Browsing by Author "Wachira, Benson M."

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    Controlling Rate of Release of Tsetse Fly Repellent Blend byEncapsulating in β-Cyclodextrin Nanoparticles
    (Journal of Nanotechnology, 2025-05) Ratemo, Bernadatte M.; Wachira, Benson M.; Masika, Eric; Ng’ang’a, Margaret M.; Hassanali, Ahmed; Mireji, Paul O.
    Tsetse flies are major vectors of African trypanosomiasis, with devastating medical and veterinary consequences in sub-Saharan region of Africa. Insect repellents are promising tool for control of tsetse flies in the region. A four-component tsetse-repellent blend (δ-nonalactone, heptanoic acid, 4-methylguaiacol, and geranyl acetone) previously formulated and optimized was encapsulated in β-cyclodextrin for a slow controlled release. Here, we explored various methods of microencapsulating (kneading, coprecipitation, heating, or freeze-drying) tsetse fly repellent blend in β-cyclodextrin nanoparticles. We assessed release kinetics of the blends and individual compounds using gas chromatography linked with flame ionization detector and evaluated laboratory and field responses (repellence) of the flies by the encapsulated blends. We compared individual performances of releases kinetics of the encapsulated blend relative to nonencapsulated composites. Overall, kneading, coprecipitation, heating, and freeze-drying microencapsulation techniques retained 72.0%, 61.0%, 59.5%, and 57.3% of the blend, respectively. Release rates of blends in 400- and 200-microns thick polythene sachets were 6.73 and 11.82 mg/h, respectively, significantly higher (p < 0.05) than that of the kneaded encapsulated blend (5.35 mg/h). Laboratory and field responses of tsetse flies to the unencapsulated native (sachet) and kneaded encapsulated odor blends confirmed our laboratory findings. Microencapsulation technology of repellent odors can be used for controlled release of active molecules in order to give an extended protection period, potentially reducing operational cost in programs for control of tsetse flies and related insect vectors.
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    Expansions of chemosensory gene orthologs among selected tsetse fly species and their expressions in Glossina morsitans morsitans tsetse fly
    (PloseOne, 2020) Kabaka, Joy M.; Wachira, Benson M.; Mang’era, Clarence M.; Rono, Martin K.; Hassanali, Ahmed; Okoth, Sylvance O.; Oduol, Vincent O.; Macharia, Rosaline W.; Murilla, Grace A.; Mireji, Paul O.
    Tsetse fly exhibit species-specific olfactory uniqueness potentially underpinned by differences in their chemosensory protein repertoire. We assessed 1) expansions of chemosensory protein orthologs in Glossina morsitans morsitans, Glossina pallidipes, Glossina austeni, Glossina palpalis gambiensis, Glossina fuscipes fuscipes and Glossina brevipalpis tsetse fly species using Cafe´ analysis (to identify species-specific expansions) and 2) differential expressions of the orthologs and associated proteins in male G. m. morsitans antennae and head tissues using RNA-Seq approaches (to establish associated functional molecular pathways). We established accelerated and significant (P<0.05, λ = 2.60452e-7) expansions of gene families in G. m. morsitans Odorant receptor (Or)71a, Or46a, Ir75a,d, Ionotropic receptor (Ir) 31a, Ir84a, Ir64a and Odorant binding protein (Obp) 83a-b), G. pallidipes Or67a,c, Or49a, Or92a, Or85b-c,f and Obp73a, G. f. fuscipes Ir21a, Gustatory receptor (Gr) 21a and Gr63a), G. p. gambiensis clumsy, Ir25a and Ir8a, and G. brevipalpis Ir68a and missing orthologs in each tsetse fly species. Most abundantly expressed transcripts in male G. m. morsitans included specific Or (Orco, Or56a, 65a-c, Or47b, Or67b, GMOY012254, GMOY009475, and GMOY006265), Gr (Gr21a, Gr63a, GMOY013297 and GMOY013298), Ir (Ir8a, Ir25a and Ir41a) and Obp (Obp19a, lush, Obp28a, Obp83a-b Obp44a, GMOY012275 and GMOY013254) orthologs. Most enriched biological processes in the head were associated with vision, muscle activity and neuropeptide regulations, amino acid/nucleotide metabolism and circulatory system processes. Antennal enrichments (>90% of chemosensory transcripts) included cilium-associated mechanoreceptors, chemo-sensation, neuronal controlled growth/differentiation and regeneration/responses to stress. The expanded and tsetse fly species specific orthologs includes those associatedwith known tsetse fly responsive ligands (4-methyl phenol, 4-propyl phenol, acetic acid, butanol and carbon dioxide) and potential tsetse fly species-specific responsive ligands (2- oxopentanoic acid, phenylacetaldehyde, hydroxycinnamic acid, 2-heptanone, caffeine, geosmin, DEET and (cVA) pheromone). Some of the orthologs can potentially modulate several tsetse fly species-specific behavioral (male-male courtship, hunger/host seeking, cool avoidance, hygrosensory and feeding) phenotypes. The putative tsetse fly specific chemosensory gene orthologs and their respective ligands provide candidate gene targets and kairomones for respective downstream functional genomic and field evaluations that can effectively expand toolbox of species-specific tsetse fly attractants, repellents and other tsetse fly behavioral modulators.
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    Repellency and Composition of Essential Oils of Selected Ethnobotanical Plants Used in Western Kenya against Bites of Anopheles gambiae Sensu Stricto
    (Taylor & Francis Group, 2020) Ywaya, David O.; Birkett, Michael A.; Pickett, John A.; Ochola, John B.; Lwande, Wilber; Wachira, Benson M.; Hassanali, Ahmed; Ng’ang’a, Margaret M.
    The essential oils of Ocimum gratissimum Linn, Hyptis suaveolens (L) Poit and Vitex keniensis, which are used traditionally in Western Kenya for personal and space protection against mosquito bites, were screened for repellence against Anopheles gambiae Sensu Stricto. Essential oils were extracted from their leaves by hydrodistillation, characterised by gas chromatography linked with mass spectrophotometer and electroantennogram detectors. The repellency of the oils and their selected blends was studied by the reduction in probing and feeding on the human arm. The oils showed promising repellency for Anopheles gambiae, O. gratissimum (RD50 = 2.77 × 10-5 mg cm-2, 95 % CI), Vitex keniensis (RD50 = 5.68 × 10-5 mg cm-2) and Hyptis suaveolens (6.27× 10-5 mg cm-2) as compared to that of DEET (control) RD50 = 1.25×10-5 mg cm-2). The bioactive constituents of each oil were identified by Gas chromatography-linked with Mass spectrometry and Electroantennography. Some compounds were confirmed by co-injections of the oil with available authentic standards. The results provide a scientific rationale for the traditional use of these plants in repelling disease vectors and other biting insects, and lay down some useful groundwork for downstream development of more effective products for personal and space protection.
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    Responses of Glossina pallidipes and Glossina morsitans morsitans tsetse flies to analogues of -octalactone and selected blends
    (Elsevier, 2016) Wachira, Benson M.; Mirejib, Paul O.; Okoth, Sylvance; Ng’ang’a, Margaret M.; William, Julius M.; Murilla, Grace A.; Hassanali, Ahmed