|HOME SCHEDULE AUTHOR INDEX SUBJECT INDEX|
Individual infection risk and epidemics of mycoplasmal conjunctivitis in wild House Finches.
Altizer, Sonia*,1, Davis, Andrew1, 1 Emory University, Atlanta, GA
ABSTRACT- Mycoplasmal conjunctivitis is a recently emerged bacterial disease affecting wild House Finches (Carpodacus mexicanus) in eastern North America. This novel strain of a poultry pathogen has caused dramatic reductions in host abundance, and follows highly seasonal epidemics with rapid increases in prevalence during the fall and winter months. We examined the epidemiology of conjunctivitis in a local population of House Finches in Atlanta, GA, a region where this pathogen reaches unusually high prevalence from August through November. To understand what factors affect changes in host susceptibility and the timing of outbreaks, we monitored monthly prevalence of conjunctivitis among wild-captured House Finches within a 20 km radius of Emory University over two successive years. We examined individual traits associated with high infection risk (including age, sex, molting status, condition, and co-infection with other parasites), and also compared how the timing of epidemics covaried with seasonal changes in flock sizes. Our results showed that during outbreaks, infection risk was significantly higher among juveniles than adult birds, suggesting that annual pulses of juvenile recruitment may affect the timing and severity of epidemics. Infection risk also depended on sex and molting status, although the directions of these associations ran counter to our predictions. House Finches infected with Mycoplasma were in poorer condition, had elevated counts of two types of WBCs, and were more likely to harbor hemoparasites and feather mites than uninfected birds. Collectively, these results point to several factors that are likely triggers of rapid changes in prevalence in this and other host-pathogen systems, including seasonal shifts in age structure and host social behavior.
Key words: host-parasite interactions, avian disease, mycoplasmal conjunctivitis , seasonal epidemics