Natural history of avian papillomaviruses

Papillomaviruses (Family: Papillomaviridae) are small non-enveloped viruses that cause skin and mucosa infections in diverse vertebrates. The vast majority have been detected in mammals. However, the number of papillomaviruses described in birds is growing, especially because of metagenomic studies. Seven complete genomes and one partial sequence have been described, corresponding to five papillomavirus genera. These have been detected from various sample types, including skin, internal epithelium, and faecal material, from seven highly diverse wild and captive avian species. This review summarizes the molecular epidemiology of avian papillomaviruses, their genomic organization, evolutionary history and diagnostic techniques used for detection. The most commonly detected avian papillomavirus lesions are cauliflower-shaped papillomas, or warts, found on the tarsus and digits of common chaffinch (Fringilla coelebs) and occasionally brambling (Fringilla montifringilla). Similar warty growths have been detected in African grey parrot (Psittacus erithacus) and northern fulmar (Fulmarus glacialis), on the head and the foot, respectively. Papillomavirus has also been detected in avian tissue with no apparent lesions, similar to findings in humans and other mammals. Papillomavirus involvement was initially suspected to cause other types of lesions, such as internal papillomatosis of parrots (IPP) and proliferative pododermatitis in waterfowl. However, determined efforts failed to demonstrate papillomavirus presence. We briefly describe avian papillomavirus genomic organization and viral gene diversity. Furthermore, we performed a detailed analysis of avian papillomavirus non-coding regions and a preliminary computational analysis of their E9 proteins.