Impact of urbanization on the house sparrow (Passer domesticus): Serum proteome and pathogen prevalence

The house sparrow (Passer domesticus) is a globally distributed species found in rural, urban and other humanised environments. In Europe, sparrow populations have significantly declined in recent decades, especially in urbanised areas. In the present study, we analysed the impact of urbanization on sparrow body condition, pathogen prevalence, and serum proteome changes. Sparrows were captured in four locations with two different urbanization status (rural/urban). Biometric data, blood samples and oral and cloacal swabs were collected. Rural sparrows exhibited significantly better body condition compared to urban sparrows, with no notable differences between sexes. Haemoparasite prevalence was higher in rural sparrows 70.16 % (87/124) than in urban sparrows 50 % (27/54). No avian influenza virus (AIV) or West Nile virus (WNV) genetic material was found, although one urban sparrow (0.58 %) had antibodies to AIV. Serum proteomics revealed that rural sparrows showed an up-regulation of proteins involved in the metabolism, in contrast to proteins of the immune system and the coagulation system, which were found to be over-represented in urban sparrows. Thus, we documented a worse body condition and immune system activation in urban sparrows in contrast to a more active metabolism and a higher prevalence of avian malaria in rural sparrows, and at least occasional exposure to AIV in urban habitats. This information suggests exposure to urban environments may alter the host-pathogen relationship. Urbanization in combination with exposure to AIV, could modulate their role in viral spread and transmission.