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SummaryMethods of transmission of Jembrana disease, an acute and severe disease of Bali cattle (Bos javanicus) caused by a recently-identified bovine lentivirus known as Jembrana disease virus, are described. During the acute disease virus can be detected in saliva and milk. There is evidence of direct transmission from acutely affected animals in close contact with susceptible cattle, possibly by virus in these secretions infecting cattle by the conjunctiva!, intranasal or oral routes, by which it was possible to infect cattle experimentally. During the acute disease the titre of infectious virus in blood is high, about 108 50% cattle infectious units (ID50)/ml, and it is probable that the virus is also transmitted mechanically by haematophagous arthropods. Recovered cattle are also a potential but probably infrequent source of infection; recovered cattle are persistently viraemic but the titre of infectious virus in blood decreases to about 101 ID50/ml by 60 days after recovery from the acute disease, and virus cannot be detected in secretions.

1A sensitive diagnostic assay for the detection of infections with the bovine 2 lentivirus Jembrana disease virus (JDV) is required in Indonesia to control the 3 spread of Jembrana disease. Immunoassays are used routinely but are 4 compromised by cross-reactive epitopes in the capsid (CA) protein of JDV 5 and the genetically related bovine immunodeficiency virus (BIV). JDV gag-6 specific primers were tested in a real-time PCR assay to detect proviral DNA 7 in peripheral blood mononuclear cells from 165 cattle from the Tabanan 8 district of Bali. JDV-specific amplicons were detected in 9% of the cattle and 9 only 33% of the real-time PCR positive cattle were also seropositive. The 10 delayed seroconversion that occurs after infection with JDV could explain the 11 low concordance between these assays but other factors may be responsible.