Seroepidemiology of rabbit haemorrhagic disease (RHD) in wild rabbits (Oryctolagus cuniculus) in the United Kingdom

Abstract

An extensive collection of blood samples from adult wild rabbits, from areas where Rabbit Haemorrbagic Disease (RHD) had not been recorded, was obtained from sites across the U.K. and parts of Eire over the winter of 1994195. Sera from 946 animals were examined for antibodies to RHD. Antibody was found in all populations, varying between 20 and 100% depending on locality, and overall 64% of rabbits were seropositive in midwinter, supporting the view that non-pathogenic RHD or RHD-like caliciviruses, which are not producing clinical disease, circulate within rabbit populations. The serological response to these agents appears to confer significant immunity on rabbits subsequently exposed to the virulent RHD virus, so the disease will not be as devastating as myxomatosis was in the early 1950s (99% mortality) but at least one-third of the c. 40 million rabbits in the U.K. are susceptible.

Epidemiological consequences of a pathogen having both virulent and avirulent modes of transmission: the case of rabbit haemorrhagic disease virus

“…The range of seroprevalence recorded in the absence of disease in the United Kingdom (10-100 %) [14,15] indicates that R 0, C has markedly different values in different populations. This large variability in seroprevalence between populations then leads us to ask, 'Can differences in population dynamics explain this range of seroprevalence, and if so then what proportion of UK populations are likely to be protected by endemic chronic-phase infection ? '…”

“…We estimate the acute phase transmission parameter, b 1 , using the following information. An outbreak occurred at Dawlish Warren in Devon [21], shortly after the seroprevalence survey was performed [14,15]. Although this site was not sampled, six others in Devon were.…”

“…However, immunity to RHDV has been found in the absence of signs of disease in both wild and captive populations from a number of locations, including the former Czechoslovakia, Switzerland, Austria, Germany and Sweden [9][10][11][12][13]. Seroprevalence was particularly high in the United Kingdom, with a mean of 64 % and a maximum of 100 % [14,15]. It has been proposed that this immunity may be due to a non-pathogenic strain of RHDV [10][11][12][13][14], such as that isolated from a rabbitry in Italy in 1996 [9,16].…”

“…Seroprevalence was particularly high in the United Kingdom, with a mean of 64 % and a maximum of 100 % [14,15]. It has been proposed that this immunity may be due to a non-pathogenic strain of RHDV [10][11][12][13][14], such as that isolated from a rabbitry in Italy in 1996 [9,16].…”

“…We examine whether this model can explain the intriguing situation in the United Kingdom, where immunity to RHDV, in the absence of observable disease, was found in all 68 of the wild rabbit populations sampled, usually at very high prevalence (mean 64 %, range 10-100%) [14,15]. Furthermore, in the United Kingdom, virulent RHDV has had little impact, nationally, in terms of the number of populations affected and the total number of rabbits that died, despite scattered lethal outbreaks having occurred in wild populations country-wide since 1994 [21 ; P. J.…”