Experts poised for rare frog hunt

The golden toad has vanished from Costa Rica’s rainforests

Scientists are set to begin a hunt for the some of the world’s rarest frogs in Costa Rica, including the iconic golden toad, last seen some 20 years ago.

A team from Manchester University and Chester Zoo are in Costa Rica to track down the highly endangered creatures.

News will follow their trek deep into the cloud forests of Monteverde.

Amphibians numbers around the world have crashed, in part because of a deadly fungus. Costa Rica has been particularly badly hit.

Expedition leader Andrew Gray, from the University of Manchester’s Manchester Museum, said: “Costa Rica’s highlands used to be major biodiversity hotspots – but in many areas amphibian populations have been completely decimated.”

Killer fungus

The killer fungus

In the late 1980s, herpetologists around the world found that amphibian populations were suffering unprecedented declines, but they struggled to understand exactly why.

A decade later, researchers isolated a previously unknown fungus, Batrachochytrium dendrobatidis, which was infecting amphibians, effectively suffocating them by making it impossible for them to breathe across their skin.

Recently, the scientists working on the Global Amphibian Assessment estimated that one-third of all amphibians were threatened by extinction and about 120 species had already become extinct since the 1980s.

Many believe the disease caused by the chytrid fungus is a key factor for this crash. Other causes are thought to include habitat destruction and changes in climate.

Frog rediscovery

Countries in Central America have been particularly badly affected by the deadly chytrid fungus, which is now widespread there. A great deal of effort is now being put into place to safeguard any remaining species.

To find this species last year that was thought to be extinct at the same times as the golden toad was incredible Andrew Gray

Andrew Gray said: “For the last 10 years, I’ve been working with others to ensure the future for frogs that have so far escaped extinction.

“One of the main things I have been doing is establishing breeding populations in Manchester Museum for a number of very, very rare species – including the splendid leaf frog (Cruziohyla calcarifer), the yellow-eyed leaf frog (Agalychnas annae) and the lemur leaf frog (Hylomantis lemur).

“I’ve also been working with the Costa Rican authorities and scientists to put conservation measures into place at the sites where any rare frogs are found.”

Last year, Mr Gray caught a glimpse of the Ithsmohyla rivularis in the cloud forests of Monteverde – a frog that was thought to have gone extinct about 20 years ago.

Manchester Museum has a splendid leaf captive breeding population

He said: “To find this species last year that was thought to have become extinct at the same time as the golden toad was incredible – it is the rarest tree frog in the world.”

He has now been given special permission by the Costa Rican authorities to collect some of the frogs to take back to Manchester.

He told : “We are returning to thoroughly search the site in the hope of finding more specimens.

“It’s not going to be easy – they live deep in the Monteverde rainforest, they are only a couple of centimetres in size and they only come out in the dead of night – and while the males do call, the females don’t make a sound.”

‘Never say never’

The rediscovery of Ithsmohyla rivularis has spurred the team on to also try to seek out a golden toad (Bufo pereglines).

This colourful amphibian, which scientists only discovered in 1966, became the iconic symbol of amphibian decline. In 1987 there were approximately 1,500 of the toads, but just two years later it had vanished from the face of the rainforest.

Mr Gray said: “We are going to be trekking through an area where the golden toad used to thrive. It is very unlikely we will find one – but as last year’s discovery showed us, never say never.”

While in the rainforest, the team will also trying to track down the miniature red-eyed tree frog (Duellmanohyla uranochroa) – a species on the brink of extinction – to investigate how some frogs may be able to prevent the chytrid fungus from taking hold.

This is a unique opportunity to study the frogs in their natural habitat Mark Dickinson

Previous research has shown that some species of tree frog have a special pigment in their skin that enables them to reflect light, allowing them to “sunbathe” without drying out.

Physicist Mark Dickinson, from Photon Science Institute at the University of Manchester, will be taking a spectrometer into the field to investigate how different frog species reflect light.

He said: “So far, I’ve only been able to investigate captive frogs in the lab. This is a unique opportunity to study the frogs in their natural habitat.”

The team believes that the ability to sit out in the Sun may allow the frogs’ skin to heat up just enough to kill off chytrid – preventing the disease from taking its grip.

Some of the team will also be heading to the last known breeding site of the green-eyed frog (Lithobates vibicarius) where Chester Zoo is helping to support a conservation programme.

Hope for end to rejection drugs

At present patients must take powerful drugs

Scientists have developed a procedure which may help end the  need for transplant patients to rely on powerful anti-rejection drugs.

The complex procedure involves mixing the patient’s infection-fighting white blood cells with cells from the donor.

One patient went eight months without immunosuppressive drugs and others were switched to low doses.

The study, by Germany’s University of Schleswig-Holstein, appears in Transplant International.

It could eventually offer patients who have had transplant surgery a much higher quality of life, free from complex drug regimes Dr James Hutchinson University of Schleswig-Holstein

Currently, transplant patients must take a cocktail of powerful drugs for life to dampen down their immune system, and prevent the new organ being rejected.

But the drugs themselves can cause side effects, and may not prevent the slow rejection of the organ over time.

The new technique involves giving transplant patients an infusion of specialised cells known as a transplant acceptance-inducing cells (TAICs).

The TAICs are created by isolating a type of white blood cell from the donor, and modifying them chemically in the lab.

Once modified, the cells gain the ability to kill off cells in the immune system which trigger the rejection process, and to boost the action of another type of immune cell which plays a beneficial role in guarding against rejection.

The cells are then cultured alongside those from the recipient – which helps prime the immune system further – before being injected into the patient.

The technique has been tested on kidney transplant patients, some of whom were given the cells before surgery, and others after the transplant, as an additional drug therapy.

Preliminary, but promising

Lead researcher Dr James Hutchinson said the technique was still at a preliminary stage, but results on 17 patients were promising.

He said: “It could eventually offer patients who have had transplant surgery a much higher quality of life, free from complex drug regimes.”

In the first stage of the clinical trials 12 patients received kidneys from deceased donors, and were given TAICs in addition to traditional anti-rejection drugs.

Ten patients were gradually weaned off the cocktail of conventional drugs, and six eventually took only a low dose of one particular drug, cutting the risk of side effects substantially.

In the second stage of the trial five patients who received kidneys from live donors were given an infusion of TAICs before their surgery was carried out.

One patient was able to go eight months without any immunosuppression drugs, and a further three were successfully weaned down to the single low-dose therapy.

Dr Hutchinson said: “Our research clearly shows that infusing TAICs into patients before they have a kidney transplant, or after the procedure has been carried out, is a practical and safe clinical option.

“Although this procedure is still being developed and refined, it poses an exciting possibility for clinicians and patients alike.”

Keith Rigg, a transplant expert and vice president of the British Transplantation Society, said: “This is interesting work which has the potential to both reduce the risk of rejection after organ transplantation and the amount of anti-rejection drugs that are required, both of which will be good news for patients.

“As the authors say this is still early and preliminary work, and further development and refinement of the process is required, but this procedure does seem to have potential.

“Further developments will be watched with interest.”