan diversity in Africa.
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2024

2024Article de revueAccès ouvert
Histopathology effects of Myxobolus pethericii Fomena, Lekeufack Folefack and Tang II, 2007 on Ctenopoma petherici Günther, 1864, in the Sangé River, Littoral Region, Cameroon
Béatrice Dambaya, Guy Benoît Lekeufack-Folefack, Bienvenu Feudjio-Dongmo, Rodrigue Fifen, Arnaud Deli, Ariane Laura Djampou et 1 autre(s)
Cameroon Journal of Experimental Biology
Histological method, becoming common in diagnostic methodology, provides information on effect of parasite and help predicting therapeutic measures for aquatic animals. Ctenopoma petherici caught in Sangé River were examined for myxozoan infections. Cyst measurements were taken and prevalence was estimated. Formalin-fixed organs were dehydrated through a graded ethanol series and embedded in paraffin. Obtained sections were stained with hematoxylin and eosin. From examined fish, 93.33% harbored elongated, ovoid or spherical cysts measuring 70 - 660 µm long × 40 - 390 µm wide in one or more of the following organs: gills, heart, stomach, liver, gonads, eyes, skin, bones, muscles, intestine, mesentery, fins, opercula, esophagus, labyrinth organs, kidney, swimbladder, and gallbladder. Cysts were arranged anarchically on affected organs and their development was asynchronous. Histological observations revealed cysts implantation mostly in loose connective tissue on which they induce one or more of the following: hyperplasia, swelling, alteration and lack of adhesion between tissue layers. In some cases, cysts were responsible of mechanical compression and distortion of blood vessels surrounding affected tissue. In many cases, significant portion of affected organs was replaced by numerous and voluminous cysts leading to tissue destruction and reduction of organ’s functional area. Generally, few sign of fish immune response to the presence of cysts was observed. Histological examination of Ctenopoma petherici appears as an important tool for rapid diagnosis to ensure farming production. Therefore, monitoring M. pethericii in farmed fish using histological method would help in early and proper drug therapy and avoid it dissemination.
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2023

2023Autre
Author response for "Range contractions and reduced body mass predicted for endemic skinks of the Cameroon Volcanic Line with future warming"
Michèle Marina Kameni N., Félix Landry Yuan, LeGrand Gonwouo N., Walter Paulin Tapondjou N., Kaitlin E. Allen, Abraham Fomena et 1 autre(s)
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2023Autre
Author response for "Range contractions and reduced body mass predicted for endemic skinks of the Cameroon Volcanic Line with future warming"
Makhimova Zh. N., Félix Landry Yuan, LeGrand Gonwouo N., Walter Paulin Tapondjou N., Kaitlin E. Allen, Abraham Fomena et 1 autre(s)
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2022

2022Article de revueAccès ouvert
Description and histopathology of Myxobolus kodjii sp. nov. and Myxobolus dzeufieti sp. nov. (Myxozoa: Myxobolidae) parasites of some Teleost fish from Maga Lake in Cameroon
Arnaud Deli, Guy Benoit LEKEUFACK-FOLEFACK, Rodrigue Fifen, Abraham Fomena
African Journal of Biological Sciences
Examination of some Teleost fish caught in the Maga Lake located in the Far North Region of Cameroon, revealed the presence of two new species of Myxosporidia belonging to the genus Myxobolus, of which morphological and histological description is given in the present study. These species are: Myxobolus kodjii sp. nov., parasite of the eyes of Labeo senegalensis and Myxobolus dzeufieti sp. nov., parasite of the skin of Oreochromis niloticus and Tilapia sp. M. kodjii sp. nov. forms ovoid myxospores, with rounded ends, 8.0 (7.0-9.0) m long, 5.9 (5.5-6.6) m wide and 3.8 (3.5-4.2) m thick. Polar capsules are pyriform, equal in size and measure 3.7 (3.2-4.0) m 1.6 (1.4-2.0) m. M. dzeufieti sp. nov. forms ovoid myxospores, with the anterior end slightly narrowed, 12.3 (11.4-13.7) m long, 9.8 (9.2-10.6) m wide and 5.7 (5.0-6.0) m thick. Its polar capsules are pyriform and equal in size and measure 4.8 (4.0-5.5) m 2.9 (2.5-3.3) m. These new species of Myxobolus are histozoic. The cysts of M. kodjii sp. nov. induce a local inflammatory reaction and their implantation in the sclera can affect the sight of the host fish. The presence of the cysts of M. dzeufieti sp. nov. on the skin did not cause an inflammatory reaction in host fish.
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2022Article de revueAccès ouvert
Malaria Transmission and Vector Resistance to Insecticides in a Changing Environment: Case of Simbock in Yaoundé-City, Cameroon
Lili Ranaise Mbakop, Parfait Awono‐Ambene, Wolfgang Eyisap Ekoko, Stanislas Elysée Mandeng, Philippe Nwane, Betrand Fesuh Nono et 6 autre(s)
Frontiers in Tropical Diseases
Ecological upheavals resulting from uncontrolled urbanization can lead to significant changes in vector borne diseases’ profiles, thus requiring a thorough revision of their prevention and control strategies. The current study aimed at characterizing malaria vector populations in the Simbock neighborhood of Yaoundé-city (Cameroon), in relation to its urbanization scheme. Adult mosquitoes were captured by human landing catches (HLC) in- and outdoors prior to (2000–2006) and during infrastructural development (2014–2016). Anophelines were morphologically identified and analyzed for Plasmodium (P.) falciparum circumsporozoite protein detection using the ELISA technique. Species of the Anopheles (An.) gambiae complex were identified using SINE-PCR. Adult An. gambiae s.l. from larvae collected between 2014 and 2017 were tested for susceptibility to insecticides (0.1% bendiocarb, 4% DDT, 0.75% permethrin and 0.05% deltamethrin) with or without piperonyl butoxide (PBO) synergist, using WHO standard bioassays. The Hot Oligonucleotide Ligation Assay was used to detect the knockdown resistance (kdr) L995F/S mutations. Overall, nine malaria vector species were identified in 2000-2006, mostly An. moucheti (49%), An. nili (13.5%) and An. gambiae s.l. (12%); the six remaining species were represented at less than 3% each. However, only three species were found in 2014-2016, with increasing proportions of An. gambiae s.l. (67%) and An. funestus (32%) (P&lt;0.0001). An. gambiae s.l. consisted An. coluzzii (&gt; 85%) and An. gambiae (&lt;15%) species during the two study periods. Plasmodium falciparum infection rates were 2.1% and 1.0% in 2000-2006 and 2014-2016 respectively (P=0.4), with decreasing entomological inoculation rates (EIR) from 0.34 infective bites per man per night (ib/m/n) to 0.02 ib/m/n (P&lt;0.0001). Anopheles gambiae s.l. was resistant to DDT and permethrin [&lt;40% mortality rates (MR)], and deltamethrin (65-89% MR), but fully susceptible to bendiocarb (100% MR). Pre-exposure of mosquitoes to PBO resulted in 90-100% MR to deltamethrin but not to permethrin. Furthermore, the two kdr L995F/S resistance alleles were recorded at 0.64 and 0.006 frequencies respectively. This study highlights a shift from rural to urban malaria transmission in Simbock, coupled with DDT and pyrethroid resistance in An. gambiae s.l. Combination vector control interventions, e.g., PBO nets and bendiocarb indoor residual spraying are needed in such areas.
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2021

2021Article de revue
Ants community structure in the urban and the city suburbs areas of Douala (Littoral-Cameroon)
Miric Biawa-Kagmegni, Armand Didier Foguieng-Saha, GUETSOP-NGOUADJIE PRUDENCE, TSEKANE JUNIOR, Boris Fouelifack-Nintidem, MOUMITE BASILE et 9 autre(s)
Journal of Insect Biodiversity
The Douala harbour represents the main gateway through which human activities introduce invasive ants, so that Solenopsis geminata (Fabricius, 1804) originating from Neotropics has been reported in several areas of the Littoral region of Cameroon. But nothing is known about the ant community structure and composition of the coastal zone. We hypothesized that environmental perturbations around Douala have repercussions on the native litter-dwelling ants. Collections conducted in 33 houses, six gardens of 225 m² each, 41 plantations of one hectare each and 34 two-year old fallows of one hectare each suggested lowly even communities, low species richness, low diversity and low dominance by a few species. Among 28 species recorded four species were mostly represented: two foreign origin species [S. geminata (Fabricius, 1804) and Trichomyrmex destructor (Jerdon, 1851), from tropical America and India respectively], one native species [Pheidole megacephala (Fabricius, 1793)] and two ambiguous native range species [Paratrechina longicornis (Latreille, 1802) and Tapinoma melanocephalum (Fabricius, 1793)] since they have long been recorded as having a widespread distribution. Alien species were highly represented than native ones (52.9% and 47.1% respectively, p<0.001). Inside houses, gardens and plantations the ant species were distributed according to the geometrical progression (Motomura’s model) while in the old fallows abundance distribution suggested an evolved ecosystem (Mandelbrot’s model). Between the three dominant species [Pa. longicornis (Latreille, 1802), Ph. megacephala (Fabricius) and S. geminata (Fabricius)], the first species was positively correlated with the third one while other associations were not significant. These dominant species appeared influencing the abundance of the rare species. Dominance and high abundance of a few species indicated that areas were influenced mostly by interspecies competition and/or disturbance by human activities.
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2020

2020Article de revueAccès ouvert
An Optimized Protocol for Myxosporidia (Cnidaria: Myxosporea) DNA Extraction for Molecular Studies
Guy Benoît Lekeufack-Folefack, Bienvenu Feudjio-Dongmo, Abraham Fomena, Billy Tene‐Fossog, Murielle J. Wondji
Open Journal of Animal Sciences
Myxosporidia constitute a major group of fish parasites which have a significant negative impact on wild and cultured fish. The used of DNA in Myxosporidia studies has progressed rapidly over the last twenty years, especially in their identification and characterization as well as determination of species diversity and investigation of their evolutionary relationships. Extraction and isolation of pure and high quality DNA are essential for any molecular study, but constitute a challenge for many laboratories especially in low and middle income countries. Myxosporidia plasmodia filled with mature myxospores were isolated from different tissues of Labeo batesii Boulenger, 1911. DNA from myxosporidia myxospores were extracted using a Livak optimized DNAs extraction protocol. Four particular phases of the original protocol were optimized. Yield and absorbance ratios of extracted DNA were determined using spectrophotometer. DNA samples were used as template for the amplification of the 18S rDNA region and amplicons resolved on 1.5% agarose gel for determination of fragment sizes and purity evaluation. The concentration of extracted DNA from all Myxosporidia species ranged from 4.6 to 26 ng/μl with purity indices ranging from 1.88 to 2.12. We successfully amplified the 1050 bp DNA fragment as targeted. The intensity, thickness and clarity of the bands were evidences of non-degradation of DNA. The optimized Livak protocol is simple, low-cost and manageable. Regarding the quantity, purity and quality of extracted DNA, the optimized Livak protocol is highly recommended for Myxosporidia studies.
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2019

2019Article de revue
Grasshopper (Orthoptera: Acrididea) assemblages in forests and savanna areas in Center, West and South-west regions of Cameroon
Alain Christel Wandji, Sévilor Kekeunou, MARCELLE MBADJOUN NZIKE, ALAIN SIMEU NOUTCHOUM, Abraham Fomena
Journal of Insect Biodiversity
Forest degradation due to human activities is a major threat to the long-term persistence of many species. It affects species richness, abundance and can lead to the extinction of some species. The present work aimed at identifying the effect of environmental variations on the species richness and composition of grasshoppers in three regions Cameroon. In each region, four vegetations (forests, agroforests, fallows and crop fields) were investigated using sweep nets and pitfalls trapping for specimens’ capture from February 2016 to February 2018. From this study, 92 grasshoppers species belonging to 3 families, 13 subfamilies and 70 genera were collected. The Acrididae was the most diverse family with 77 species. The Catantopinae was the richest subfamily (22 species), while the Pterotiltus was the richest genus with 7 species. Overall, the average sample success was 92.49%. We found that the species richness was strongly influenced by the study site (region), the vegetation type, and the capture method. The dissimilarity index revealed that the grasshopper communities of West and Center region were similar to each other, like those of fallows and crop fields. Twenty-four species of grasshopper could be reported for the first time in Cameroon. This study updates the database on the grasshopper fauna of Cameroon and brings to 238 the number of grasshopper species known in Cameroon. Key words: Grasshoppers, species richness, forests, agroforests, fallows, crop fields
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2018

2018Article de revue
Seasonal Polyphenism in Bicyclus dorothea (Lepidoptera: Nymphalidae) Across Different Habitats in Cameroon
Michel A. K. Dongmo, Timothy C. Bonebrake, Rachid Hanna, Abraham Fomena
Environmental Entomology
Many organisms exhibit changes in phenotypic traits as a response to seasonal environmental variation. We investigated the role of habitat in generating seasonal polyphenism in different populations of the light bush brown butterfly Bicyclus dorothea (Cramer, 1779) (Lepidoptera: Nymphalidae) in Cameroon. Butterflies were caught during the wet and dry seasons across four localities representing two distinct habitats, namely forest and ecotone (forest-savanna transition zone) over a 2-yr period (2015-2016). We found distinct variation in the wing pattern characteristics of butterflies in response to seasonality and habitat. Specifically we observed that: 1) all wing characters are not seasonally plastic in B. dorothea; 2) populations from ecotone tend to be more variable, with individuals exhibiting wings with large spots during the wet season and very reduced spots in the dry season while in forest populations, individuals exhibit wings with large spots during the wet season, but in the dry season, spots are not as greatly reduced as their ecotone counterparts; 3) this polyphenism in B. dorothea alternated consistently during the wet and dry seasons over the 2 yr of sampling. Bicyclus species have become a textbook example of seasonal polyphenism while this study extends this model system to the unique forest-ecotone gradient of Central Africa and demonstrates the complexity of seasonal forms in different habitats.
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2017

2017Article de revueAccès ouvert
Description of Myxidium tetraodoni Sp. Nov., Myxidium anisocapsularis Sp. Nov. and Myxobolus magai Sp. Nov. (Myxosporea: Bivalvulida) Infecting Some Freshwater Fishes in Cameroon (Central Africa)
Deli Arnaud, Lekeufack Folefack Guy Benoît, Abraham Fomena
Fisheries and Aquaculture Journal
International audience
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2017Article de revue
Life history notes on Bicyclus dorothea Cramer (Nymphalidae: Satyrinae) in Cameroon
Michel A. K. Dongmo, Timothy C. Bonebrake, Abraham Fomena, Rachid Hanna
CGSPace A Repository of Agricultural Research Outputs (Consultative Group for International Agricultural Research)
Bicyclus d. dorothea (Cramer, 1779) is a widely distributed butterfly inhabiting much of the northern part of the tropical African rainforest. The biology of the species has not been well studied despite it being relatively common throughout its distribution. In this study, we report on the life history of B. d. dorothea following three years of research on the species in Cameroon. We describe the life cycle of the species and report on key life history aspects such as distribution, habitat, reproduction, and host plant relationships.
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2016

2016Article de revue
Macro Invertebrates Functional Feeding Groups, Hilsenhoff Biotic Index, Percentage of Tolerant Taxa and Intolerant Taxa as Major Indices of Biological Assessment in Ephemeral Stream in Sudano-Sahelian Zone (Far-North, Cameroon)
D. Madomguia, Serge Hubert Zébazé Togouet, Abraham Fomena
International Journal of Current Microbiology and Applied Sciences
The aim of this study carried out in Mayo Tsanaga River was to determine the major indices which are more appropriate to characterize ephemeral stream in Sudano-Sahelian zone. Despite the influence of human activities in watershed physicochemical characteristics did not reveal a poor quality of water due to organic pollution. But the HBI values, the dominance of tolerant taxa to organic pollution on intolerant taxa at all sampling periods and the dominance of macroinvertebrates community by collectors-gatherers showed a site rich in organic matter, specially FPOM in suspension. The river is colonized by multivoltine species which are able to accomplish several life cycles during the short flow duration.
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2015

2015Article de revue
Aquatic invertebrate fauna of wells in a tropical mountain climate, western Cameroon
G Nana Nkemegni, SH Zébazé Togouet, Abraham Fomena, OF Pountougnigni, Christophe Piscart
African Journal of Aquatic Science
The present study, conducted between May 2012 and September 2013, aimed to determine the distribution of groundwater invertebrates in the Bamoun tableland, Cameroon. A total of 216 samples taken from 30 wells in four localities – Foumban, Foumbot, Kouoptamo and Magba – contained 80 invertebrate taxa belonging to Crustacea, Oligochaeta, Arachnida, Insecta, Nematoda, Tardigrada, and Gastropoda. The community was relatively rich, diverse, and was dominated by crustaceans. The distribution of groundwater fauna was influenced mainly by local factors, especially those related to the physical structure of wells such as the presence of a margin, a closing system, and total depth. At the regional scale, elevation and season were the only factors influencing the distribution of fauna. Further research needs to be conducted to highlight the relationship between groundwater invertebrates and human impacts in rural areas.
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2014

2014Article de revue
Ant Diversity in Different Cocoa Agroforest Habitats in the Centre Region of Cameroon
Zéphirin Tadu, Champlain Djiéto‐Lordon, Yédé, E.B. Messop Youbi, Abraham Fomena, Régis Babin
African Entomology
Agroforestry systems may represent refugia for native fauna in highly disturbed environments. In the context of ongoing intensive destruction of tropical rainforest by agricultural activities, there is a wealth of information on the influence of agricultural practices on arthropod diversity on southern Cameroon cocoa farms. The present study examined the diversity and the composition of ant communities on traditional cocoa farms in relation to agricultural practices along a south—north latitudinal gradient in the Centre Region of Cameroon. Ants were sampled in 21 plots using the chemical knock-down technique, along a latitudinal gradient from Ngomedzap (forest) in the south through Obala (forest-savanna) to Bokito (savanna) in the north. Species richness, Shannon diversity index and Bray-Curtis distance were used to characterize diversity of ant communities and their dissimilarity between habitats. A total of 66 ant species, belonging to 24 genera and seven subfamilies were identified from a sample of 114 843 workers. The ant diversity of Obala is higher than that of Ngomedzap and Bokito. Estimation of Bray-Curtis distances demonstrated that the ant communities of Ngomedzap and Obala were similar to each other, but very different from that of Bokito. The ant communities of Centre Cameroonian cocoa farms appeared relatively diversified. These communities varied in species composition and diversity in relation to agricultural practices along south—north latitudinal gradients.
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2013

2013Article de revue
Influence of insecticide treatment on ant diversity in tropical agroforestry system: Some aspect of the recolonization process
Zéphirin Tadu, Champlain Djiéto‐Lordon, Régis Babin, Edith Blandine Messop-Youbi, Abraham Fomena
Agritrop (Cirad)
In order to assess the influence of insecticides treatment on ant diversity and recolonization processes in cocoa based agroforestry systems, sampling was performed using chemical knock-down technique during two consecutive cocoa campaigns (2006 and 2007) in six smallholding cocoa farms located in tree localities of the Centre Region of Cameroon. These localities are located along the South-North agroecological benchmark ranging from Ngomedzap in the humid tropical rainforest in the south through Obala in mixed degraded forest / savannah in the transitional zone to Bokito in savannah landscape. From sampled ants, community diversity was measured using Shannon index and similarities between communities calculated using the Bray Curtis distance. After one-year recolonization following insecticide treatment, species richness increased in all the study sites, from 23 to 48 species at Ngomedzap, from 39 to 46 at Obala, and from 37 to 40 at Bokito. The diversity index increased from 2.15 to 2.29 at Obala while decreasing respectively from 2.12 to 2.04 at Ngomedzap and from 2.0 to 0.89 at Bokito. After one year recolonization following treatment, a total of 35 newly establish ant species were observed. Among them 11 were arboreal and two ground-nesting species. Comparison of the community composition and population size between the two sample periods suggested that certain arboreal nesting species such as Oecophylla longinoda, Tetramorium aculeatum and some species of the genus Crematogaster may survive insecticide treatment, thanks to their nesting behaviour. Also, recolonization process may be strongly influenced by border effects.
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2012

2012Autre
Distribution spatiale des fourmis arboricoles Hymenoptera : Formycidae dans les systèmes agroforestiers traditionnels du cacao
Zéphirin Tadu, Régis Babin, Désirée Chantal Aléné, Yédé, Edith Blandine Messop-Youbi, Abraham Fomena
Agritrop (Cirad)
À partir de méthodes d'analyse spatiale, les caractéristiques de distribution des fourmis ont été étudiées dans trois exploitations cacaoyères traditionnelles dans la Région Centre du Cameroun. L'étude a été menée dans le but d'évaluer (1) l'influence du système d'ombrage sur la distribution des fourmis et (2) la dynamique spatiale et temporelle des populations de fourmis sous l'effet d'un traitement insecticide. Pour la réaliser, des parcelles de 100 cacaoyers adjacents ont été délimitées et cartographiées y compris les arbres voisins, qui ont été identifiés à des espèces. Des points de coordonnées cartésiennes ont été attribués et enregistrés pour chaque arbre. De plus, la surface horizontale de la couronne a été estimée pour chaque arbre en mesurant la projection de la couronne au niveau du sol. L'ouverture de la canopée et le pourcentage de lumière transmis à travers la canopée ont été estimés en analysant des photographies hémisphériques. Les fourmis ont été collectées pendant deux cycles de culture consécutifs par une technique de Chemical Knock Down. La loi binomiale négative et des semivariogrammes ont été utilisés pour définir la distnbution des populations de fourmis. Ensuite, une Pondération inverse à la distance a été utilisée pour des cartes d'interpolation destinées à localiser des colonies éparses. Les résultats montrent que les populations des espèces dominantes comme Oecophyllalonginoda, Tetramoriumaculeatum, Crematogastergabonensis, C. clariventriset C. striatula étaient généralement regroupées et présentaient une forte dépendance spatiale. Camponotus acvapimensis qui est une espèces sous-dominante commune dans la plupart des agrosystèmes à base de cacaoyers était répartie de façon aléatoire et suivait un effet de pépite pur et simple d'un point de vue spatial. Les cartes d'interpolation spatiale ont montré de fortes corrélations entre des densités élevées de populations de O. longinoda et de Caacvapimensis et des zones de luminosité élevée dans les exploitations. À l'opposé, T. aculeatum, C. gabonensis, C. clariventris et C. striatula étaient très regroupées dans les zones ombragées. L'utilisation de certaines espèces comme O. longinoda and T. aculeatuin comme agents de lutte biologique pour la protection des cultures doit prendre en compte l'influence de ces facteurs pour favoriser l'expansion des colonies dans les exploitations cacaoyères.
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2011

2011Article de revue
Current distribution and population dynamics of the little fire ant supercolony in Cameroon
Maurice Tindo, Paul Serge Mbenoun Massé, Martin Kenné, Ruth Mony, Jérôme Orivel, A. Doumtsop Fotio et 6 autre(s)
Insectes Sociaux
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2011Article de revue
Structure and population dynamics of myxobolus infections in wild and cultured Oreochromis niloticus Linnaeus, 1758 in the Noun division (West-Cameroon)
Elysée Nchoutpouen, Guy Benoicirc, t Lekeufack Folefack, Abraham Fomena
Journal of Cell and Animal Biology
Myxosporidian parasites of Oreochromis niloticus Linnaeus, 1758 from the Noun River at Kouoptamo and the Foumban fish ponds in west Cameroon, were investigated from May 2008 to June 2009. Out of 537 Tilapia (267 cultivated and 270 wild) examined, 64.8% (n=173) specimens from the fish farming and 61.1% (n=165) from the Noun River harbored Myxosporean parasites. A total of ten parasite species were found. Myxobolus kainjiae, Myxobolus sarigi were scarce in both study sites; Myxobolus Tilapiae, Myxobolus equatorialis scarce in Foumban and Kouoptamo, respectively. M. agolus, M. brachysporus, M. camerounensis, M. equatorialis, Myxobolus Heterosporus, Myxobolus israelensiswere secondary in the two sites. M. Tilapiae, M. equatorialis appeared secondary in the Noun River and the fish ponds respectively. Myxosporean spores were most encountered in the kidney (61.3 and 49.0%, respectively in cultured and wild fish) and the spleen (50.5% in Foumban and 47.5% in Kouoptamo) but no host sex preference was found. In the Foumban fish farm site, high significant infection rate was observed for M. tilapiae, M. camerounensis and M. israelensis during the rainy season, while in the Noun River, no significant seasonal effect was found. Older hosts were significantly most infected at the fish ponds while youngs Tilapia were most commonly infected in the River. Key words: Myxosporean, Oreochromis niloticus, prevalence, fish-farm, Noun River, Cameroon.
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2010

2010Article de revueAccès ouvert
Deux espèces nouvelles de Myxidium (Myxosporea : Myxidiidae) parasites de poissons d’eau douce du Cameroun
Abraham Fomena, Guy Benoît Lekeufack Folefack, G. Bouix
Parasite
The study of Myxosporidia infecting Clarias pachynema Boulenger, 1903 (Clariidae), Ctenopoma petherici Günther, 1864 (Anabantidae) and Parachanna obscura (Günther, 1861) (Channidae) from the basin of Nkam in Cameroon, revealed the presence of two new species of Myxosporidia of the genus Myxidium Bütschli, 1882, all found in the gall bladder of their hosts. These new species were: Myxidium nkamensis n. sp., found in Clarias pachynema and M. sangei n. sp. found in the gall bladder wall of Parachanna obscura. Two other species, Myxidium petrocephali Fomena and Bouix, 1986 and M. distichodi Kostoïngué, Faye and Toguebaye, 1998 were found in new hosts. The list of Myxidium species parasitizing African fresh water fishes is given.
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2009

2009Autre
Diversity and mosaic structure of ant (Hymenoptera: Formicidae) community in traditional cocoa agroforestry systems in southern Cameroon
Zéphirin Tadu, Champlain Djiéto‐Lordon, Abraham Fomena, Régis Babin, G. Mahiane, Yédé
Agritrop (Cirad)
In cocoa agrosforestry systems, ants are the major arthropod component of the canopy. Since dominant ant species are usually active predators of insects. Ant community may contribute to protect cocoa against insect pests, and especially from cocoa mirids. On the other hand, ant activities may be involved in disease epidemics, and then lead to significant crop losses. In Cameroon, little information is available on ant community in cocoa agroforests and on their contribution to cocoa health. Therefore, the main objective of this study was to characterize the ant mosaic in cocoa farms by assessing the diversity of ant species, the nature of ant associations and their ecological statute. For two consecutive years, we collected ants using a chemical knock-down sampling method, in 21 cocoa plantations, situated in three different agro ecological areas of the center region of Cameroon. The ant diversity was assessed using the species richness, Shannon`s index of diversity and the Sorensen`s similarity index. Kendall`s correlation coefficient was used to determine the association nature between ant species. The robustness of associations was appreciated using chi-square test with Yates corrected test. Fifty one ant species were collected the first year of experimentation and sixty five the second year. Ants of the subfamilies Formicinae and Myrmicinae were the most abundant and the most diverse in cocoa plantations. According to the Shannon`s index of diversity, ant community was less diversified in the plantations located in the savannah compared to those of the forest areas. Oecophylla longinoda, Crematogaster clariventris, Crematogaster striatula and Camponotus acvapimensis were the most abundant species for the first year, with 50.9%, 35.2%, 21.1% and 14.1% individual respectively. The second year, O. longinoda, Tetramorium aculeatum, the army ant Dorylus (Anoma) nigricans and C. striatula were the most abundant, with rates of 82.2%, 44.1%, 39.2% and 29.4% respectively. Among the dominant species, O. longinoda and T. aculeatum are known to be profitable for cocoa. On the other hand, Crematogaster spp. are usually positively associated with aphids, mealybugs and scale insects, and may be involved in epidemics of the black pod rot of cocoa. The use of our results for integrated crop management strategies is discussed. (Texte intégral)
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2007

2007Article de revue
New Species of Myxobolus (Myxosporea: Myxobolidae) Parasites of Fresh Water Fishes in Cameroon (Central Africa)
Abraham Fomena, G.B. Lekeufack, C. Tang
Journal of Biological Sciences
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2007Article de revueAccès ouvert
Structure and Dynamics of Myxosporean Parasites Component Communities in Two Freshwater Cichlids in the Chari River (Republic of Chad)
Abaka Ousman, Bilong Bilong Bil, Thomas Njiné, Abraham Fomena
Pakistan Journal of Biological Sciences
Myxosporean parasites of two freshwater Tilapia species from the Chari River, Chad Republic, Oreochromis niloticus and Sarotherodon galilaeus, were investigated from November 2001 to October 2002. A total of 360 specimens per Cichlid species were examined. Eleven parasite species were found in both cases with different prevalences. Myxobolus agolus, M. brachysporus, M. clarii, M. cichlidarum, M. heterosporus, M. tilapiae and M. camerounensis in O. niloticus) appeared common while M. equatorialis, M. nyongana (and M. camerounensis in S. galilaeus) were secondary; lastly M. israelensis (and M. kainjiae in O. niloticus) were rare. The gills, fins, eyes and teguments were preferential locations of cysts building pathogens while the kidneys then the gall bladder were most commonly infected by myxosporean spores. In the Chari ecosystem, no significant host sex and size effects were found for the parasite cystic load. A clear seasonal occurrence was observed for most of these pathogens. In the view of pathogenic control, this study raised the necessity in a farm fish station to identify the most important myxosporean species and the period of their potential demographic explosion.
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2006

2006Article de revue
Comparison of the in vitro drug sensitivity of Trypanosoma brucei gambiense strains from West and Central Africa isolated in the periods 1960–1995 and 1999–2004
A.C. Lékané Likeufack, R. Brun, Abraham Fomena, Philippe Truc
Acta Tropica
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2004

2004Article de revueAccès ouvert
Description de trois espèces nouvelles de Myxosporidies (Myxozoa : Myxosporea) parasites de Citharinus citharus (Geoffroy Saint-Hilaire, 1809) (Citharinidae) au Tchad (Afrique Centrale)
Abraham Fomena, Abakar-Ousman, Pierre Ngassam, G. Bouix
Parasite
The study of Citharinus citharus (Geoffroy Saint-Hilaire, 1809) (Teleost, Citharinidae) captured in the Chari river in Chad revealed the presence of three new myxosporidian which are described in the present paper: Thelohanellus taguii sp. nov., a systematic parasite; Myxobolus mbailaoi sp. nov., which affects operculum, skin and intestine, Myxobolus charii sp. nov., a parasite of the skin.
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2000

2000Article de revueAccès ouvert
Henneguya mbakaouensis sp. nov., Myxobolus nounensis sp. nov. and M. hydrocyni Kostoingue & Toguebaye, 1994, Myxosporea (Myxozoa) parasites of centropomidae, Cichlidae and Characidae (Teleosts) of the Sanaga basin in Cameroon (Central Africa)
Abraham Fomena, G. Bouix
Parasite
The study of 102 teleost freshwater fishes of Sanaga basin in Cameroon revealed the presence of three myxosporean species, among which two were new. Host fishes were of three families: Centropomidae, Cichlidae and Characidae. New species were identified as Henneguya mbakaouensis sp. nov., a gill parasite of Lates niloticus and Myxobolus nounensis sp. nov. found in the kidney and spleen of Sarotherodon galilaeus and Tilapia mariae. Myxobolus hydrocyni Kostoïngue & Toguebaye, 1994, previously described in Chad, was also found in Cameroon; complementary informations were given on that parasite which seemed to be specific to its host.
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2000Article de revue
Myxosporidies (Myxozoa, Myxosporea) parasites des poissons Cichlidae du Cameroun, du Sénégal et du Tchad avec la description de deux nouvelles espèces
Modou Fall, Abraham Fomena, B. Kostoïngué, Cheikhna Diebakate, N. Faye, Bhen Sikina Toguebaye
Annales des Sciences Naturelles - Zoologie et Biologie Animale
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1986

1986Autre
[Myxosporidians of freshwater fishes in Cameroon. I. New species of Myxidium Bütschli, 1882].
Abraham Fomena, G. Bouix
PubMed
This work deals with the study of myxosporidians parasitizing freshwater fishes in Cameroon. Fishes belonging to four families are concerned: Cyprinodontidae, Distichodontidae, Cyprinidae and Mormyridae. Five new species of Myxidium, all inhabiting the gall-bladder of their hosts, are described and named. They are as follows: Myxidium birgii, M. camerounensis, M. petrocephali, M. nyongensis and M. brienomyri. We have paid particular attention to vegetative stages in distinguishing species.
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2025Article de revueAccès ouvert

Spatial Distribution of Five Myxozoans (Cnidaria: Myxobolidae) Species on the Gills of Labeobarbus habereri (Steindachner, 1912) from the Moliw&#232; River, Cameroon

Guy Benoît Lekeufack-Folefack, Amandine Estelle Tchoutezo-Tiwa, Nelly Ornelle Onana-Ateba, Abraham Fomena

Open Journal of Animal Sciences

The distribution of parasites on fish gills is shaped by the organ’s structural heterogeneity. This study focuses on the spatial distribution of Myxozoan species on the gills of L. habereri in natural conditions, as most known Myxozoan species infect fish gills. The gill apparatus of each host was divided into regions to determine infection site and cyst counts for each parasite species. Data were analyzed at both species and xenocommunity levels, assessing site specificity and comparing mean cyst loads across gill regions. Five cyst-forming Myxozoan species were identified: Myxobolus paludinosus, Myxobolus makombensis, Myxobolus nyongana, Myxobolus sp., and Thelohanellus assambai. Their prevalence ranged from 14.61% to 98.16%, with mean cyst loads varying between 7.18 ± 0.64 and 598.56 ± 29.92. No significant differences in epidemiological indices were noted based on the side of the gill. The prevalence of M. paludinosus, M. makombensis, Myxobolus sp., and T. assambai was lower in holobranch IV, where cyst accumulation of M. paludinosus was also reduced. Epidemiological indices were similar between hemibranchs, except for M. makombensis, which showed a higher mean cyst load on the anterior hemibranch. While M. makombensis occupied holobranch portions with various patterns, the other Myxozoan species exhibited similar distribution across the gill portions. Myxobolus paludinosus, M. makombensis, M. nyongana, and T. assambai developed more cysts in the median gill sector of some holobranchs. This study represents the first analysis of Myxozoan distribution on L. habereri gills, highlighting the affinity of certain parasites for specific gill microhabitat.

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2024Article de revueAccès ouvert

Indoor residual spraying of experimental huts in Cameroon highlights the potential of Fludora® Fusion to control wild pyrethroid-resistant malaria vectors

Riccado F. Thiomela, Magellan Tchouakui, Benjamin D. Menze, Elysée Nchoutpouen, Emilie S. Ngongang-Yipmo, Oliver R. Wood et 4 autre(s)

BMC Infectious Diseases

Elevated resistance to pyrethroids in major malaria vectors has led to the introduction of novel insecticides including neonicotinoids. There is a fear that efficacy of these new insecticides could be impacted by cross-resistance mechanisms from metabolic resistance to pyrethroids. In this study, after evaluating the resistance to deltamethrin, clothianidin and mixture of clothianidin + deltamethrin in the lab using CDC bottle assays, the efficacy of the new IRS formulation Fludora® Fusion was tested in comparison to clothianidin and deltamethrin applied alone using experimental hut trials against wild free-flying pyrethroid-resistant Anopheles funestus from Elende and field An. gambiae collected from Nkolondom reared in the lab and released in the huts. Additionally, cone tests on the treated walls were performed each month for a period of twelve months to evaluate the residual efficacy of the sprayed products. Furthermore, the L1014F-kdr target-site mutation and the L119F-GSTe2 mediated metabolic resistance to pyrethroids were genotyped on a subset of mosquitoes from the EHT to assess the potential cross-resistance. All Anopheles species tested were fully susceptible to clothianidin and clothianidin + deltamethrin mixture in CDC bottle assay while resistance was noted to deltamethrin. Accordingly, Fludora® Fusion (62.83% vs 42.42%) and clothianidin (64.42% vs 42.42%) induced significantly higher mortality rates in EHT than deltamethrin (42.42%) against free flying An. funestus from Elende in month 1 (M1) and no significant difference in mortality was observed between the first (M1) and sixth (M6) months of the evaluation (P > 0.05). However, lower mortality rates were recorded against An. gambiae s.s from Nkolondom (mortality rates 50%, 45.56% and 26.68%). In-situ cone test on the wall showed a high residual efficacy of Fludora® Fusion and clothianidin on the susceptible strain KISUMU (> 12 months) and moderately on the highly pyrethroid-resistant An. gambiae strain from Nkolondom (6 months). Interestingly, no association was observed between the L119F-GSTe2 mutation and the ability of mosquitoes to survive exposure to Fludora® Fusion, whereas a trend was observed with the L1014F-kdr mutation. This study highlights that Fludora® Fusion, through its clothianidin component, has good potential of controlling pyrethroid-resistant mosquitoes with prolonged residual efficacy. This could be therefore an appropriate tool for vector control in several malaria endemic regions.

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2023Article de revueAccès ouvert

Range contractions and reduced body mass predicted for endemic skinks of the Cameroon Volcanic Line with future warming

Michèle Marina Kameni N., Félix Landry Yuan, LeGrand Gonwouo N., Walter Paulin Tapondjou N., Kaitlin E. Allen, Abraham Fomena et 1 autre(s)

Diversity and Distributions

Abstract Aim The vulnerability of montane species to environmental change has been increasingly recognized in recent years. However, most of these species are regionally endemic with restricted distributions, limiting dispersal necessary for avoiding extinction. The outcome of threats posed for montane lizards is further complicated in species exhibiting mass–temperature relationships where body size increases with cooling temperatures, and thus with altitude, causing intraspecific physiological and behavioural differences. We aimed to identify areas suitable for montane endemic skinks of the Cameroon Volcanic Line (CVL) under current and future climates to reveal patterns of persistence and vulnerability based on an intersection of climate and body mass. Location Cameroon Volcanic Line Methods We recorded occurrences and measured body mass in the field for two CVL‐endemic skink species. We supplemented occurrences with online repository records. We projected current and future habitat suitability in the region by implementing bioclimatic species distribution models‐based on occurrences. We tested for elevational variations in body mass, and integrated both occurrence and body mass information in a trait‐based model to estimate current and future body mass. Results Projected currently suitable habitat for both species was limited to higher elevation regions, which are inhabited by numerous other threatened herpetofauna. We additionally detected Bergmann clines in body mass for both species. Given this variation in body mass, trait model projections covered slightly larger geographical ranges than bioclimatic estimates. Under future warming, both models project substantial contractions in suitable areas, potentially constraining species to mountain tops. Through the trait‐based approach, we further detected potential warming‐induced body mass reductions in projected suitable areas. Main Conclusions We demonstrate how combining occurrence records with species trait information in ecological modelling can reveal complementary trends for comprehensive warming impact assessments. Overall, challenges toward the persistence of CVL‐endemic skinks should prompt urgent responses in national conservation management and local community engagement.

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2022Article de revueAccès ouvert

Nesting System and Foraging Behaviour of &lt;i&gt;Crematogaster (Nematocrema) stadelmanni &lt;/i&gt;Mayr, 1895 (Hymenoptera: Formicidae: Myrmicinae) in Douala (Littoral-Cameroon)

Mohamed Basile Moumite, Patrick Steve Tuekam-Kowa, Rameline Prudence Guetsop-Ngouadjie, Sedrick Junior Tsekané, Boris Fouelifack-Nintidem, Miric Biawa Kagmegni et 9 autre(s)

American Journal of Entomology

Nesting system, diet behaviour, activity rhythm and predatory behaviour of Crematogaster (Nematocrema) stadelmanni Mayr, 1895 were studied in the field situation in suburbs of Douala (Littoral-Cameroon). Polycalic and polydomous nesting system were recorded. Large independent nests were positioned on the bark surface of trunks (50.8%) or the underside bark of the fork of large branches (49.2%) of cultivated or wild trees (45.8% and 54.2% respectively). Workers collected nectar from 18 plants from eight families: Asteraceae, Costaceae, Ehretiaceae, Euphorbiaceae, Mimosaceae Phyllantaceae, Poaceae and Rutaceae. They collected honeydew from Aleyrodidae and four Hemipteran families from Sternorrhyncha suborder: Aphididae, Coccidae Pseudococcidae and Stictococcidae. These Hemipterans proliferated on 11 plant families: Anacardiaceae, Annonaceae, Apocynaceae, Asteraceae, Costaceae, Euphorbiaceae, Myrtaceae, Poaceae, Rutaceae, Solanaceae and Urticaceae. Solid particles brought back to the nest were mostly from plants (72.5%) and weakly preys (27.5%). Sugary liquids were preferred over fats, carbohydrate sources, and even preys. Products were collected continuously (day and night) in the foliage of the host plant and neighbouring plants, shrubs and grasses. Workers occasionally brought back to the nest dead or dying larvae of grasshoppers and small particles of other arthropods (ants, flies, caterpillars). The sequence of behavioural acts recorded during the capture of larvae of Ruspolia differens (Orthoptera: Tettigoniidae) and adults of Zonocerus variegatus (Orthoptera: Pyrgomorphidae) (3 to 5 mm and 15 to 20 mm long respectively) were compared. The main sequence presented succession of seven acts: (1) detection by contact; (2) antennation; (3) attack-seizure; (4) short-range recruitment of nestmates in the vicinity; (5) spread-eagling of preys; (6) cutting up the prey on the spot; and (7) transport of pieces or whole prey to the nest. The stinging phase was not recorded. The duration of the capture of small prey (66 min. to 1 hr. 25 sec.; mean ± se: 1 hr. 57 min. 25 sec. ± 12 min. 2 sec.; 10 essays) was lower than that of large preys (2 hrs. 33 sec. to 4 hrs. 16 sec.; 2 hrs. 58 min. 32 sec. ± 17 min. 15 sec.; 10 essays; Mann-Withney test: T = 72.00; p = 0.014). The long duration of captures suggested that spread-eagling and cutting up preys on the spot lasted a long time. Cr. stadelmanni is a poor predator indirectly harmful for wild or cultivated trees since their predatory aptitude is low compared to aggressive dominant arboreal-nesting ants and is counterbalanced by the propensity to honeydew.

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2021Article de revue

Description of Heteracris lecoqi Yetchom-Fondjo &amp; Kekeunou sp. nov. and Heteracris hannai Wandji &amp; Kekeunou sp. nov. and redescription of Heteracris guineensis (Krauss, 1890) (Orthoptera: Acrididae) with comments on its ecology in the Southern part of Cameroon

Alain Christel Wandji, Jeanne Agrippine Yetchom Fondjo, Sévilor Kekeunou, Martin Kenné, Alain Didier Missoup, Maurice Tindo et 5 autre(s)

Zootaxa

The specimens studied were collected with sweep net and pitfall in the forests, agro-forests, herbaceous fallows, and crop fields of 14 localities in the southern part of Cameroon, from August 2015 to February 2018. The results show that Heteracris hannai sp. nov. and Heteracris lecoqi sp. nov. differ from previously known species of the same genus by the pattern of coloration and the details or shape of the phallic complex. H. lecoqi sp. nov. is characterized by light brownish body; male cercus with flattened, downcurved and obtuse apex; lophus strongly curved; interlophal space with V shape; apodeme of cingulum bow, convergent, with V-shape; valve of cingulum in lateral view longer than apical valve of penis; ramus in ventral view joined. H. hannai sp. nov. is distinct to other species by brown to grey body; male cercus with apex rounded, curved inside; lophus curved; interlophal space with U-shape; apodeme of cingulum thick, slightly parallel, with U shape; valve of cingulum in lateral view hardly longer than apical valve of penis; ramus in ventral view opened. The characteristics of H. guineensis are closer to H. hannai sp. nov. than to H. lecoqi sp. nov. H. lecoqi sp. nov. was collected only in the fallows while H. hannai sp. nov. was collected in the forests, agro-forests, fallows, and crop fields. Compared to H. guineensis, both new species are scarce in the natural vegetation and their distribution area is limited to two and four localities respectively for H. lecoqi sp. nov. and H. hannai sp. nov. All these three grasshopper's species were recorded as accidental species in all types of vegetation.

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2021Article de revueAccès ouvert

Local adaptation in thermal tolerance for a tropical butterfly across ecotone and rainforest habitats

Michel A. K. Dongmo, Rachid Hanna, Thomas B. Smith, Komi K. M. Fiaboe, Abraham Fomena, Timothy C. Bonebrake

Biology Open

Thermal adaptation to habitat variability can determine species vulnerability to environmental change. For example, physiological tolerance to naturally low thermal variation in tropical forests species may alter their vulnerability to climate change impacts, compared with open habitat species. However, the extent to which habitat-specific differences in tolerance derive from within-generation versus across-generation ecological or evolutionary processes are not well characterized. Here we studied thermal tolerance limits of a Central African butterfly (Bicyclus dorothea) across two habitats in Cameroon: a thermally stable tropical forest and the more variable ecotone between rainforest and savanna. Second generation individuals originating from the ecotone, reared under conditions common to both populations, exhibited higher upper thermal limits (CTmax) than individuals originating from forest (∼3°C greater). Lower thermal limits (CTmin) were also slightly lower for the ecotone populations (∼1°C). Our results are suggestive of local adaptation driving habitat-specific differences in thermal tolerance (especially CTmax) that hold across generations. Such habitat-specific thermal limits may be widespread for tropical ectotherms and could affect species vulnerability to environmental change. However, microclimate and within-generation developmental processes (e.g. plasticity) will mediate these differences, and determining the fitness consequences of thermal variation for ecotone and rainforest species will require continued study of both within-generation and across-generation eco-evolutionary processes. This article has an associated First Person interview with the first author of the paper.

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2019Article de revue

Geographic distribution and abundance of the Afrotropical subterranean scale insect Stictococcus vayssierei (Hemiptera: Stictococcidae), a pest of root and tuber crops in the Congo basin

A. Doumtsop, Rachid Hanna, Maurice Tindo, W. Tata-Hangy, Apollin Fotso Kuate, Komi K. M. Fiaboe et 3 autre(s)

Bulletin of Entomological Research

Stictococcus vayssierei is a major pest of root and tuber crops in central Africa. However, data on its ecology are lacking. Here we provide an updated estimate of its distribution with the aim of facilitating the sustainable control of its populations. Surveys conducted in nine countries encompassing 13 ecological regions around the Congo basin showed that African root and tuber scale was present in Cameroon, Central African Republic, Congo, Democratic Republic of Congo, Equatorial Guinea, Gabon and Uganda. It was not found on the sites surveyed in Chad and Nigeria. The pest occurred in the forest and the forest-savannah mosaic as well as in the savannah where it was never recorded before. However, prevalence was higher in the forest (43.1%) where cassava was the most infested crop, compared to the savannah (9.2%) where aroids (cocoyam and taro) were the most infested crops. In the forest habitat, the pest was prevalent in all but two ecological regions: the Congolian swamp forests and the Southern Congolian forest-savanna mosaic. In the savannah habitat, it was restricted to the moist savannah highlands and absent from dry savannahs. The scale was not observed below 277 m asl. Where present, the scale was frequently (87.1% of the sites) attended by the ant Anoplolepis tenella. High densities (>1000 scales per plant) were recorded along the Cameroon-Gabon border. Good regulatory measures within and between countries are required to control the exchange of plant materials and limit its spread. The study provides information for niche modeling and risk mapping.

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2019Article de revueAccès ouvert

Larvicidal Activity of Two Cymbopogon Species Leaf Extracts and Essential Oils against Anopheles gambiae Gilles (Diptera: Culicidae)

Aurore Christelle Sengue Batti, Lame Younoussa, Elias Nchiwan Nukenine, Mallam Kary Oumarou, Abraham Fomena

Journal of Applied Life Sciences International

Aims: The present investigation aimed to assess the toxic effect of hexane, acetone and methanol extracts of Cymbopogon citratus and Cymbopogon giganteus against 3rd and 4th instar of Anopheles gambiae larvae under laboratory conditions. Place and Duration of Study: Plant products were extracted from November 2017 to February 2018 in the Chemistry laboratory, while the larvicidal tests were conducted from April to June 2018 in the laboratory of Applied Zoology of the Faculty of Science, University of Ngaoundere, Cameroon. Methodology: Twenty five (25) 3rd and 4th instars of An. gambiae were subjected to methanol, acetone and methanol plant extracts of the two plants at doses of 1000, 500, 250 and 125 mg/L each while their essential oils were tested at concentrations of 200, 100, 50 and 25 mg/L. Dichlovos tested at the recommended dose of 1000 mg/L was performed as positive control while 1mL of tween-80 in 99 mL of natural breeding site water was used as negative control. Larval mortality was recorded after 24 h post treatment for plant extracts and after 1, 6, 12, 18 and 24 h post-exposure for plant essential oils. Results: At the highest concentration of 1000 mg/L, C. citratus extract caused 100% mortality of mosquito larvae while 84, 81 and 88% mortality of larvae were recorded with hexane, acetone and methanol leaf extract of C. giganteus, respectively. C. citratus (LC50=58.32 mg/L) and C. giganteus (LC50=372.36 mg/L) hexane extracts were more potent than acetone and methanol extracts of the plants. C. citratus extracts were the most effective against larvae compared to C. giganteus extracts. Essential oil of C. citratus (LC50=27.98 mg/L after 1h) was also the most toxic on mosquito larvae compared to C. giganteus (LC50=180.07 mg/L after 1h) essential oil. Conclusion: C. citratus plant and specially its hexane extract and essential oil could be taken into consideration as a new source of botanical insecticide and may be used in the mosquito control programs for An. gambiae larvae elimination in their breeding sites.

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2019Article de revueAccès ouvert

Malaria Transmission around the Memve’ele Hydroelectric Dam in South Cameroon: A Combined Retrospective and Prospective Study, 2000–2016

Lili Ranaise Mbakop, Parfait Awono‐Ambene, Stanislas Elysée Mandeng, Wolfgang Eyisap Ekoko, Betrand Fesuh Nono, Christophe Antonio‐Nkondjio et 4 autre(s)

International Journal of Environmental Research and Public Health

Dam constructions are considered a great concern for public health. The current study aimed to investigate malaria transmission in the Nyabessan village around the Memve’ele dam in South Cameroon. Adult mosquitoes were captured by human landing catches in Nyabessan before and during dam construction in 2000–2006 and 2014–2016 respectively, as well as in the Olama village, which was selected as a control. Malaria vectors were morphologically identified and analyzed for Plasmodium falciparum circumsporozoite protein detection and molecular identification of Anopheles (A.) gambiae species. Overall, ten malaria vector species were identified among 12,189 Anopheles specimens from Nyabessan (N = 6127) and Olama (N = 6062), including A. gambiae Giles (1902), A. coluzzii Coetzee (2013), A. moucheti Evans (1925), A. ovengensis Awono (2004), A. nili Theobald (1903), A. paludis Theobald (1900), A. zieanni, A. marshallii Theobald (1903), A. coustani Laveran (1900), and A. obscurus Grünberg (1905). In Nyabessan, A. moucheti and A. ovengensis were the main vector species before dam construction (16–50 bites/person/night-b/p/n, 0.26–0.71 infective bites/person/night-ib/p/n) that experienced a reduction of their role in disease transmission in 2016 (3–35 b/p/n, 0–0.5 ib/p/n) (p < 0.005). By contrast, the role of A. gambiae s.l. and A. paludis increased (11–38 b/p/n, 0.75–1.2 ib/p/n) (p < 0.01). In Olama, A. moucheti remained the main malaria vector species throughout the study period (p = 0.5). These findings highlight the need for a strong vector-borne disease surveillance and control system around the Memve’ele dam.

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2019Article de revue

Prevalence and Mean Intensity of Myxobolus spp. Parasitizing Oreochromis niloticus in Cameroon

Guy Benoît Lekeufack Folefack, Chanceline Mala Kengne, Bienvenu Feudjio Dongmo, Abraham Fomena

International Journal of Biology

Oreochromis niloticus, being one of the most commonly cultured fish on earth constitutes a favorable biotope for myxosporidia. This study provides information concerning the prevalence and mean intensity of Myxobolus species recorded in the kidney and spleen of O. niloticus. O. niloticus were sampled in farming ponds at Bamendou in Cameroon. Classic methods concerning fishing, fish autopsy and search of Myxosporidia were used. Prevalence and mean intensity was calculated. Data analysis based on the chi-square test, Kruskal-Wallis H test and Mann-Whitney U test was done. The study revealed the presence of six Myxobolus species in the kidney and spleen of O. niloticus. All parasites species appeared frequent while their mean intensity was low or very low. The occurrence of M. fotoi was statistically lower (P &lt; 0.05) in the kidney&rsquo;s anterior portion while the mean intensity of M. agolus was statistically (P &lt; 0.01) higher in the anterior portion of the spleen. Myxobolus cichlidarum was not found in kidney of young fish and occurrence of M. agolus statistically increases (P &lt; 0.05) with host age. Host sex has significant influence (P &lt; 0.05) on: occurrence of M. agolus, M. fotoi, M. agolus, M. brachysporus and M. heterosporus; and mean intensity of M. fotoi. The study revealed that in O. niloticus, the kidney and spleen harboured the same parasites species and there were only few variations in occurrences and mean intensities of parasites species recorded as function of host organs, age and sex.

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2014Article de revueAccès ouvert

Structure et dynamique des infracommunautés de Myxosporidies parasites de Ctenopoma petherici GÜNTHER, 1864 (Anabantidae), Clarias pachynema BOULENGER, 1903 (Clariidae) et Hepsetus odoe (BLOCH, 1794) (Hepsetidae) dans la rivière Sangé au Cameroun

GB Lekeufack Folefack, Abraham Fomena

International Journal of Biological and Chemical Sciences

L’examen de Ctenopoma petherici, Clarias pachynema et Hepsetus odoe récoltés dans la rivière Sangé au Cameroun entre janvier 2008 et mars 2009 a révélé la présence de 11 espèces de Myxosporidies. Parmi les espèces parasites identifiées, Myxobolus pethericii et Henneguya pethericii sont apparues fréquentes (Pr > 50%); Myxobolus sp.1, Myxobolus sp.2, Myxobolus gariepinus, Myxobolus africanus, Henneguya nkamensis, Myxidium petrocephali et Myxidium nkamensis sont apparues secondaires (10% £ Pr £ 50%), tandis que Myxobolus camerounensis et Myxidium sangei sont apparues rares (Pr < 10%). La charge kystique moyenne est apparue élevée (x̄ > 100 kystes) pour H. pethericii et H. nkamensis; moyenne (50 kystes < x̄ £ 100 kystes) pour Myxobolus sp.1, Myxobolus sp.2, M. pethericii, M. africanus, et très faible (x̄ < 10 kystes) pour M. gariepinus. Le pourcentage d’infestation décroît lorsque la taille du poisson augmente pour les espèces parasites suivantes : M. pethericii, M. gariepinus, H. pethericii, H. nkamensis et M. nkamensis. Par ailleurs, la charge kystique moyenne diminue lorsque la taille de l’hôte augmente pour M. pethericii et H. pethericii. Hormis le fait que les individus femelles sont fréquemment plus parasités par H. pethericii que les mâles, le sexe de l'hôte n'a pas d'influence sur le parasitisme des Myxosporidies étudiées. La saison sèche s’est avérée favorable à l’occurrence de Myxobolus sp.2 alors que M. petrocephali, M. nkamensis et M. gariepinus ont été plus fréquentes en saison de pluies. La charge kystique moyenne de H. pethericii et M. pethericii est plus importante en saison sèche.Mots clés : Prévalence, charge kystique, poisson, eaux douces

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2012Article de revue

Pratiques agricoles et épidémiologie du paludisme en zone soudano-sahélienne du Cameroun

Jean Atangana, Abraham Fomena, Joseph Lebel Tamesse, Étienne Fondjo

Bulletin de la Société de pathologie exotique

Une étude comparative a été réalisée sur la dynamique de la transmission du paludisme dans le village de Mokolo-Douvar, situé en zone rurale d’agriculture traditionnelle, et celui de Gounougou, zone rizicole irriguée, en 2004, en août et novembre, et en 2006, en mai et octobre, dans l’objectif de mesurer le comportement des vecteurs, le taux d’inoculation entomologique (TIE) et la prévalence du paludisme au sein d’une cohorte d’enfants âgés de 0 à 15 ans. Les moustiques ont été collectés par deux méthodes de capture complémentaires: la capture nocturne sur volontaires humains et la capture diurne au pyrèthre. Un total de 5 961 moustiques ont été collectés au cours de cette étude. Les anophèles collectés étaient: Anopheles gambiae s.s, Anopheles arabiensis, Anopheles funestus, Anopheles pharoensis, Anopheles rufipes, Anopheles ziemanni et Anopheles squamosus. A. arabiensis était l’espèce majeure (56,2 %) et le vecteur majeur du paludisme dans les deux sites, suivi d’A. funestus (32,6 %). Le TIE était élevé dans la zone rizicole de Gounougou (1,42 piqûres infectées par homme par nuit [pi/h/n]), tandis qu’en zone non irriguée de Mokolo-Douvar, le TIE était bas en saison des pluies (0,245 pi/h/n). À Gounougou, un total de 655 enfants ont été examinés. L’indice plasmodique (IP) moyen était de 21,1 %. Il en résulte que les changements intervenus dans l’exploitation rizicole irriguée et la mise en place des barrages ont influencé la dynamique de la transmission du paludisme, d’où la nécessité de prendre des mesures de contrôle facilement adaptables à l’environnement éco-épidémiologique de la région.

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2009Article de revue

Ectoprotozoan And Myxosporean Infections In Some Freshwater Fish Of Fako Division, South West Province Of Cameroon

BN Tendonge, KJN Ndamukong, Abraham Fomena, Benedicta Oshuware Oben

Bulletin of animal health and production in Africa

Une étude a été menée dans le district de Fako dans la province du sud-ouest du Cameroun en vue de recueillir des données sur la prévalence et la répartition des parasites des poissons d’eau douce, et d’évaluer les facteurs physiques et chimiques de l’eau susceptibles d’influencer la santé des poissons et les infections parasitaires. Au total, 146 échantillons de Clarias gariepinus, Oreochromis noliticus, Barbus camptacanthus et B. occidentalis provenant de quatre différents habitats ont étéexaminés. Deux ciliés ectoparasitaires (Ichthyophthirius multifiliis et Trichodina spp) et trois myxosporeans (Myxobolus njinei, un Myxobolus non identifie et Henneguya sp) ont été identifiés sur les poissons. L’état physique et chimique de l’eau a permis de connaître le niveau de pollution des divers habitats. Les poissons qui étaient dans les sites pollués étaient plus exposés à l’infection que ceux des sites non pollués. Le ruisseau de Ndongo et les étangs de Great Soppo qui avaient le taux d’infection le plusélevé (69,2% et 100% respectivement) avaient aussi le taux le plus faible d’oxygène dissous (3,3mg/L et 4mg/L) et de saturation d’oxygène (26,8% et 37,2%), et les températures les plus élevées (25,20C et 25,10C respectivement).A study was carried out in Fako Division of South West Province, Cameroon to provide baseline data on the prevalence and distribution of freshwater fish parasites and assess the physicochemical factors of water that may affect fish health and parasite infection. A total of 146 fish samples of Clarias gariepinus, Oreochromis noliticus, Barbus camptacanthus and B. occidentalis from different habitats were examined. Two ectoparasitic ciliates (Ichthyophthirius multifiliis and Trichodina sp) and threemyxosporeans (Myxobolus njinei, an unidentified Myxobolus sp and Henneguya sp) were identified from the fish. The level of pollution in the different habitats was indicated by the physicochemical parameters of the water. Fish in polluted sites were more exposed to infection than those in non-polluted sites. Ndongo stream and Great Soppo fish tanks which had the highest prevalence of infection (69.2% and 100% respectively)were also the sites with the lowest dissolved oxygen content (3.3mg/L and 4.0mg/L respectively) and oxygen saturation (26.8% and 37.2% respectiv ely), and highest temperature (25.20C and 25.10C respectively).

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2009Autre

Influence of insecticide treatment on ant diversity in tropical agroforest system: The case of Cameroonian cocoa farms

Zéphirin Tadu, Champlain Djiéto‐Lordon, Abraham Fomena, Régis Babin, Yédé, G. Mahiane

Agritrop (Cirad)

In order to understand the influence of anthropogenic disturbance on ant communities in tropical region; we conducted a study in southern Cameroonian cocoa farm. The survey aim to assess the influence of phytosanitary treatment on ant diversity and recolonization process of cocoa farm by ant species. During two consecutive years 2006-2007 and 2007-2008 ants sampling was performed using Chemical Knock-down technique in six traditional cocoa farms located in tree localities under different agro ecological environmental condition. Ant diversity was assessing using Shannon index of diversity and Sorensen index of similarity. After treatment: (1) the most abundant and most diverse sub-families were Formicinae and Myrmicinae; (2) at a local scale, with a small exception, specific richness of ant increase in plantations whereas diversity decrease; (3) at a regional scale, the specific richness increase and remain high both in forest (S= 46) and transitional (S= 46) areas compare to savannah (S= 42); diversity increase in transitional area whereas in forest and savannah diversities slide; (4) we have collected 10, 13 and 26 news ant species respectively in Bokito, Obala and Ngomedzap. Among the news establish species, Dorylus (Anoma) nigricans (Illiger) workers collected at Ngomedzap were the most abundant (36,36 %) and most frequent (53 %) on the tree; whereas among formerly establish species Oecophylla longinoda (Latreille) and Crematogaster gabonensis (Mary) were the most abundant respectively in Bokito (55,63 %) and Obala (31,48 %). Our result suggests formally that Phytosanitary treatment may affect ant diversity and favorise the establishment of some species like army ant D. (Anoma) nigricans (I.). In spite of the treatment certain ant species like O. longinoda (L.) and some species belonged to Crematogaster genus according to their nesting behavior may resist against treatment. This Knowledge may help to develop an integrate pest management program combine benefic ant species and selective insecticide spraying to protect tropical crops against scale insect. (Texte intégral)

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2009Article de revue

Seasonal variations of malaria transmission in Western Cameroon highlands: entomological, parasitological and clinical investigations.

Jean Atangana, Étienne Fondjo, Abraham Fomena, Joseph Lebel Tamesse, Salomon Patchoké, Hamadou N.M. Ndjemaï et 1 autre(s)

Journal of Cell and Animal Biology

A cross-sectional study on malaria transmission was carried out in Mangoum, a village situated in the western highland region of Cameroon in October 2005 and May 2006, to assess malaria parasite prevalence in a cohort of children and vectors biting habits and entomological inoculation rate. Mosquitoes were collected by landing catches on volunteers. Members of the Anopheles gambiae complex and molecular forms were identified using Polymerase Chain Reaction method.Infection intensity was determined by counting the number of infected red blood cells against 200 leucocytes. A total of 1195 Anopheles were collected, 183 and 1012 respectively in the dry and rainy seasons. Two Anopheles species were identified: A. gambiae s.l. and Anopheles funestus. A. gambiae s.s. was the only member of the A. gambiae complex found and the main malaria vector in this region. The sporozoite rate of A. gambiae was higher in the rainy season (9%). The average inoculation rate was 90 infective bites per man per year. A total of 699 children were examined. Two parasites species were identified: Plasmodium falciparum and Plasmodium malariae. The mean parasite rate was 41. 3%. In the age range of 2 - 9 years, the parasite rates were 49% in the dry season and 34.7% in the rainy season. The mean spleen rate of the age range 2 - 9 years varies from 26. 7% in rainy season to 22. 3% in the dry season, and was not significantly different (p = 0, 3). The Western highlands region can be considered as an area of high malaria transmission intensity. Key words: Malaria, transmission, Anopheles vectors, biting habits, sporozoite rate, parasites species, western Cameroon highlands.

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Abraham FOMENA

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