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The aim of my work was to investigate the diversity of adenoviruses in wild birds, mainly falconids, and the possible coevolution between viruses and their hosts.

Up to now, a single adenovirus type has been described from falcon species already, falcon adenovirus 1 (species Falcon aviadenovirus A). The virus may cause mortality in aplomado falcon (Falco femoralis), orange-breasted falcon (Falco deiroleucus), merlin (Falco columbarius) and taita falcon (Falco fasciinucha), as well as in the hybrid of gyrfalcon (Falco rusticolus) and peregrine falcon (Falco peregrinus). Peregrine falcons are considered to be the natural host and reservoir species for this virus, and as a consequence of the long-term virus-host coevolution, the infection is usually asymptomatic in them.

In this study, a total of 188 samples, predominantly from falconids, were screened for the presence of adenoviruses using the polymerase chain reaction. Based on agarose gel electrophoresis, 50 samples were considered positive, and 49 from these originated from falconids. By sample type, one of nine organ samples (11.1%), 29 of 136 swab samples (21.3%) and 20 of 43 faecal samples (46.5%) were positive. The nucleotide sequences of 36 purified PCR products were determined and a phylogenetic tree was reconstructed based on the derived partial DNA polymerase amino acid sequences. Of the typed strains, nine were of the genus Aviadenovirus, 26 of the genus Siadenovirus and one of the genus Atadenovirus; and the virus strains were classified into three avi-, four si- and one atadenovirus types. The type falcon adenovirus 1, the only falcon adenovirus type known to date, was not detected.

The eight new adenovirus types described first in this study are thought to represent seven species. The high positivity rate and diversity of falcon siadenoviruses further support the theory that the genus Siadenovirus has been co-evolving with the avian class for a considerable time.

To date, adenoviruses of wild birds have been poorly studied, therefore by the restricted information available, the hypothesis that these pathogens contribute to the decline of bird populations cannot be excluded. The results of my study confirm, that more financial resources are needed for the investigations focusing on the coevolution and biodiversity of these viruses. The long-term impact of the falcon adenoviruses at individual and at population levels is unknown yet, therefore the adenovirus infections of predatory birds should be investigated further.