Open questions and recent advances in the control of a multi-host infectious disease: animal tuberculosis

Animal tuberculosis (TB) control is globally important for public health, economics and conservation. Wildlife species are often part of the Mycobacterium tuberculosis complex (MTC) maintenance community, complicating TB control attempts. We describe the current knowledge on global TB distribution and the significance of wildlife hosts; identify insufficiently known aspects of host pathology, ecology and epidemiology; present selected time series in wildlife TB; and summarize ongoing research on TB control, providing additional insight on vaccination. Six specific research needs are identified and discussed, namely: 1) complete the world map of wildlife MTC reservoirs and describe the structure of each local MTC host community; 2) identify the origin and behaviour of generalized diseased individuals within populations, and study the role of factors such as co-infections, re-infections and individual condition on TB pathogenesis; 3) quantify indirect MTC transmission within and between species; 4) define and harmonize wildlife disease monitoring protocols, and apply them in a way that allows proper population and prevalence trend comparisons in both space and time; 5) carry out controlled and replicated wildlife TB control experiments using single intervention tools; 6) analyse cost-efficiency and consider knowledge transfer aspects in promising intervention strategies. We believe that addressing these six points would push ahead our capacities for TB control. A remaining question is whether or not interventions on wildlife TB are at all justified. The answer depends on the local circumstances of each TB hotspot, and is likely to evolve during our collective progress towards TB control in livestock and in wildlife.