Abstract: Dengue (DENV) and Yellow fever (YFV) viruses are medically important flaviviruses that are transmitted by Aedes mosquito vectors of the subgenus Stegomyia especially Aedes aegypti and Aedes bromeliae, respectively, in East Africa.Urbanization has been identified as a major driver in the emergence of these diseases because of the permissive environment it creates promoting the convergence of susceptible human hosts and local vectors. However, while dengue outbreaks have mainly been ...
Abstract: The African wild silkmoth, Gonometa postica Walker produces silk of high quality. A study on the spatial distribution and biology of G. postica on host and non-host plants and the parasitism rates and reproductive strategy of its parasitoids was conducted during the long and short rainy seasons in 2006 and 2007. Three sites, each in the Imba and Mumoni forests of Mwingi eastern Kenya, were selected for sampling. One hundred trees of the host plants of G. postica were sampled at eac...
Abstract: The livestock tropical bont tick, Amblyomma variegatum Fabricius, is a pest of major economic importance in Africa where it is the vector of Cowdria ruminantium that causes Heartwater, disease in cattle. Its control has relied mainly on commercial acaricides, which have many problems associated with, environmental pollution, development of resistant strains of ticks against acaricides and escalating costs. It has, therefore, become necessary to look for alternative methods of tick ...
Abstract: The rate and the degree of reversible change in the phase characteristics of the desert locust, Schistocerca gregaria (Forskal), on crowding and uncrowding have been compared by two new parameters, aggregation pheromone titre (as measured by released phenylacetonitrile) and haemolymph pigment composition (as measured by absorbance ratio at 460 and 680nm) with colour and morphometrics. Changes in the four parameters followed different patterns. Adults of the F0 generation resulting ...
Abstract: The Malagasy migratory locust, Locusta migratoria capito (Saussure, 1884), is the most destructive pest in the Malagasy agricultural production system. The recent plague between 1996 and 2000 during which economic losses amounting to ca. US$ 50 million mainly in rice fields, were recorded, is an indication that, the locust menaces is far from being resolved in Madagascar. Control operations against locusts have focused entirely on large-scale application of synthetic chemical insec...
Abstract: Trypanosomes are protozoans causing African trypanosomiasis, a neglected tropical disease in Africa affecting humans and animals. Despite advancement in African Trypanosomiasis research, the disease continues to threaten millions of people and animals in Sub-Saharan Africa. Control methods have focused on the use of drugs which have adverse effects and vector control methods which have proved to be ecologically unsustainable while vaccines are still not available due to antigenic v...
Abstract: Trichogramma species parasitise eggs of Lepidoptera and have been extensively used in augmentative biological control. Studies were conducted during 1997-2001 on the native egg parasitoids occurring in Kenya. The objectives of the study were (i) to identify the native egg parasitoids that attack Helicoverpa armigera and Plutella xylostella, (ii) to study the conventional and molecular taxonomy of the native Trichogramma species, (iii) to evaluate the response of two native Trichogr...
Abstract: Manduca sexta vitellogenin is a phosphoglycolipoprotein (Mr - 500,000) that contains two copies of the apoproteins (apovitellogenin-1, Mr 180,000 and apovitellogenin-11, Mr 45,000), 13 percent lipids, 3 percent carbohydrates and 0.6 percent phosphorus. The two apoproteins are immunologically distinct polypeptides and apovitellogenin-11 is not completely accessible to the aqueous environment in the intact molecule. The carbohydrate moiety located on apovitellogenin-1 has a high mann...
Abstract: Integrated pest management (IPM) systems utilizing the use/release of the parasitoid Diadegma semiclausum have been developed to replace the pesticides only approach to diamondback moth (DBM) Plutella xylostella (L.), worldwide the worst insect pest of cabbage family. The successful introduction of the DBM natural enemy in Kenya as a biological control agent under the IPM system is a good achievement towards a solution to excessive insecticides use. Data collections were done for 1...
Abstract: A comparison of the resistance/susceptibility levels of ten cowpea cultivars to the pod borer Maruca testulalis revealed that VITA l was the most susceptible. TVU 946 most resistant and VITA 5, chola local and kamboinse local rroderately resistant. In all the cultivars which were compared, flowers and pods suffered the heaviest damage compared to the stems. Colonizing responses of M. testulalis namely oviposition, larval orientation, feeding, utilization of ingested food, larval de...
Abstract: One of the most important and largely consumed African Indigenous Vegetables (AIV) is amaranth. It is known to have a high nutritional value, agronomical assets and economic attributes. Amaranth production is however constrained by numerous biotic factors such as insect pests, occurring as a complex of species among which lepidopteran defoliators are found to be the most destructive. Investigations on their bio-ecological and control options were conducted. Field experiments were c...
Abstract: The African mosquito species Anopheles gambiae and An. funestus are ranked high among the world's most efficient vectors of human malaria. Their juvenile stages develop in aquatic environments while adults are terrestrial. Chemical signals guide gravid females of these vectors to their egg-laying sites. Several attributes of a pond including presence of other organisms influence egg hatching success and larval survival. Gravid An. gambiae females strongly discriminate among potenti...
Abstract: This thesis describes the asymmetric phase-transfer catalysed (PTC) Darzens condensation of aldehydes and ketones with the chiral reagents 1-menthyl chloromethanesulphonate, (S)-(-)-N-chloromethylsulphony l-2 -thoxymethylpyrrolidine,(S)-(-)-tert-butyl N-(chloromethylsulphonyl)prolinate and (+)-0-methyl-N-(chloromethylsulphonyl)ephedrine using triethylbenzylammonium chloride (TEBA) as the phase-transfer catalyst.The chiral reagent 1-menthyl chloromethanesulphonate was obtained by th...
Abstract: Hexane, ethyl acetate and methanol extracts of Commiphora swynertonii Burtt., Turraea cormicopia (L), T abyssinica, T. floribunda and Melia volkensii Gurke were tested for anti-tick activity against the larvae and adult Rhipicephalus appendiculatus Neuman using the packet method bioassay. The hydrodistilled oil of the leaves of C. swynertonii was tested for acaricidal and repellency activities against ! adult R. appendiculatus using the packet and climbing bioassay method, respecti...
Abstract: Ticks of the genus Rhipicephalus are important parasites of livestock in the world. Rhipicephalus ticks cause huge economic losses to cattle and have a great capacity to develop resistance to chemical acaricides. There is the need therefore to develop alternative strategies that could complement the existing control methods of this ectoparasite. Entomopathogenic fungi are being considered as a promising option for the control of ticks on-host and off-host. The aim of this study was...