Interactions between urbanization, malaria infection and avian cloacal microbiome.

Urbanization, a major component of global change, has drastically modified the landscape, and is generally associated with biodiversity loss. Pollutants and low-quality food resources, among other urban stressors, can alter the physiology of urban-dwelling birds, ultimately affecting their interactions with other organisms, including pathogens and symbiotic microorganisms. The house sparrow (Passer domesticus) is one of the most common passerine species closely associated with anthropized environments. Here, we explored the association between the level of habitat urbanization, avian malaria infection (Plasmodium and Haemoproteus are grouped together in this study) and their combined effects on the composition of the cloacal microbiome of wild house sparrows. Urban birds showed a lower parasite prevalence than those from natural and rural habitats. In addition, the association between avian malaria infection and avian cloacal bacterial-microbiome composition depended on the habitat type. In natural habitats, infected birds showed a nearly significant increase in bacterial richness and significant differences in the relative abundance of various taxa, compared to uninfected individuals. In contrast, infection status was not associated with any microbiome parameter in birds from rural and urban habitats. In conclusion, habitat type is associated with avian malaria prevalence in house sparrows and may modulate the relationship between parasite infection and the bacterial composition of avian cloacal microbiome.