Characterization of Mycoplasma gallisepticum infection in captive house finches (Carpodacus mexicanus) in 1998

Since 1995, the epidemic of mycoplasmal conjunctivitis in eastern house finches has affected the Auburn, AL, house finch population. To better characterize the current status of this host-parasite interaction, we established a captive flock of 38 seronegative, healthy finches in fall 1998. After a minimum quarantine period of 4 wk, two Mycoplasma gallisepticum (MG)-infected house finches were introduced into this flock. Over a 12-wk period, the flock was captured every 2 wk and each bird was observed for conjunctivitis. Blood and choanal swabs were collected from each bird for serologic analysis and for the detection of MG by polymerase chain reaction. The infection spread rapidly through the flock just as it had in a similar study performed in 1996 at the height of the epidemic. Unlike the earlier study in which birds remained chronically infected, most of the birds in our study recovered rapidly, and only three of the birds died during the study. Two patterns of host response to infection with MG were observed. Twenty-seven birds (73%) experienced an acute conjunctivitis that resolved, and the birds appeared to clear the infection. Ten birds (27%) suffered prolonged clinical disease, and MG could be detected in these birds intermittently throughout the experiment. These results, in conjunction with our surveys of MG in the wild population, suggest an evolving host-parasite interaction.