Summary: Age, sex, and season affect the risk of
mycoplasmal conjunctivitis in a southeastern
house finch population
Sonia Altizer, Andrew K. Davis, Katherine C. Cook, and John J. Cherry
Abstract: House finches (Carpodacus mexicanus (Muller, 1776)) in eastern North America have been affected by an-
nual epidemics of an eye disease caused by the bacterium Mycoplasma gallisepticum since 1994. To identify factors as-
sociated with seasonal changes in prevalence and variation in host susceptibility, we monitored mycoplasmal
conjunctivitis among wild house finches in a region of high prevalence in southeastern North America. We captured
888 birds between August 2001 and December 2003 and observed seasonal outbreaks characterized by rapid increases
in prevalence from August to October each year. During periods of high prevalence, infection probability was signifi-
cantly higher among juveniles than adults, and the severity of conjunctivitis among juvenile females was greater than
for any other host category. We found no evidence linking moulting status to elevated infection risk among adult birds.
Finally, house finches with conjunctivitis were in poorer condition than birds with no clinical signs of infection, partic-
ularly among those with severe infections. Results from this study are consistent with recent reports of seasonal and re-
gional variation in mycoplasmal conjunctivitis and suggest that annual changes in host reproduction, behaviour, and age
structure might be important determinants of the timing and magnitude of local epidemics.
Résumé : Depuis 1994, les roselins familiers (Carpodacus mexicanus (Muller, 1776)) de l'est de l'Amérique du Nord
sont affectés par des épidémies annuelles d'une maladie de l'oeil, causée par la bactérie Mycoplasma gallisepticum.
Nous avons suivi l'évolution de la conjonctivite mycoplasmique chez des roselins familiers sauvages dans une région
de forte prévalence de la maladie dans le sud-est de l'Amérique du Nord afin d'identifier les facteurs associés aux