Isolation of the Thosea asigna virus (TaV) from the epizootic Setothosea asigna larvae collected in South Sumatra and a study on its pathogenicity to Limacodidae larvae in Japan.

In 2005, natural epizootics were observed during an outbreak of Setothosea asigna (Lepidoptera: Limacodidae) larvae in an oil palm plantation in South Sumatra, Indonesia. The causative agent was filterable, which implied it was a virus. Since preliminary testing using reverse PCA gave a positive result for the Thosea asigna virus (TaV), we experimented with the purification of the viral agent from the diseased larvae. Electron microscopy revealed nonenveloped virus-like particles that were spherical in shape and about 40 nm in diameter. eDNA cloning followed by sequencing demonstrated that RNA purified from the particles contained two large openreading- frames (OAFs) with a partly shared sequence and extensive homology (> 98% identity at the nucleotide level) with OAFs of TaV encoding an RNA-dependent RNA polymerase and the capsid protein, respectively. 3' RACE suggested that there is, like in TaV genomic RNA, no poly(A) tract at the 3'-terminus of the RNA. The pathogenicity of the purified particles against Limacodidae larvae in Japan was demonstrated to be very strong for Monema f/avescens and Austrapoda dentata. These results indicated that the agent causing the epizootic disease among S. asigna larvae in the oil palm plantations was TaV which also has potential as a biological control agent for Limacodidae pests in Japan. [ABSTRACT FROM AUTHOR]