Using fluorescence in situ hybridisation to detect Oryctes rhinoceros nudivirus infection in coconut rhinoceros beetle (Oryctes rhinoceros)

Coconut rhinoceros beetle (CRB; Oryctes rhinoceros) has been an invasive pest species of coconut and oil palm across the Asia/Pacific region since the early 20th Century. These invading CRB populations were successfully limited by a virus, Oryctes rhinoceros nudivirus (OrNV), in what is now a landmark case for classical biocontrol. The recent re-emergence of CRB as an invasive pest and discovery of the virus-tolerant CRB haplotype (CRB-G) has led to the need to explore additional options for biocontrol, including unique OrNV isolates capable of establishing and maintaining infection in CRB-G. CRB infection status is currently determined using a combination of PCR assays and histology from midgut tissue. While the combination of the two methods provides a conclusive answer to whether an individual is infected, there are limitations to both. PCR provides limited information on the viral locality and the severity of infection, while positive histology assessments can only be made in mid to late-stage infection. To expand our toolkit for assessing infection status and improve our knowledge of infection dynamics, we recently developed an assay using fluorescence in situ hybridisation (FISH). FISH allows us to directly detect OrNV at earlier stages of infection and better understand the extent of infection. By improving our understanding of infection progression, we can better evaluate distinct OrNV isolates in the context of finding an isolate capable of causing disease in CRB-G.