Degree

Doctor of Philosophy (PhD)

Department

Veterinary Clinical Sciences

Document Type

Dissertation

Abstract

Feeder insects, and in particular crickets, are becoming more popular as food for humans and domesticated animals. However, disease outbreaks continue to decimate commercial populations. The goals of this dissertation were to characterize the epidemiology of different viral and bacterial pathogens affecting the survival of European house crickets (Acheta domesticus) being raised under mass rearing conditions and identify methods to reduce the impact of these pathogens.

Crickets from nine different producers across the United States were sampled during different seasons to better estimate the prevalence of three pathogenic viruses: Acheta domesticus densovirus (AdDV), Acheta domesticus volvovirus (AdVVV), and cricket iridovirus (CrIV). All farms tested positive for each of the viruses, but there were differences in the prevalence and viral loads between producers, seasons, and age groups. Across all studies, AdVVV consistently produced higher prevalence rates (20-100%) and higher viral loads (105-6) in the warmer, summer months as compared to colder, winter months (0-100%, 101-3). AdDV (13-100% prevalence) and CrIV (100% prevalence) viral loads varied between studies, but in general appeared to produce higher rates/loads in the winter months.

When evaluating for differences between clinically healthy and sick crickets, there was no difference between viral statuses (AdDV: χ2=2.2, p=0.5; AdVVV: KW=5.9, p=0.1; CrIV: F=2.8, p=0.07). However, there was a significant difference between the 16S microbiomes with sick crickets having an increase in reads from the phylum Proteobacteria (95% CI: 67.8 ± 10.5%) and subsequent losses from the phyla Firmicutes and Bacteroidetes. The clinically healthy crickets had more even distributions across the three major phyla.

In an effort to improve the production efficiency of crickets in a high-density system where all three viruses exist and shifts in the bacterial microbiome are known to happen in clinically diseased animals, Saccharomyces cerevisiae, a yeast, was used as a probiotic candidate. Diets with 0.5% inclusion of yeast reduced the incidence of Gamma-proteobacteria and improved cricket yields by 18%. Further probiotic testing with members of the Acheta domesticus core microbiome (Parabacteroides, Bacteroides, Dysgonomonas, and Enterococcus spp.) should be performed to assess if any greater improvements can be made with these bacteria.

Date

4-4-2024

Committee Chair

Mitchell, Mark

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