Abstract
Urban wildlife populations often carry zoonotic pathogens that pose considerable public health risks through direct contact with humans. However, disease prevalence in urban settings is generally reported at the city level, which disregards spatial heterogeneity due to local differences in habitat structure or resource availability in the urban landscape. This study therefore examines the fine-scale spatial heterogeneity of Chlamydia psittaci, a generalist bacterium that frequently infects feral pigeons, in Antwerp, Belgium. We collected samples from 377 pigeons at 23 locations and performed qPCR screening for C. psittaci. At the same time, we performed an extensive literature review that includes 20 studies from 29 unique cities globally. Our findings indicate that the prevalence variance within Antwerp (CV = 0.70) is comparable to the variation reported among cities worldwide (CV = 0.88), suggesting that distinct locations within a single city can exhibit differences comparable to those between entirely different cities. Our data suggest that citywide or even countrywide are likely confounded by small scale spatial infection heterogeneity. A combination simulation showed that at least 12 unique sampling sites are necessary to accurately assess the true prevalence at the city level. Finally, we could show that also the screening method influences reported prevalence, with blood samples and non-PCR screening inflating reported prevalence rates. Taken together, we recommend that urban surveillance reports include at least 12 sampling sites, use standardized screening protocols and provide site-level data so that fine-scale heterogeneity can be taken into account.