Progression of rabbit haemorrhagic disease virus 2 upon vaccination in an industrial rabbitry: a laboratorial approach

Abstract

Rabbit haemorrhagic disease virus 2 (RHDV2) emerged recently in several European countries, leading to extensive economic losses in the industry. In response to this new infection, specific inactivated vaccines were developed in Europe and full and rapid setup of protective immunity induced by vaccination was reported. However, data on the efficacy of these vaccines in an ongoing-infection scenario is unavailable. In this study we investigated an infected RHDV2 indoor industrial meat rabbitry, where fatalities continued to occur after the implementation of the RHDV2 vaccination, introduced to control the disease. The aim of this study was to understand if these mortalities were RHDV2-related, to discover if the dead animals showed any common features such as age or time distance from vaccination, and to identify the source of the outbreak. Anatomo-pathological analysis of vaccinated animals with the virus showed lesions compatible with systemic haemorrhagic disease and RHDV2-RNA was detected in 85.7% of the animals tested. Sequencing of the vp60 gene amplified from liver samples led to the recognition of RHDV2 field strains demonstrating that after the implementation of vaccination, RHDV2 continued to circulate in the premises and to cause sporadic deaths. A nearby, semi-intensive, RHDV2 infected farm belonging to the same owner was identified as the most probable source of the virus. The main risk factors for virus introduction in these two industries were identified. Despite the virus being able to infect a few of the vaccinated rabbits, the significant decrease in mortality rate observed in vaccinated adult rabbits clearly reflects the efficacy of the vaccination. Nonetheless, the time taken to control the infection also highlights the importance of RHDV2 vaccination prior to the first contact with the virus, highly recommendable in endemic areas, to mitigate the infection's impact on the industry.

Retrospective studies on rabbit haemorrhagic disease outbreaks caused by RHDV GI.2 virus on farms in France from 2013 to 2018

“…Recent studies proved that the vaccines used on farms provide sufficient protection against the GI.2 strains found in the field (Carvalho et al, 2017, Le Minor et al, 2017, Le Minor et al, 2019. The increase in RHD prevalence in the 2016-2017 period might be linked to an increase in virus virulence as suggested by Capucci et al (2017).…”

“…Little knowledge is available on the epidemiology of RHD due to GI.2 virus on industrial rabbit farms in Europe. Carvalho et al (2017) described the course of the infection on a farm where emergency vaccination was applied. Rosell et al (2019) recently published a 30-yr retrospective survey on occurrences of RHD in commercial farms in Spain.…”

Recombinant myxoma virus infection associated with high mortality in rabbit farming (Oryctolagus cuniculus)

“…Just in Great Britain, tens of millions of rabbits died (Bartrip, 2008). Spill over between the wild and domestic animals has been appointed as source of infection for outbreaks in the industry (C. L. Carvalho et al, 2017). Given the impact that viral infectious diseases may have in this sector, it is critical to monitor the sanitary status of industry and of the wild populations.…”

The Health and Future of the Six Hare Species in Europe: A Closer Look at the Iberian Hare

“…The system was designed to amplify a 127-nucleotide-long RNA region located within the vp60 gene, being able to detect as few as 9 RNA molecules. The method has proven a valuable tool to diagnose most of RHDV2 circulating strains and useful to monitor viral loads [118], disease progression, and vaccination efficacy [119]. The system figures in the OIE Manual as a recommended method for nucleic acid detection (https://www.oie.int/fileadmin/ Home/eng/Health_standards/tahm/3.06.02_RHD.pdf).…”