Evaluation Of Control Strategies For Eradication Of Bovine Tuberculosis In Endemic Settings

Abstract

Bovine tuberculosis (bTB) is an infectious disease of cattle that has an important impact in animal and public health. In spite of many efforts and resources invested in its eradication, bTB is still endemic in many countries. The intradermal tuberculin test- and- slaughter of bTB positive animals, with the slaughter surveillance, are the basis of bTB-control and eradication programs in place. However, the accuracy of intradermal testing tends to vary broadly with factors inherent to the country and to the individual immunity of the animal. In Uruguay, in spite of many efforts dedicated to bTB eradication, this disease has reached unprecedented prevalence levels in large, intensified dairy systems in the past years (2010-2018). This raised concerns regarding the suitability of the bTB-control strategies to reach eradication in this evolving demographic and management scenarios. In this dissertation we aimed to assess current and alternative control strategies for bTB in high-prevalence endemic settings, considering the identified demographic and management risk factors, to guide the design and implementation of optimal control and eradication procedures through mathematical modeling. Overall, we demonstrate that JD has an effect in bTB-diagnostic results at the herd and individual level in high prevalence bTB and JD coinfected populations studied, which needs to be addressed in the planning of bTB-control programs, specifically in regards of the performance of the bTB-diagnostic tools used. Still, in this co-infected scenario, the use of IGRA notably improved the sensitivity of detection in these herds, which can be beneficial in declining initial high bTB-prevalence levels. However, it is crucial to incorporate bTB-testing in young animals (<12 months) to break disease transmission and achieve eradication. Further studies would be required in order to determine the best bTB-control strategy resulting from the interaction between bTB- and JD- epidemiology, test performance, and economic costs, while acknowledging the country logistics and socio-cultural perceptions. Nevertheless, this research represents the first attempt to integrate field risk factors for the diagnosis of bTB, and JD-coinfection in the design of control strategies for heavily infected herds that can be the foundation of optimal bTB-control strategies to reach eradication when depopulation is not suitable.