Browsing by Author "Kepha, Stella"

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    Effects of Metarhizium anisopliae on sand fly populations in their natural habitats in Marigat sub- County, Baringo County, Kenya
    (Centre for Biotechnology Research & Development,, 2010) Ngure, Peter Kamau; Ngumbi, Philip; Kasili, Sichangi; Anjili, Christopher O.; Karanja, Robert M.; Kaburiae, Josyline C.; Mwangi, Milkah; Kinuthia, Geoffrey K.; Kiarie, Martha; Nzau, Anastasia; Kepha, Stella; Maniania, Nguya K.; Irungu, Lucy
    Leishmaniasis is one of the neglected tropical diseases that pose a threat to people in the endemic regions. In Africa, transmission is through the bite of an infected female phlebotomine sand fly. Disease control with chemotherapy is logistically difficult, toxic and expensive. Entomopathogenic fungi (EPF) hold great potential as alternative vector control for sandflies as demonstrated by their efficacy in recent laboratory experiments. The impressive results have merited testing of the effect of EPF on sand flies in their natural habitats. The goal of this study was to test the effect of EPF on sand fly populations on a small scale in a leishmania-endemic area in Kenya. Entomopathogenic fungi isolates were cultured on Sabourand dextrose agar (SDA) in Petri dishes and incubated at 22-280C. Conidia were produced on long white rice substrate and harvested by sifting the substrate through a 295 μm mesh size sieve and stored at 4- 2 6 0C before being used in the experiments. Metarhizium anisopliae isolates were selected for use in the field after showing 76.8 and 100% mortality in laboratory bred target insects. 2.0 x 1014 of dry conidia of the fungus were introduced into ten termite mounds through the shafts using a modified foot pump in Rabai, Marigat area of Baringo County, Kenya. The site harbours both Phlebotomus martini and P. duboscqi sandfly vectors. Sand fly densities, mycoses and survival after capture from the mounds were observed from week one post-treatment to week thirteen. Results indicate that the fungi in termite mounds caused three to ten-fold mortalities in the population of sand flies nine weeks after application. Longevity of sand flies collected from treated termite mounds was reduced to less than nine days after collection, whereas 90% of those from control mounds lived well over the nine days. Sand flies collected from the treated termite mounds during week nine had 100% mortality compared to 10.7% of those from the control mounds. Metarhizium anisopliae infection was observed in 42% of the sand fly cadavers collected from the treated termite mounds and 0% in the control group. The high susceptibility of sand flies to M. anisopliae suggests that fungi can be developed as potential vector control alternatives to synthetic chemical insecticides or preferentially be applied in integrated control strategies in order to gain maximum impact on adult sand fly populations. Further studies to determine the best methods for delivery and application in the diverse ecological settings of various leishmaniasis vectors are recommended.
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    Evaluation of the Adjuvanticity of Artemisinin with Soluble Leishmania Major Antigens in BALB/C Mice
    (Elsevier, 2009) Karanja, Muhia Robert; Ngure, Peter Kamau; Ingonga, Johnstone; Gicheru, Michael M.; Kepha, Stella; Njeru, Laban Ireri; Wachira, Dorcas; Mwangi, Milkah; Nyamwamu, Lydia B.; Kimutai, Albert; Tonui, Willy K.
    Objective; To determine the adjuvant potential of artemisinin with a soluble leishmanial antigen in vaccinating BALB/c mice. Methods; Seventy two female BALB/c mice were randomly assigned into six groups. The mice were vaccinated with soluble leishmania antigens (SLA) alone, artemisinin co-administered with SLA, SLA and Bacille Calmette Guérin (BCG) vaccine, and artemisinin and BCG alone. Unvaccinated mice formed the control group. The induction of cell-mediated immunity following vaccination was determined by measuring in vitro lymphocyte proliferation and the production of interleukin (IL)-4, IL-5 and gamma interferon (IFN-γ) determined by flow cytometry. Protection against L. major was determined by quantifying parasite burdens in L. major infected footpads using a limiting dilution assay and by measuring lesion sizes of the infected footpad compared to the contralateral uninfected footpad. Results; Mice receiving SLA plus artemisinin produced significantly high levels of IL-4 and IL-5 (P < 0.05) and low levels of IFN-γ, resulting in exacerbated disease. In addition, subcutaneous administration of SLA + artemisinin, artemisinin alone or SLA alone resulted in the development of large footpad swellings and high parasite loads that were comparable to those of the control unvaccinated mice (P > 0.05), resulting in exacerbated disease. Conclusion; These data suggest that artemisinin is not a suitable adjuvant for Leishmania vaccines. However, since artemisinin has been shown to be effective against Leishmania parasites in vitro and in vivo, further studies ought to be conducted to determine its immunochemotherapeutic potential when co-administered with Leishmania antigens.
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    Immunostimulatory responses to crude extracts of Warburgia ugandensis (sprague) subsp ugandensis (canellaceae) by Balb/c mice infected with Leishmania major
    (Pan African Medical Journal., 2014-01-18) Ngure, Peter Kamau; Ng’ang’a, Zipporah; Kimutai, Albert; Kepha, Stella; Mong’are, Samuel; Ingonga, Johnnie; Tonui, Willy K.
    Introduction: To determine the immunostimulatory potential of crude extracts of Warburgia ugandensis subsp. ugandensis with a soluble leishmanial antigen in vaccinating BALB/c mice. Methods: Seventy two female BALB/c mice were randomly assigned into six groups. The mice were vaccinated with soluble leishmania antigens (SLA) alone, hexane, ethyl acetate, and dichloromethane extract co-administered with SLA. Unvaccinated mice formed the control group. The induction of cell-mediated immunity following vaccination was determined by measuring in vitro lymphocyte proliferation and the production of interleukin (IL)-4 and gamma interferon (IFN-γ) determined by flow cytometry. Protection against L. major was determined by quantifying parasite burdens in L. major infected footpads using a limiting dilution assay and by measuring lesion sizes of the infected footpad compared to the contralateral uninfected footpad. Results: On vaccination with extracts of W. ugandensis subsp. ugandensis alone or as adjuvants when used in combination with Leishmania antigens, the hexane extract and the dichloromethane extract plus SLA stimulated moderate production of IFN-γ and low levels of IL-4.These mice were partially protected from cutaneous leishmaniasis as shown by the slow development of lesions and comparatively less parasite burdens. Conclusion: These data suggest that extracts of W. ugandensis subsp. ugandensis are suitable adjuvants for Leishmania vaccines. However, since W. ugandensis subsp. ugandensis has been shown to be effective against Leishmania parasites in vitro and in vivo, further studies ought to be conducted to determine its immunochemotherapeutic potential when co-administered with a soluble leishmanial antigen in vaccinating BALB/c mice.
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    Potential Effects Of Pyrethrin Incorporated In Sucrose Baits Against Phlebotomus Duboscqi Neveu Lemaire (diptera: Psychodidae) In Leishmaniasis Control Strategies
    (Webmedcentral, 2010-11-06) Ireri, Laban N.; Mucheru, Obadiah; Ngure, Peter Kamau; Kepha, Stella; Kimutai, Albert; Cirindi, Josyline; Tonui, Willy K.
    Background: Due to challenges of controlling leishmaniasis in Kenya through the vector, the efficacy of pyrethrin EC (Pymos™ 0.6% W/V) a mosquito adulticide was evaluated against Phlebotomus duboscqi while incorporated in sucrose as a possible complementary method. Methods: Pyrethrin was prepared into concentrations of 0.08, 0.25and 0.5 mg/ml using 10% sucrose. Ten male and female sand flies were each aspirated into jars and fed separately with the prepared solutions using cotton wool pads placed atop experimental jars and mortality monitored each day. The experiments were replicated three times. Results: Significant mortality (P< 0.05) for both sexes was observed. The concentration of 0.08mg/ml gave low adult mortality in 24 hours but amplified with time. In the 0.25 bioassay, mortality of females were 10 (33.3%) and males had 21 (70%) in 24 hours. The LD50 for females and males tied at 0.1 mg/ml in 48 hours of exposure. The concentration of 0.25 mg/ml was ideal at 48 hours of feeding where majority of the sand flies succumbed to the insecticide. There were significant mortality differences (P <0.05) between the concentrations but no significant difference (P>0.05) was observed in male and female mortality at 48 hours of exposure however. Although we cannot rule out sand fly mortality due to contact with the test material, the results of this study however suggest that control strategies using low-dose pyrethrin-sugar combinations as baits may be effective against phlebotomine sand flies and other sugar feeding pests of medical importance.