Rabbit haemorrhagic disease virus (RHDV) is a lagovirus that causes rabbit haemorrhagic disease (RHD) in European rabbits (Oryctolagus cuniculus). In 2010, a new genotype called RHDV2 emerged in France. It exhibits a larger host range than classical RHDV strains by sporadically infecting different hare species, including the European hare (Lepus europaeus). Phylogenetic analyses revealed that closely related RHDV2 strains circulate locally in both hares and rabbits, and therefore that RHDV2 strains infecting hares do not belong to a lineage that has evolved only in this species. We showed that RHDV2 is widely distributed in France and that it was responsible for more than a third of cases of lagovirus disease in European hare populations in 2015. The oldest RHDV2 positive hare was sampled in November 2013 and we reported two hares co-infected by EBHSV and RHDV2. All together, our results raise important epidemiological and evolutionary issues. In particular, along with the potential emergence of recombinant EBHSV/RHDV2 strains in hares, the enlargement of the host range changes the host population structure of RHDV2 and may alter the impact of the virus on rabbit and hare populations.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-017-0473-y) contains supplementary material, which is available to authorized users.

The eastern cottontail (Sylvilagus floridanus) is an American lagomorph. In 1966, it was introduced to Italy, where it is currently widespread. Its ecological niche is similar to those of native rabbits and hares and increasing overlap in distribution brings these species into ever closer contact. Therefore, cottontails are at risk of infection with the two lagoviruses endemically present in Italy: Rabbit Haemorrhagic Disease virus (RHDV) and European Brown Hare Syndrome Virus (EBHSV). To verify the susceptibility of Sylvilagus to these viruses, we analyzed 471 sera and 108 individuals from cottontail populations in 9 provinces of north-central Italy from 1999 to 2012. In total, 15–20% of the cottontails tested seropositive for EBHSV; most titres were low, but some were as high as 1/1280. All the cottontails virologically tested for RHDV and EBHSV were negative with the exception of one individual found dead with hares during a natural EBHS outbreak in December 2009. The cottontail and the hares showed typical EBHS lesions, and the EBHSV strain identified was the same in both species (99.9% identity). To experimentally confirm the diagnosis, we performed two trials in which we infected cottontails with both EBHSV and RHDV. One out of four cottontails infected with EBHSV died of an EBHS-like disease, and the three surviving animals developed high EBHSV antibody titres. In contrast, neither mortality nor seroconversion was detected after infection with RHDV. Taken together, these results suggest that Sylvilagus is susceptible to EBHSV infection, which occasionally evolves to EBHS-like disease; the eastern cottontail could therefore be considered a “spill over” or “dead end” host for EBHSV unless further evidence is found to confirm that it plays an active role in the epidemiology of EBHSV.

a b s t r a c tDespite the importance of conservation and management of the European hare, a game species that has declined throughout Europe, little is known about its natal dispersal process. To date, only one radiotracking study in a mixed cropping-farmed landscape provides a fine description of the dispersal pattern of this species. The study shows in particular a negative density dependence dispersal, juvenile hares dispersing more in a low-density hunting zone rather than in a high density non-hunting zone. Unfortunately, the effect of conspecific density on dispersal remains ambiguous due to the confounding effect of hunting. To provide more insight into the influence of conspecific numbers on the dispersal propensity in hares, we renewed the study in a harvested high density population.Our results confirmed the known sex-biased and age-related dispersal in this species but we did not find any effect of the birth site density on either the propensity to disperse or the distance moved in juvenile hares. Overall, the dispersal rate and bias were equal to those previously found in the high density non-hunting zone, where density was almost the same as in our population even though hunting pressure differed. Our results emphasize that natal dispersal is a ubiquitous feature in this species, which may respond more to density than hunting.

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