Assessment of insect antimicrobial peptides in management of enteric redmouth disease in rainbow trout (Oncorhynchus mykiss)

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Abstract

Insects are a rich source of bioactive compounds, and they also represent a potentially economical way to convert organic waste into high quality protein meal for use in animal feeds. However, these applications have rarely been considered simultaneously; that is, little attention has been paid to whether bioactive compounds present in insect meals from species such as black soldier fly (Hermetia illucens), yellow mealworm (Tenebrio molitor), or common housefly (Musca domestica) might affect their utility as a protein source. In this dissertation, I use enteric redmouth disease and its causative agent, Yersinia ruckeri, as a model to probe the effects of insect antimicrobial peptides on the microbiome and infection state in rainbow trout (Oncorhynchus mykiss). These studies contribute to our understanding of insect meal and fish health in the following areas: 1) development of a qPCR-based assay for detection of Y. ruckeri in the intestine of fish; 2) assessment of the effects of a purified insect AMP on the survival, microbiome, and carrier state of trout infected with Y. ruckeri; 3) comparison of diets made from insects with different levels of AMP transcription on survival, microbiome, and carrier state of trout infected with Y. ruckeri.The findings of these studies lead to several conclusions in addition to opening a number of new paths of inquiry. Y. ruckeri is capable of persisting in the tissues of infected fish for at least several months after exposure, and detection rates vary significantly depending on the assay and tissue used. A diet containing the insect AMP cecropin A not only altered the composition of the gut microbiome, but also appeared to increase the load of Y. ruckeri in fish that survived infection. This suggests that at least under certain conditions, the presence of insect AMPs in the diet could lead to undesirable effects. Finally, using a genetic model of immune regulation to vary the levels of AMPs between two insect meals did not result in significant differences in infection state. Potential applications of this approach to production insect species including black soldier flies (Hermetia illucens), yellow mealworms (Tenebrio molitor), and common houseflies (Musca domestica) are discussed.

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164 pages
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2022-08
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Antimicrobial peptide; Aquaculture; Farmed Insects; Microbiome; Rainbow trout; Yersinia ruckeri
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Marquis, Helene
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Selvaraj, Vimal
Kraft, Cliff
Degree Discipline
Food Science and Technology
Degree Name
Ph. D., Food Science and Technology
Degree Level
Doctor of Philosophy
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Government Document
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Attribution-ShareAlike 4.0 International
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dissertation or thesis
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