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

Abstract

To mitigate the negative impacts of invasive rabbits in Australia, land managers are permitted to release the biocontrol virus, rabbit hemorrhagic disease virus (RHDV), to reduce rabbit numbers. However, it is strongly recommended that RHDV is not released when young rabbits are present in the population as infection in this cohort is sublethal and induces life‐long virus immunity. The recruitment of these rabbits into the breeding population may make the population harder to control in future, potentially leading to increasing rather than decreased population size. To investigate whether the recommended release guidelines are followed, we obtained data on the supply and release of RHDV by land managers. We then used generalized additive models to investigate Australia‐wide and state‐specific annual and long‐term temporal trends in the supply and release of RHDV. Half of all RHDV supply (47%) and three quarters of reported releases (74%) Australia‐wide occurred during the anticipated major rabbit breeding seasons and when the risk of immunizing young rabbits is greatest. We found evidence of both RHDV supply and release during the anticipated major rabbit breeding seasons in almost all states for which data existed. RHDV supply increased with below average annual rainfall. This may indicate a tendency for land managers to notice, and want to control, rabbits and their impacts more following drier years when both rabbits and their impacts are potentially more damaging. Our study raises concerns regarding the inappropriate release of RHDV by land managers and whether its supply should be restricted to ensure ongoing and effective management of invasive rabbits. More broadly, our study serves as a warning to other conservation and pest management activities reliant on land managers or citizens following implementation guidelines. In some cases, good intentions may have adverse outcomes.

Social interactions of juvenile rabbits (Oryctolagus cuniculus) and their potential role in lagovirus transmission

“…This is of particular importance for RHDV-mediated biocontrol transmission, as juvenile rabbits can shed RHDV for many weeks following infection, without developing the disease. This has implications for the timing of virus release, and further investigation should focus on the effect this may have on a resistant breeding population versus increased virus spread for the management of wild European rabbits [ 24 ]. Further investigation should also be made into the effect of juvenile shedding status, and temporal variation in juvenile rabbit behaviour on the transmission of lagoviruses could lead to improved timing of RHDV-mediated biocontrol and better management of lagoviruses for the preservation of rabbit populations in their native range [ 11 , 60 ].…”

“…European rabbits [24]. Further investigation should also be made into the effect of juvenile shedding status, and temporal variation in juvenile rabbit behaviour on the transmission of lagoviruses could lead to improved timing of RHDV-mediated biocontrol and better management of lagoviruses for the preservation of rabbit populations in their native range [11,60].…”

“…The presence of the interacting variants complicates the epidemiology of RHD in Australia and the role that juvenile rabbits play in the transmission of RHDV and RHDV GI.4c is somewhat uncertain [ 20 , 23 , 24 ]. They are potentially important because juveniles can carry and shed both pathogenic and non-pathogenic RHDV [ 25 ].…”

“…If juveniles are infected with RHDV1 during 6–12 weeks of age, immunity may become permanent and provide cross-immunity between lagovirus strains, enabling the establishment of a resistant breeding generation [ 25 , 27 ]. These immunities have implications for the spread and establishment of lagoviruses in wild European rabbit populations and hence the effectiveness of circulating and new lagovirus strains for population biocontrol and the timing of control programs [ 24 ]. Because juvenile rabbits can carry pathogenic viruses without developing disease, they are at increased likelihood of playing an important role in influencing the effects of lagoviruses on rabbit populations through their movements and pairings with other rabbits.…”

Sustained Impact of RHDV2 on Wild Rabbit Populations across Australia Eight Years after Its Initial Detection

“…[ 8 , 9 , 10 ], and can fatally infect rabbits that are resistant to infection with virulent RHDV1 at a very young age [ 11 , 12 ]. Furthermore, recent work has shown that this ability to infect young rabbits enables RHDV2 to amplify in susceptible populations earlier [ 13 ]. Together with the ability to overcome pre-existing immunity to RHDV1, these attributes have been proposed as a key factor driving RHDV2′s epidemiological competitiveness over RHDV1, resulting in its global spread.…”