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sur le développement des zones arides et semi-arides

Titre : Bovine tuberculosis in Ethiopian local cattle and wildlife : epidemiology, economics and ecosystems

Auteur : Tschopp, Rea

Université de soutenance : University of Basel

Grade : Doctor of Philosophy (PhD) 2010

Résumé partiel
Ethiopia has recently been focusing on intensive dairy cattle farming in order to supply the growing demand for milk. For this purpose Holstein Frisians have been imported, bred and distributed in farms especially around Addis Ababa. However, Holstein (Bos taurus) although giving more milk than traditional zebus (Bos indicus) seem to be more susceptible to bovine TB (BTB). Ethiopia ranks worldwide 8th in the number of newly diagnosed TB cases, and the incidence of extra pulmonary TB was shown to be high. Therefore, the following research questions have been raised : What is the prevalence of BTB in cattle ? What is the contribution of M. bovis in the national TB prevalence ? Which strains of M. bovis are present in cattle and humans ? A consortium funded by the Wellcome Trust (UK) and involving institutions from the UK, Switzerland, Ethiopia, Ireland and Kenya was established in 2005 study BTB in Ethiopia and to address these questions. The overall ultimate goal of the project is to measure the cost of BTB by assessing its impact on the livestock and public health sector and to suggest the most profitable intervention strategies. This thesis contributes to the overall BTB project by providing baseline epidemiological and economical data needed for the development of a SIR animal-human transmission model, and for the estimation of the economical impact of BTB in the livestock sector in Ethiopia. We assessed field prevalence of BTB using the comparative intradermal test (CIDT) in 6194 cattle in 5 different Woredas (districts) from Amhara, Oromia, and SNNPR regions. Four of our study sites were located in the Ethiopian Highlands and were characterized by extensive mixed crop-livestock farming with predominantly local zebu breeds, whereas the last study site was a pastoralist area in the lowlands of south Omo (SNNPR). We performed a repeated cross-sectional study in cattle in 3 of the Woredas, over 3 years. In comparison to Central Ethiopia, which is characterized by the presence of a higher number of exotic breeds and more intensive farming practice, apparent prevalence of BTB in our study sites was very low (when using the official OIE definition for positive reaction), with a minimum of 0% in the Bale Mountains and a maximum of 1.3% in Bako-Gazer and South Omo. We discussed the use of different cut-offs for the interpretation of the skin test results.

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