Establishing a serological surveillance protocol for rabbit hemorrhagic disease by combining mathematical models and field data: implication for rabbit conservation

Abstract

Rabbit hemorrhagic disease (RHD) became endemic in wild rabbit (Oryctolagus cuniculus) populations in the Iberian Peninsula after its first arrival in 1988. This had significant implications for both the economy and environmental conservation because rabbits are one of the main game species in the Iberian Peninsula and a keystone species in the Mediterranean ecosystems. As a consequence, it is planned to include RHD surveillance in the Spanish Wildlife Disease Surveillance Strategy. Nevertheless, there is no practical methodology included in this program to help conservationists and gamekeepers understand the impact of disease on wild rabbit populations. Results from sera collected during the hunting season from 11 rabbit populations of Central and South Spain, which differed in their population abundance and trends, allowed us to use mathematical models to interpret the serological results gathered and determine the best strategy for finalizing a plan of RHD surveillance. Put simply, we focused our field surveys within the hunting season (October-January), and those times when the rabbit populations are at their highest (June or July). Field results showed that both rabbit abundance and population trend are closely related to the prevalence of RHD antibodies when rabbit abundance was at its annual low point (usually October-November). Rabbit population trends were positive only if antibody prevalence was high (>40%), and always negative if prevalence was low. Moreover, rabbit populations where abundance was low always showed low antibody prevalence. Since our models predicted a low variability in the prevalence obtained during the hunting season, it is suggested that future serological surveys should be carried out within this period to avoid problems related to the low sample size in low density rabbit populations.