Co-infection does not predict disease signs in tortoises.

In disease ecology, the host immune system interacts with environmental conditions and pathogen properties to affect the impact of disease on the host. Within the host, pathogens may interact to facilitate or inhibit each other's growth, and pathogens interact with different hosts differently. We investigated co-infection of two and the association of infection with clinical signs of upper respiratory tract disease in four congeneric tortoise host species () in the United States to detect differences in infection risk and disease dynamics in these hosts.