A novel group A rotavirus associated with acute illness and hepatic necrosis in pigeons (Columba livia), in Australia

Abstract

Cases of vomiting and diarrhoea were reported in racing pigeons in Western Australia in May, 2016. Morbidity and mortality rates were high. Similar clinical disease was seen in Victoria in December and by early 2017 had been reported in all states except the Northern Territory, in different classes of domestic pigeon-racing, fancy and meat bird-and in a flock of feral pigeons. Autopsy findings were frequently unremarkable; histological examination demonstrated significant hepatic necrosis as the major and consistent lesion, often with minimal inflammatory infiltration. Negative contrast tissue suspension and thin section transmission electron microscopy of liver demonstrated virus particles consistent with a member of the Reoviridae. Inoculation of trypsin-treated Vero, MDBK and MA-104 cell lines resulted in cytopathic changes at two days after infection. Next generation sequencing was undertaken using fresh liver samples and a previously undescribed group A rotavirus (genotype G18P[17]) of avian origin was identified and the virus was isolated in several cell lines. A q-RT-PCR assay was developed and used to screen a wider range of samples, including recovered birds. Episodes of disease have continued to occur and to reoccur in previously recovered lofts, with variable virulence reported. This is the first report of a rotavirus associated with hepatic necrosis in any avian species.

Fig 1. Enlargement of the spleen (*) with mild haemorrhage was seen in some early cases.

Fig 2

a) Hepatocellular dissociation with necrosis and macrophage infiltrate (*), in the absence of other inflammatory response, was the distinctive finding in all birds, although severity varied. Islands of relatively normal parenchyma (arrow) remained. (b) Biliary proliferation (*) was sometimes seen.

Fig 3

a) Negative contrast electron microscopy revealed non- enveloped viral particles. Viral particles (arrows) have electron dense cores, where stain has penetrated the interior of the particles, clearly demonstrating a wheel-like appearance consistent with the family Reoviridae, genus Rotavirus. Scalebar represents 100nm. b) Ultrathin section of infected pigeon liver tissue. Arrow indicates an array or cluster of virus particles egressing from a dying cell. RBC = Red blood cell. Scale bar represents 1μm.

Fig 4. Cytopathic effect induced by pigeon rotavirus in MA-104 cells, three days post-infection.

(A) Uninfected control cells. (B) Infected cells.

Fig 5. Phylogram indicating genetic relationships of complete nucleotide sequences of VP7 of pigeon rotavirus strain RVA /pigeon-wt/AUS/VIC/2016/G18P[17] (in red) from Australia with representatives of known human and animal rotavirus genotypes.

The tree was generated by the Maximum Likelihood method using MEGA7. Bootstrap values (1000) above 70 are shown. Scale bar indicates nucleotide substitutions per site.