13 Apr Amphibian disease in the UK: the importance of biosecurity during amphibian surveys
Biosecurity measures to prevent the spread of disease in UK amphibian populations were a topic of discussion at the Herpetofauna Workers Meeting 2012.
This article presents an overview of the symptoms of, and research on, the two main diseases threatening our native amphibians: Ranavirus and Chytridiomycosis. It also outlines how anyone coming into contact with amphibians can employ some basic measures to help amphibian conservation.
Worldwide and UK threats to amphibians
Estimates suggest that more than one third of amphibian species worldwide are threatened with extinction. The main threats to amphibians include habitat loss, the introduction of non-native species and disease.
The UK is home to seven native species of amphibian: common frog, pool frog, common toad, natterjack toad, smooth newt, great crested newt and palmate newt.
The two main diseases threatening amphibians in the UK are Ranavirus and Chytridiomycosis. It is thought likely that the diseases originated in the UK from the introduction of infected non-native species in to wild native populations. Neither disease is known to infect humans.
Ranavirus and Chytridiomycosis in the UK: the science and the symptoms
There are two main symptoms of Ranavirus infection in common frog: ulceration of the skin and haemorrhaging. The latter is associated with a visible loss of muscle mass; other symptoms of Ranavirus infection include lethargy, emaciation and redness of the skin. Ranavirus is also known to infect other native amphibian species such as toads and all three species of newt.
Chytridiomycosis, or ‘chytrid’, is a disease caused by the fungus Batrachochytrium dendrobatidis. It was first identified in the UK in 2004 and has since been found in all UK native amphibian species and two non-natives. It is currently thought that the fungus disrupts the movement of salts through the skin and can lead to cardiac arrest. It is not yet clear whether chytrid is having a detrimental impact on UK amphibian populations, but current research indicates that prevalence of the disease is low. There are no visible symptoms in diseased amphibians.
Preventing the spread of amphibian disease
Precautions during field surveys are essential to avoid the spread of disease, and amphibian survey work should be undertaken with reference to the guidance note published by the Amphibian and Reptile Groups of the UK (ARG UK). Wherever possible, dedicated survey equipment (bottle traps, canes and pond nets) should be used for each separate survey site/pond. Following each survey visit, footwear should be disinfected and allowed to dry before next use. If survey equipment is re-used at another site, it should be similarly disinfected.
Whether you are a professional ecologist or a wildlife enthusiast, everyone can do their bit. If you have a pond or water feature at home that supports amphibians then similar precautions should be taken to prevent the spread of diseases between populations and you should never transfer frog spawn or amphibians between ponds, as tempting as it might seem.
BSG Ecology and amphibian surveys
We conduct surveys of amphibians throughout the UK, particularly in relation to great crested newts and development proposals. Our large in-house team has significant experience in survey, impact assessment, mitigation and European Protected Species (EPS) licensing. If you need a survey or advice on amphibians, or would like to discuss any other ecological consultancy services then please contact us for further help and advice.