Changes in European wild rabbit population dynamics and the epidemiology of rabbit haemorrhagic disease in response to artificially increased viral transmission

Abstract

European wild rabbit (Oryctolagus cuniculus) populations are severely affected by rabbit haemorrhagic disease (RHD), currently aggravated by the spread of the new lagovirus serotype RHDV2 that replaced the classical RHDV strains (RHDV/RHDVa). This virus causes high mortality in both adult and young rabbits and to date, there is no management tool to effectively reduce its impact on wild rabbit populations. This hinders the success of common strategies, such as habitat management or restocking, in areas where rabbits are native. However, the present study, conducted on enclosed wild rabbit populations, showed that spreading RHDV2 on baits during breeding periods induced infection of young rabbits, reducing mortality rates, presumably due to maternal antibody protection. This reduced the young rabbit mortality hazard by a third, and more juvenile rabbits immune to RHDV2 were recruited into the adult breeding population. Young rabbits from populations in which the force of infection of RHDV2 was increased, however, exhibited considerably higher susceptibility to infection by RHDV than those from non-treated control populations. Since co-circulation of classical RHDVs was ruled out, differences in the type and degree of immunization, the level of cross-protection and/or other unknown factors, such as the circulation of undetected non-pathogenic lagoviruses, arose as possible explanations. This meant that although the present study demonstrated the possibility of successfully modulating the impact of RHD in wild populations, the epidemiological complexity of the situation where several lagoviruses circulate requires additional research to determine final applicability of the proposed method.

High Mortality of Wild European Rabbits during a Natural Outbreak of Rabbit Haemorrhagic Disease GI.2 Revealed by a Capture-Mark-Recapture Study

“…Abundance increased in the following spring (353 ± 99 rabbits in July 2022), although it did not attain the values of the previous year (Figure 1(a)). It should be noted that the density of the study population was unnaturally high (>200 rabbits/hectare) as the apparent mortality was <20% before the outbreak, as expected for an enclosure with supplemental feeding and no terrestrial predators [46]. Te seroprevalence before the outbreak was extremely low (12.5%-15.6%), which suggests that our model system could be close to a naïve population [47].…”

Good intentions with adverse outcomes when conservation and pest management guidelines are ignored: A case study in rabbit biocontrol

“…Recent experimental studies on enclosed wild rabbit populations show that the release of RHDV2 during the rabbit beeding season induced infection in young rabbits and substantially reduced their mortality rate due to maternal antibody protection (Calvete et al, 2021). This is of direct relevance to the results of our study and the predicted implications of unseasonal RHDV releases.…”

Immunological Cross-Protection between Different Rabbit Hemorrhagic Disease Viruses—Implications for Rabbit Biocontrol and Vaccine Development

“…GI.2 can cause disease in younger rabbits from four weeks of age, and the pathogenicity of Australian GI.2 variants is close to 100% in susceptible animals [ 20 ]. However, young rabbits with GI.2 maternally derived immunity are resistant to disease with GI.2 [ 21 , 35 ]. Experimental work using passively immunised kittens, to mimic the presence of maternal antibodies, demonstrated a robust antibody response after virus challenge [ 21 ].…”