The expansion of cities not only transforms the urban landscape, but also brings with it health challenges, especially with regard to zoonoses, diseases transmitted between animals and humans, caused by viruses, bacteria or parasites and which are transmitted directly, through the ingestion of contaminated food or water, or through vectors such as mosquitoes or ticks. In this context, a recent study led by the Autonomous University of Madrid, together with other experts from Spanish universities, has focused on Madrid, one of the largest European cities, to investigate the role of urban fauna in the spread of pathogens potentially dangerous to human health.
The study, which used an innovative metabarcoding methodology to analyse faecal samples from nine species of urban vertebrates that have frequent contact with people, either directly or indirectly (white stork, lesser black-backed gull, rock pigeon, house sparrow, Argentine parakeet, red-bellied parakeet, bat, European rabbit and common raccoon), focused on two main objectives. The first, to identify which potentially zoonotic pathogens are present in the city’s fauna and to determine which animal species act as their main reservoirs. The second, to compare the prevalence of these pathogens between urban and rural rabbits, taking this species as a reference due to its distribution in different environments.
Potentially zoonotic bacterial genera were detected in all the species analysed, of which ten are under mandatory monitoring in the European Union due to their risk to public health.
The results, published in Science of The Total Environment, were revealing. Potentially zoonotic bacterial genera were detected in all the species analysed, ten of which are subject to mandatory monitoring in the European Union due to their risk to public health. In particular, urban birds – especially house sparrows and pigeons –, along with bats, emerge as the species with the greatest potential risk. Among the most relevant pathogens are Campylobacter and Listeria in birds, and Chlamydia and Vibrio cholerae in bats, which underlines the danger associated with contact with the faeces of these animals.
In the case of rabbits, the study revealed a significantly higher prevalence of Campylobacter in urban rabbits (more than 50% of the samples) compared to their rural counterparts, where it was detected in only 11% of the cases. This finding suggests that animals living in urban areas could be exposed to a higher number of pathogens due to factors such as population density, availability of food in garbage and close coexistence with humans.
Metabarcoding, a powerful tool for controlling pathogens
In addition, the study evaluated the effectiveness of metabarcoding as a tool for monitoring pathogens in urban environments. The results confirmed that this technique can be key for the early detection of zoonotic pathogens, providing a valuable source of information to direct control and prevention efforts on the most relevant species and pathogens.
This work highlights the importance of monitoring the health of urban wildlife and underlines the role that animals such as birds and bats can play in the transmission of diseases to humans. With increasing urbanization and greater interaction between humans and wildlife, these studies become essential to mitigate the risk of future epidemics of zoonotic origin.
