Risk factors associated with mycoplasmal conjunctivitis in house finches

Observations from a citizen-based survey were used to identify potential risk factors associated with mycoplasmal conjunctivitis (Mycoplasma gallisepticum) in eastern house finches (Carpodacus mexicanus). Between November 1994 and October 1996, 778 volunteers provided 7,224 monthly observations at residential bird feeding sites across an eight state region in the eastern USA. Information collected by questionnaires included health status of house finches and four sympatric passerine species, types and number of bird feeders maintained, neighborhood housing locale and altitude of the observation site. Bivariate analyses revealed that house finches were 14 to 72 times as likely to be observed with conjunctivitis than the sympatric species studied. Year of the study, season, and the presence of platform, hopper, and tube type feeders were significantly associated with conjunctivitis in house finches. Multivariate analysis using a logistic regression model suggests that increased risk of conjunctivitis in house finches was associated with the second year of the study (the third year of the outbreak), the cooler non-breeding periods from September through March, and the presence of tube style feeders. In addition, the presence of raised platform type feeders may have been protective against conjunctivitis in house finches. Prevention of spread of this disease may include modifying bird feeding activities based on season and type of feeder.