Browsing by Author "Mwangi, Milkah"

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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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    Immunization with a combination of Leishmania major lipophosphoglycan (LPG) and Phlebotomus duboscqi salivary gland lysates (SGLs) abrogates protective efect of LPG against L. major in BALB/c mice
    (African Journal of Health Sciences, 2011) Robert Karanja; Ingonga, Johnstone; Mwangi, Milkah; Mwala, Dennis; Lugalia, Reuben; Magambo, Japhet; Tonui, , Willy K.
    The use of vector-derived antigens has become widely acknowledged as a possible answer to vaccination against vector borne diseases. Sand fly saliva is one such vector-derivative that has been targeted for vaccine development, either alone or in combination with other antigens. Previous studies have suggested a synergistic protective effect accruing from a parasite-derived and vector-derived cocktail vaccine. This study sought to evaluate such a synergistic effect in a cocktail vaccine comprising Phlebotomus duboscqi salivary gland lysates (SGLs) mixed with L. major lipophosphoglycan (LPG). Mice were immunized subcutaneously with SGLs, LPG or a cocktail of the two. The immunizations were then boosted twice every 2 weeks, followed by a challenge with 105 L. major metacyclic promastigotes 2 weeks after the last boost. Lesion growth was monitored over 35 days using vernier calipers, and footpad parasitaemia determined by simple limiting dilution assay. Immunizations with LPG alone gave effective protection against L. major infection (P < 0.05) compared to controls, whereas SGLs, and the LPG + SGLs cocktail failed to protect. This study did not demonstrate a protective synergistic effect accruing from LPG + SGLs cocktail vaccine, and suggests a need to evaluate the effects of saliva in vaccinations with other Leishmanial antigens.