Correlation between some environmental variables and abundance of Almophrya mediovacuolata (Ciliophora: Anoplophryidae) endocommensal ciliate of an anecic earthworms (Oligochaeta: Annelida) in Bambui (North-West Cameroon)

This study was devoted to accessing the influence of some soil physico-chemical parameters on the abundance of Almophrya mediovacuolata Ngassam, 1983, astome ciliate of the digestive tract of earthworms (EW) of the species Alma nilotica collected along “Fa’a ntsa” stream in Bambui. The survey primarily involved soil samples collection from the same spots of EW collection and preparation for physico-chemical analysis; evaluation in situ of the volumic density (VD) of worms (number /dm3 soil), their dissection, isolation and counting of ciliates with respect to different portion of EW’s gut (fore, mid and hindgut). Furthermore, correlation analysis between soil physico-chemical parameters and biological responses (EW volumic density and ciliate abundance) were performed. The results reveal that EW abundance was positively and significantly correlated with the following physico-chemical parameters: Cation Exchange Capacity CEC (p <0.01) and Mg2+ (p <0.05). A positive and significant correlation was found between Almophrya mediovacuolata and the pH of KCl in the foregut and midgut (p <0.01) while a negative and significant correlation was found between the abundance of Almophrya mediovacuolata and Ca2+ in the foregut (p <0.05). Almophrya mediovacuolata were found mostly in the foregut. This result shows that each portion of the digestive tract of Alma nilotica can be considered as a set of natural microhabitat in which a number of physico-chemical factors generate ecological niches suitable for the survival of different species of microorganisms among which ciliated protozoa. The fore and midgut was noticed to be the preferential zones of Almophrya mediovacuolata.Keywords: Biotic parameters, ciliated protozoa, microhabitat, soil physico-chemical parameters

Assessment of pest insects of Capsicum annuum L.1753 (Solanaceae) in a cultivation cycle in Yaoundé

Pepper, Capsicum annuum is appreciated in tropical regions for its taste and its ability to increase the appetite level of food. This study aimed at investigating pest insects’ diversity of pepper right from pricking out to harvest. It also examined how aphids and whiteflies populations vary in the plant’s life cycle and specific fruit pests’ effects on the yield. During five months, individual plant organs were examined weekly. Insects encountered were captured, counted and identified. Immature stages were bred for identification purposes. Regular sampling allowed us to identify 28 species from 7 orders. During the pre-flowering phase, 5 orders were obtained: Hemiptera, Hymenoptera, Coleoptera, Lepidoptera and Orthoptera. The same orders were found at Flowering-fruiting phase, with appearance of one new order, the Thysanoptera. At this stage, exponentialgrowth of Hemiptera and Hymenoptera was also observed. During  maturation, Diptera and Lepidoptera were the most abundant pests. Ceratitis capitata and Cryptophlebia leucotreta were responsible for yield losses (20.46%). Aphids and whiteflies affected plant’s fitness, either directly through sap sucking or indirectly through viral transmissions. Ants’transport, disseminate and protect Hemipterans. Since plants phenology influences pest diversity, it should be taken into account in the efforts of developing IPM strategies.Keywords: Spice, phenology, yield, IPM

Composition et distribution spatio-temporelle des protozoaires ciliés dans un petit lac hypereutrophe du Cameroun (Afrique centrale)

La composition et la distribution spatio-temporelle des ciliés du Lac Municipal de Yaoundé (Cameroun) ont été analysées d’avril à décembre 1997, en relation avec des paramètres physico-chimiques du milieu. Trois stations pélagiques et l’herbier littoral ont été échantillonnés. 58 espèces de protistes ciliés ont pu être identifiées, parmi lesquelles environ 60 % d’espèces littorales et périphytiques et 37 % d’espèces pélagiques. Les espèces les plus courantes sont les espèces pélagiques Uronema nigricans et Coleps hirtus. L’abondance saisonnière des ciliés a atteint une valeur maximale de 21 800 ind•L-1, les valeurs les plus élevées étant enregistrées dans la couche trophogène du lac, particulièrement au cours de la grande saison des pluies. Les variations de la biomasse totale des ciliés sont plus faibles, avec des maxima correspondant également aux fortes pluies. Les espèces dominantes en matière de biomasse sont Prorodon africanum, Coleps hirtus et Uronema nigricans. Enfin, les fluctuations saisonnières de l’abondance et de la biomasse des ciliés sont discutées en relation avec les paramètres environnementaux, parmi lesquels le régime pluvial tient apparemment un rôle central.The Municipal Lake of Yaoundé (3° 51’ 37’’ N and 11° 30’ 40’’ E) is a shallow water body (Zm = 4.3 m), situated in downtown Yaoundé, the political capital of Cameroon (Central Africa). The composition and the spatio-temporal distribution of ciliates in combination with physical and chemical water variables were measured in this lake from April to December 1997. Sampling was carried out weekly, at 5 depths (surface, 0.5 m, 1 m, 1.5 m and 2.5 m) and at 3 pelagic stations, A, B and C, representing the upper, middle and the lower parts of the lake, using a Van Dorn sampling bottle. In the littoral station, the periphytic fauna is collected by agitation of the vegetation in a bucket and filtration of water. The water temperature was measured with a thermometer and the pH was measured in the field with a portable pH-meter. The oxygen concentration was determined according to the Winkler method and the transparency of the water column was determined with a Secchi disk. Light availability was measured with a luxmeter. Water colour, suspended solids and ammonium-nitrogen (NH4-N) were analyzed spectrophotometrically using APHA methods. Ciliate species were identified using appropriate and specific keys and were counted under a stereomicroscope at magnifications of 250X and 500X.Results showed that the lake was hypereutrophic. Throughout the study, the temperature and pH values of the water remained around 25°C and 7, respectively. The dissolved oxygen concentration decreased with depth to almost zero at the lake bottom, while the Secchi disk transparency did not exceed 1 m. Spatio-temporal variations of these variables indicated that the middle zone (0.5 to 1.5 m) was the stratum with a critical role in the functioning of the lake. Indeed, it represented the transitional zone between the trophogenic upper layer where photosynthetic activity occurred and the bottom water layer, formed by the microaerophilic to anaerobic tropholitic layers where reducing processes were important.Fifty-eight ciliate species, belonging to 10 orders and 28 families, were identified among which five (Holophrya sp., Lagynophrya rostrata, Lagynophrya simplex, Pseudoprorodon sp. and Histriculus sp.) were new records for Cameroon fauna. This population contained 62% of littoral species and 37% of pelagic species respectively. Within these taxa, dominant species were Uronema nigricans (present at all pelagic stations) and Coleps hirtus (present at more than 97% of the pelagic stations). Their abundance was greater than 2,000 ind•L-1 during the study period showing variation with many peaks. Prorodon africanum occurred sporadically between October and November when rainfall decreased and their densities reached 5,700 ind•L-1 in November at 0.5 m depth at station A. After November, this species was replaced by Prorodon sp. Most of the species collected were cosmopolite or characteristic of shallow tropical water bodies.The total abundance of the ciliate community was high reaching 21,800 ind•L-1 at station A, at 0.5 m depth. According to several authors, the abundance of ciliates in such tropical water bodies varies from 3.6 to 9.75 x 104 ind•L-1. The highest abundances were observed at depths of 0.5 m to 1.5 m at all 3 stations, especially during the rainy season. This corroborated the importance and the role of this stratum in the functioning of Lake Yaoundé. The lowest abundance of ciliates was observed at station A, at the bottom (2.5 m depth). The total abundance of ciliates showed one or several peaks during the period from July to November. With respect to the total biomass, the variation was more regular with generally one peak during the rainy season. At certain depths at stations B and C, several peaks were observed during the period of April to June and from September to November. The total biomass values obtained were higher than those reported by other authors. This can be explained by the fact that reported values in these latter studies were expressed as dry weight while values reported in this study were expressed as wet weight. With respect to biomass, the dominant species was Prorodon africanum (5,300 µg•L-1), followed by Coleps hirtus (3,800 µg•L-1) and Uronema nigricans (3,100 µg•L-1). The highest biomass was 130 x 105 µg•L-1, and was observed at station A, at 0.5 m depth.Generally large size ciliates were more abundant during the dry season whereas small size species were abundant during rainy season. Chilodonella uncinata and Prorodon africanum grew in surface layers (between the surface and 1 m depth) while Paradileptus conicus and Uronema nigricans preferred deep water (1 to 2.5 m depth). There was a great development of ciliates during the transitional period between the rainy and dry seasons. Moreover there was a close relationship between environmental parameters and the ciliate community. In fact, 2 to 3 physico-chemical predictors (dissolved oxygen, temperature and conductivity or pH) explained spatio-temporal distributions of different species. The variation of the total biomass in station A was explained by the dissolved oxygen concentration (r2 = 0.366; p<0.001) and by the pH (r2 = 0.274; p<0.001); at stations B and C, the variation was explained by ammonium-nitrogen (r2 = 0.178 and r2 = 0.294 for p<0.01). The most important abiotic factor that influenced the density and biomass variation of ciliate communities of Lake Yaoundé was the precipitation rate. Throughout the study, station B was the most characteristic of the structure of the ciliate community of this lake

Population genetic structure of the malaria vector Anopheles nili in sub-Saharan Africa

<p>Abstract</p> <p>Background</p> <p><it>Anopheles nili </it>is a widespread efficient vector of human malaria parasites in the humid savannas and forested areas of sub-Saharan Africa. Understanding <it>An. nili </it>population structure and gene flow patterns could be useful for the development of locally-adapted vector control measures.</p> <p>Methods</p> <p>Polymorphism at eleven recently developed microsatelitte markers, and sequence variation in four genes within the 28s rDNA subunit (ITS2 and D3) and mtDNA (COII and ND4) were assessed to explore the level of genetic variability and differentiation among nine populations of <it>An. nili </it>from Senegal, Ivory Coast, Burkina Faso, Nigeria, Cameroon and the Democratic Republic of Congo (DRC).</p> <p>Results</p> <p>All microsatellite loci successfully amplified in all populations, showing high and very similar levels of genetic diversity in populations from West Africa and Cameroon (mean Rs = 8.10-8.88, mean He = 0.805-0.849) and much lower diversity in the Kenge population from DRC (mean Rs = 5.43, mean He = 0.594). Bayesian clustering analysis of microsatellite allelic frequencies revealed two main genetic clusters in the dataset. The first one included only the Kenge population and the second grouped together all other populations. High Fst estimates based on microsatellites (Fst > 0.118, P < 0.001) were observed in all comparisons between Kenge and all other populations. By contrast, low Fst estimates (Fst < 0.022, P < 0.05) were observed between populations within the second cluster. The correlation between genetic and geographic distances was weak and possibly obscured by demographic instability. Sequence variation in mtDNA genes matched these results, whereas low polymorphism in rDNA genes prevented detection of any population substructure at this geographical scale.</p> <p>Conclusion</p> <p>Overall, high genetic homogeneity of the <it>An. nili </it>gene pool was found across its distribution range in West and Central Africa, although demographic events probably resulted in a higher level of genetic isolation in the marginal population of Kenge (DRC). The role of the equatorial forest block as a barrier to gene flow and the implication of such findings for vector control are discussed.</p

Antimicrobial activity against gram negative bacilli from Yaounde Central Hospital, Cameroon

BACKGROUND: Antimicrobial resistance among bacteria pathogens is a world-wide issue. The antimicrobial susceptibility patterns of common pathogenic bacteria are essential to guide empirical and pathogen-specific therapy; unfortunately, these data are scarse in Cameroon. OBJECTIVE: To determine the antimicrobial susceptibility patterns of Gram-negative bacilli isolated in Yaounde Central Hospital Laboratory of Bacteriology. METHODS: Gram-negative bacilli isolates (n = 505), obtained from a wide range of clinical specimens (urine, pus and blood) in Yaounde Central Hospital Laboratory of Bacteriology between March 1995 and April 1998, were evaluated for resistance to antibiotics (amoxicillin, amoxicillin/clavulanate, piperacillin, cefazolin, cefoxitin, cefotaxime, ceftazidime, aztreonam, imipenem, gentamicin, tobramicin, ofloxacin and trimethoprim/sulfamethoxazole) by the Kirby-Bauer disk diffusion method. RESULTS: High rates of resistance were found in most of the bacteria studied. Resistance to all isolates was mostly observed for amoxicillin (87%), piperacillin (74%) and trimethoprim/sulfamethoxazole (73%). Susceptibilities to third generation cephalosporins (cefotaxime, ceftazidime) and monobactame (aztreonam) were = 91% for Escherichia coli, = 71% for Klebsiella spp., = 98% for Proteus mirabilis, = 50% for Enterobacter spp. and Citrobacter spp. Pseudomonas aeruginosa was less susceptible to cefotaxime (2%) and aztreonam (33%), and highly susceptible to ceftazidime (72%) whereas Acinetobacter baumannii was highly resistant to aztreonam (100%), to cefotaxime (96%) and cetazidime (62%). Imipenem (98%) was the most active antibiotic followed by the ofloxacine (88%). Susceptibility of all isolates to gentamicin was 67%. CONCLUSION: These results indicate that surveillance to antimicrobial resistance in Cameroon is necessary to monitor microbial trends, antimicrobial resistance pattern, and provide information for choosing empirical or direct therapy to physicians

Description de trois espèces nouvelles de Myxosporidies (Myxozoa : Myxosporea) parasites de Citharinus citharus (Geoffroy Saint-Hilaire, 1809) (Citharinidae) au Tchad (Afrique Centrale)

L'examen de Citharinus citharus (Geoffroy Saint-Hilaire, 1809 (Teléostéen, Citharinidae), récolté sur le fleuve Chari au Tchad, a révélé la présence de trois espèces nouvelles de Myxosporidies dont nous donnons ici la description complète : Thelohanellus taguii n. sp., parasite systémique; Myxobolus mbailaoi n. sp., parasite des opercules, de la peau et de l'intestin et Myxobolus charii n. sp., parasite de la peau

Description de trois espèces nouvelles de Myxosporidies (Myxozoa : Myxosporea) parasites de

L'examen de Citharinus citharus (Geoffroy Saint-Hilaire, 1809 (Teléostéen, Citharinidae), récolté sur le fleuve Chari au Tchad, a révélé la présence de trois espèces nouvelles de Myxosporidies dont nous donnons ici la description complète : Thelohanellus taguii n. sp., parasite systémique; Myxobolus mbailaoi n. sp., parasite des opercules, de la peau et de l'intestin et Myxobolus charii n. sp., parasite de la peau

Antimicrobial activity against gram negative bacilli from Yaounde Central Hospital, Cameroon

Background: Antimicrobial resistance among bacteria pathogens is a world-wide issue. The antimicrobial susceptibility patterns of common pathogenic bacteria are essential to guide empirical and pathogen-specific therapy; unfortunately, these data are scarse in Cameroon. Objective: To determine the antimicrobial susceptibility patterns of Gram-negative bacilli isolated in Yaounde Central Hospital Laboratory of Bacteriology. Methods: Gram-negative bacilli isolates (n = 505), obtained from a wide range of clinical specimens (urine, pus and blood) in Yaoundé Central Hospital Laboratory of Bacteriology between March 1995 and April 1998, were evaluated for resistance to antibiotics (amoxicillin, amoxicillin/clavulanate, piperacillin, cefazolin, cefoxitin, cefotaxime, ceftazidime, aztreonam, imipenem, gentamicin, tobramicin, ofloxacin and trimethoprim/sulfamethoxazole) by the Kirby-Bauer disk diffusion method. Results: High rates of resistance were found in most of the bacteria studied. Resistance to all isolates was mostly observed for amoxicillin (87%), piperacillin (74%) and trimethoprim/sulfamethoxazole (73%). Susceptibilities to third generation cephalosporins (cefotaxime, ceftazidime) and monobactame (aztreonam) were = 91% for Escherichia coli, = 71% for Klebsiella spp., = 98% for Proteus mirabilis, = 50% for Enterobacter spp. and Citrobacter spp. Pseudomonas aeruginosa was less susceptible to cefotaxime (2%) and aztreonam (33%), and highly susceptible to ceftazidime (72%) whereas Acinetobacter baumannii was highly resistant to aztreonam (100%), to cefotaxime (96%) and cetazidime (62%). Imipenem (98%) was the most active antibiotic followed by the ofloxacine (88%). Susceptibility of all isolates to gentamicin was 67%. Conclusion: These results indicate that surveillance to antimicrobial resistance in Cameroon is necessary to monitor microbial trends, antimicrobial resistance pattern, and provide information for choosing empirical or direct therapy to physicians. Keywords: antimicrobial agents, resistance, Gram-negative bacilli, bacteria susceptibility testing, Cameroon.> African Health Sciences Vol. 6 (4) 2006: pp. 232-23

Révision de la sous-famille des Metaracoelophryinae de Puytorac 1972 (Oligohymenophora : Hoplytophryida : Hoplytophryidae), ciliés astomes du tube digestif d’oligochètes terricoles d’Afrique : description de cinq espèces nouvelles

Cinq nouvelles espèces de ciliés astomes, présentes dans le tube digestif de vers oligochètes du genre Alma du Cameroun, ont été décrites. Les techniques utilisées sont : l’observation vitale, la coloration au DAPI, la microscopie électronique à balayage et les imprégnations argentiques selon Fernandez Galiano, 1966. Ce travail confirme la présence des genres Paracoelophrya et Dicoelophrya dans le tube digestif des oligochètes du genre Alma du Gabon et du Cameroun ; il permet de faire une synthèse récapitulative de la sous-famille des Metaracoelophryinae. De plus, est confirmée l’homogénéité de ce groupe, et est reposée la question de la parenté phylogénétique des Hoplitophryida