Impact of aqueous extracts of Cassia occidentalis, Eucalyptus camaldulensis and Hyptis suaveolens on the entomofauna and the seed yield of Gossypium hirsutum at Boklé (Garoua, Cameroon).

There is a frightening decline in the population pollinators around the world due to the over usage of synthetic pesticides, leading to the directly reduce of plant production. Plant extracts with insecticidal properties could be eco-friendly alternatives to synthetic pesticides in maintaining the pollinator population and the diversity of the ecosystem. The impact of aqueous extracts of Cassia occidentalis L., Eucalyptus camaldulensis Dehnh. and Hyptis suaveolens L. was investigated on the entomofauna and the seed yield of Gossypium hirsutum L. cotton. The study was carried out in RCBD, four times replicated: 3 extracts x 1 standard synthetic insecticide (TEMA) x 1 control x 4 groups of flowers (group 1: flowers free to insect visits, group 2: flowers protected from insects using gauze bags, group 3: protected flowers and opened exclusively to Amegilla sp. and group 4: protected flowers opened from time to time without any visit of insect). Gossypium hirsutum was found to be visited by the insects belonging to five orders, 10 families and 18 species. Amegilla sp.1 and Apis mellifera were the major pollinators during the rainy and dry seasons, respectively. The number and quality of seeds visited exclusively by Amegilla sp.1 were significantly improved by H. suaveolens extract. During the dry season, E. camaldulensis and H. suaveolens extracts as well as the standard insecticide improved the number of seeds and the percentage of normal seeds harvested from the flowers allowed to be visited by insects; that was probably due to their insecticidal effects which protected plants from pest damage. Therefore, aqueous extracts of E. camaldulensis and H. suaveolens are good candidates for incorporation in integrated pest management programs to minimize the risk of synthetic pesticides to pollinators, hence to increase the yield and the quality of seeds.

New cassava germplasm for food and nutritional security in Central Africa.

Cassava is a key food security crop in Central Africa, but its production depends largely on the use of local farmers' varieties characterized by inherently low yield which is compounded by generally high susceptibility to various growth and yield-limiting pests and diseases. Improved cassava genotypes have demonstrated the potential to substantially improve cassava's contribution to food security and the development of the cassava industry and the improvement of nutrition status elsewhere in Western Africa. Eleven improved cassava genotypes were compared with a local landrace (LMR) used as a check under field conditions over two years in eight locations, grouped in four agro-ecologies in Cameroon. Pest and disease abundance/incidence and damage severity were evaluated. At harvest, root yield and carotenoid content were measured. Best linear unbiased predictors showed the lowest breeding value for LMR with the cassava mosaic virus disease (+ 66.40 ± 2.42) compared with 1.00 ± 0.02% for the most susceptible improved genotype. Two genotypes (I010040-27 and I011797) stood out for having higher predicted fresh root yield means which were at least 16 times greater compared with LMR. Predicted total carotenoid content was the highest (+ 5.04 ± 0.17) for improved genotype I070593 compared with LMR which showed the lowest (- 3.90 ± 0.06%) and could contribute to the alleviation of vitamin A deficiency from cassava-based food systems. Diffusion of high-yielding and nutritious genotypes could alleviate food and nutritional security in Central Africa.

Thrombocytopenia according to antiretroviral drug combinations, viremia and CD4 lymphocytes among HIV-infected patients in Cameroon: a snapshot from the City of Yaoundé.

OBJECTIVE: Thrombocytopenia is an abnormal decrease in blood platelets, which can affect the prognosis of people living with HIV (PLHIV). In order to assess the burden of this haematological disorder, we evaluated the frequency of thrombocytopenia according to antiretroviral drug combinations, viremia and the immune status of PLHIV. RESULTS: A cross-sectional and analytical study was conducted from June to November 2016 among 310 PLHIV at the "Chantal BIYA" International Reference Centre, Yaoundé, Cameroon. Overall rate of thrombocytopenia was 19.0% (59/310). The rate of thrombocytopenia was 64.6% (42/65) versus 6.9% (17/245) in ART-naïve versus ART-treated patients respectively, p < 0.0001. Following viral load, rate of thrombocytopenia was 15.8% (20/130) in those with undetectable viral load, and 34.1% (27/79) with viral loads > 3 log10 RNA/ml (p = 0.03). As concerns CD4-count, rate of thrombocytopenia was 16.2% (42/259) in those with ≥ 200 CD4/mm3 versus 33.3% (17/51) with < 200 CD4/mm3 (p = 0.0003). After adjusting for sex, ART, viral load and CD4, Viral load and ART exposure were significantly associated with decreased risk of thrombocytopenia (p < 0.05). Thrombocytopenia occurs especially among ART-naïve, high viremia and severe immune-compromised patients. Interestingly, ART coverage appears as an independent factor in preventing the occurrence of thrombocytopenia.

Control of Callosobruchus maculatus (Coleoptera: Chrysomelidae) Using Fractionated Extracts from Cameroonian Hemizygia welwitschii (Lamiaceae) Leaf on Stored Vigna unguiculata (Fabales: Fabaceae).

Bioassays were conducted to assess the individually insecticidal activities of hexane, acetone, and methanol extracts from Hemizygia welwitschii Rolfe-Ashby leaves powder against Callosobruchus maculatus (F.). The extracts were applied at 2, 4, 6, and 10 g/kg of cowpea and the untreated seeds served as negative control. Treatments were arranged in a complete randomized design with four replications. Adult mortality, F1 progeny emergence, as well as insect population increase, seeds damage, and seeds germination were carried out. The results obtained showed that the three extracts of H. welwitschii were very effective in protecting stored cowpea against C. maculatus at the highest dosage (10 g/kg) 7 d after treatment. There was no F1 progeny emergence of C. maculatus in cowpea treated with hexane extract at the dosage of 10 g/kg, while, at the same dosage, acetone and methanol extracts almost completely inhibited the F1 progeny emergence. Also, the different concentration levels significantly protected the seeds with regard to seed damage caused by C. maculatus compared with the untreated control after 3 mo storage. The viability of seeds was not affected by the extracts. Because of their effectiveness, the three extracts of H. welwitschii leaves powder could be a good candidate in pest management programs, especially against C. maculatus in stored cowpea grains, in Cameroon and other developing countries.

Gut bacteria of the cowpea beetle mediate its resistance to dichlorvos and susceptibility to Lippia adoensis essential oil.

Bacteria inhabiting the gut of insects provide many benefits to their hosts, such as aiding in food digestion, reproduction, and immunity, tissue homeostasis, adaptation to environment and resistance to pathogen and pesticides. The cowpea beetle, Callosobruchus maculatus, is a serious cosmopolitan pest of pulses. This beetle has lent itself as a guinea pig for several ecological studies. It harbors a consortium of bacterial communities in its gut, but the evidence for their role in its physiology is fragmentary. In this work, we hypothesized that gut microbiota mediates C. maculatus resistance to dichlorvos (DDVP or O,O-dimethyl O-2,2-dichlorovinylphosphate) and represent the target of Lippia adoensis (Gambian Tea Bush) essential oil (EO). Symbiotic and aposymbiotic beetles were exposed to artificial cowpea seeds earlier treated with DDVP or EO. Adult mortality and changes in gut bacterial community composition and abundance were examined at F1 and F5 generations. The susceptibility of experimental beetles to DDVP was significantly affected by their symbiotic status. The adult mortality decreased across generations in DDVP treatments, and remained significantly higher in aposymbiotic groups. In EO treatments, the mortality was consistent irrespective of symbiotic status and experimental generations. When compared to DDVP and the Control, EO treatments had significantly lower bacterial richness and diversity, as well as lower abundance of Proteobacteria, Firmicutes, and Bacteroidetes. These results support our hypothesis and describe the responses of gut microbial communities to pesticide treatments. This could be of interest for developing new management strategies of this pest.

Toxicity of Boswellia dalzielii (Burseraceae) Leaf Fractions Against Immature Stages of Anopheles gambiae (Giles) and Culex quinquefasciatus (Say) (Diptera: Culicidae).

Mosquitoes are vectors of several human pathogens, and great attention has recently been placed on insecticides from plant-derived products, in search for mosquito control agents. This study, thus, investigated the potency of Boswellia dalzielii methanol leaf extract and its four fractions as mosquito ovicide, larvicide, and pupicide against Anopheles gambiae and Culex quinquefasciatus. The plant products were tested at the following concentrations: 125, 250, 500, 1000, and 2000 ppm on eggs and 312.5, 625, 1250, and 2500 ppm on the larvae and pupae of the mosquitoes. For results, hatchability of A. gambiae eggs was reduced to 5% with n-hexane fraction at 2000 ppm. Among the plant products tested, n-hexane fraction was most toxic against A. gambiae (LC50 = 385.9 ppm) and C. quinquefasciatus (LC50 = 3394.9 ppm). The n-hexane fraction of B. dalzielii might be used as a mosquitocidal agent in the breeding sites of A. gambiae and C. quinquefasciatus.

Laboratory Evaluations of the Fractions Efficacy of Annona senegalensis (Annonaceae) Leaf Extract on Immature Stage Development of Malarial and Filarial Mosquito Vectors.

BACKGROUND: Within the framework to control mosquitoes, ovicidal, larvicidal and pupicidal activity of Annona senegalensis leaf extract and its 4 fractions against Anopheles gambiae and Culex quinquefasciatus were evaluated in the laboratory conditions. METHODS: Ovicidal test was performed by submitting at least 100 eggs of mosquitoes to 125, 250, 500, 1000 and 2000 ppm concentrations, while larvicidal and pupicidal effects were assessed by submitting 25 larvae or pupae to the concentrations of 2500, 1250, 625 and 312.5 ppm of plant extract or fractions of A. senegalensis. RESULTS: The eggs of An. gambiae were most affected by N-hexane (0.00% hatchability) and chloroform (03.67% hatchability) fractions compared to Cx. quinquefasciatus where at least 25 % hatchability were recorded at 2000 ppm. For larvicidal test, N-hexane (LC50= 298.8 ppm) and chloroform (LC50= 418.3 ppm) fractions were more effective than other fractions on An. gambiae larvae while, a moderate effectiveness was also observed with N-hexane (LC50= 2087.6 ppm), chloroform (LC50= 9010.1 ppm) fractions on Cx. quinquefasciatus larvae. The highest mortality percent of the pupae were also recorded with N-hexane and chloroform fractions on An. gambiae at 2500 ppm. As for Cx. quinquefasciatus only 50 % and 36 % mortality were recorded with N-hexane and chloroform fractions respectively. CONCLUSION: The extract of A. senegalensis was toxic on immature stage of mosquito species tested. By splitting methanolic crude extract, only N-hexane and chloroform fractions were revealed to possess a mosquitocidal effects and could be considered and utilized for future immature mosquito vectors control.

Efficacy of Plectranthus glandulosus (Lamiaceae) and Callistemon rigidus (Myrtaceae) Leaf Extract Fractions to Callosobruchus maculatus (Coleoptera: Bruchidae).

As part of on-going efforts to use eco-friendly alternatives to chemical pesticides, methanol crude extracts of Plectranthus glandulosus and Callistemon rigidus leaves were sequentially fractionated in hexane, chloroform, ethyl acetate, and methanol to establish the most active fraction(s) against Callosobruchus maculatus in cowpea. Cowpea seeds (25 g) were treated with 0.5, 1, 2, and 4 g/kg of extract to evaluate the contact toxicity and F1 progeny production of the beetles in the laboratory. Mortality was recorded 1, 3, and 7 d postexposure. P. glandulosus hexane fraction was more toxic than the other fractions recording 100% mortality at 4 g/kg, within 7 d with LC50 of 0.39 g/kg. Hexane fraction of C. rigidus showed superior toxicity, causing 100% mortality at 4 g/kg within only 1 d of exposure with LC50 of 1.02 g/kg. All the fractions greatly reduced progeny emergence, with C. rigidus hexane fraction being the best progeny inhibitor. Fractions of P. glandulosus and C. rigidus leaves had sufficient efficacy to be a component of storage pest management package for C. maculatus.

Creams formulated with Ocimum gratissimum L. and Lantana camara L. crude extracts and fractions as mosquito repellents against Aedes aegypti L. (Diptera: Culicidae).

Mosquitoes are the most deadly vectors of parasites that cause diseases such as malaria, yellow fever, and filariasis. In view of the recent increased interest in developing plant origin insecticides as an alternative to chemical insecticides, the objective of this study was to determine the repellent activity of creams formulated with methanol crude extract (MCE), hexane fraction (HF), and ethyl acetate fractions (EAFs) of Ocimum gratissimum and Lantana camara leaves in single and combined actions against female Aedes aegypti. Evaluation was carried out in the net cages (30 by 30 by 30 cm) containing 60 blood-starved female mosquitoes each and were assayed in the laboratory condition following World Health Organization 2009 protocol. All formulations (single and mixture) were applied at 2, 4, 6, and 8 mg/cm(2) in the exposed area of human hands. Only acetone + white soft paraffin served as negative control and odomos (12% DEET) as positive control. All the formulations presented good protection against mosquito bites without any allergic reaction by the human volunteers. The repellent activity was dependent on the strength of the extracts and fractions. Among the tested formulations, the maximum protection time was observed in MCE (120 min) and EAF (150 min) of O. gratissimum; MCE:MCE (150 min) and HF:HF (120 min) mixtures of both plants. In addition, MCE:MCE and HF:HF mixtures from both plants showed possible synergistic effect. From the results, the combination of O. gratissimum and L. camara to formulate natural mosquito repellent using small amount of extracts can be encouraging to be an alternative to conventional DEET.

Signaling pathways bridging microbial-triggered inflammation and cancer.

Microbial-triggered inflammation protects against pathogens and yet can paradoxically cause considerable secondary damage to host tissues that can result in tissue fibrosis and carcinogenesis, if persistent. In addition to classical pathogens, gut microbiota bacteria, i.e. a group of mutualistic microorganisms permanently inhabiting the gastrointestinal tract and which plays a key role in digestion, immunity, and cancer prevention, can induce inflammation-associated cancer following the alterations of their microenvironment. Emerging experimental evidence indicates that microbiota members like Escherichia coli and several other genotoxic and mutagenic pathogens can cause DNA damage in various cell types. In addition, the inflammatory response induced by chronic infections with pathogens like the microbiota members Helicobacter spp., which have been associated with liver, colorectal, cervical cancers and lymphoma, for instance, can also trigger carcinogenic processes. A microenvironment including active immune cells releasing high amounts of inflammatory signaling molecules can favor the carcinogenic transformation of host cells. Pivotal molecules released during immune response such as the macrophage migration inhibitory factor (MMIF) and the reactive oxygen and nitrogen species' products superoxide and peroxynitrite, can further damage DNA and cause the accumulation of oncogenic mutations, whereas pro-inflammatory cytokines, adhesion molecules, and growth factors may create a microenvironment promoting neoplastic cell survival and proliferation. Recent findings on the implication of inflammatory signaling pathways in microbial-triggered carcinogenesis as well as the possible role of microbiota modulation in cancer prevention are herein summarized and discussed.