OIE Terrestrial Manual 2008
983
C H A P T E R 2 . 7 . 3 / 4 .
CAPRINE ARTHRITIS-ENCEPHALITIS
& MAEDI-VISNA
SUMMARY
Maedi-visna (MV) and caprine arthritis-encephalitis (CAE) are persistent lentivirus infections of
sheep and goats and are often grouped together as the small ruminant lentiviruses (SRLVs). Maedi-
visna is also known to as ovine progressive pneumonia (OPP). Phylogenetic analyses comparing
nucleotide sequences of MV virus (MVV) and CAE virus (CAEV) has demonstrated that these are
closely related lentiviruses. One source of CAEV and MVV transmission is colostrum and milk. The
source of horizontal transmission in the absence of lactation remains unknown; however, faeces
and lung fluids are known to harbour infectious virus. Ovine lentiviruses have been identified in
most of the sheep-rearing countries of the world, with the notable exceptions of Australia and New
Zealand. The distribution of CAEV is highest in industrialised countries, and seems to have
coincided with the international movement of European breeds of dairy goats. Clinical and
subclinical MV and CAE are associated with progressive, mononuclear cell inflammatory lesions in
the lungs, joints, udder and central nervous system. Indurative mastitis is common in both species,
and its economic significance may be underestimated. Laboured breathing associated with
emaciation caused by progressive pneumonitis is the predominant features in clinically affected
sheep, whereas polyarthritis is the main clinical sign in goats. However, most lentivirus-infected
sheep and goats are largely asymptomatic, but remain persistent carriers of virus and are capable
of transmitting infection via colostrum or milk and respiratory secretions. The most practical and
reliable approach to confirming a diagnosis of MV or CAE is a combination of serology and clinical
evaluation. Although serology represents the most cost-effective method of diagnosing persistently
infected, clinically normal animals, it should be understood that testing error