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 or ha-MYXV), in the summer of 2019, the recombinant 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
myxoma virus (ha-MYXV) 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.