PHD-School of Pure And Applied Sciences

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This collections contains bibliographic information and abstracts of PHD theses and dissertation in the School of Pure And Applied Sciences held in Kenyatta University Library

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ADH/ADLH polymorphism as biochemical and genetic markers in study of alcohol tolerance in selected Kenyan populations
(2011-08-16) Korir, Elena Doudoladova
Excessive alcohol consumption is a major health hazard worldwide. Alcohol is commonly used and often abused in Kenya, especially by the youth. For European, Asian, Australian and American populations, studies have shown linkage between polymorphisms of the alcohol dehydroggenase (ADH) and aldehyde dehydrogenase (ALDH), the ethanol metabolizing enzymes, with the increase of alcohol intake. For Africans, no studies on heterogeneity of ADH and ALDH and its relationship to alcoholism, alcohol intake and alcohol drinking behaviour have been reported. The aim of this study was to find out the distribution of alleles of ADH 2, ADH 3, and ALDH 2 loci in the selected Kenyan populations namely the Kolweny, Siaya, Longisa, Limuru and Rugunga and to investigate the association of these ADH/ALDH alleles with alcohol drinking and alcoholism. These five Kenyan populations represent two major African groups namely the Bantu and Nilotes. Different gender and age groups of the selected Kenyan communities were screened for ADH 2, ADH 3 and ALDH 2 polymorphisms via phenotyping of hair lysates using high resolution isoelectric focusing.. In addition, information on education, marital status, occupation, drinking behaviour, alcohol sensitivity, alcohol intake, age of regular alcohol drinking, alcohol drinking experience, alcohol dependence, emotional response to alcohol and preference of alcoholic drinks was collected via a questionnaire. The data obtained on ADH 2, ADH 3 and ALDH 2 polymorphism and alcohol drinking behaviour was statistically analyzed using chi-square, t-test and Fisher's exact test. Three hundred and seventy one adult volunteers participating in the project from all Kenyan study groups were divided into groups on the basis of alcohol tolerance. Alcohol-drinking parameters of alcohol use were analyzed with respect to alcohol tolerance. The significant difference in alcohol intake, alcohol drinking experience, alcohol sensitivity, emotional response to alcohol, the role of ADH 3*1 allele in the drinking behaviour and preference of alcoholic drinks were determined among individuals with high and low alcohol tolerance. ADH 2, ADH 3 and ALDH 2 polymorphism showed significant relation to alcohol intake (among alcoholics), alcohol drinking experience (among nonalcoholics), sensitivity to alcohol, alcohol drinking behaviour, mode of alcohol drinking, and preference of alcoholic drinks. ADH and ALDH heterogeneity was not associated with the difference in alcohol intake (among nonalcoholics), age of regular drinking and emotional response to alcohol. The role of different socio-demographic, biochemical and genetic factors in alcohol drinking and spread of alcoholism were identified for each Kenyan study group. The Kolweny, Siaya, Limuru and Rugunga populations have dominance of individuals with high alcohol tolerance and relatively low spread of alcoholism in the populations. The Longisa population had relatively high proportion of individuals with low alcohol tolerance and high occurrence of alcoholism in the community. The research findings may be used to formulate ethnically adequate methods of diagnosis, treatment, and management of alcoholism in relation to alcohol tolerance in the studied Kenyan populations
Agrobacterium tumefacients mediated introgression of Nicotiniana Protein Kinase (NPK1) gene in selected Kenyan maize genotypes to enhance drought tolerance
(2011-08-12) Muoma, John Vincent Omondi; Machuka, Jesse; Geoffrey Muluvi
In the last decade, the production of maize has gone down because of biotic and abiotic constraints, and this has resulted to prevalent famine. Of the abiotic stresses, drought is the most important stress affecting productivity of maize in Africa leading to up to 70% crop loss and in certain cases total crop loss. Conventional breeding, molecular marker assisted breeding and genetic engineering have already had, and will continue to have, important roles in maize improvement. The rapidly expanding information from genomics and genetics combined with improved genetic engineering technologies offer a wide range of possibilities for enhanced maize production. Genetic engineering of plants has been achieved through direct uptake of naked DNA into target cells and via Agrobacterium mediated transformation. Agrobacterium mediated transformation is increasingly becoming the method of choice due to its ability to generate transformed events containing low copy insertions. However this mode of maize transformation is dependant on genotype, age and physiological condition of the target explant and the infecting strain of A. tumefaciens. For every successful transformation protocol a reproducible regeneration system and transformation by a reporter gene is a necessity. The optimal regeneration condition for the shoot tips and immature zygotic embryos was observed to be 9µM 2, 4-D, 8.88µM BAP supplemented with 296µM adenine and 9µM 2, 4-D respectively for calli maintenance and shoot induction. Root induction in case of shoot apices was alleviated by the use of 1.97µM indole-3- butyric acid while immature zygotic embryos readily formed roots on MS without hormone after a maturation step. Transient expression of GUS was used to assay the explants for transformation frequency considering embryogenic calli formation, shoot induction and root formation had been optimized in the regeneration step. In these experiments, 10 days old seedlings shoot apex derived calli exhibited GUS activity at a transformation frequency (TF) of 0-4.2% while the 15 days old immature zygotic embryos derived calli exhibited a higher TF of 613% GUS activity making immature zygotic embryos better explant for transformation of the selected genotypes. Immature zygotic embryos were thus preferably transformed for drought with a gene that codes for an upstream transcription signal factor MAPKKK cascade (NPK1) triggered under drought stress (DS). The transformation efficiency for the four genotypes was TL08 0.79%, DHO1 4.87%, DLC1 2.64% and PTL001 5.35%. The seeds of the transgenic events were harvested, planted and both DNA and RNA extracted from the T1 events for southern, northern, and RT-PCR analysis to check on copy numbers and expression levels of the NPK1 gene. The T1 plantlets of tropical inbred TL08-(2)4, single hybrid cross of a PTL001, a multiple cross hybrid DHO1 and a dry land cultivar DLC 1 genotypes were planted in the green house and assessed for morphological and physiological changes associated with increase in DS tolerance when under water stress condition. The results showed that NPK1 effectively enhanced drought tolerance in TL08-(2)4 and PTL001, and there was no significant morphological difference between transgenic controls (well watered) and transgenic tests (subjected to moderate drought stress) using Turkeys Kramer HSD (p<0.05). Overall, there was between 20-35% enhancements of yield on comparison of the transgenic stressed events with non-transgenic stressed control
An analysis of international tourism demand for Kenya
(2014-08-18) Ngugi, Kamau W. L.
Tourism sector in Kenya plays an important role in the national economy and has been identified as one of the six priority sectors in vision 2030 meant to drive the economy to attain 10 percent economic growth. International tourism demand for Kenya lags behind other African countries like Egypt, Morocco, Tunisia and South Africa. Furthermore, the number of tourists‟ arrivals to Kenya from different world regions does not increase constantly but have experienced cyclical fluctuations over the years. Moreover, the Kenya tourism product offered is becoming increasingly noncompetitive. There is need therefore, for Kenya to offer demand driven tourism products that ensure visitors come to Kenya and stays longer. GOK, tourism planners and marketers therefore need to clearly understand which important factors influence international tourists‟ decision to visit Kenya as their destination. Motivated by this need, the study sought to investigate the determinants of international tourism demand for Kenya. Specifically the study established the effect of economic factors, tourist socio-demographic characteristics, political factors and destination characteristics on international tourism demand for Kenya. The study used both longitudinal and cross sectional research designs. The study used panel data for economic variables from eleven countries for the period 1991 to 2011 collected from the World Bank database, United Nations database, International Monetary Fund database and Kenya National Bureau of Statistics. Survey data were collected from individual tourists leaving the country through Jomo Kenyatta International Airport using questionnaires. The study used a dynamic panel regression model to determine the effect of economic factors on international tourism demand for Kenya and a count data regression model to determine the effect of socio-demographic characteristics, political factors and destination characteristics on international tourism demand. The study results indicated that tourism price, travelling cost, trade openness and word of mouth effect were the main economic factors influencing international tourism demand for Kenya. The dummy variable representing the 2008 post election clashes and the lagged dependent variable representing the word of mouth effect were also significant. In addition, the tourist‟s socio-demographic characteristics such as annual household income, age and occupational status were found to significantly influence international tourism demand. The political factors composite index and destination characteristics composite index were also important determinants of international tourism demand. Taking into consideration of all these factors affecting tourism demand, the government and all the tourism stakeholders should work towards making Kenya tourism product competitive by ensuring that the prices remain competitive, diversifying tourism by creating tourism products which meets the needs of specific groups. The existing tourism products should also be improved in order to remain competitive, the tourism infrastructure and services should be well established and of good quality. The government should continue to engage in bilateral trade. Therefore, all the tourism stakeholders should work towards making Kenya a destination of choice.
Anopheles larval productivity and diversity in Mwea irrigation scheme, Kirinyaga district, Kenya
(2011-11-08) Mwangangi, Joseph Mumo
The use of irrigation to flood agricultural land during rice cultivation has over the years been associated with an increase in the number of disease vectors and corresponding increase in health burden due to malaria and other vector and waterborne diseases. In this study, field and laboratory studies were used to examine the primary factors responsible for regulating the aquatic stages of malaria vectors in a rice agro-ecosystem prior to implementation of a larval control programme. The objective of this study was to determine the environmental and agricultural factors that regulate malaria vector productivity and diversity in Mwea Irrigation Scheme, Kirinyaga district, Kenya. The study was conducted in 3 villages representing planned (Mbui Njeru), and unplanned rice cultivation with varying amount of land under rice (Kiamachiri and Murinduko). The physico-chemical variables were measured using different field based hand held equipments or visual assessment. Experimental plots were used to closely monitor the factors associated with Anopheles larval densities in the rice fields. A total of 29,252 immature stages of anopheline mosquitoes were collected in the three villages comprising of'78.23% (n = 22,885) early instars, 10.91% (n = 3,192) late instars and 10.85 % (n = 3,173) pupae. Anopheles gambiae s.l. was the most abundant and was found in all habitats that were positive for late anopheline instars in the 3 villages. Larval abundance was significantly higher in Murinduko compared to the other villages (F(2, 182) = 38.685, p< 0.01). Rainfall was positively associated with Anopheles gambiae s. l. larval abundance in Kiamachiri (r = 0.759) and Mbui Njeru (r = 0.602) but negatively associated in Murinduko (r = - 0.267). Multiple logistic regressions showed Anopheles larval density to be significantly associated with many interrelated biotic and abiotic variables including presence of other invertebrates, percentage Azolla cover, distance to nearest homestead, water turbidity, water temperature, conductivity, pH, and water depth. Anopheles productivity from different habitat types showed that paddies had most emergent mosquitoes (n = 143) followed by marshes (n = 65). Succession of Anopheles species was evident with An. gambiae colonizing the paddies throughout the rice growth cycle with peaks during the early stage of rice growth while An. rufipes and An. coustani occurred during the late vegetative stages. Larval densities were significantly higher at the centre of the paddy compared to the periphery during the transplanting period (F (1,166) = 4.809, P = 0.030) but the difference was not significant during the tillering period (F (1,362) = 0.037, P = 0.848). The survivorship of immatures in the paddies showed that there was 98.26% mortality of larvae. In conclusion, rice paddies and associated canals are the most productive habitats types throughout the year while peridomestic habitats are important during the long and short rains. The results further indicate that several biotic and abiotic factors interact to regulate Anopheles larval densities in aquatic habitats. These findings demonstrate the need to target larvicidal application in the entire paddy between transplanting and tillering stages in order to achieve effective larval control.
Anthropogenic Impacts on Distribution and Abundance of Mountain Catfish (Amphilias Uranoscopus, Pfeffer, 1889) and Other Fishes, in the Sagana and Thego Streams, Nyeri, Kenya
(Kenyatta University, 2019-04) Odhiambo, Charles Oduor
The clearance of forest for agriculture, settlement and grazing has had some of the most widespread human impacts on natural ecosystems globally. In Kenya large tracks of indigenous forests continue to be cleared to give way for human settlement and exotic tree plantations. The catchment on the slopes of Mt. Kenya has experienced such major losses that have affected the aquatic ecosystem. The objective of this study was therefore to document the extent of impact of anthropogenic activities on the distribution, abundance and population sizes of the mountain catfish (Amphilius uranoscopus Pfeffer, 1889) and other fish species along two second order tropical forested streams, Sagana and Thego on the slopes of Mt. Kenya. This study was done from June 2016 through May 2017. Fish samples were caught using an electrofisher and recorded for distribution, population sizes, reproductive strategies and feeding habits. Water samples for physiochemical parameters were determined in situ and a socio-economic survey of the riparian community carried out using a structured questionnaire. The smallest sized catfish were caught in November 2016 at the Thego station T2 midstream while the largest specimen electrofished was a I9.0 cm fork length (92.19 female caught in the downstream station (T3) of the Thego. There was a significant difference (t-test, t : - 3.35; p:0.007) in the mean number of catfish caught per hour of electrofishing between the Thego stations (T2 and T3). A comparison between Catch per unit effort (CPUE) in Sagana and Thego (ANOVA, F : 6.82; p : 0.004) showed a significant difference in catches between the two streams. Results from this study shows that there have been major significant changes in the distribution patterns of both the native species as well as the salmonid species in the two streams and that the mountain catfish has expanded its territory while the introduced salmonid species zones have shrank or become thin. Catfish exhibited a wider food base overlapping with those of the other species such as rainbow trout, brown trout and barbus. The occurrence of the mountain catfish (Amphilius uranoscopus), Barbus sp. and Labeo sp. inthe midstream of the Thego and downstream of the Sagana and Thego, the absence of rainbow trout in the midstream of the Thego and the restriction of the brown trout to the near pristine reaches of the Sagana at an altitude above 2150 metres are some of the changes that have occurred since 1960s due to the impact of human settlement in the watersheds of streams in the slopes of Mt. Kenya. Major factors associated with the variation in catfish distribution and abundance among the study stations included increased temperatures, elevated stream water conductivity and decline in water discharge. These clearly show that the catfish population is likely to move fuither upstream in Thego than in Sagana unless urgent measures to control human related anthropogenic activities in Thego catchment area are adopted. This study supports the hypothesis that the mountain catfish distributional range will continue to expand at the expense of other fish species unless corrective measures are considered to control anthropogenic human driven settlement activities in the watershed of the Sagana and Thego. Management strategies should focus on the values of the society and recognize that the continuous expansion of mountain catfish home range is an indicator of environmental perturbation arising from change in landuse and increase in human activities.
Anti-Obesity, Cognitive Enhancing, Neurobehavioral, Antioxidant Effects And Phytochemical Profile Of Dichloromethane Leaf Extract Of Gnidia Glauca (Fresen)
(Kenyatta University, 2019-11) Makori, Wycliffe Arika
Obesity is a chronic metabolic disorder characterized by increased adipose tissue mass due to positive energy balance. The epidemic of obesity is currently on the rise probably due to increasingly sedentary lifestyles combined with easy availability of palatable, high-fat foods. It presents modifiable risk factor for cognitive impairements, anxiety and motor deficits. Globally, its prevalence has shown a startling increase in all age groups and have been associated with increased morbidity and mortality. Prescription of anti-obesity drugs can be useful adjuncts to diet and exercise for obese patients who have failed to achieve weight loss. However, these drugs are ineffective, not readily available, unaffordable and have been associated with adverse effects. Therefore, medicinal plants have drawn a sharp focus in recent times as complementary and alternative medicines owing to their biocompatibility, affordability and are assumed to be safe due to their long-term clinical application. Hereby, determination of therapeutic activities and identification of active principles from herbal prescriptions have become the prime focus in the validation of their folkloric usage and in drug discovery programs. The present study aimed to determine the anti-obesity effects, cognitive enhancing, neurobehavioral, antioxidant effects and phytochemical profile of dichloromethane leaf extract of Gnidia glauca. Obesity was experimentally induced by feeding the rats with prepared high-fat-diet (HFD) and water ad libitum for a period of 6 weeks. The in-vivo anti-obesity effects were determined by oral administration of the extract at dosage levels of 200, 250 and 300mg/kg body weight in HFD-induced obese rats from the 6th to 12th week along with HFD. Cognitive-enhancing effects of the extract in HFD-induced obese rats were determined using the Morris Water Maze experiment. The effects of the extract on neurobehaviors (locomotor activity, anxiety and exploration-like behaviors) in HFD-induced obese rats were tested using the Open Field Test. The in vitro antioxidant properties of the extract were determined using non-enzymatic assays. The phytochemical profile of the extract was determined using GC-MS. The results indicated that the extract exhibited potent anti-obesity effects in HFD-induced obese rats. It significantly reduced the body weight, organ weights, organo-somatic indices, anthropometric indices, the total fat content, adiposity index, atherogenic index as well as the lipid profiles (Triglycerides, Total Cholesterol, Low-Density Lipoproteins, and Very Low-Density Lipoproteins). However, it significantly increased levels of High-Density Lipoproteins. The extract increased levels of white blood cells, differential leukocyte counts, platelet count as well as red blood cells and related parameters. The extract improved hippocampal-dependent spatial learning and memory retention in HFD-induced obese rats. Moreover, it showed anxiolytic effects, increased spontaneous locomotor activity and exploration-like behaviors in HFD-induced obese rats. The extract also indicated in vitro antioxidant effects. The phytochemical analysis revealed the presence of 28 bioactive compounds in the extract. The anti-obesity effects, antioxidants activities, cognitive-enhancing effects and the improved locomotor and exploration-like behaviors could be attributed to the phytochemical compounds present in the plant extract. The present study, therefore, scientifically validated the traditional use of this plant and generated data that can serve as guide in the recruitment of the extract as a potential candidate for the synthesis of a new effective drug against obesity and associated complications. However, there is a need for bioassay-guided fractionation of bioactive compounds in Gnidia glauca. Besides, it is recommended to conduct comprehensive toxicity studies to establish the safety profiles of Gnidia glauca.
Antibacterial Efficacy and Safety of Selected Kenyan Medicinal Plants
(2013-08-15) Abiba, Alfred Ogao
Many disease-causing organisms have become resistant to conventional antibiotics. The toxicity and side effects of conventional drugs have also become increasingly unmanageable, while their costs are prohibitive. It has therefore become necessary to continue searching for alternative medicines to treat such diseases. The possibility of developing pharmaceutical industries using local raw materials should be looked into critically so that the cost of drugs can be affordable to the local people. This study involved screening of various medicinal plants commonly used by herbal medicine practitioners for bioactive compounds against bacteria. Standard bioassay methods were employed throughout this study. They included preliminary screening bioassay against human pathogenic bacteria strains using Agar Disc Diffusion method, Minimum Inhibitory Concentration (MICs), Minimum Bactericidal Concentration (MBCs), Time kill kinetics, phytochemical determination methods and one dose in vivo toxicity tests using mice. Hexane, dichloromethane, acetone and methanol extracts of ten (10) medicinal plants: Dichrostachyus. cinerea, Combretum molle, Euclea divinorum, Ficus sur, and other five plants were screened by preliminary bioassay against nine (9) human pathogenic bacteria strains (E. coli, ATCC 25922 S. aureus ATCC 85923, Pseudomonas aeruginosa NCTC 10662, Escherichia coli, Shigella flexinery, Pseudomonas aeruginosa, Staphlococcus aureus, Shigella dysenteriae and Klebsiella hospital isolates) using agar disc diffusion method. Acetone, methanol extracts of D. cinerea and C. molle showed remarkable inhibitory activity against all nine human pathogenic bacteria. Acetone and dichloromethane of E. divinorum and F. sur showed activity against all human pathogenic bacteria except P. aeruginosa and klebsiella. All extracts of six (6) plants were inactive against the test human pathogenic bacteria. MICs of acetone and methanol extracts of the four (4) plants D. cinerea, C. molle, and dichloromethane and acetone extracts of E. divinorum and F. sur were active against the test bacteria. MIC results showed that acetone and methanol extracts of D. cinerea, and C. molle gave very good low MICs ranges (0.3-2.5mg/ml), dichloromethane and acetone extracts of E. divinorum and F. sur gave MICs ranging between 7.5-100mg/ml. MBCs of acetone and methanol extracts of D. cinerea, and C. molle were as low as 0.3mg/ml while the highest being 5mg/ml. Phytochemical determination showed that both methanolic and acetone extracts of D. cinerea and C. molle contained alkaloids, tannins, steroids and triterpenoids, flavone glycones, anthrocyanins and reducing sugar. Kill kinetics studies of the bioactive organic extracts on the tested bacteria indicated that acetone extracts of D. cinerea, acetone extracts of C. molle, methanol extracts of C. molle, methanol extracts of D. cinerea at 4, 6 and 8mg/ml against Staphylococcus aureus ATCC 85923, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa NCTC 10662, displayed dose and time dependent rapid kinetics of the bacterial killing. Because the toxicity of a drug to the bystander host cells could render it unsuitable for therapeutic purposes, the toxicity of the active plant extracts against the tested bacteria was assessed. The reduced growth rate, organ weights, white and red blood cells counts, plus increased levels of biochemicals in the serum in plant extract treated animals relative to that of the controls, indicate that these extracts contained constituents with toxic effects on them. Such constituents include some of the phytochemicals present in these extracts. The mineral content may also cause toxicity but this was not the case with the measured minerals since their levels were below the recommended daily allowance except for potassium which was 67 to 141 times the recommended daily allowance.
Antidiabetic activities of ethyl acetate and aqueous extracts of pappea capensis, senna spectabilis, maytenus obscura, ocimum americanum and launaea cornuta
(2014-08-18) Karau, Geoffrey Muriira
Pappea capensis, Senna spectabilis, Maytenus obscura, Launaea cornuta and Ocimum americanum have been used traditionally in the management of several diseases including diabetes mellitus but their efficacy and safety after long term use is not scientifically evaluated. The aim of this study was to determine in vivo hypoglycemic activity and safety of aqueous and ethyl acetate extracts of leaves and stem barks from plants in male BALB/c mice. The extracts were orally screened for their hypoglycemic activity in alloxan induced diabetic mice using a glucometer. The safety of these extracts was studied in mice orally administered with 1g/kg body weight daily for 28 days by monitoring the changes in body weight, hematological and biochemical parameters. Mineral composition of the plant powders were estimated using energy dispersive X-ray fluorescence system (EDXRF); vitamins were estimated using HPLC system; while the types and quantities of phytochemicals present were assessed using standard procedures. Individual volatile phytochemicals in the extracts were determined using GC-MS system. Proximate composition of the dry plants parts powers was estimated using standard procedures while the energy content was determined using the Atwater factor. Oral administration: of both the leaf and stem bark ethyl acetate and aqueous extracts of P. capensis, S. spectabilis, M. obscura, L. cornuta and O. americanum in doses of 50, 100 and 200 mg/kg body weight lowered blood glucose; of the three tested doses of aqueous leaf and stem bark extracts of P. capensis and aqueous leaves extracts of M. obscura could not significantly alter the blood glucose levels in alloxan induced diabetic male BALB/c mice; of the aqueous extracts of L. cornuta at 50 and 200 mg/kg body weight dose raised the glucose levels beyond that of the diabetic control mice. Oral administration of aqueous leaves extracts of P. capensis, and O. americanum and ethyl acetate leaves extracts of S. spectabilis at 1 g/kg body weight daily in mice for 28 days significantly reduced the weekly body weight gain. The same oral dose of P. capensis (L and SB), S. spectabilis (L and SB), M. obscura (L and SB), L. cornuta and O. americanum altered the red blood cell count, hemoglobin levels, packed cell volume, mean cell hemoglobin concentration, mean cell volume, platelets; white blood cell count and their differential counts; altered the levels of blood urea nitrogen and the activities of alanine and aspartate aminotransferases, alkaline phosphatase and creatine kinase. The plants powders contained phenols, tannins, saponins, flavonoids, alkaloids, terpenoids, phylobatannins, cardiac glycosides, sterols, fatty acids and reducing sugars; vitamins C, E, B1, B3, retinol, β-carotene, lycopene and cryptoxanthin; minerals selenium, iron, zinc, copper, chromium, manganese, vanadium, molybdenum, cobalt and heavy metals nickel, aluminium, lead and mercury. The observed hypoglycemic activity and/or slight toxicity in the bioactive plants extracts could be associated with the phytonutrients and minerals present in these plants. This study recommends use of safe plants with antidiabetic activity as herbal remedies
Antidiabetic Properties and Safety of Aqueous Extracts of Triticum Aestivum, Hordeum Vulgare, Urtica Massaica and Cynanchum Viminale in a Rat Model
(Kenyatta University, 2021) Kimani, Njoroge Gideon; Eliud MN Njagi; Nicholas . K. Gikonyo; Mathew P. Ngugi
The primary goal in the management of diabetes mellitus is to realize normoglycemia as much as possible. In conventional medicine, oral insulin secretagogues and parenteral insulin are used as hypoglycemic agents. However, they have known side effects such as insidious hypoglycemia, lactic acidosis, liver injury and neurological deficit. On the other hand, numerous phytotherapeutics that have been used in traditional, complimentary or alternative medicine for the treatment of diabetes have not been evaluated for their effectiveness and or their toxicity effects. The objective of this study was to evaluate the in vivo glycemic and toxicity effects of aqueous extracts of Triticum aestivum, Hordeum vulgare, Urtica massaica and Cynanchum viminale. Diabetes was induced by intraperitoneally administering 10% alloxan monohydrate into Wistar rats. Rats with fasting blood glucose levels above 200 mg/L 72 hr post alloxan administration were used in this study to evaluate efficacy of doses of aqueous plants extracts against glibenclamide and insulin as reference drugs. Toxicity studies were done by oral or intraperitoneal administration of doses of aqueous plant extracts for 28 days. The rats were euthenized and blood taken for hematological and biochemical studies. Gross and relative organ weights were taken. Presence of minerals, phytonutrients and phytochemicals in the plants extracts was also established. A p < 0.05 was consindered statistically significant. The results obtained in this study indicates that both orally and intraperitoneally administered aqueous plants extracts used in this study exhibited varying degrees of blood glucose lowering effects. When orally administered, all the plants extracts did not have significant different effect on cardiac and pancreatic systems, liver and kidneys relative to the control. Significant variations in some gross organ and relative organ weights between the extracts administered and control rats though observed were not supported by haematological or biochemical changes hence not pathologically associated. However, statistically significant effects were recorded when some of the plants extracts were intraperitoneally administered compared to the controls. Flavonoids, alkaloids, saponins, steroids, cardiac glycosides, minerals and vitamins were found to be present in the aqueous plants extracts. In conclusion, the aqueous plants extracts evaluated in this study have demonstrated blood glucose reduction properties and validates their use in control and mitigation of diabetes mellitus. Further, results obtained on phytonutrients and bioactive secondary metaboloites assay indicate the presence of various functional groups. The synergistic activities of the various compounds present in the aqueous plants extracts in this study are attributable to the plant’s observed blood glucose lowering effects. When orally taken, none of the logarithmic doses of either of the plants extracts demonstrated any toxicity effects while some of the plants extracts exhibited toxicity when intraperitoneally administered. Thus, based on the findings of this study, continued use of the plants extracts and following proper monitoring and evaluation protocol in management of diabetes mellitus is recommended. However, caution should be observed in intraperitoneal administration of some of the extracts. Further isolation and structural characterization of the active constituents of phytochemicals of the plants and ellucidation of the actual mode of action is recommended. Translational clinical reseach is equally recommended on the background of the data obtained in this study to facilitate advances and the integration of the studied alternative botanical therapies for treating diabetes into modern medicine.
Antimicrobial efficacy of selected medicinal peanuts used by Kenyan herbal doctors
(2012-05-07) Okemo, P. O.
Herbal medicine is practiced by many countries of the world including Kenya, but scientific data to support the efficacy of herbal preparations has been lacking. Sixteen indigenous plants used by herbal doctors in Kenya were chosen from seven provinces and screened for antimicrobial activities using the disc diffusion method for preliminary selection. The most active plants, Entada abssyinica (Stem bark), Terminalia spinosa (Stem bark), Harrizonia abyssinica (roots), Ximenia caffra (roots), Azadirachta indica (stem bark and laves), and Spilanthes mauritiana (flowers and roots), were chosen for subsequent analysis, to determine efficacy and to identify a source of new possible antimicrobial agents. These plants were soxhlet extracted with methanol and tested for bioactivity. In the bioassay, the microtitre broth dilution method and the agar dilution method were compared to determine suitability for use. The microtitre method was found superior with a mean of 0.856 mg/ml compared to 2.958 mg/ml for the agar dilution method. Subsequently 110 strains of pathogenic bacteria from six genera were tested for activity using the microtitre broth dilution method. Their minimum inhibitory concentration (MICs) in mg/ml and minimum bactericidal concentrations (MBC's) in mg/ml were determined as a measure of their efficacy. The extracts had a bacteriostatic effect on Gram-negative bacteria and bactericidal effect on Gram-positive bacteria. Bacteria with special significance and some protozoa were examined separately. Mycobacteria species which were tested because of tuberculosis upsurgence in Human Immunodeficiency virus victims were found to be resistant to the extracts. Helicobacter pylori no known cure was killed by T. spinosa extracts (MIC range 62.5 - 500 g/ml). A protozoa, Acanthamoeba castellanii which causes granulomatous brain lesions has no known cure but responded to extracts of E. abyssinica, T. spinoss, X. caffra, A. indica and S. mauritiana when tested in vitro. Strains of pathogenic fungi from 2 genera Candida and Aspergilus were tested and found to be sensitive to more than 60% of the extracts used. As a result of this evaluation, four plant extracts E. abyssinica (stem bark), T. spinosa (stem bark), X. caffra (roots), and A. indica (stem bark) were found substantially bioactive. Candida albicans (ATCC 90873), E. coli (ATCC 29213) and a potent -lactamase producing organism, Pseudomonas aeruginosa (ATCC 27853), were used to perform time kill kinetics studies, in an effort to assess the rate and extent of the destruction of the said microorganisms by the above plant extracts. The mode of action was investigated by the kill kinetics experiments using an electron microscope. By this technique, any morphological changes in the microbial cell structure with continued exposure to the extracts would be detected. Results showed cell wall malfunction leading to failure to form septa and lysis of several microbial cells. Finally, the plant extracts were screened for the presence of coumarins, tannins saponins and other classes of compounds, which were considered active plant constituents. T. spinosa contained 75% of the classes of compounds screened, S. mauritiana 60%, H. abyssinica 56.3% and A. indica 56.3%.
Antiretroviral resistance and genetic diversity of human immunodeficiency virus among antenatal clinic respondents on nevirapine from North-Rift Kenya
(2011-07-11) Kiptoo, Michael Kibet
Mother-to-child transmission (MTCT) of HIV-1 is responsible for infection of hundreds of thousands of infants every year. It is estimated that 600,000 newborns are infected yearly worldwide, with MTCT accounting for 90% of these infections. Human immunodeficiency virus (HIV) can be transmitted from mother-to-child at various stages of pregnancy including in utero and intra partum. A number of feasible and effective interventions to reduce MTCT among women of child hearing age are available. These interventions include prevention of primary HIV infection, avoiding unwanted pregnancies among HIV positive women, reduction of transmission from infected mothers to infants during pregnancy, labour, delivery and breathfeeding through provision of voluntary counselling and testing (VCT) services, antiretroviral therapy (ART), safe delivery practices, and breast milk substitutes. However, these approaches are not always possible in resource-poor countries. The use of antiretroviral (ARV) drugs, in particular revirapine, zidovudine and zidovudine/lamivudine combination, has been studied in both developing and developed countries. Although these studies have shown reduction in transmission of HIV, concerns regarding the development of drug resistant strains have been raised. The Ministry of Health in Kenya has implement nevirapine regimen to reduce MTCT in the public health facilities. This study aimed to investigate drug resistance in an MTCT setting in Kenya. A total of 309 HIV seropositive pregnant women taking part in the prevention of mother of child transmission of HIV (PMTCT) programme in three hospitals, namely, South Nandi Hills, Kapsabet, and Kitale district hospitals were enrolled in this study. A structured questionnaire was used to collect demographic information. Venous blood was collected into vacutainer tubes containing EDTA as anticoagulant. The enumeration of T-lymphocytes was carried out by flow cytometry and viral load was determined by nucleic acid amplification. The proviral HIV DNA extracted from peripheral blood mononuclear cells (PBMCs) was sequenced to determine the drug resistance associated mutations and HIV-1subtypes. The significance of associations was investigated by chi-square test and odds ratios. The HIV prevalence among the pregnant women was 6.7% (309 of 4638). The majority (85%) of the women visiting the antenatal clinic were not aware of their HIV status. Sixty percent (60%) of pregnant women had a CD4 count of more than 350cells/mm3 . The HIV transmission rate was 6% (4 of 59 infants). Drug resistance associate mutations were detected as minor population except in one mother-child pair where major populations were found. Nevirapine drug resistance was detected in 19.4% (7 of 36) and 100% (3 of 3) of the women and infants tested respectively. Even though the women had not been exposed to nucleoside reversed transcriptase inhibitors (NRTIs), drug resistance associated mutations were detected in 8 mothers (22.2%) as minor populations. The major circulating HIV-1 subtype in North-Rift Kenya was identified as A1 (50% and 71.8%) based on the env (C2V3) and pol (RT) regions respectively. Human immunodeficiency virus type 1 subtypes D (12.8%), C (10.3%), A2 (2.6%) and G (2.6%) were also detected based on sequencing of the pol region. Drug resistance outcomes in mothers and infants should be considered as an important secondary end point in PMTCT assessment.
Application of Taxonomic and Dna Barcoding Techniques in Identifying Commonly Traded Herbal Plant Species in Selected Counties, Kenya
(Kenyatta University, 2022) Mwaura, Ann; Joseph Kamau; Omwoyo Ombori; Barbara Gravendeel
Over eighty percent of the world’s population depends on herbal products for their basic health care needs. However, this widespread popularity is counterbalanced with the lack of relevant research to authenticate the source and purity of the traditional herbal products. There exists an extensive history on use of herbal products but lately there are concerns on authenticity and safety of these products. The objectives of the study were: determine plant species commonly traded as herbal products, assess the products using taxonomic and DNA barcoding techniques, application of DNA barcoding technology in reference barcodes generation, and determine if the plant herbal products are accurately labeled. The study was carried out in selected markets in three counties in Kenya (Kajiado, Narok and Nairobi). Data collection involved use of structured questionnaires, species observation, taxonomic and DNA barcoding techniques. Structured questionnaires were administered to individual herbalists and complementary interviews with key herbalists to enrich the data collected. The local and common names were recorded and later translated to scientific names using para-taxonomists and previously published data. Scientific names listed on labels of packaged plants products were as well recorded. The generated species list guided the collection of voucher specimens and creation of a reference library of DNA barcodes. DNA barcoding technology was used to authenticate the herbal product samples. The common single species samples were analyzed using Internal Transcribed Spacer (ITS) and ribulose -1,5-bisphosphate carboxylase Large subunit (rbcL) DNA barcoding markers while metabarcoding was applied in multi-species samples using nrITS2 marker. The study revealed that 86 plant species belonging to 43 families were traded as herbal products in the regions. Most of these plants were shrubs (66 %) traded as stem and bark. Majority of herbal plant species belong to Fabaceae, Apocynaceae and Rhamnaceae families. The DNA technology successfully generated barcode sequences that were used as reference for herbal products identification. Single species samples were found to be more authentic compared to the mixed species samples as most species were identified to species level as listed on the label. Adulteration in single species samples was mainly by substitution with closely related and/or looks alike species, which raises concern on value and quality of the herbal products sold in the studied counties. Kajiado County had more authentic samples in comparison to Narok and Nairobi. DNA metabarcoding technology was successful in identification of mixed species sample at 92 % to species level and 4 % each to genus and family level. This study has made the first attempt to identify herbal plant species traded in selected markets in Kenya using DNA barcoding technology in combination with morphological and literature methods. Authentication using DNAbarcoding provided a more reliable and accurate results compared to morphological identification. DNA barcoding should therefore be applied in identification and verification of herbal products. DNA barcodes successfully generated and deposited in National Centre for Biotechnology Information (NCBI) Genbank form crucial reference data for future studies and can be used as a baseline library for useful medicinal plants of Kenya.
An assesment of the use of botanical extracts and pheromes for the off-host and on-host control of amblyomma variegatum tick
(2012-01-12) Toure, Alioune
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 Headwater, 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 control, which are environmentally friendly, relatively cheap and which involve farmers directly. In this regard, the purpose of this study investigated the potential of pheromones in attracting ticks to a trap off-host and toxicating them with Neem products and the repulsion of ticks on-host using repellent plant. The use of pheromone components comprising Attraction-Aggregation-Attachment Pheromone (AAAP), 1-octen3-ol and 2,6-dichlorophenol to attract A. variegatum to traps containing botanical extracts on the vegetation was explored. The possibility of enhancing attraction of ticks to AAAP with 1-octen-3-ol and 2,6dichlorophenol was first investigated in a T-tube olfactometer in the laboratory. Whereas males were attracted to increasing proportions of 1-octen3-ol, females were repelled. A combination of 8 ng of 1-octen-3-ol with 1.1 mg of AAAP was adopted as an optimum for the attraction of both sexes, enhancing the attraction of ticks by 20% (p<0.0001). Unlike 1-octen-3-ol, 2,6dichlorophenol did not improve the attraction of A. variegatum in the laboratory (p=0.0667). In the field, the attraction of A. variegatum to different doses of AAAP+1-octen-3-ol combination from various distances was investigated. The longest distance from which ticks were significantly attracted was 7 m. The effects of continuous and intermittent release of carbon dioxide (CO2) on the performance of AAAP and 1-octen-3-ol in attracting ticks in the field were also investigated. The results showed that CO2 increased the range of attraction to 8 m and the continuous and the intermittent release of CO2 were not significantly different. The efficacy of traps treated with Neem Cake Extracts (NCE) and baited with AAAP, 1-octen-3-ol and CO2 was evaluated. The attraction to the traps as well as the modality of A. variegatum were significant (p<0.0001). The modality of attracted ticks was dependent on the concentration of NCE and the time of exposure. 98% modality was recorded for a concentration of 30% of NCE. The volatiles of two of the predilection feeding sites of A. variegatum (scrotum and lower dewlap) were tested against the odour of the ear. The scrotum and the lower dewlap were found very attractive to the ticks. The possibility of using plant extracts with repellent properties in reducing the number of ticks arriving and attaching at predilection sites was also investigated. Boscia senegalensis, Ocimum suave and Ocimum kilimandscharicum were tested as repellents. Ocimum kilimandscharicum was found to repel adult A. variegatum by 33%. This technology of using botanical traps baited with pheromones and CO2 as well as repellent plants could be improved and can be transferred to farmers where it can be incorporated in an Integrated Tick Management Strategy.
Assessment by performance attributes of indigenous egg parasitoids (hymenoptera: trichogrammatidae for biocontrol of african bollworm (helicoverpa armigera) in Kenya
(Kenyatta University, 2004-08) Kalyebi, A.
Trichogrammatid egg parasitoids are used extensively for the control of several lepidopteran pests in many areas of the world. They ar~he most promising biological control agents for inundative releases against the African bollworm Helicoverpa armigera, an injurious pest of several agricultural crops in Kenya and elsewhere in Africa. To enhance their potential impact in Kenya as well as eastern Africa, collections of indigenous species/strains (Trichogramma sp. nr. mwanzai and Trichogrammatoidea sp. nr. lutea from low altitude, Trichogramma sp. nr. mwanzai and Trichogrammatoidea sp. nr. lutea from medium altitude and Trichogramma bruni and Trichogrammatoidea sp. nr. lutea from high altitude) were made from different altitudes in Kenya and were evaluated following different criteria to select potential candidates for use against H. armigera. The major focus was their adaptation to a range of temperature and humidity \regimes. The criteria included functional response, lifetime parasitism and development and population growth characteristics at six temperatures (10, 15, 20, 25, 30 and 35°C) and two humidity regimes (40-50 and 70-80%). Preference of parasitoids for target pest and relative suitability for development among five lepidopteran hosts was also \ investigated, in addition to testing their capacity to attack H. armigera eggs occurring on two host plants (tomato and okra) in laboratory and field experiments. Functional response studies revealed that temperature affected parasitisation rates of the strains significantly, while relative humidity did not. Trichogrammatoidea sp.nr. lutea from high altitude, Trichogramma sp. nr. mwanzai from low altitude and T. sp. nr. mwanzai from medium altitude showed higher parasitism across the widest temperature range. There was no relationship between source altitude/climate and performance of the strains at the temperatures tested. Temperature and humidity interactions affected lifetime fecundity and progeny production. The highest parasitism at the two humidity levels was at 30°C for all the strains. The interaction of the two factors also affected adult longevity, which was longer at the lower than higher humidity. Survival followed a type l-survivorship curve at lower temperatures and a type III survivorship curve at the higher temperatures. These studies revealed that T sp. nr. mwanzai from both low and medium altitudes and T sp. nr. lutea from medium altitude appear as promising candidates for augmentative biocontrol of H. armigera. Temperature and humidity interactions also affected the population growth and development of parasitoids although temperature appeared to be more important. Developmental time was inversely related to temperature. The intrinsic rate of increase was found to increase with increasing temperature up to 30°C. The finite rate of increase also followed the same trend. The net reproduction rate also increased with increasing temperature up to a maximum at 30°C. Both net reproduction and intrinsic rate of increase were higher at the lower humidity. Temperature negatively affected generation time ofparasitoids regardless of the humidity level. Host acceptability studies showed that all the six species/strains did accept all the tested host species, although acceptance levels varied among strains and hosts. Most species/strains showed greater preference for noctuids over pyralids and yponomeutids. Suitability of hosts for progeny development varied from one species/strain to another. The different species/strains did not show significant differences in parasitising eggs of H. armigera when placed on two host plants, namely tomato and okra. From these studies, T. sp. nr. mwanzai CM), T. sp. nr. mwanzai CL) and T. sp. nr. lutea (M) offer great potential as candidates for augmentative biocontrol of H. armigera in Kenya.
Assessment of Mangrove Phenology and the Role of Insect Pollinators in Fruit Production at Nyeke and Michamvi Mangrove Forests, Zanzibar
(Kenyatta University, 2016-05) Ali, Abdalla Ibrahim
Mangrove forests are evergreen estuarine and open systems which receive nutrients, fresh water and sediments from terrestrial environments. They vary both in their salinity tolerance and the degree to which salinity may be necessary to maintain their growth and competitive dominance. Mangroves grow throughout the tropics wherever the average monthly minimum temperature is at least 200C. The ecological importance of mangroves are due to the ecosystems’ ability to maintain marine life, their high productivity and role in supplying organic material to other coastal marine ecosystems as reported by many studies. Mangroves trees have been proven to be very important in the mangroves ecosystem. Anthropogenic activities have been shown to be the primary cause of mangrove depletion worldwide. Rising mangroves forest destruction has negatively impacted on pollinator diversity and fruit set significantly. However, little is known about the magnitudes of these issues in East Africa. This research was therefore designed to assess diversity and abundance of mangrove insect pollinators and their role in fruit set in four mangrove species at Nyeke and Michamvi mangrove forests, Zanzibar. The study was conducted in two mangrove sites in South region of Zanzibar, Nyeke mangrove forest located between 60 19’ and 60 24` S and 390 25` E, and Michamvi mangrove forest located between 60 14’ S and 390 49’ E. The distance between the two sites is approximately 25km. Four mangrove species which are pollinated by insects (Rhizophora mucronata, Bruguiera gymnorhiza, Ceriops tagal and Avicennia marina) selected from Nyeke and Michamvi mangroves forests were used in the study. The reproductive phenology, reproduction relationships of mangroves, pollinator species diversity and richness, and effect of pollination on fruit set were investigated. The study found that reproductive phenology varied among species and sites. The peak fruit set varied among species and sites. There was a positive relationship between temperature and reproduction but not with rainfall and relative humidity. In both sites the findings showed a weak relationship between fruit set and number of fruits. The study also revealed that increase in number of insect flower visitors and visits did not result in increased fruit sets. However, increase in number of flowers increased the number of insect flower visitors and visits. A total of 18029 insect flower visitors representing 70 species in 7 orders and 40 families were observed visiting flowers of the four mangrove species in both sites. Family Apidae of the order Hymenoptera was the most common and insects of this order were found in all four mangroves species. Apis mellifera was the most dominant flower pollinator for Bruguiera gymnorhiza, Ceriops tagal and Avicennia marina. Hypotrigona gribodoi was predominantly found on RM and is potentially the flower pollinator of this species. Higher number of Apis mellifera 721 (32.2%) was recorded in Bruguiera gymnorhiza at Nyeke site. Bagged experiment that prevented most pollinators accessing the flower, showed a high percentage of flower abortion and lowest fruits produced than other treatments in this study. A. marina had confirmed lower fruit set compared to the other species. Pollen Supplement (PS) (hand cross pollination) produce higher percentage of fruits set and fruits in some mangroves species in both sites. This not only shows that additional pollen enhances fertilization but also that pollination is necessary for fruit production. The study concludes that, in depth research on various variables of mangroves including inventory of pollinators, biodiversity, social economic significance, potential threats and phenology for other species and climate alteration are important for strengthen biodiversity conservation and mitigation.
Banana Rhizosphere Microbial Diversity, Low-Cost Tissue Culture Bananas (Musa spp.) Micropropagation, Genetic Fidelity and Acclimatization Using Arbuscular Mycorrhizal Fungi
(Kenyatta University, 2024-05) Wahome, Caroline Nyawira
Banana production in Kenya predominantly involves smallholder farmers, yet current yields fall short of meeting local and international market demands due to constraints faced by these farmers among them being soil health and lack of clean planting materials. To address this issue, the study assessed banana cultivation practices in Kisii, Nyamira, and Embu counties, aiming to understand strengths and challenges within these regions. In this study, rhizospheric soil physicochemical properties and the diversity of microbial communities was assessed, shedding light on soil health status. Furthermore, the efficacy of a cost-effective micro-propagation technique for local banana cultivars was determined, considering contamination susceptibility and acclimatization efficacy of arbuscular mycorrhizal fungi on micropropagated banana plantlets. The study revealed a reliance on ineffective traditional propagation methods, with over 30% of the smallholder farmers facing a banana seedlings shortage. The soil physic-chemical parameters indicated signs of degradation, with low pH and nutrient deficiencies raising concerns with Embu County having the lowest pH measured (4.43). Soil metagenomic studies by NGS showed that proteobacteria and basidiomycota were the two most prevalent bacterial and fungus divisions, respectively. Based on the Shannon diversity indices, the highest bacterial and fungal community diversity was in soil samples obtained from Embu County and Kisii County respectively. To evaluate efficacy using low cost tissue culture technology, selected banana cultivars were utilized and results indicated the highest survival rate of 100 % in Kiganda, Muraru and Kienyeji banana cultivars established in BAP and IAA. Ng’ombe cultivar best responded to low cost micropropagation with the highest shoot establishment (80.5 %) and shoot emergence rates (75.5 %) producing the highest number of shoots per culture (10.61). To investigate clonal fidelity of the tissue culture plantlets Inter Simpler Sequence Repeats (ISSR) and the research demonstrated genetic homogeneity in banana seedlings generated via low cost tissue culture to the mother plant. During the micropropagation process the presence of bacterial and fungal contaminants in the tissue culture laboratory was noted with the most predominant bacterial and fungal contaminants being Microccoccus luteus and Cladosporium sp respectively. Additionally, broad-spectrum antimicrobial agents nalidixic acid (30 µg) and carbendazim+ triadimefom (0.3 µg and 0.6 µg) exhibited 100% inhibition rates against these contaminants. To determine the response of the micropropagated plantlets to AMF acclimatization, it was observed that Kiganda cultivar responded best to Rhizophagus irregularis which showed the highest recorded biomass at 0.97. There is need to emphasize collaborative efforts among various stakeholders in establishing sustainable practices. Additionally, low-cost TC is a viable tool for producing disease-free seedlings and intergrating antimicrobial agents is recommended to minimize contamination risks. Finally, the use of AMF treatment in acclimatization with further research needed for validation across different agroecological conditions. These recommendations aim to enhance productivity, sustainability, and resilience in banana farming systems.
Behavioural responses of rhipicephalus appendiculatus neumann 1901 and rhipicephalus evertsi, neumann 1987 (Acari: ixodidae) to host and non-host semiochemicals
(2012-05-02) Noel, Sika Fra Kutua
On-host observations and laboratory behavioral assays were undertaken to investigate the role played by semiochemicals in the location of feeding sites by unfed adults of Rhipicephalus appendiculatus Neumann and Rhipicephalus evertsi Neumann. The semiochemicals were derived from the host ear and anal region of bovine cattle and from conspecifics. The potential of host-derived allomones from unpreferred feeding sites and extracts of a tick repellent plant, Ocimum suave Willd as disrupting factors to on-host orientation by the two tick species to their target sites were also assessed. Orientative behaviour of R. appendiculatus on host was characterized by stereotyped sequences of behaviours, which included stationary/scanning phase, random search, directional movement and arrestment closer to and at the site source. Patterns of tick migratory paths to their respective feeding sites were characterized and quantified in both species. These were made up of runs with intermittent stops, all producing curvilinear tracks. The results of locomotory activities demonstrated a high promotion of completion of paths to the preferred feeding sites, along with high success rates of feeding site location (67.5-90.0% for R. appendiculatus; 69.8-85.6% for R. evertsi). The results also showed variations in mean walking speed between sexes, species and release points on the host. Mean velocity for males and females averaged 0.09 and 0.41cm/min in R. appendiculatus and 0.24 and 0.58cm/min in R. evertsi. Assays of tarsi painting on R. appendiculatus and R. evertsi showed that these were capable of discriminating their respective feeding sites using olfactory cues. In both species, tarsi-coated individuals were less able to orient toward or locate efficiently the relevant anal or ear sites (P<0.001). In situ and laboratory assays have implicated primarily site-borne stimuli as mediating factors in this orientation. This kairomone-driven mediation appears to be enhanced by intraspecific signals emitted by feeding ticks present at the feeding site, since ear sites loaded with live ticks (P<0.01) or rinses of fed ticks (P<0.01) were more attractive, although not significantly, compared to control tick-free ears. Specific behaviours leading to the location and finding of the feeding sites namely: arousal, activation, arrestment and aggregation in response to olfactory stimuli were examined. Arousal tests (in a Y-olfactometer) on R. evertsi and R. appendiculatus exposed to odour extracts from ear and anus resulted in scanning and residence response patterns that correlated with the stimulatory or inhibitory nature of each extract. Release of ticks in situ resulted in the activation of the tick by the host odours after a short latent period which decreased with decrease in distance from the feeding site. Likewise, walking speed of both species resulted in gradual decrease and eventual arrestment in the proximity to the feeding site. Tick velocity correlated with distance and arrestment was more evident at close range (25 cm away from any site). On the other hand, artificial substrates impregnated with feeding site materials (anal or ear extracts) caused walking arrestment of the relevant species (P<0.01) and evoked in the tick characteristic klinokinetic path patterns on the odourized arena. Significant aggregation responses of male and female ticks of R. appendiculatus occured on calved scrotum smeared with hexane rinses obtained from fed male and female ticks (P<0.05). The aggregation responses increased slightly with increasing concentrations of the rinses. The aggregation factor remains to be characterized. Olfactometric assays showed that extracts in washings from various body parts, namely belly/axillae, neck/dewlap and leg were less or unattractive to the adults of R. appendiculatus. On the other hand, ear and anal extracts elicited strong attraction to the adults of R. appendiculatus (P<0.001) and R. evertsi (P<0.001), respectively, in a dose-dependent fashion. Nymphs and larvae of R. appendiculatus, in contrast, were significantly repelled (P<0.01). Trapped volatiles from the host were significantly attractive to the ticks than the washes (P<0.001), but the blend of the two was m ore attractive compared to the individual extracts. The additive effect of the two suggests a dual kairomonal set of components comprising short-range/contact signals and volatile components which mediate feeding selection in this tick. Cross-assays involving the use of extracts from a site preferred by one tick species showed strong repulsive effect on the other species. Thus, a 'push-pull' mechanism has been proposed to explain highly successful tick orientation and feeding site finding on host and the difference in this regard in these two tick species. The 'pull' component is made of interspecific signals from the preferred sites augmented by intraspecific signals from successfully feeding ticks. The 'push' component comprised of repellents from unpreferred site, which ensures that the tick does not mistakenly orient in that direction. Repellent extracts from unpreferred feeding host sites and the essential oil of Ocimum suave (a tick repellent shrub) were used to study possible disorientation of R. appendiculatus and .R.. evertsi toward their respective feeding sites. Cattle repellent extracts and the essential oil of O. suave applied as smears to serve as barriers across tick migratory paths to the feeding sites, were disruptive at all concentrations tested. The host extract (P<0.05) as well as the plant extract (P<0.001) significantly reduced the success of R. appendiculatus and R. evertsi to reach their target site. Ear and anal extracts were found to have short-lived persistent effect on the target ticks, unlike the essential oil of O. suave, which was effective for several days during the test period. This may be attributed to differences in concentration rather than intrinsic activity. These results suggest possibilities of manipulating the host and feeding site location behavior of ticks on-and- and off-host using appropriate semiochemicals as tactics in the management of tick populations.
Biodiversity of wild silkmoths (lepidoptera) and their potential for silk production in East Africa
(2012-04-11) Kioko, Esther N.
Wild silk production is a unique eco-friendly agro-practice with the potential for environmental amelioration, employment and income generation. The present utilisation of wild silkmoths hardly accounts for 5% of the rich potential and most of the production is from the Far East countries. The steadily growing demand for silk in all consuming countries provides excellent opportunities for any country to venture into wild silk production. In East Africa, wild silk production would be ideal for generation of supplementary income to resource-poor farmers, reducing the destruction of their host plants, promoting conservation of the silkmoths and at the same time permitting positives utilisation of these biology resources by the local community. In Kenya, Uganda and Tanzania, 58 wild silkmoth species of three lepidoptera families, Saturniidae,Lasiocampidae and Thaumetopoeidae were recorded. These species diversity varied in these three families. In family Saturniidae, 19 species were recorded in 6 genera, 33 species in 17 genera in the family Lasiocampidae and 6 species in one genus in family Thaumetopoeidae. Two case studies carried out on the distribution of Bridelia micrantha (Hochst) Bail (Euphorbiaceae) the hostplant of the wild silkmoth Anaphe panda (Boisduval) (Thaumetopoeidae) and Sclerocarya birrea, (A. Rich.) Hochst. (Anacardiaceae) the host plant of the silkmoth Argema minosae (Boisduval)(Saturniidae) revealed that the hostplants are widely distributed in the three East African countries. In western Kenya, a ground survey confirmed the availability of B. micrantha with 84% of the farmers having it in varying numbers in their land. A questionnaire distributed to 50 local farmers near the Kakamega forest responded positively (98%) to the potential of initiating wild silk farming as an extra source of income. Further phenological studies on selected species, Gonometa sp. (Lasiocampidae) at Nguni, Mwingi and A. mimosae at Sultan Hamud, Makueni, Kenya showed that these silkmoths have two generations each year. The adult moth emergence synchronised with the hostplant state, which was also influenced by weather conditions. A high larval mortality of the silkworms of both species was observed in the field. The overall mortality from the first instar to the onset of cocoon spinning for Gonometa sp. reared on caged Acacia elatior Brenan was 82.9% during the short rains of 1996 and 78.9% during the short rains of 1997. In A. mimosae, reared on the hostplant Sclerocarya birrea, 80.6% larval mortality was recorded during the short rains of 1997. Rearing the Gonometa sp. silkworms in net sleeves tied to the hostplant branches reduced the mortality to 23.9% In both species, the pupal stage was the longest indicating the possibility of pupal diapause. Gonometa sp. pupae observed in controlled environmental conditions in an incubator had a significantly shorter life span (87.2 + 3.6 days) compared to those observed under room condition (124.0 + 11.2 days). This is an indication that the pupal diapause in these species can be manipulated for continuous cycle of the silkmoth generations depending on the foodplant state. Predators attacking Gonometa sp. and A. mimosae in the field belonged to three insect ordes, Hemiptera, Orthoptera and hymenoptera. Formicid ants were abundant. Pentatomid bugs of the sub-family Asopinae, Maccroraphis spurcata Walker were observed in Sultan Hamud sucking fluids and killing larvae of A. mimosae. Field collected eggs and cocoons of Gonometa sp. and A. mimosae yielded hymenopteran and dipteran parasitoids. Mesocomys pulchriceps Cameron and Pediobius anastati (Crawford) were identified from the eggs of both silkmoth species. Telenomus sp. and an unidentified Encyrtidae were recorded from Am mimosae eggs. No parasitoids were obtained from A. mimosae cocoons. From Gonometa sp. cocoons, unidentified Tachinidae together with hymenopterans Goryphus sp., Eurytoma sp and unidentified Chalcidoidea were recorded. These parasitoids from the cocoons spoilt the continuity of the silk fiber by making exit holes for the adults to emerge. Cocoons of A. mimosae were not reelable but those of Gonometa sp. gave long filaments of lustrous brown silk. Females gave longer silk thread (706.34 + 222.4 m) compared to males (521.49 + 204.2 m). The mean weight of silk from females was 0.43 + 0.2 g and 0.21 + 0.10 g from males. 2,326 to 4,762 cocoons are required to make one kilogram of Gonometa sp. silk.
Bioecology and population dynamics of red spider mites( a cari: tetranychidae) on tomato in small scale production systems in Kenya
(2012-01-03) Sarr, Ibrahima
Tomato, Lycopersicon esculentum Mill. (Solanaceae) is one of the most important vegetables grown in Eastern and South Africa for local consumption and income generation by small scale farmers. Yet, yields of the crop are far below the potentials due to many factors including damage caused by red spider mites. This is aggravated by unsustainable control strategies relaying solely on highly toxic pesticides with long term harvest intervals and subsequent contamination of human and the environment. Sustainable and environmentally friendly integrated production and pest management approaches are therefore urgently required. This study aimed at providing basic information on the bioecology and the population dynamics of red spider mite, Tetranychus evansi pritchard and Baker and the two spotted red Spider mite, Tetranychus urticae Koch appeared to form the acarine complex in field tomatoes in Kenya. In laboratory life table studies, T. evansi, the most damaging red spider mite on tomatoes showed a high potential of increase at 30°c with a short overall developmental time from egg-to-adult of 8.82±0.21 days, a more female biased sex ratio of 1.75 female per male despite a low hatchability of the eggs. None of the female deutonymphs emerged at 100°c and a significantly slower overall developmental time from egg-to-adult of 55.13±2.83 days at 15°C (p<0.05) was recorded. The lower thermal developmental threshold for T. evansi was 12°C. The spatio-temporal and within plant distribution patterns of the two spotted red spider mite, T.urticae revealed the lower tomato canopy layer as the preferred zone for these spider mites. Furthermore, T. urticae was a very aggregative species. The preliminary sampling plan derived from this aggregative distribution patterns showed that a precision of 0.25 ( a ration of mean to standard error) was reasonable and still adequate for the density estimate of T.urticae adults in field tomatoes. The study carried out on the effect of the predators on T. Evansi, showed that five species of predators were associated with T. Evansi,and included; Phytoseiuhus persimilis Athias -Henriot (A cari: Phytoseiidae), Pronematus spp. (A cari: Tydeidae), Oligota spp. (Coleoptera: Staphylinidae) and Stethorus spp. (Coleoptera: Coccinellidae) However, these predators did not seem to have any impact on the population of T. evansi. An intensive regression analysis and a graphical description carried out between the T. urticae rate of increase, the plant quality, the predators and the weather data from three tomato growing seasons revealed that, the plant quality was positively associated with the rate of increase, while rainfall and temperature relative humidity interaction showed a negative relationship with the rate of increase. Further more, the stepwise regression between the rate of increase, the plant quality, the predators and the weather data showed that 40% of the variation in red spider mite numbers over the three growing seasons was explained by the biotic factors and weather condition. The population dynamics was a function of the initial level of infestion and the rate of increase
Bioecology of the new invasive fruit fly Bactrocera invadens (Diptera:Tephritidae) in Kenya and its interaction with indigenous mango-infesting fruit fly species
(2011-07-11) Ivan, Rwomushana
Bactrocera invadens Drew, Tsuruta & White (Diptera: Tephritidae), an alien invasive fruit fly species of Asian origin was first detected in Kenya in 2003. This pest has rapidly spread across sub-Saharan Africa and is currently reported from at least 24 countries. Because of its novelty status, there was no information on its biology and ecology that could aid development of management efforts. There was also evidence that B. invadens co-infested the same fruits with native fruit fly species and it was speculated that this could result in competitive displacement of native fruit flies. This study, therefore, was initiated to establish the bioecology of B. invadens in Kenya and its interaction with indigenous mango-infesting fruit fly species. The first step was to identify the most suitable temperature range for development and survival of immature stages of this pest. Studies were conducted in the laboratory at four constant temperatures of 15, 20, 25, 30 and 35°C. The longest development period occurred at 15°C (75.74 days) and was shortest at 30°C (17.76 days). The optimal temperature for survival was found to be 25°C while 35°C was the most lethal temperature. Countrywide surveys were then initiated to establish the host plants of this pest. The survey revealed that B. invadens infested fourteen plant species particularly Mangifera indica L., Musa sp. AAA and citrus [C. limon (L.) Burm. f., C. sinesis (L.) Osbeck and C. reticulata Blanco.] and the wild plants Sclerocarya birrea (A. Rich) Hochst. and Terminalia catappa L. In laboratory host preference studies, M. indica and Musa sp. were found to be the most preferred host plants among the nine cultivated plant species tested. The spatial and temporal population dynamics of this pest was also studied and revealed that three fruit fly species infested mango namely B. invadens, Ceratifs capitata (Wiedemann) and Ceraftis cosyra (Walker). The relative abundance index (RAI) of these pests in infested fruit was in the order B. invadens > C. cosyra > C capitata which was similar to the indices of adult population obtained by trapping. Percent fruit fly infestation and B. invadens fruit fly density was found to be always higher in mango on the ground than on the trees, demonstrating that mango fruits that fall to the ground serve as a major breeding site and may be a reservoir of non-immigrant B. invadens population in mango orchards in Kenya. The efficacy of the Easy, Multilure and Lynfield traps all baited with Nulure, Torula Yeast, Corn steepwater and a locally produced yeast product for trapping B. invadens was also evaluated. The multilure trap baited with torula yeast or nulure was the most attractive trap-bait combination and captured 19.7-30.3 B. invadensltrap/day and 10.54 -22.97 flies/trap/day respectively. In interspecific competition studies, there were significant differences in the larval developmental time, weight of puparia and number of adults that emerged of B. invadens, C. capitata and C. cosyra when the insects were soquentially co-infested on rearing medium at constant temperatures. When B. invadens was introduced into whole fruit before C. cosyra, the number of emergent adults of the IMa was greatly suppressed. Higher number of C. capitata adults was, however, recovered when in cross infestation with B. invadens particularly in the treatments where G capftata had a two or three days head start. This study demonstrated that the oedumisms contributing to the displacement of C. cosyra by B. invadens may be erodated with intricate interactions between resource pre-emption and fluctuations in temperature in mango agroecosystems

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