Date of Graduation

5-2022

Document Type

Thesis

Degree Name

Master of Science in Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

DuRant, Sarah E.

Committee Member

Lewis, Jeffrey A.

Second Committee Member

Forbes, Kristian M.

Keywords

Anthropogenic; Diet; Disease; Host; Macronutrient; Pathogen

Abstract

Macronutrients in the diet are vital to the physiological processes necessary for an organism to effectively clear a pathogen. Diet can be important to a host’s susceptibility to infection and severity of pathology, though results can vary across host-pathogen systems (Sen et al. 2016). Manipulating the ratio of specific macronutrients in the diet is an effective method to begin understanding how individual macronutrients, rather than food types, have on immune responses. Using an avian host-pathogen system, I explored the effects of dietary macronutrient composition, specifically lipid and protein content, on disease pathology and behavior of canaries (Serinus canaria) infected with Mycoplasma gallisepticum (MG). To do this I conducted two experiments. In experiment one, I provided isocaloric diets comprised of identical ingredients that varied in macronutrient content (20:80 lipid:protein [high protein} or 80:20 lipid:protein [high lipid]) to female canaries, then measured several possible disease outcomes in birds either infected with MG or that were sham infected. In a second experiment, MG- and sham-infected canaries were offered both the high protein and high lipid diets prior to and during infection to assess whether birds exhibit macronutrient specific feeding behaviors during infection. In the first experiment, canaries fed a protein-rich diet, whether infected or not, consumed more calories per week than canaries fed a lipid-rich diet. All birds that were infected exhibited illness-induced anorexia in the first week post infection and experienced a significant decline in body mass. Infected birds fed the high protein diet had a significant decline in fat stores post infection. Diet did affect visible pathology of the infection; infected birds fed the high lipid diet exhibited clinical signs of infection (swollen eye conjunctiva) 5 ± 3 days longer than birds on the protein diet, as measured by eye score. Despite these differences in eye score over time, the post-infection prevalence of MG specific antibody and pathogen load was not significantly different between infected birds in either diet treatment, suggesting that a high protein diet leads to greater tolerance of MG-infection than a high lipid diet. Results of the second experiment indicated that when birds had access to both the high lipid and high protein diets, the protein diet was consumed in higher quantities than the lipid diet prior to infection but declined after infection, while lipid consumption remained consistent. Physical recovery of birds in experiment two was similar to birds in the first experiment that were only fed the protein diet. These data indicate that diet macronutrients play an important role in individual variation in disease severity among hosts infected with a pathogen. This could have important implications on disease transmission in populations and could reveal anthropogenic food solutions that could improve community health.

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