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Disease in Amphibians

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Written by Ellia Cobb, Transforming Lives Trainee

Disease is a huge issue for our amphibian population, Ranavirus and Chytridiomycosis being two of the main diseases that threaten our native species. It is thought that these diseases were introduced by non-native species being released into the wild. One third of all amphibians are at risk of extinction with heavy declines across the globe.

A frog with ranavirus (c) Dee Wilkinson

Ranavirus is somewhat new to the UK and is mainly found in common frogs, some of the symptoms are skin ulcers which are commonly seen on the skin around the legs and pelvic area. The frogs infected will also suffer from internal bleeding which you may only be able to identify from redness around the mouth and cloaca. Frogs may also show signs of lethargy, but they won’t always show obvious symptoms of this virus. Ranavirus is only active during warmer temperatures, but can be devastating to pond populations around summer time, it is fatal and can affect the entire pond population.

Chytrid infection has been responsible for mass mortalities within the UK’s amphibian population and in some cases, it has caused extinctions. Most native natterjack toad populations have tested positive for the infection, but seem to be unaffected. That however, doesn’t stop them from spreading it to other amphibian populations. Evidence suggests that chytrid causes death by preventing sufficient uptake of salts through the skin. Amphibians need these salts for their circulation and without this, their hearts cease to function. Symptoms of this include ulcers, reddening, shedding and unusual behaviours.

There are steps everyone can take to prevent the spread of amphibian disease:

  1. Do not transfer animals or plants from one pond to another. 
  2. Do not purchase wild-caught spawn, tadpoles or adult amphibians online. Not only is this against the law, but you do not know the origin of the animals. 
  3. Do not release pet/exotic amphibians into the wild. It is against the law and can cause severe damage to not only the released amphibian, but the local population too. 
  4. If you suspect disease in an amphibian, report it to Garden Wildlife Health

Animation (voiced by Stephen Fry) Highlights the Devastation of Ranavirus

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Comedian, author, writer and frog enthusiast Stephen Fry has lent his voice to an emotive new animation created by international conservation charity ZSL (Zoological Society of London), hoping to raise the profile of the deadly Ranavirus threatening UK common frogs.

Introduced to Great Britain by humans in the 1980s, Ranavirus mainly affects common frogs (Rana temporaria) but also affects other amphibians and could affect fish and reptiles. Research from ZSL, which formed the basis of the film’s content, found that at least 20% of Ranavirus cases over the past 30 years could be attributed to human-caused introductions such as pond owners introducing fish, frog spawn or plants from other environments.

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Stephen Price, amphibian disease expert at ZSL’s Institute of Zoology and UCL said: “Having studied Ranavirus for more than a decade, it was becoming ever more apparent that we needed to do something different to get people‘s attention and alert them to this deadly disease unfolding in their back gardens – because they can do something about it. People can help stop the spread by avoiding moving potentially infected material such as spawn, tadpoles, pond water and plants into their own pond. Disinfecting footwear or pond nets before using them in other water bodies will also help, while building wildlife ponds that mimic more natural freshwater habitats, which provide shade, will help frogs to keep cool and therefore lower the severity of the disease.”

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Amphibians are vital to the world’s ecosystems, they are one of the most incredibly diverse forms of life, found almost everywhere. They are essential components of food webs; frogs and newts keep the insect and slug populations in check and serve as prey for foxes and birds. Without frogs, localised ecological collapse could follow.

Members of the public can assist by reporting sick or dead amphibians to ZSL’s Garden Wildlife Health Project, which helps track diseases affecting British garden wildlife:www.gardenwildlifehealth.org

For information on what Froglife are doing to tackle amphibian diseases, take a look here. 

Take a look at ZSL’s Ranavirus fact sheet here.

Watch the animation narrated by Stephen Fry below:

 

Croaking Science: Citizen science and monitoring wildlife heath

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Citizen scientists have been an essential part of our understanding of the natural world for hundreds of years but their contribution and importance have only been formalised and widely recognised in the last decades. Such unpaid members of the public, ranging from experts to beginners, can collect a great diversity of biological data, often in the form of species records in a variety of habitats. In addition, citizen science can be employed to answer complex biological questions and, provided that adequate measures are incorporated in the design, it can do so in a robust and cheap way while covering a very large spatial scale. The potential to cover huge areas of land, even at continental scale, over a long period of time and including private land which is otherwise difficult to access, is one of the main advantages of incorporating citizen science projects in biological monitoring. However, creating a functional framework for citizen science is not straightforward and recruiting and maintaining high volunteer engagement can be equally complicated. In this context, a new review published this month is aiming to evaluate the potential for citizen science to be incorporated for wildlife disease surveillance, including reviewing the benefits for the scientists, for participating members of the public and for wildlife species alike, as well as the logistical and financial implications and the limitations.

Newt searching, RT Feb10

Diseases have always represented one of the major factors driving the dynamics of animal and plant populations, but in recent years this has become especially relevant given that the fast pace of globalisation is bringing together organisms that have been separated by millions of years and creating the conditions for catastrophic disease outbreaks, such as the much-discussed chytrid fungus devastating amphibian populations on four continents. Similarly, in the 1990s Froglife and the Institute of Zoology in London have used citizen science in the form of reports from members of the public, to understand, identify and discuss the presence of a new amphibian disease, called ranavirosis, that was only emerging then and was impacting strongly common frog populations in large parts of England. The virus had most likely been brought to the UK and mainland Europe by the pet trade with fish or the trade with aquatic ornamental plants. Although much remains unclear, primarily how to successfully treat the disease, we now know that moving frogspawn and tadpoles between ponds could accelerate the spread of the disease and that the presence of fish species, such as goldfish, in garden ponds, is likely to exacerbate the severity of the disease in amphibians (North et all, 2015). Given that the data was collected in private garden ponds it is very likely that without the power of citizen science it would have remained hidden for much longer. All of this was changed and made possible using the data collected by members of the public and reported to Froglife.

The Frog Mortality project has now been continued with the Garden Wildlife Health project and is aiming to continue to use both opportunistic and standardised garden surveys to monitor the health of wildlife species, not just amphibians but also reptiles, mammals such as hedgehogs and birds. If you haven’t yet participated in this project, this is your chance to record incidents in your local wildlife heaven, the urban garden, and in this way become a citizen scientist and contribute to a much greater understanding of biological questions and help the conservation of these wildlife species.

References and further reading: 

North AC, Hodgson DJ, Price SJ, Griffiths AGF (2015) Anthropogenic and Ecological Drivers of Amphibian Disease (Ranavirosis). PLoS ONE 10(6): e0127037. doi:10.1371/journal.pone.0127037

Lawson B, Petrovan SO, Cunningham AA (2015) Citizen Science and Wildlife Disease Surveillance. Ecohealth, DOI: 10.1007/s10393-015-1054-z