Relationship between the excretion of eggs of parasitic helminths in roe deer and local livestock density.

Because of their continuing expansion, wildlife ruminant species that prosper in rural landscapes may be increasingly affected by and/or contribute to the circulation of certain generalist pathogens also infecting domestic ruminants, when they share common spaces or resources. In this study, we aimed to test the hypothesis that parasitism with gastrointestinal nematodes (GINs) of wild roe deer inhabiting different rural landscapes is correlated with livestock density. We used faecal egg counts of GINs and spatial data of 74 GPS-collared roe deer, inhabiting various landscapes from closed forests to open fields, together with weekly records of livestock abundances on pasture. We tested whether the excretion of GIN eggs in roe deer was influenced by the density of livestock in their home range over the grazing season. Our results showed that all of the roe deer home ranges, except four, contained pastures occupied by livestock. Excretion of GIN eggs occurred in 77% of the roe deer. The excretion of GIN eggs in roe deer tended to increase with livestock density in their home range. This result suggests, but does not prove, a higher risk of ingesting GIN larvae originating from livestock dung. In the context of increasing overlap between roe deer and livestock ranges, the exchange of pathogens between both hosts is plausible, although species identity of the parasites present was not determined. Assessing which GIN species are shared between wild and domestic ruminants, and how this may affect the health of both hosts, is a central question for future research in the context of interspecific pathogen circulation.

Does body growth impair immune function in a large herbivore?

According to the principle of allocation, trade-offs are inevitable when resources allocated to one biological function are no longer available for other functions. Growth, and to a lesser extent, immunity are energetically costly functions that may compete with allocation to reproductive success and survival. However, whether high allocation to growth impairs immune system development during the growing period or immune system performance during adulthood is currently unknown in wild mammals. Using three roe deer (Capreolus capreolus) populations experiencing contrasting environmental conditions, we tested for potential costs of growth on immune phenotype over both the short-term (during growth), and the long-term (during adulthood) over the course of an individuals' life. We investigated potential costs on a set of 12 immune traits that reflect both innate and adaptive responses, and compared them between sexes and populations. Although fast growth tended to be associated with low levels of some humoral traits (globulins) during the growing period and some cellular immune traits (i.e. eosinophil and neutrophil counts) during adulthood, evidence for a trade-off between growth and other immune components was limited. Unexpectedly, no detectable growth costs on immunity were found in females from the population experiencing the least favourable environment. We discuss our findings in the light of the complex interplay between resource allocation strategies among reproduction, maintenance and immunity, in relation to local environmental conditions experienced by roe deer.

Exposure of Wildlife to the Schmallenberg Virus in France (2011-2014): Higher, Faster, Stronger (than Bluetongue)!

The Schmallenberg virus (SBV) has recently emerged in Europe, causing losses to the domestic livestock. A retrospective analysis of serodata was conducted in France for estimating seroprevalence of SBV among six wildlife species from 2011-2012 to 2013-2014, that is during the three vector seasons after the emergence of the SBV in France. Our objective was to quantify the exposure of wildlife to SBV and the potential protective effect of elevation such as previously observed for bluetongue. We also compared the spatiotemporal trends between domestic and wild animals at the level of the departments. We tested 2050 sera using competitive ELISA tests. Individual and population risk factors were further tested using general linear models among 1934 individuals. All populations but one exhibited positive results, seroprevalence up to 30% being observed for all species. The average seroprevalence did not differ between species but ranged from 0 to 90% according to the area and period, due to the dynamic pattern of infection. Seroprevalence was on average higher in the lowlands compared to areas located up to 800 m. Nevertheless, seroprevalence above 50% occurred in areas located up to 1500 m. Thus, contrary to what had been observed for bluetongue during the late 2000s in the same areas, SBV could spread to high altitudes and infect all the studied species. The spatial spread of SBV in wildlife did not fully match with SBV outbreaks reported in the domestic livestock. The mismatch was most obvious in mountainous areas where outbreaks in wildlife occurred on average one year after the peak of congenital cases in livestock. These results suggest a much larger spread and vector capacity for SBV than for bluetongue virus in natural areas. Potential consequences for wildlife dynamics are discussed.

Prevalence of Anaplasma phagocytophilum in small rodents in France.

Anaplasma phagocytophilum is an emerging zoonotic tick-borne pathogen affecting a wide range of mammals. Rodents are suspected to be natural reservoirs for this bacterium, but their role in the epidemiologic cycles affecting domestic animals and wild ungulates has not been demonstrated. This study aimed to improve our knowledge on A. phagocytophilum prevalence in Apodemus sylvaticus, A. flavicollis and Myodes glareolus using data collected in 2010 in one area in eastern France and in 2012-2013 in two others areas in western France. Rodents were captured in each site and infection was tested using qualitative real-time PCR assays on either blood or spleen samples. Prevalence showed high variability among sites. The highest prevalence was observed in the most eastern site (with an average infection rate of 22.8% across all species), whereas no rodent was found to be PCR positive in the south-west site and only 6.6% were positive in the north-west of France. Finally, a significant increase in prevalence was observed in autumn samples compared to spring samples in the north-west, but no change was found in the other two sites.