Efficacy of a competitive enzyme-linked immunosorbent assay (cELISA) for estimating prevalence of immunity to rabbit haemorrhagic disease virus (RHDV) in populations of Australian wild rabbits (Oryctolagus cuniculus)

Abstract

This study examines the efficacy of a cELISA in estimating the prevalence of immunity to rabbit haemorrhagic disease virus (RHDV) in wild rabbits in Australia. Rabbits (n = 343) captured from six locations in Victoria and Queensland were experimentally challenged with a lethal oral dose (1500 50%-lethal doses, LD50) of RHDV. Death or survival to challenge was used to determine the performance characteristics of the test. The diagnostic specificity, sensitivity and accuracy were highly variable between sites, making it difficult to select a representative cut-off value for all sites that achieved a reasonable level of accuracy for the prediction of surviving and non-surviving rabbits. Estimates of prevalence of immunity were biased owing to effects of site of capture (time of capture) and age structure of the population. Using predictive equations, the best estimates of survival were ±10% but these results came from a limited range of sites, all of which had survival in the range 49–70%. The cELISA will determine whether the RHDV is present in rabbit populations but it should be used with caution when estimating the prevalence of immunity to RHDV. The cELISA may thus be limited in its application for examining the epidemiology of RHDV in Australian rabbit populations.