Date of Graduation
8-2024
Document Type
Thesis
Degree Name
Master of Science in Biology (MS)
Degree Level
Graduate
Department
Biological Sciences
Advisor/Mentor
DuRant, Sarah E.
Committee Member
DeGregorio, Brett A.
Second Committee Member
Forbes, Kristian M.
Third Committee Member
Adelman, James
Keywords
Pathology; Heterogeneity; Mycoplasma gallisepticum; Immunity; Secondary infection
Abstract
Pathology during a second infection can be influenced by immunity and an increase in resistance or tolerance of individuals. Population-level differences in the ability to maintain immunity can lead to contrasting survival outcomes between groups and determine how future outbreaks will spread. However, long term wildlife disease surveillance can be challenging due to lack of infrastructure and host-pathogen specific tests. Calculating disease transmission likelihood requires understanding individual-level heterogeneity in pathology and behavior, and there is limited knowledge in understanding how populations in different stages of an epidemic will transmit disease. In Chapter I, we aim to help fill a gap in our understanding of transmission by experimentally determining the contribution of previous exposure to disease on future transmission using an avian host-pathogen system. We determined differences in Mycoplasma gallisepticum (MG) transmission between first and second infection index birds, the impact of infected birds’ physiological, behavioral, and pathological measures on transmission likelihood and how the physiology of non-infected birds impacts likelihood of reception of MG. Flocks of four domestic canaries (Serinus canaria domestica) were divided into two treatments: all naïve to MG or all that were previously exposed to MG once. We inoculated one male bird from each flock with MG and monitored the flock for transmission, pathology, and behavior for 28 days. We found that both first and second-infection index birds became infected, experienced pathology, and had similar peak pathogen loads, but only first infection birds transmitted infection. We found that only hematocrit was in the top selected model comparing transmitting and non-transmitting birds, but not significantly different. We found that mass was significantly lower in birds that received MG. In Chapter II, we address long term immunity to wildlife disease in a lab setting. We determined whether previously exposed birds still had immunity to MG after three years. We first infected 20 birds in June through August 2020, monitored each individual until they recovered from MG, and then kept them completely isolated from MG until they were re-infected in April 2023. During infection, we monitored their bacterial loads, eye lesion severity, white blood cell counts, hematocrit, body condition, and antibody presence for three weeks. We found that the canaries used in our study retained partial immunity to MG for three years after their original infection. We also found evidence of increased tolerance and resistance. Our research has important implications for understanding MG epidemics in wild populations of birds as well as disease in wildlife more broadly. We suggest that flock survival could be improved significantly if a majority of surviving non-hatch year individuals had been previously exposed to MG. Additionally, as infected birds may only live for a few years after their infection, three years could represent lifetime protection for individuals who survive their first infection and a reduction in risk for other members of their flock.
Citation
Sudnick, M. (2024). Partial immunity to Mycoplasma gallisepticum after an initial infection is long-lasting and reduces transmission in flocks of canaries. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/5422
