Wild songbirds, parasites and urbanization

Doctoral student Catherine Bradley is monitoring several infectious diseases, including West Nile virus, in cardinals and other songbirds along an urban-rural gradient in metro-Atlanta. The overarching goal of this research is to relate processes and patterns in urban landscapes to disease risk in wildlife hosts. With a large-scale field observation study, Cat is evaluating the condition of individual hosts at local sites along the urban gradient and examining hosts for evidence of exposure to West Nile Virus (WNv). This information, along with measures of host abundance and diversity, will be used to test predictions of the ‘dilution effect’. Using geospatially referenced land use maps, census data, climatic data, and ground measures Cat is also assessing the degree of urban impact at each sampling site. Applying a multivariate statistical approach, her goal is investigate condition and disease occurrence in avian hosts to predict exposure influenced by urban landscape types.

Cat has collected condition measures, fecal and serum samples from over 700 individuals between 2004 and 2005 in the metro Altanta and surrounding areas.

Colleagues at the Southeastern Cooperative Wildlife Disease Study (SCWDS) analyze serum samples to detect previous exposure to WNv using an epitope-blocking ELISA. Of those sampled to date, 11% of birds are seropositive across all sites.

Dynamics of mycoplasmal conjunctivitis in House Finches in Georgia
With collaborators at the Cornell Lab of Ornithology, we investigated factors associated with outbreaks of a recently emerged eye disease in wild House Finches around metro Atlanta. This disease is caused by the bacterium Mycoplasma gallisepticum (MG). House Finches infected with MG develop mild to severe clinical signs that include swelling, redness, and discharge of conjunctival tissue around their eyes. In extreme cases, the birds are blinded when their eyes swell shut, although birds in both captive and wild populations can recover from infections. Between 2001-05, members of our lab regularly monitored the prevalence and spread of this disease by systematically trapping House Finches each month . We measured characteristics of infected and non-infected birds, including age, sex, body condition, and co-infection with other parasites.

House Finch Research Team in Ithaca, NY November 03

Past projects include:

Investigating host characteristics associated with infection risk, including age, sex, and molting status, and examining associations between the severity of clinical signs and host body condition

Examining leukocyte differentials of healthy and infected birds to determine how innate immunity and stress covaries with MG infections

Assessing the presence of blood parasites, including Hemoproteus and Plasmodium spp. (shown) to determine if the presence and severity of conjunctivitis is associated with increased risk of additional infections

Comparing the feeding behavior of healthy and infected birds to determine whether conjunctivitis is associated with foraging ability and aggression at feeders

Exploring genetic variation in the MG bacterium from different locations in eastern N. America