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A study by UU researchers on a fungal infection carried by some dogs in their nose shows that the fungus evolves in its dog host and adapts to their immune system. They investigated the active genes in both fungi and dogs and discovered a large genetic variability of the fungal genes and in-host adaptation to their specific dog host. Their results were published in Nature Biofilms and Microbiomes this November.

The fungus responsible for this infection in dogs is Aspergillus fumigatus. It forms a thin layer covering large parts of the nasal area which might even spread to the brain if left untreated. An Aspergillus infection often results in a chronic state of inflammation.

Aspergillus fumigatus not only infects dogs, but a wide range of animal species including cats, birds, mice, and humans. It can cause serious illnesses in people with weakened immune systems or lung problems and even lead to death.

The dog host battles the fungal infection in several ways. Recognition by the immune system results in inflammatory and cell-mediated responses directly fighting the infection. It also reacts by decreasing available nutrients at the site of infection. The combination of these stress factors results in a hostile environment for the fungus.

In order to overcome these obstacles, Aspergillus fumigatus adapts to this highly selective environment in the dog’s nose by evolving, resulting in a large genetic diversity within the fungal layer. These genetic alterations allow the fungus to disrupt the specific dog’s immune system and it improves the efficiency of nutrient uptake.

Up to now, Aspergillus infections were mainly studied in mouse and rat models. This study, however, investigates natural infections in dogs which were diagnosed with Aspergillus. As removing the fungus from the nose is part of standard treatment, this can be easily done. This way of studying natural infections is a nice step forward, as it is more representative than the lab models and it surpasses the need for using lab animals altogether.

Altogether this innovative way of studying Aspergillus infection highlights the in-host adaptation of the fungus and shows the constant genetic battle between Aspergillus fumigatus and the host’s immune system.