Arch Virol (1999) 144: 817–827
Phylogenetic characterization of a highly attenuated strain
of equine arteritis virus from the semen of a persistently
infected Standardbred stallion
J. F. Patton
, U. B. R. Balasuriya
, J. F. Hedges
, T. M. Schweidler
P. J. Hullinger
, and N. J. MacLachlan
Department of Pathology, Microbiology and Immunology,
School of Veterinary Medicine, University of California,
Davis, California, U.S.A.
California Department of Food and Agriculture, Sacramento, California, U.S.A.
Accepted October 3, 1998
Summary. An avirulent, novel variant of equine arteritis virus (EAV; CA95G)
was isolated from the semen of a persistently infected Standardbred stallion.
The CA95G virus caused subclinical infection and seroconversion in susceptible
horses, and virus was isolated only once from blood and nasal secretions collected
from 6 experimentally infected horses. Sequence analysis of genes encoding the
known EAV structural proteins shows that this highly attenuated strain of EAV is
genetically similar to virulent ﬁeld strains of EAV and, in particular, to a strain
of EAV that was isolated during an outbreak of equine viral arteritis in western
butgeneticdiversity of the virus is generated inthe course of persistent infection of
carrier stallions. The subtle genetic changes that facilitate and maintain persistent
EAV infection of the stallion’s reproductive tract likely inﬂuence phenotypic
properties of the virus such as virulence.
The GenBank accession numbers of the sequences reported in this paper are, respec-
tively: ORF2 and OFRs 5 through 7 for each virus: U81022, U81023 (CA95G); U81026,
U81027, (CA95Gs); and U81024, U81025 (CA95I); ORFs 5 through 7 of the following
viruses: U81013 (VBS53); U81014 (KY63); U81018 (PA76); U81015 (KY77); U81016
(KY84); U81017 (KY93); U81021 (CAN86); U81019 (ARVAC); and U81020 (ATCC).