Backyard chickens are increasingly popular, and their husbandry varies widely. How backyard chickens are housed may influence the accessibility of chicken feed and water to wild birds, and thus, the contact rates between both groups. Increased contacts have implications for pathogen transmission; for instance, Newcastle disease virus or avian influenza virus may be transmitted to and from backyard chickens from contaminated water or feed. Given this potentially increased pathogen risk to wild birds and backyard chickens, we examined which wild bird species are likely to encounter backyard chickens and their resources. We performed a supplemental feeding experiment followed by observations at three sites associated with backyard chickens in North Georgia, USA. At each site, we identified the species of wild birds that: (a) shared habitat with the chickens, (b) had a higher frequency of detection relative to other species and (c) encountered the coops. We identified 14 wild bird species that entered the coops to consume supplemental feed and were considered high-risk for pathogen transmission. Our results provide evidence that contact between wild birds and backyard chickens is frequent and more common than previously believed, which has crucial epidemiological implications for wildlife managers and backyard chicken owners.

Field surveys indicate that host population size, rather than density, is the most important determinant of monogenean infection dynamics. To verify this prediction, epidemic parameters were monitored for 70 days at five host population sizes held at constant density using a goldfish – Gyrodactylus kobayashii laboratory model. During the first 20 days, the rate of increase of prevalence and mean abundance was faster in small host populations. Total mean prevalence and total mean abundance throughout the experiment were not significantly affected by host population sizes. Higher transmission rates were detected in larger host populations. However, there were no significant differences in effective contact rates among the five host populations on each sampling day during the first 20 days, implying that contact rates may be saturated at a sufficiently high host density. These results demonstrate that the epidemic occurs more quickly in smaller host populations at the beginning of the experiment. However, the epidemic is independent of the host population size due to the similar effective contact rates in the five population sizes. Significant negative influence of the initial body condition (Kn) of uninfected goldfish on total mean abundance of parasites suggests that susceptibility of hosts is also a determinant of parasite transmission.

Baylisascaris procyonis is a common parasitic nematode of the raccoon Procyon lotor. In intermediate or accidental hosts, including humans, B. procyonis can cause severe disease and mortality, and the parasite is increasingly viewed as an important wildlife conservation and public health concern. The prevalence of B. procyonis was assessed over a 4-year period in a population of raccoons in a forested region of lower New York. Prevalence ranged from 0% (undetected) to 21%, which was relatively low compared to values reported in other studies from the north-east. During year three of the study, a subset of the raccoon population was experimentally manipulated through altered resource distribution to enhance the contact of individuals. Within the manipulated subpopulation, prevalence of B. procyonis increased to 54% which was significantly greater than prevalence in the same subpopulation before perturbation or than prevalence among raccoons that were not subject to increased intraspecific contact. These observations suggest that altered resource distributions that directly influence raccoon behaviour may indirectly play a role in the ecology of B. procyonis.