Browsing by Author "Feleke Adey"

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    A Comparative Study of Four Indigenous Cattle Breeds for Tick Resistance and Tick- Borne Diseases in Ghibe Valley
    (Addis Ababa University, 2003-06) Feleke Adey; Petros Beyene (PhD)
    The purpose of the study was to obtain information on the resistance levels of four indigenousbreeds of cattle (Abigar, Gurage, Horro and Sheko) to natural infestation with ticks in theGhibe Valley. Monthly collection of ticks from randomly selected cohort of 15 heifers ofeach breed, in the period January through October 2002, showed the most common tickspecies to be: Amblyomma variegatum (39.5%), Boophilus decoloratus (39.1%), A. cohaerens(10.5%) and Rhipicephalus evertsi evertsi (6.7%). Species of least abundance include, R.praetextatus, Haemaphysalis aciculifer, Hyalomma marginatum rufipes, R. bergeoni, R.lunulatus, R. muhsame and R. pravus, altogether comprising 4.2% of the overall tick species.The monthly abundance of adult and immature ticks, their feeding sites on the hosts and themale to female sex ratio were determined. Resistance to ticks between breeds was evaluatedbased on the cumulative log transformed counts of total ticks, fully engorged females andadult ticks and was analysed by the method of least squares. The results revealed that thecount of total ticks in Horro and Gurage (mean count of 5 ticks per month per breed) waslower than those of Abigar and Sheko (7 ticks per month per breed) (P< 0.001). The meancount of fully engorged females in Horro and Gurage cattle breeds was also lower (2 ticks permonth per breed) than Abigar and Sheko (3 ticks per month per breed) (P< 0.05). The meancount of adult ticks was the lowest in Horro (4 ticks per month per breed), followed byGurage (5 ticks per month per breed), Abigar and Sheko (6 ticks per month per breed) (P<0.01). Based on the three parameters, Horro and Gurage breeds were found to exhibitsignificantly higher resistance to ticks than Abigar and Sheko breeds. Packed Cell Volume(PCV) of the study animals was monitored monthly during the study period and negativecorrelation was found between tick burden and PCV levels in all the animals (P< 0.05).Infection with tick- transmitted parasites/ pathogens: Anaplasma marginale (84.2%), Babesiabigemina (87.1%) and Theileria mutans (54.2%) was confirmed serologically by indirect ELISA. Sera were also screened using indirect ELISA to investigate the animals for anti- Amblyomma variegatum antibody responses by using larval homogenate. Comparisons between antibody responses of each breed showed the presence of variations in IgG responses between the cattle breeds. Higher IgG response was found in Horro than the other three breeds (P< 0.05). The relationships between infestation with A. variegatum and the level of IgG were positive in Abigar (r = 0.3, P> 0.05), Gurage (r = 0.4, P< 0.05) and Sheko (r = 0.5,P< 0.05) breeds, while weak negative correlation (r = - 0.2, P> 0.05) was observed in Horro breed, indicating the possible role of IgG in the acquisition of host resistance to ticks.
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    Microbial diversity and Molecular Biomonitoring for Efficient Treatment of Tannery Wastewater: Laboratory and Field- Scale Studies
    (Addis Ababa Universty, 2013-11) Feleke Adey; Assefa Fassil (PhD)
    This dissertation reports on culture- dependent and culture- independent characterization of microorganisms of from tannery wastewater, with special reference to degradation of selected retanning chemicals, In the culture- based study, four bacterial strains isolated ll'om a temporary storage site of composite tanncry wastewater were reported to grow and utilizc the retanning agcnts named as Basyantan AN and Retanal MD80 as their carbon and nitrogen sources. Ultra Performance Liquid Chromatography (UPLC) analysis of compounds in the retanning agents from batch cultures over a period of 14 days revealed an average of 18, 26 and 33% degradntion of the three detected peaks of Basyantan by isolate B45. The same isolate also showed an average of 34% degradation of Retana!' Kinetic studies conducted on this isolnte showed the dependence of growth on the concentration of Retanal as a substrate, with a maximum grO\\1h rate (Jlma,)of 1450 cells mr'.hr" and a half saturation constant (Ks) of 10.16 mg.r'. On the basis of 16S rRNA gene amplification, sequencing and phylogenetic analysis, the four isolates werc identified as Micrococcus luleus strain B lR, Brevibacleriulll pilyocalllpae strain B4500R, Lysinibacillus sphaericlls strain R 1902R and Enlerococcus gallina/'lllJl Strain R280 I R. Bench- scale study involving a sequencing batch reactor (SBR) run for 42 days for studying the biodegradation of Basyantan and Retanal revealed a pronounced degradation up to 100% regarding peak 2 of Basyantan. Dynamics of sludge microbial sub- communities as followed by T-RFLP showed the dominance of membcrs of the class Burkholderaceae and a less diverse community in the first five batches of the SBR run; which was then succeeded by members belonging to the phylum Bacteroidetes and classes Rhodocycalaceae, Rhodobacteraceae, Pseudomonadaceae and Bradyrhizobiaceae; with increased diversity towards the end of the run. Flow cytometric analysis of bacterial cells in the sludge was used to create pattcrns mirroring dynamics of bacterial community over the period of SBR run. The patterns were resolved in 30 sub, clusters eight of which wcre sOlicd and members identified. Correlation of the bacterial abundancc in thc sortcd sub- clusters with the measured abiotic data showed the prcsence of a strong (p< 0.0 I) positive correlation bctween degradation of Basyantan and Retanal with mcmbers of Bacteroidetes and Protcobactcria, indicating the key degradation role played by thesc members. Ficld- scale study on the structure and diversity of the microbial community in the sludge of the Anaerobic- aerobic reactors as well as the root area of a constructed wetland treating tannery effluent located in Modjo tannery was conducted using the 16S ribosomal RNA gene scquencing performcd for cach of the reactors. The results revealed a total of 31 different phylotypes with the dominant members belonging to FirllliclIIes, Bacleroidia, Proleobacleria, Sphingobacleria and S)'Ilergislia in the anaerobic and aerobic reactors. In the constructcd wetland, members of thc group C)'({l1obaCleria were also identified in addition to Firmicules, 13acleroidia and Proleobaclel'ia. Thc presence of members of groups that arc associated with reduction of sulfate and removal of chromium, nitrate and degradation of synthetic aromatic compounds indicates their implication in the current performance of the treatment system. Furthermore, physicochemical data (total Nitrogen, total Carbon, pH, Sulphate, Nitrate) have been recorded in the anaerobic, aerobic and constructed wetlands and analyses of these data elucidate the key factor structuring the observed microbial communities.