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Exploratory analysis of the black soldier fly virome
Before 2021, no viruses were known to infect black soldier flies (BSF, Hermetia illucens). Research in the field of insect rearing has pointed out the high economic impact that viruses could have for the industry. Viral disease in mass-reared insects, like crickets, highlights the need to pre-emptively identify potential viral threats against the relatively young industry of mass-rearing BSF.
As more members of the BSF rearing industry and hobbyists have opened up to us, this has provided crucial insight into experiences with reared BSF colonies and BSF health in general. Symptoms and death in BSF colonies are being experienced more regularly in multiple BSF farms. Previous attempts to find the cause of these occurrences in BSF colonies have not appeared fruitful. This could be due to the varied approaches in feed and rearing conditions for BSFs, which can make it harder to detect the causes or exact sources. To avoid an exhaustive set of experiments, two initial approaches have been taken by this project in order to identify more targeted ventures for experimental characterization of viruses interacting with BSF.
First, computer analyses were performed on genetic material that was extracted from ill and healthy BSF adults and larvae. This approach allowed us to have a general look at the microbiome of the BSF and zoom in on the virus community (virome). By scanning this virome, we were able to find sequence data which provide us with evidence of five virus candidates, which are closely related to viruses infecting other insects. We have also linked some of the virus candidates with symptomatic or dying BSF. Since we now have a base map of what kind of viruses that we could expect to find, we can plan experiments on BSF and the virus candidates more easily.
The second approach comes with a twist. Instead of looking for present viral infections, we used different computerized methods to explore the genetic material of BSF for past viral infections. In other words, we can use detective work to find clues in BSF genomes and these can tell us what kind of viruses have infected BSF before. This approach has provided a second set of viral sequences which are also related to other insect viruses. Encouragingly, a collection of the sequences was very closely-related to one of the viral candidates that we had obtained with the first approach.
Now that we have found several virus candidates, the next step is to determine whether these viruses are indeed responsible for the symptoms and deaths experienced in some BSF farms, and if they may have any other effects on BSF. This will allow further assays to study virus transmission, fly pathology and hopefully management of the diseases.