Date of Award
The bacterium Mycoplasma gallisepticum is an avian respiratory pathogen that causes inflammation and swelling of conjunctiva in domestic poultry and wild finches. In the past, severity of conjunctivitis symptoms has been used to quantify infection severity and host resistance. However, many songbirds function as hosts to M. gallisepticum but do not develop this symptom at all. The absence of conjunctivitis, as well as other clinical signs, hinders our understanding of M. gallisepticum infection in the songbird community because some species are responding very differently than others. One such species is the Eastern Bluebird (Sialia sialis), a common songbird of the southeastern United States. In efforts to determine if M. gallisepticum is a respiratory pathogen of Eastern Bluebirds, data and samples collected from an experimental infection of wild-caught, captive housed birds were used. We quantified relative bacterial load in the eye conjunctiva and choanal cleft palate of infected birds and found that M. gallisepticum did not localize in the conjunctiva but was present in the palate of six out of nine birds 13 days following experimental infection. At this same time point, infected birds showed no significant difference in body condition measures when compared to controls but had significantly lower levels of circulating hemoglobin than did controls. Among infected birds, individuals with the greatest number of M. gallisepticum in their palate 13 days following infection lost more mass than did those with fewer bacteria. Hemoglobin levels and other measures of condition were not significantly correlated with pathogen load. These results suggest that although Eastern Bluebirds do not develop conjunctivitis, they are suffering from physiological consequences of infection. Furthermore, this could be the case in other host species that also do not develop conjunctivitis.
Fry, Meredith A., "Effects of Mycoplasma gallisepticum on experimentally infected Eastern Bluebirds (Sialia sialis)" (2019). Honors Theses. 1116.
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