RHDV2 epidemic in UK pet rabbits. Part 2: PCR results and correlation with vaccination status

Abstract

To report PCR results and vaccination status of rabbits with rabbit haemorrhagic disease following an investigation into sudden or unexpected death. Materials and MethOds: PCR testing for RHDV2 and RHDV1 was performed on rabbit liver samples at two laboratories. Laboratory A reported results as positive or negative; Laboratory B reported results quantitatively as RNA copies per mg liver, categorised as negative, inconclusive or positive. The vaccination status of rabbits with both histopathological features of rabbit haemorrhagic disease and positive PCR test results were collated. results: PCR results matched histopathological findings in 188 of 195 (96%) cases. Seven individuals showed equivocal results, all of which had histopathological features of RHD but three tested PCRnegative and four results conflicted between laboratories. RHDV2 was the serotype detected in all PCR-positive cases. Histological features of rabbit haemorrhagic disease and PCR test results were positive in 125 rabbits; 51 unvaccinated, 56 in-date with Nobivac Myxo-RHD and 13 vaccinated against RHDV2-although nine of these were vaccinated within 10 days of death. clinical significance: PCR testing complements histopathology in cases of sudden death in rabbits by confirming the diagnosis and identifying virus serotype, but there can be false negatives. Although RHDV2 is currently prevalent in UK pet rabbits, vaccination against both RHDV1 and RHDV2 is recommended. Failures of RHDV2 vaccine are infrequent.

Incursions of rabbit haemorrhagic disease virus 2 in Canada—Clinical, molecular and epidemiological investigation

“…Haemorrhages were observed in both the lungs (Figure 2c) and heart (Figure 2d) in two of the animals. Gross lesions observed were similar to those reported previously for RHDV2 for both experimental infections (Neimanis et al., 2018, Le Gall‐Reculé et al, 2013) and outbreaks (Harcourt‐Brown et al., 2020). However, gross lesions are often subtle and only a few images are available (Duarte et al, 2015; Camarda et al., 2014).…”

“…However, gross lesions are often subtle and only a few images are available (Duarte et al, 2015; Camarda et al., 2014). The histopathology observed was mostly consistent with that described previously (Harcourt‐Brown et al., 2020; Neimanis et al., 2018) and included periportal to mid‐zonal hepatocellular necrosis with multifocal periportal non‐suppurative hepatitis, extensive microthrombosis of renal glomerular capillaries, splenic necrosis with lymphocytolysis and fibrin deposition, pulmonary haemorrhage with microthrombosis and myocardial haemorrhage with microthrombosis. Although Neimanis et al documented the viral distribution in tissues using immunohistochemistry (IHC); here, we present the distribution of RHDV2 RNA in tissues by ISH.…”

“…Haemorrhages were observed in both the lungs (Figure 2c) and heart (Figure 2d) in two of the animals. Gross lesions observed were similar to those reported previously for RHDV2 for both experimental infections (Neimanis et al, 2018 and outbreaks (Harcourt-Brown et al, 2020).…”

“…However, later the RHDV2 variants showed increased pathogenicity (Capucci et al, 2017) by killing rabbits of all age groups, and a number of Mediterranean, European and Alpine hare species (Camarda et al, 2014;Hall et al, 2017;Le Gall-Reculé et al, 2017;Puggioni et al, 2010;Velarde et al, 2017). In 2017, a new nomenclature and classification system for lagoviruses was proposed (Le Gall-Reculé et al, 2017), and based on the new nomenclature, the classical RHDV2 was classified under the genotype GI.2 and the classical RHDV strains under genotype GI.1 RHDV2 (GI.2) is currently endemic in Europe, and outbreaks have been recently reported from Canada, USA, China, Ireland, Netherlands, UK, Tunisia, Morocco, Senegal, Côte d'Ivoire and Ghana (Bell et al, 2019;Dalton et al, 2015;Fitzner & Niedbalski, 2018;Hu et al, 2020;Miao et al, 2019;Neimanis et al, 2018;Rocchi et al, 2019;WAHIS OIE Report Event summary, 2020).…”

Death in four RHDV2‐vaccinated pet rabbits due to rabbit haemorrhagic disease virus 2 (RHDV2)

“…Harcourt‐Brown et al . (2020) also reported cases of mortality in rabbits despite RHDV2 vaccination.…”