Long-Term Determinants of Tuberculosis in the Ungulate Host Community of Doñana National Park.

Patricia Barroso,Pablo Palencia,Joaquín Vicente,Francisco Carro,Pelayo Acevedo,María José Torres,José A Barasona,Juan José Negro,Ramón C Soriguer,Christian Gortázar

doi:10.3390/pathogens9060445

Abstract

Animal tuberculosis (TB) is endemic in wild boar (Sus scrofa), red deer (Cervus elaphus), fallow deer (Dama dama) and cattle in south and central Spain. In order to clarify the processes that operate in the medium and long-term, we studied TB at the wildlife–livestock interface in Doñana National Park for 14 years (2006–2018) in relation to host density, stochastic factors (rainfall) and environmental features (e.g., aggregation points such as waterholes). Wild boar showed the highest prevalence of TB (76.7%), followed by red deer (42.5%), fallow deer (14.4%) and cattle (10.7%). We found evidence of relevant epidemiological processes which operate over the long-term and interact with host and community ecology. Interestingly, the effect of high wild boar population density on increased TB rates was mediated by sows, which could determine high incidence in young individuals already in maternal groups. Rainfall significantly determined a higher risk of TB in male red deer, probably mediated by sex-related differences in life history traits that determined more susceptibility and/or exposure in comparison to females. The positive association between the prevalence of TB in fallow deer and cattle may indicate significant interspecies transmission (in either direction) and/or similar exposure to risk factors mediated by ecological overlapping of grazing species. The identification of long-term drivers of TB provided evidence that its control in extensive pastoral systems can only be achieved by targeting all relevant hosts and integrating measures related to all the factors involved, such as: population abundance and the aggregation of wild and domestic ungulates, environmental exposure to mycobacteria, cattle testing and culling campaigns and adjustments of appropriate densities.

Highlights

A central problem concerning studies on the ecology of wildlife diseases is that many of the most important ecological, evolutionary and human-driven processes affecting host and pathogens may occur over multiple years or even decades
Considering age classes, overall, increasing age trends were indicated by the prevalence of Tuberculosis-Like Lesions (TBL) (Figure 1A, statistical results are shown below)
Contrasted prevalences of TBL were apparent among areas, showing a decreasing north to south gradient (Figure 1C; statistical results are presented below)

Summary

Introduction

A central problem concerning studies on the ecology of wildlife diseases is that many of the most important ecological, evolutionary and human-driven processes affecting host and pathogens may occur over multiple years or even decades. Some advantages of long-term approaches in wildlife disease epidemiology are the possibility of carrying out: (i) analyses of density-dependent effects; (ii) analysis of stochastic factors; (iii) evaluations of time-delayed effects, including the effects within/among species; (iv) studies for detecting disease emergence patterns; (v) evaluation of epidemiological processes on multiple scales, from individual to population; (vi) analyses for detailing the role that social systems and between- and within-individual heterogeneity in infection transmission; (vii) studies that provide valuable information applicable to the management of sanitary and socio-economic problems; and (viii) assessments of risk management strategies, adaptive strategies [3,5,6]. TB is endemic in cattle and wild ungulates in south and central

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