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

Abstract

Myxomatosis is an emergent disease in Iberian hare, having been considered a rabbit disease for decades. Genome sequencing of the strains obtained from affected Iberian hares showed to be distinct from the classical strains that circulated in rabbits since the virus introduction in Europe, in 1952. The main genomic difference concerns the presence of an additional 2.8Kb region disrupting the M009L gene and adding a set of genes with homology to the MYXV genes M060R, M061, M064 and M065R originated in poxviruses. After the emergence of this recombinant virus (MYXV-Tol, ha-MYXV ), in the summer of 2019, recombinnat MYXV was not detected in rabbit surveys suggesting apparent species segregation with the MYXV classic strains persistently circulating in rabbits.Recently, a group of six unvaccinated European rabbits (Oryctolagus cuniculus cuniculus ) from a backyard rabbitry in the South Portugal, developed signs of myxomatosis (anorexia, dyspnoea, oedema of eyelids, head, ears, external genitals and anus, and skin myxomas in the base of the ears), five of them dying within 24-48 hours of symptoms onset. Molecular analysis revealed that only the recombinant myxoma virus was present. This is the first documented report of a recombinant myxomatosis virus in farm rabbits associated with high mortality, which aggravates the concern for the future of the Iberian hare and wild rabbits and the safety of the rabbit industry against which the existing vaccines may not be fully protective.