Browsing by Author "Gatongi, PM."

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Changes in lipids utilisation during moisture and temperature stress of infective (L3) and its implication on the epidemiology of Haemonchus contortus in arid and semi arid lands
(Maxwell science publishing, 2011-03-05) Siamba, Donald N.; Gatongi, PM.; Mulambalah, CS.; Ngeiywa, MM.; Wamae, LW.; Wambugu, A.
A study was undertaken to establish the pattern and level of lipid utilization in third stage infective larvae (L_3) of Haemonchus contortus under temperature and moisture stress conditions. The stress factors were representative of an arid and semi arid site in Kenya. The L_3 were subjected to gradual increase and reduction in temperature and moisture, respectively, using a programmable cold/heat testing chamber. Optical density per area (Corrected average pixels) derived from image analysis of individual stained larvae using an image analysis software (UN SCAN IT gel^(r)), were used to estimate the lipid content of larvae subjected to different stress treatments. It was observed that lipid content of the L_3 declined and was negatively correlated with duration of exposure with significantly (p = 0.012) lower rates in moisture compared to temperature stressed L3. It was also observed that the decline occurred in phases signifying possible adaptive physiological process aimed at preserving lipid reserves and viability. During revival, there was a drastic decline in lipid reserves probably as a result of increased lipid utilisation by the reviving larvae. The epidemiological significance of these findings in field larvae is discussed
Exsheathment characteristics and infectivity of revived anhydrobiotic L_ (3) of haemonchus contortus
(Maxwell science, 2012-10-20) Siamba, Donald N.; Mulambalah, CS.; Ngemaeiywa, MM.; Gatongi, PM.; Wamae, LW.
This study was conducted to determine the effect of temperature and moisture stress on exsheathment process and infectivity of the infective larvae of the parasitic nematode ＂Haemonchus contortus＂. Laboratory conditions were used in which infective (L_(3)) of ＂H. contortus＂ were either subjected to gradually increasing temperatures, decreasing moisture or both. Post stress viability and exsheatment of L_(3) was determined prior to infection experiments. The viability of ＂H. contortus＂ after induction of anhydrobiosis declined significantly (p＜0.05) from 85 to 60% in about 60 days. The results showed significant (p＜0.05) delay in exsheathment in stressed larvae compared to unstressed larvae leading to low overall establishment (Infection). However, the proportion of the immature in relation to the mature parasites (hypobiosis) was significantly (p＜0.05) higher in stressed compared to the unstressed L_(3). These results indicate that delayed exsheatment in stressed L_(3) contributes to low infectivity in ruminants.
Morphological and metabolic response of infective larvae (L3) of Haemonchus contortus to temperature and moisture stress
(Moi university, 2009) Siamba, Donald N.; Gatongi, PM.; Ngeiywa, M.; Wamae, LW.; Wambugu, A.
The ability of certain species of parasitic nematodes to survive desiccation for considerable periods is a fascinating example of adaptation to the demands of fluctuating environments that occasionally can become extreme and life threatening. Behavioural and morphological adaptations associated with desiccation survival serve primarily to reduce the rate of drying, either to prolong the time taken for the nematode's water content to reach lethal low levels or, in true anhydrobiotes, to enable the structural and biochemical changes required for long-term survival to take place. Examples of these adaptations are reviewed, together with information on the factors involved in rehydration that ensure successful exit from the dormant state. Information on desiccation survival is central to effective management and control options for parasitic nematodes. It is also required to assess the feasibility of enhancing the longevity of commercial formulations of entomopathogenic nematodes, both before and after application; current research and future prospects for enhancing survival of these bio-insecticides are discussed.
The potential role of trehalose as a signal molecule in Hypobiosis of trichostrongyles
(Moi university, 2009) Siamba, Donald N.; Wamae, LW.; Gatongi, PM.; Ngeiywa, M.; Wambugu, A.
Parasites need necessary and timely adaptations that guarantee their survival in its challenging environment which may be external or internal to the host. The adaptations can be morphological, nutritional, life cycle, immunological or biochemical. These adaptations are the sharp weapons used by the small parasites to fight against the harsh environment surrounding it. Thorough analysis of these adaptations is the need of the hour to understand the weak points of the parasites. This will help us to design a better control strategy as well as to modify the existing control measures against them.