AboutZoos, Since 2008


Cap­tive breed­ing intro­duced infec­tious dis­ease to Mal­lor­can amphibians

pub­lished 20 Feb­ru­ary 2013 | mod­i­fied 20 May 2017

Although not exactly ‘news’, it is still worth not­ing the (world­wide) mea­sures that were taken to pre­vent such an unfor­tu­nate result of con­ser­va­tion efforts by the Zoo­log­i­cal com­mu­nity to hap­pen again [Moos]

Mallorcan midwife toadA poten­tially deadly fun­gus that can kill frogs and toads was inad­ver­tently intro­duced into Mal­lorca by a cap­tive breed­ing pro­gramme that was rein­tro­duc­ing a rare species of toad into the wild, accord­ing to a new study pub­lished on Sep­tem­ber 23, 2008, in the jour­nal Cur­rent Biol­ogy.

The study, by researchers from Impe­r­ial Col­lege Lon­don and inter­na­tional col­leagues, reveals that cap­tive Mal­lor­can mid­wife toads released into the wild in 1991 were infected with the chytrid fun­gus Batra­chochytrium den­dro­ba­tidis (Bd). Mea­sures to screen the health of the toads did not pick up the fun­gus, because at the time it was not known to sci­ence.

The chytrid fun­gus, which lives in the water and on the skin of host amphib­ians such as frogs, toads, sala­man­ders and newts, has been known to cause amphib­ian pop­u­la­tion extinc­tions in Europe. Glob­ally, the dis­ease has been found in over 87 coun­tries and has dri­ven rapid amphib­ian declines in areas includ­ing Aus­tralia and Cen­tral Amer­ica, push­ing some species to extinc­tion. Bd is cur­rently rare in the UK, hav­ing only been detected in three loca­tions.

The new study sug­gests that an endan­gered species of frog from South Africa, Xeno­pus gilli, which was housed in the same room as the Mal­lor­can mid­wife toads, was respon­si­ble for spread­ing the infec­tion to them.

The cap­tive breed­ing and rein­tro­duc­tion pro­gramme for the Mal­lor­can mid­wife toad has been highly suc­cess­ful in increas­ing the num­bers of the rare toad on the island. Over half of all the cur­rent pop­u­la­tions on Mal­lorca are derived from rein­tro­duc­tions. Although the chytrid fun­gus can be deadly, toads appear to be doing well in three out of the four pop­u­la­tions in Mal­lorca infected with the chytrid fun­gus. This find­ing sug­gests that there are uniden­ti­fied fac­tors that are pre­vent­ing these pop­u­la­tions from extinc­tion. The sit­u­a­tion is being closely mon­i­tored by the Mal­lor­can con­ser­va­tion author­i­ties.

Global efforts to save amphib­ians from extinc­tion hinge on species being taken into cap­tiv­ity and bred until they can be rein­tro­duced to the wild. The researchers behind the new study say their find­ings reveal the risks of rein­tro­duc­ing species into the wild even when health screen­ing is car­ried out, and high­light the need to ensure that species bred in cap­tiv­ity do not become infected with pathogens from other species.

As soon as Bd was dis­cov­ered in the late 1990s, screen­ing for the dis­ease was incor­po­rated into amphib­ian con­ser­va­tion plans. Zoos are now mov­ing towards breed­ing threat­ened frogs in strictly quar­an­tined, biose­cure facil­i­ties in an effort to pre­vent the dis­ease spread­ing in cap­tiv­ity.

The chytrid fun­gus has also been added to a list of dis­eases that need to be quar­an­tined com­piled by the World Organ­i­sa­tion for Ani­mal Health (OIE). It is hoped that these quar­an­tine mea­sures will help those involved in con­ser­va­tion efforts to stop Bd from spread­ing fur­ther, by con­trol­ling the inter­na­tional trade in infected ani­mals.

Dr Mat Fisher, one of the authors of the study from the Depart­ment of Infec­tious Dis­ease Epi­demi­ol­ogy at Impe­r­ial Col­lege Lon­don, said:

Our study has shown that species rein­tro­duc­tion pro­grams can have unpre­dicted and unin­tended effects. How­ever in this case we believe that the toads are going to sur­vive the infec­tion. The global con­ser­va­tion com­mu­nity is united in its goal of sav­ing species from the effects of Bd and we now have inter­na­tional leg­is­la­tion which should pre­vent this dis­ease being acci­den­tally intro­duced into the wild.

The researchers reached their con­clu­sions after com­par­ing the spe­cific geno­type of Bd from infected wild toads from across Mal­lorca, and infected toads from main­land Spain, the UK and the rest of the world. They found that the dis­ease in all Mal­lor­can toads was of the same geno­type, and that this was a dif­fer­ent geno­type from those on main­land Europe and else­where.

Bd infects amphib­ians’ skin and is thought to inter­fere with their abil­ity to absorb water. Over 257 amphib­ian species are known to be affected by Bd. Some species are very sus­cep­ti­ble and die quickly while oth­ers, which are more resis­tant, are car­ri­ers of the pathogen.

(Source: Impe­r­ial Col­lege Lon­don News Release, 23.09.2008)

UN Biodiversity decade
WWF Stop Wildlife Crime
Fight for Flight campaign
End Ivory-funded Terrorism
Support Rewilding Europe
NASA State of Flux

Goal: 7000 tigers in the wild

Tiger range countries map

Tiger map” (CC BY 2.5) by Sander­son et al., 2006.

about zoos and their mis­sion regard­ing breed­ing endan­gered species, nature con­ser­va­tion, bio­di­ver­sity and edu­ca­tion, which of course relates to the evo­lu­tion of species.
Fol­low me on: