Active and Covert Infections of Cricket Iridovirus and Acheta domesticus Densovirus in Reared Gryllodes sigillatus Crickets.

Kristin R Duffield,José L Ramirez,Scott K Sakaluk,John Hunt,Karyna Rosario,Ben M Sadd,Robert W Behle,Brenda Oppert

doi:10.3389/fmicb.2021.780796

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 a symptomatic population, and evidence of covert CrIV infections in a healthy population. 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 better understand the pathology of mass-reared insects and ultimately develop the prevention, mitigation, and intervention strategies needed for economical production of insects as a commodity.

Highlights

Insect production is a rapidly growing industry globally
That either population was infected with additional DNA (AdMADV, G. bimaculatus nudivirus (GbNV), A. domesticus volvovirus (AdVVV)) or RNA viruses (CrPV, A. domesticus iflavirus (AdIV), A. domesticus virus (AdV)) (Table 2)
Entomopathogenic viruses are known to cause significant losses to the reared insect industry (Maciel-Vergara and Ros, 2017); little is known about their diversity, biology, and host association

Summary

Introduction

Insect production is a rapidly growing industry globally. While the practice of farming insects has been around for millennia (e.g., silkworm farming and apiculture) (Defoliart, 1995), applications for mass-produced insects continue to expand beyond traditional uses (Castro-López et al, 2020; van Huis, 2020b), to include chitin production (Hahn et al, 2020), waste management and valorization (Surendra et al, 2016, 2020; Gasco et al, 2020), and use as feed for both pets, including cats and dogs (Bosch et al, 2014), and agricultural animals (Makkar et al, 2014; Henry et al, 2015; Tomberlin et al, 2015). The demand for mass-produced insects is steadily increasing due to their utility with relatively low associated costs (Wilkie, 2018); there are several obstacles that hinder farmed insects from becoming an extensively utilized resource, including a dearth of rigorous empirical data (van Huis, 2017; Stull and Patz, 2020). Critical among these gaps is a lack of research on the entomopathogenic microbes that negatively impact reared insect colony health and production despite infectious disease outbreaks plaguing modern insect farms for decades (Eilenberg et al, 2018; Maciel-Vergara et al, 2021). As a direct response to these outbreaks, many producers switched to farming alternative species, including Gryllodes sigillatus in North America due to reports that they were less susceptible to AdDNV (Weissman et al, 2012)

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Conclusion