Abstract
In a context of (re)emerging infectious diseases with wildlife reservoirs, understanding how animal ecology shapes epidemiology is a key issue, particularly in wild ungulates that share pathogens with domestic herbivores and have similar food requirements. For the first time in Europe, brucellosis (Brucella melitensis), a virulent zoonosis, persisted in an Alpine ibex (Capra ibex) population and was transmitted to cattle and humans. To better understand disease dynamics, we investigated the relationships between the spatial ecology of ibex and the epidemiology of brucellosis. Combining home range overlap between 37 GPS-collared individuals and visual observations of 148 visually-marked individuals monitored during the 2013–2016 period, we showed that females were spatially segregated in at least 4 units all year round, whereas males were more prone to move between female units, in particular during the rutting period. In addition to ibex age, the spatial structure in females largely contributed to variation in seroprevalence in the whole population. These results suggest that non-sexual routes are the most likely pathways of intraspecific transmission, crucial information for management. Accounting for wildlife spatial ecology was hence decisive in improving our ability to better understand this health challenge involving a wildlife reservoir.
Highlights
Wild animals have been identified as key components in theemergence and worldwide spread of disease[1,2,3]
We focused on the first report of brucellosis (Brucella melitensis) transmission from wildlife to domestic ruminants and humans, which was revealed in 2012 in the northern French Alps (Bargy massif; 46°00′N, 6°28′E, 1500–2438 m above sea level)[18,19]
Given that a previous outbreak involving a very similar Brucella strain had occurred in 1999 in livestock in the same area and that all other 205 domestic herds that grazed in the massif from 1999 up to 2012 were found brucellosis-free before they were taken to alpine pastures, wildlife was suspected of being the source of disease persistence and re-emergence
Summary
Wild animals have been identified as key components in the (re)emergence and worldwide spread of disease[1,2,3]. Identifying the drivers of animal and disease distributions has become a key issue in preventing the transmission of infections between wildlife and domestic herds and the subsequent formation of reservoirs in wildlife[8]. In this context, large herbivores have been recognized as relevant species for studying disease processes in free-ranging populations and for understanding how wildlife-livestock interactions may affect such processes[9]. The spatial ecology (e.g. area-restricted space use, partial migration) and social organization (e.g. fission-fusion dynamics, spatial and/or sexual segregation) of wild herbivores give rise to complex host-to-host interactions (intra- or interspecific) and make disease dynamics in these species tricky In an attempt to control the wildlife reservoir, several management actions were undertaken by the French Authorities between 2013 and 2015, including an important ibex slaughtering program: 251 individuals over 5 years old, representing > 44% of the estimated population, were culled in October 2013 and May 2014 (see Methods)
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