First evidence of avian pox-like outbreaks in Eurasian coots, Fulica atra, from Europe: A widespread phenomenon?

Avian pox is a disease caused by Avipoxvirus spp. that is known to produce self-limiting, proliferative epithelial lesions in over 275 bird species from 70 families. Although generally benign, this emerging disease can sometimes provoke significant outbreaks of mortality. In rallids, there is a single serological record of Avipoxvirus. In this study, we report on field evidence for two avian pox-like outbreaks in Eurasian coots, Fulica atra. In Utterslev Mose, Denmark, 17 birds were found in the winter and early spring of 2006 with putative signs of pox-like lesions on the frontal shield and bill. Similar lesions were detected in a population of c. 30 Eurasian coots from a small wetland in eastern Spain in the winter of 2018. Birds with active lesions were detected up to 73 days after first finding, and percentage of birds with lesions also increased in this period (from 9.1% to 69.6%), then declined. Lesions of individual birds were observed to heal in 2 weeks. Three young coots exhibited severe lesions that hampered breathing. In other 17 wetlands from the same region, pox-like lesions were detected in 8 out of 843 Eurasian coots from three localities (maximum prevalence: 18.8%) and 1 of 8 Crested coots, Fulica cristata, in one locality. Reports from European birdwatchers describing coots with abnormal frontal shields suggest that some of these birds likely suffered also from avian pox. This disease, unnoticed thus far, could be geographically widespread, thus its potential population impact should not be underestimated, especially in Crested coots.