Petros Beyene (PhD)Feleke Adey2018-06-132023-11-092018-06-132023-11-092003-06http://etd.aau.edu.et/handle/123456789/779The 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.enBiologyThesis