Development of a recombinase polymerase amplification lateral flow dipstick (RPA-LFD) for the field diagnosis of caprine arthritis-encephalitis virus (CAEV) infection.

Caprine arthritis-encephalitis (CAE) in goats is a complex disease syndrome caused by a lentivirus. This persistent viral infection results in arthritis in adult goats and encephalitis in lambs. The prognosis for the encephalitic form is normally poor, and this form of the disease has caused substantial economic losses for goat farmers. Hence, a more efficient detection platform based on recombinase polymerase amplification (RPA) and a lateral flow dipstick (LFD) was developed in the present study for detecting the proviral DNA of caprine arthritis-encephalitis virus (CAEV). Under the optimal incubation conditions, specifically, 30min at 37°C for RPA followed by 5min at room temperature for LFD, the assay was found to be sensitive to a lower limit of 80pg of total DNA and 10 copies of plasmid DNA. Furthermore, there was no cross-reaction with other tested viruses, including goat pox virus and bovine leukemia virus. Given its simplicity and portability, this RPA-LFD protocol can serve as an alternative tool to ELISA for the primary screening of CAEV, one that is suitable for both laboratory and field application. When the RPA-LFD was applied in parallel with serological ELISA for the detection of CAEV in field samples, the RPA-LFD assay exhibited a higher sensitivity than the traditional method, and 82% of the 200 samples collected in Taiwan were found to be positive. To our knowledge, this is the first report providing evidence to support the use of an RPA-LFD assay as a specific and sensitive platform for detecting CAEV proviral DNA in goats in a faster manner, one that is also applicable for on-site utilization at farms and that should be useful in both eradication programs and epidemiological studies.