Potential use of essential oils from local Cameroonian plants for the control of red flour weevil Tribolium castaneum (Herbst.) (Coleoptera : Tenebrionidae)

Animal feed is food constituted for breeding stock animals because it possesses vital nutrients for animal growth. Animal feed or their ingredients as constituted by cereal flour and are stored after formulation for ulterior breeds. These provender or cereal grains used are commonly attacked by storage insects principally of the genus Tribolium. Firstly, contact and ingestion test by two essential oils of aromatics plants Ocimum gratissimum L (Lamiaceae) and Xylopia aethiopica Dunal A. Rich (Annonaceae) were done firstly on adults and aged larvae of Tribolium castaneun. Secondly, the contact and inhalation test by three essential oils of the aromatic plants Annona senegalensis L. (Annonaceae), Lippia rugosa L.  (Lamiaceae) and Hyptis spicigera Lam. (Verbenaceae) were done for the control larvae, young and aged adults of the red flour weevil Tribolium castaneum Herbst (Coleoptera : Tenebrionidae) very resistant pest to chemical pesticides. Essential oils of Ocimum gratissimum and Xylopia aethiopica have no contact and  ingestion effect on adults of Tribolium castaneum; their insecticidal activity is characterized mostly by their inhibition of the  nymphosis of aged larvae of the same species. On the other hand contact and inhalation tests with crude essential oils of Lippia rugosa and Hyptis spicigera are the most promising because of their efficacy on the other life stages. They are more efficient, with 100% mortality, on larvae at early  stages and young adults. On resistant aged larvae and adults, the insecticidal  efficacy decreases but remains significant. Since this insect, Tribolium castaneum is the major pest of stored flours and provender, the incorporation of these  promising essential oils in flours or in storage formulations of these foods for animals could contribute to their better cereal food conservation. The important and indispensable element of cereals for storage, growth and reproduction animal feed could be preserved from insects attack by use of natural product and may  contribute to diminish toxicity of feeder, environmental pollution and the resistance phenomenon of insects.Key words: Essential oils, Tribolium castaneum, Pesticides

Effect of Plectranthus glandulosus and Ocimum gratissimum Essential Oils on Growth of Aspergillus flavus and Aflatoxin B1 Production

Essential oils of Ocimum gratissimum and Plectranthus glandulosus leaves were extracted by steam distillation and analysed by GC-MS, and their effects on growth and aflatoxin B1 production by Aspergillus flavus were tested at five levels (i.e 200, 400, 600, 800 and 1000 mg/l) using SMKY agar medium. The main components of O. gratissimum were thymol (47.7%) and -terpinene (14.3%) whereas those of P. glandulosus were represented by -terpinene (30.8%) and terpinolene (25.2%). After 8 days of incubation on essential oil-supplemented medium, growth of A. flavus was totally inhibited by 800 mg/l of O. gratissimum essential oil and by 1000 mg/l of P. glandulosus essential oil. The effect of essential oils on aflatoxin B1 synthesis was evaluated in SMKY broth. The medium supplemented with different essential oil concentrations, was inoculated with A. flavus mycelium and incubated at 25 °C. At 2, 4, 6 and 8 days, aflatoxin B1 concentrations in the supernatant were estimated using Enzyme Linked Immuno-Sorbent Assay (ELISA). Results showed that aflatoxin B1 synthesis was inhibited by 1000 mg/l of both essential oils of O. gratissimum and P. glandulosus after 8 days of incubation. Results obtained in the present study indicate the possibility of exploiting O. gratissimum and P. glandulosus essential oils in the fight against strains of A. flavus responsible for biodeterioration of stored food products

Suivi de la qualité physico-chimique et bactériologique des eaux des cours d’eau de Ngaoundéré, au Cameroun

Dans le souci d’évaluer l’influence possible des activités anthropiques sur les eaux de surface à Ngaoundéré, des analyses des paramètres physico-chimiques et bactériologiques indicateurs de pollution ont été effectuées sur dix sept (17) points d’échantillonnage retenus en fonction de leur sollicitation par les populations et leur exposition aux sources probables de pollution. Les paramètres physico-chimiques (température, pH, conductivité, turbidité, matière organique en suspension, oxydabilité au permanganate de potassium, fer, bicarbonates, nitrates, phosphates et ammonium) et bactériologiques (streptocoques fécaux et vibrions) ont été analysés et comparés aux normes internationales. Les résultats montrent des fortes concentrations en matière organique (9,30 à 10,56 mgO<sub>2</sub>/L), Fer (1,69 à 5,57 mg/L), Phosphates (1,73 à 3,09 mg/L), ammonium (1,78 à 2,19 mg/L) et une de turbidité 63,32 à 64,05 NTU dans ces eaux. En plus ces eaux hébergent d’importantes communautés microbiennes parmi lesquelles les streptocoques fécaux et les vibrions. Les teneurs de ces polluants diffèrent d’un point à un autre et selon la période de prélèvement. Une approche statistique multi-variée des résultats montre que l’activité anthropique reste la source majeure des rejets polluants dans les eaux.Mots-clés: pollution, physico-chimie, bactériologie, eaux de surface, Ngaoundéré, Cameroun. Survey of physico-chemical and bacteriological quality of water along the Ngaoundere stream (Cameroon)To evaluate the possible influence of human activities and nature on Ngaoundere stream, some physicochemical and bacteriological pollution indicators were analyses carried out on 17 sites selected on the basis of their probable exposure to pollution. Physicochemical parameters (temperature, pH, conductivity, turbidity, suspended matter, organic matter, iron, bicarbonates, nitrogen, phosphates and ammonium) and bacteriological parameters (fecal streptococcus and vibrio) were determined and compared to international standards.  Results obtained showed a high concentration in organic matter (9.30 to 10.56 mgO<sub>2</sub>/L), iron (1.69 to 5.57 mg/L), phosphates (1.73 to 3.09 mg/L), ammonium (1.78 to 2.19 mg/L) and turbidity of 63.32 to 64.05 NTU. The presence of high quantities of test micro-organisms was noted in these water samples, that is fecal streptococcus and vibrio. The levels of these pollutants in the different water samples varied from one site to another and with sampling period. A multivariate statistical approach demonstrated that human activities remained the major sources of pollutants in surface water.Keywords: pollution, physicochemical, bacteriological, surface water, Ngaoundere, Cameroon

Qualité microbiologique du kilishi (produit carné séché) produit dans la ville de Ngaoundéré (Cameroun)

Microbiological Quality of Kilishi (Traditional Dried Beef) Produced in Ngaoundere, Cameroon. In order to verify the hypothesis that the total microbial load of kilishi samples and the strain of micro-organism they contain would have an influence on their hygienic quality, twenty-four samples of spiced and non spiced kilishi, a traditional sun-dried beef were collected from seven production and sales points in Ngaoundere (North Cameroon). In this regard, aerobic mesophilic flora, coliforms, Staphylococcus aureus, Bacillus cereus, Salmonella spp., sulphito-reducing Clostridium, yeast and moulds were counted on kilishi samples that were diluted serially (ten-fold) and inoculated on selective media. Results obtained showed that 33.34% and 50% of the spiced kilishi samples were contaminated by B. cereus and Salmonella spp., respectively, whereas 83.34% of the non spiced kilishi samples were contaminated by these two micro-organisms. Furthermore, the other investigated micro-organisms were found in all kilishi samples, independent of the type of product. The ratio A/B expressed as the mean level of contamination of spiced kilishi (A) to that of non spiced kilishi (B) was determined for each type of micro-organisms counted. The mean value was 0.43 for sulphito-reducing Clostridium, while the highest value was 0.63 for Salmonella spp. and the lowest 0.27 for Bacillus cereus. This confirms that samples of non spiced kilishi were more contaminated by foodborne pathogens than those of spiced kilishi (P< 0.05). The mean levels of contamination by B. cereus and Salmonella spp. found in some kilishi samples (> 102 CFU/g) were higher than the recommended microbiological standards for cooked meat products (absence in 25 g of product), thus presents a risk of foodborne intoxication for consumers

Long term effect of municipal solid waste amendment on soil heavy metal content of sites used for periurban agriculture in Ngaoundere, Cameroon

An assessment of the impact of amendment using untreated municipal solid wastes on the trace element contents of periurban areas soils was carried out in  Ngaoundere. Waste samples were collected in November and soil samples were collected in November, January, April and July. Heavy metal total concentrations in urban wastes differed significantly among sites and ranged from 0.48 to 7.64 mg/kg for Cd, 38.3 to 236 mg/kg for Cu, 44.06 to 58.03 mg/kg for Ni, 117 to 528 mg/kg for Pb and 270 to 2110 mg/kg for Zn. These levels were out of the critical level for agricultural use at Camp prison (for Pb and Zn), Norvegien (for Cd, Cu and Zn), and Sabongari Gare site (for Cd, Cu and Zn). The levels of Ni in urban wastes from all sites and the levels of all heavy metals in urban wastes from Douze Poteaux site were lower than the critical level. The results revealed that the soil total  concentrations of Cu, Zn, Cd and Pb were below the typical agricultural soil critical level for the soil control and out of the critical level for amended soils. The levels of Ni were found to be within the normal range at all sites. The highest available  concentration of Zn (139.17 mg/kg) was found in November, Fe (843.23 mg/kg) and Pb (38.82 mg/kg) in January and Cu (19.09 mg/kg) and Ni (8.98 mg/kg) in July.  The available concentrations of Cd did not differ among periods. The highest   bioavailable factor (BF) of Zn, Ni and Pb was found at Douze Poteaux site and of Cd and Cu at Sabongari Gare site.Key words: Heavy metals, soils, municipal solid wastes, amendment, bioavailability factor

PERSISTENCE OF ACTIVE COMPOUNDS OF ESSENTIAL OILS OF CLAUSENA ANISATA (RUTACEAE) AND PLECTRANTHUS GLANDULOSUS (LABIATEAE) USED AS INSECTICIDES ON MAIZE GRAINS AND FLOUR

ABSTRACT Maize occupies an important place in the resolution of food insecurity problems in the sub-Saharan region of Africa. However due to poor post-harvest technologies, more than 35% of annual crop yield is often lost during storage as a consequence of insect attack. While chemical pesticides constitute an efficient tool for reducing these losses, current excessive usage runs the risk of modifying the quality and safety of foods produced from these grains. The use of essential oils of plant origin for grain storage has been advocated as a non invasive method with limited or no effect on the quality and safety of the grains or their products. This study was carried out as an evidence of bioactivity of two essential oils of Clausena anisata (Willd.) Hook and Plectranthus glandulosus Hook F. against adults of Tribolium castaneum Herbst and Sitophilus zeamais Motschulsky, which are two important stored product insect pests in Northern Cameroon. Because of the low persistence of the insecticidal activities of these plants, their essential oils to achieve a complete protection of the stored products must be applied at frequent delays. The present investigation focuses on the occurrence of residues of these oils on treated maize grain and flour. The doses of crude essential oils used to treat adults of S. zeamais and T. castaneum in a contact and inhalation process were their LD 99 s. After the evaluation of their insecticidal activity the persistence of each essential oil was observed every 2 days till 14 days. After the disappearance of their insecticidal activities, essential oil was re-extracted and their residual compounds were identified from treated grain and flour. The major compounds of C. anisata are, estragole, α-humulene, germacrene D and (E)-nerolidol. In P. glandulosus they are: fenchone, α-terpinolene and piperitenone oxide. After 14 days, only 64.24% of compounds of C. anisata were recovered on treated flour and 55.16% on grains. Concerning P. glandulosus, 48.94% was recovered on grains and 61.23% on flour

Chronic Toxicity Of Essential Oils Of 3 Local Aromatic Plants Towards Sitophilus Zeamais Motsch (Coleoptera : Curculionidae)

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