Browsing by Author "Berhanu Abera"

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    A History of Chalia Warada, 1941-1991
    (Addis Ababa University, 2023-05-01) Berhanu Abera; Tesema Ta‟a (Prof)
    The primary purpose of this thesis is to reconstruct the socio economic and political history of Chalia warada from 1941-1991. The study covers the period from the liberation of Ethiopia and the restoration of Emperor Haile Selasie I to the throne in 1941 up to the collapse of the Darg government in 1991. During this time span, the inhabitants of the warada similar to the other countryside people of in what is now Oromia region experienced important socio economic and political changes. It begins with historical study of the warada by treating various changes and cultural aspects in the warada before the Italian occupation. The restoration of Imperial administration and the reforms that were undertaken by the Imperial government in different fields, in relation to the administration and land issues and the reaction of the inhabitants of the warada to these developments will be the main concern of the discussion. In addition to this, the study treats land tenure issues, evictions and the impact of labor service and taxation in the warada. It also points out maladministration and problem of security in the warada. The study also attempted to discuss changes and developments that the warada had undertaken during the Darg period. The Darg government attempted to strength its power by adopting different measures which had impacts on the political and socio economic conditions of the people of Chalia warada. The study also tried to assess the socio economic conditions of the warada in which the area has not received much attention from the government. In this study, oral sources as well as written materials were used. Besides, there is also some archival materials were used in the study. To write this thesis, efforts have been made in order to analyze the oral sources crosschecking it with written materials. To avoid the bias in the use of oral sources necessary measures have been taken, in choosing knowledgeable informants, use of collected data, evaluating and checking them with the existing literature as important steps that were accomplished. This thesis would also help the historians as a stepping stone for the further studies of the warada since a history of Chalia was not much studied. Most of scholars who study several regions did not give attention to Chalia warada. To this end, this study pointed out various changes and developments in the warada like other parts of Oromia region.
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    Modeling bovine tuberculosis transmission dynamics and disease control interventions in selected dairy farms of Ethiopia
    (Addis Ababa University, 2024) Berhanu Abera; Prof. Gezahagn Mamo; Dr. Rebecca L. Smith; Prof. Balako Gumi
    Deepening poverty; sluggish performance of the agricultural sector in general, livestock development in particular; accelerated resource depletion and emerging zoonotic disease in Ethiopia have always concerned policy makers and researchers and urged them to search for effective research and policy tools. The present PhD research work; therefore, aims to reveal peculiarities of information on bTB transmission dynamics and control, relevant data for the implementation of a model-based disease control system and factors that might hamper the control of the disease in order to optimize resources. The studies included in my PhD thesis are summarized below: 1. In the first study, non-biological factors affecting bovine tuberculosis control and prevention in dairy herds was analyzed. The results indicated that the KAP level among dairy farmers varied depending on herd size, milk-shed, training availed, veterinary consultation and their previous farming experiences. Farmers from medium and large-scale farms knew more about bTB than those from small scale farms, by a factor of 2.8 and 7.7 respectively. Similarly, farmers who had been farming for more than 6 years and farmers from Selale milk-shed had higher odds of being knowledgeable about bTB, by a factor of 5.7 and 10.4 respectively, compared to others. Only 12% of the study participants were aware of test and slaughter method, likewise, 18% of farmers tended to avoid buying cattle from risky sources. The finding revealed a dearth of knowledge on the production loss incurred (12%) and the probability of human infection (1.9%), instead a substantial number of farmers (25%) believed that bTB infection could badly affect the dairy market. These limitations may explain how bTB will continue to be a major threat. All these negatively impact disease surveillance and control intervention programs. 2. The second study assessed the incidence of bTB in a dairy herd with repeated irregular skin test and slaughter programme, and found that these incidences exhibited an oscillating pattern over subsequent time period. The study highlighted the importance of consistent testing and control measures to manage the risk of bTB in dairy herds. Penultimate test result, and herd composition were significantly associated with the odds of them becoming a reactor to the SICCTT at a subsequent test (P<0.05). The study findings indicated that animals undergoing two consecutive repeated skin tests had an approximately 11 times higher risk of bovine tuberculosis (bTB) infection compared to newly introduced animals. Moreover, animals that had inconclusive results in previous tests were more likely to be bTB reactor, and high probable to have visible lesions at slaughter than those with a negative penultimate SICCTT result, emphasizing the need for careful monitoring and follow-up. It‟s crucial for dairy farms to implement regular and systematic skin testing and slaughter control programs to effectively control the spread of bTB. This not only protects the health of the herd but also ensures the safety of milk products for consumers. 3. In the third study, the impact of repeated test and slaughter for bovine tuberculosis control was examined. The effect of the intervention measures on resultant incidences, and its consequence on herd demographic changes were evaluated. Despite repeated testing and removal measures, the incidence did not exhibit a substantial reduction trend along the successive test and slaughter rounds. The time interval between successive SICCTT tests varied from 0.95 years to 1.84 years, which were excessively prolonged and inconsistent time intervals. Apart from the incompetence on incidence reduction, the study identified a vital knock-on effect on herd demography due to culling of a substantial number of cows (n=342) which played a crucial role in shaping the average herd age, parity and breed composition of the study herd. With an increased culling rate, the average age of the herd and the average number of lactations per cow decreased, which was not favorable for herd demography maintenance. Similarly, animal entries and exits also influenced the breed composition of the herd. The proportion of purebred Boran animals declined to 5%, while high-grade animals (75% Holstein blood) increased almost five-fold between the first and fourth test rounds. It is recommended that culling should be carried out with no or minimal significant impact on herd demography change. Compliance to conventional test and slaughter procedural protocol is supposed to play an important role in succeeding bTB control measures. Therefore, at least a minimum of 2-month a maximum of 6-month testing interval, and two consecutive negative whole herd testing should be carried out in order to declare a herd free of bTB. 4. The fourth study, “Bayesian modeling of bovine tuberculosis prevalence”, estimate the true prevalence and test characteristics (sensitivity and specificity) of SICCTT from the apparent prevalence in semi-intensive dairy farm over time. True disease states are uncertain in practice due to imperfect specificity and sensitivity, and so the true prevalence and characteristics of SICCTT were inferred using Markov Chain Monte Carlo estimation with prior distributions. Median sensitivity estimates using standard and severe interpretations were 68.6% (BPI; 50.3-84.3%) and 78.1% (BPI; 62.5-90.9%), while the specificity median were 96.8% (BPI; 94.3-98.9%) and 94.5% (BPI; 91.5-97.1%), respectively. Furthermore, adjusted true prevalence estimates (median and 95 %; BPI) were produced for each testing round using the Rogan-Gladen estimator (RGE). Bayesian estimation with informative priors exhibited much wider credible intervals and strong coverage compared to uninformative priors and frequentist method (RGE). Classic apparent prevalence estimates are overly precise when uncertainty around test performance is high. These Bayesian approaches provided a more accurate estimate of bTB prevalence in the study herd and provide a baseline data for the future true prevalence estimates using linked combined data. 5. The fifth study estimated the within-herd transmission dynamics of bovine tuberculosis in a commercial dairy herd, and predict the efficiency of the envisaged control interventions. The study developed a stochastic compartmental SORI (Susceptible, Exposed (latent), and Infectious) model to simulate within herd transmission dynamics of M. bovis in intensively managed dairy farm. Several parameters related to bTB spread, in particular the cattle-to-cattle transmission rate (β) and the rate at which infected cattle become infectious (α) was inferred. Data for parameter inference was obtained from farms where there were epidemiological evidences of bTB introduction into the herd through the purchase of infected animals, which allowed us to have data on: a) the date of introduction of infection into the herd, b) initial number of infected animals introduced and c) final number of infected animals (when infection of the herd is detected). A Markov Chain Monte Carlo-Approximate Bayesian Computation (MCMC-ABC) method was used to generate posterior distributions of bTB transmission parameters. The results from the studies-I has been accepted by Ethiopian Veterinary Journal, study II has been published on Asian III, IV and V included in the present PhD Thesis have been published or accepted or submitted for publication in international scientific peer-reviewed journals: