Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Bachelor of Science in Biology

Degree Level

Undergraduate

Department

Biological Sciences

Advisor/Mentor

DuRant, Sarah

Committee Member/Reader

Brewer, Lorraine

Committee Member/Second Reader

Walker, James

Committee Member/Third Reader

Davidson, Fiona

Abstract

As we face the threat of global pandemics, one thing becomes clear: biological research is not just about the pursuit of the unknown, but about protecting our future. Understanding disease transmission and predicting pathogen epidemics is more important than ever. Prior studies have indicated that in populations where one sex engages in more social behaviors and movement that sex may drive disease transmission. This supports sex as a factor to consider in the study of epidemic dynamics. Host physiology and immune strategies are another factor that can influence epidemics. Two commonly examined strategies are tolerance and resistance. Tolerance is the ability to endure pathogen loads with minimal sickness symptoms while resistance is the strategy of fighting off infection and minimizing the pathogen. However, the effect of sex on host immune strategies in wildlife is under researched and poorly understood. In this experiment, I use a common avian pathogen to determine if differential infection response strategies exist between sexes. I hypothesized that both males and females will favor a tolerance strategy. Males may prioritize tolerance because they have higher levels of testosterone, which is immunosuppressive. While females may also employ a tolerance strategy as a way to protect their ova by minimizing self-damage from strong immune responses. By using domesticated canaries in the laboratory setting with identical Mycoplasma gallisepticum exposure, I was able to observe strictly the physiological effects of sex on infection defense strategies. We observed that after exposure, MG-exposed male canaries increased their relative monocytes and eosinophils levels while MG-exposed female canaries decreased relative eosinophils levels and maintained monocyte levels. Further, MG-exposure males produced more MG-specific antibodies, had greater pathology, and greater pathogen growth when compared to MG-exposed females. Thus, males have less effective MG resistance while females tolerate infection and keep MG loads lower while producing fewer antibodies. This contradicts my initial hypothesis that differential immune strategies do not exist between sexes in the avian conjunctivitis system. In conclusion, sex differential immune response exists in the avian conjunctivitis system. Since sex is a factor of disease dynamics and immune response, further research is necessary to explore this perspective.

Keywords

Mycoplasma gallisepticum; MG; conjunctivitis; sex; immune response

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