Garden ponds may help spread lethal frog disease

Keen gardeners stocking their domestic ponds with exotic or wild aquatic species could be inadvertently fuelling the rapid spread of the lethally infectious frog disease ranavirus, according to new research by scientists from UCL, the Zoological Society of London (ZSL) and Queen Mary University of London. The research - the most comprehensive investigation into the pathogen's spread across UK amphibian populations to date - was carried out alongside Herpetofauna Consultants International (HCI), and sheds new light on how ranavirus managed to spread so quickly across the UK in recent decades. While the infection can arrive with the natural movement of amphibians, the expansion of its range appears to have been exacerbated by human transfers of infectious material between their own garden ponds, or direct from a common source such as commercial aquatics retailers. The study found that virulent viruses have been introduced to the UK at least twice, with human interventions combining with natural amphibian dispersal to facilitate a rapid invasion. The risk of disease was higher in areas of higher human density, while a corresponding reduction in risk in less populated areas suggests that human population density is a more significant predictor of disease spread than other factors like the local climate. Data analysis also indicated that fewer disease outbreaks occurred in less affluent neighbourhoods, raising the possibility that the fashion for introducing exotic or wild animals into ornamental ponds and other water features in British suburbs may be inadvertently fuelling the pathogen's spread.