Are suburban garden ponds spreading lethal frog disease?

A UK study suggests gardeners may be sparking the outbreak of a deadly frog disease. 

Common frogs living in the UK, like this one, are being effected by the spread of ranavirus thought to be spread by human activity

Keen gardeners stocking their domestic ponds with exotic or wild aquatic species could be fuelling the rapid spread of the lethally infectious frog disease ranavirus, according to new research led by scientists from 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 – sheds new light on how ranavirus managed to spread so quickly across the UK in recent decades. It was carried out alongside UCL and Herpetofauna Consultants International (HCI).

While the infection can arrive with the natural movement of amphibians, the growth of its reach appears to have escalated due to human transfers of infectious material between their own garden ponds, or direct from a common sources such as  aquatic shops.  

The study found that destructive viruses have been introduced to the UK at least twice, with human interventions together with natural amphibian movement helping to bring a rapid invasion.

The risk of disease was higher in areas with more humans, while a reduced risk in less populated areas suggests that the number of humans are a better predictor of disease spreading than other factors like the local climate. 

Data analysis also indicated that fewer disease outbreaks happened in less wealthy 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 fuelling the pathogen spreading. 

Common frogs living in the UK, like this one, are being effected by the spread of ranavirus thought to be spread by human activity

Commenting on the study, lead author Dr Stephen J. Price from ZSL said: “Ranavirus is one of the most serious health threats currently facing the UK’s amphibian population, so our findings that humans seem to have helped move the virus around, facilitating its rapid spread, could be translated into some straightforward ways to manage the risk of disease outbreaks. 

“It seems that well-meaning homeowners stocking their garden ponds with frogs, fish or spawn translocated from neighbouring ponds or beyond could inadvertently be fuelling the spread of this serious amphibian disease."

"We certainly don’t want to discourage people from adding ponds to their urban gardens – this remains one of the most positive steps we can all take to support wildlife – but equally we would strongly urge people to try to limit how much potentially-infectious material they’re moving into and out of their gardens in the process.”

The study comes from two decades of citizen science data recorded by the Frog Mortality Project – originally through HCI/ZSL and conservation charity Froglife, then the ZSL-coordinated Garden Wildlife Health.

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