Lack of evidence for differences in the spread of classic (Lagovirus europaeus/GI.1) and novel (Lagovirus europaeus/GI.2) rabbit haemorrhagic disease viruses in Europe and North Africa.

Background: Fast-spreading diseases affecting wildlife populations threaten biodiversity. Two caliciviruses, Lagovirus europaeus/GI.1 and Lagovirus europaeus/GI.2, caused rabbit haemorrhagic disease virus (RHDV) in wild rabbits. Despite having different characteristics, these variants spread quickly, posing a threat to wild rabbit populations.

Methods: In this study, we conducted a thorough review of the scientific literature and reports of international organisations of first detections of both variants of RHDV in the Euro-Mediterranean region. We concentrated on this area to avoid bias due to intentional human introductions.

Results: The estimated mean spread rate of GI.2 was higher than that of GI.1 (GI.2: 479 km/year, range: 47-7346; GI.1: 330 km/year, 37-6248). These differences were not statistically significant. This lack of difference may be due to the interactions between each variant's virulence characteristics. Humans may have a dominant effect on their spread. Potential limitations associated with the observational process could have hindered our ability to identify statistical differences.

Conclusions: The lack of difference in the spread patterns of the two variants could be due to a biological cause, human facilitation or a lack of statistical power. Adapting protocols to detect diseases in wildlife using homogeneous criteria will be indispensable in the coming years.