Temporal Trend of Tuberculosis in Wild Ungulates from Mediterranean Spain

Abstract

SummaryTuberculosis (TB), a chronic disease caused by infection with the Mycobacterium tuberculosis complex, is endemic in wild boar (Sus scrofa) and red deer (Cervus elaphus) in south-central Spain. Understanding the temporal dynamics of this chronic infection requires long time series data collection over large areas. The aim of this paper was to identify the determinants of TB prevalence and severity in both species in Ciudad Real province, Spain, from 2000 to 2012. Study variables included management, population dynamics, and a range of geographical and climatological factors. The prevalence of TB in wild boar increased from 50% to 63% since the study commenced. This may be due to an increased hunting bag (a proxy for population abundance), which was correlated with TB infection rates. Low rainfall (a stochastic factor) was associated with higher individual risk of TB presence and progression, resulting in an increased proportion of severe cases of wild boar TB in dry years. This was probably a result of increased food restriction leading to a higher susceptibility to TB. In contrast, red deer TB showed an apparent stable trend, which may be a consequence of the species' higher and stable population size. Hunting management, characterized by fencing, was associated with a higher risk of TB in both wild boar and red deer, suggesting that intensive hunting management may have contributed to exacerbated TB figures. This difference was more marked in red deer than in wild boar, probably because fencing imposes less restriction on movement, population mixing and TB spread to wild boar than to deer. Our findings on TB dynamics are fundamental for assessing the impact of future disease-control actions (e.g. field vaccination). Moreover, such control plans must operate in the long term and cover large areas.

Interactions between four species in a complex wildlife: livestock disease community: implications for Mycobacterium bovis maintenance and transmission

“…TB is prevalent in this area despite test-and-slaughter schemes, affecting 3.54 % of cattle herds in the area in 2012 (RASVE 2014). Large-scale and long-term sampling studies have also revealed a high prevalence in wild boar (59.0 %) and red deer (9.4 %) in the region (Vicente et al 2013).…”

“…These results suggest that the possible role of red deer in the disease system in this region of Spain should receive further investigation, though the pathogenesis and excretion of a pathogen by each species need to be considered. Regarding TB, red deer prevalence in the region has been shown to be stable around a mean of 9.4 %, whilst mean wild boar TB prevalence is 59.0 % and has been increasing over the last decade (Vicente et al 2013). Further research into direct and indirect interactions between wild boar and livestock is also necessary.…”

“…The presence of wildlife has also been shown to be a significant risk factor for bovine TB at the individual farm level (Cowie et al 2014). Both cattle and wildlife display high TB prevalence in south-central Spain, and levels in wild boar and red deer have increased over the last 12 years (Vicente et al 2013). It is thought that the presence of these wildlife reservoirs is contributing to the failure to eradicate TB in the cattle population despite a long-standing test-and-slaughter scheme (Diez et al 2002;Naranjo et al 2008;Gortazar et al 2011).…”

Testing Eurasian wild boar piglets for serum antibodies against Mycobacterium bovis

“…The native Eurasian wild boar (Sus scrofa) is considered the greatest TB hazard of all wildlife species in Europe (Hardstaff et al, 2014) and particularly is the single most important MTC maintenance host species in Mediterranean ecosystems of the Iberian Peninsula Naranjo et al, 2008). High TB prevalence of above 60% is sometimes reported in wild boar from sites with a high infection pressure in central and southern Spain (Vicente et al, 2013).…”

Scientific Opinion on African swine fever

“…The probability of transmission of infectious diseases through direct or indirect contact between susceptible wild boar populations depends on many factors, including the population density (Diekman et al, 1995). The correlation between the wild boar density and the possible presence and duration of other infectious diseases, such as Aujesky disease, classical swine fever, foot and mouth disease, porcine circovirus type 2 and tuberculosis, has already been described (Vicente et al, 2004(Vicente et al, , 2013Rossi et al, 2005;Gortázar et al, 2006;Acevedo et al, 2007;Boadella et al, 2012;EFSA, 2014b. However, it is currently impossible to know the population density threshold for ASFV spread in wild boar populations, due to lack of knowledge on the exact population size and population dynamics and the epidemiology of ASF in wild boar.…”