Active and covert infections of cricket iridovirus and Acheta domesticus densovirus in reared Gryllodes sigillatus crickets

Authors: Duffield, Kristin; HUNT, JOHN - Western Sydney University; SADD, BEN - Illinois State University; SAKALUK, SCOTT - Illinois State University; Oppert, Brenda; ROSARIO-CORA, KARYNA - University Of South Florida; Behle, Robert; Ramirez, Jose

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2021
Publication Date: 11/30/2021
Citation: Duffield, K.R., Hunt, J., Sadd, B.M., Sakaluk, S.K., Oppert, B.S., Rosario-Cora, K., Behle, R.W., Ramirez, J.L. 2021. Active and covert infections of cricket iridovirus and Acheta domesticus densovirus in reared Gryllodes sigillatus crickets. Frontiers in Microbiology. 12. Article 780796. https://doi.org/10.3389/fmicb.2021.780796.
DOI: https://doi.org/10.3389/fmicb.2021.780796

Interpretive Summary: Mass-produced insects represent a potential solution to the food shortage expected to increase in the future and offer a sustainable and healthy source of protein for both livestock animals and humans. Crickets are especially popular because they are nutritious, easy to produce, and can be utilized in multiple applications. However, the production of crickets has been severely impacted by diseases caused by viruses, about which we know little. The research reported here allows us to fill this research gap by identifying and characterizing an unknown virus causing disease in a lab-reared population of Gryllodes sigillatus crickets, a species popular in the farmed cricket industry. We used molecular and genomic approaches to identify and quantify the microbial pathogen infecting these crickets. We found these crickets to be infected with two viruses, both known to cause devastating disease in farmed colonies: cricket iridovirus (CrIV) and Acheta domesticus densovirus (AdDNV). The symptoms present, in addition to high viral loads found in diseased crickets, strongly suggest that CrIV is the disease-causing virus. Beyond describing these viruses for the first time in this species of cricket, our study provides the most complete genome of the lizard-cricket iridovirus (Liz-CrIV), so-called because it is known to infect both lizard and cricket hosts. These results add to the foundational research needed to increase our understanding of the viruses that cause disease in reared insects. This new knowledge will also allow us to ultimately develop the disease management strategies needed for the economic development of insects as a commodity.

Technical Abstract: Interest in developing food, feed, and other useful products from farmed insects has gained remarkable momentum in the past decade. Crickets are an especially popular group of farmed insects due to their nutritional quality, ease of rearing, and utility. However, production of crickets as an emerging commodity has been severely impacted by entomopathogenic infections, about which we know little. Here, we identified and characterized an unknown entomopathogen causing mass mortality in a lab-reared population of Gryllodes sigillatus crickets, a species used as an alternative to the popular Acheta domesticus due to its claimed tolerance to prevalent entomopathogenic viruses. Microdissection of sick and healthy crickets coupled with metagenomics-based identification and real-time qPCR viral quantification indicated high levels of cricket iridovirus (CrIV) in symptomatic populations, and evidence of covert CrIV infections in healthy populations. Our study also identified covert infections of Acheta domesticus densovirus (AdDNV) in both populations of G. sigillatus. These results add to the foundational research needed to increase our understanding of the pathology of mass-reared insects and ultimately develop the prevention, mitigation, and intervention strategies needed for economical production of insects as a commodity.