Sala­man­ders on the edge

Geographical - - WORLD­WATCH -

Sci­en­tists are rac­ing to pre­vent a deadly dis­ease that kills sala­man­ders from reach­ing the USA

More than 40 per cent of the world’s am­phib­ians are cur­rently threat­ened with ex­tinc­tion. Chytrid­iomy­co­sis, an emerg­ing in­fec­tious dis­ease, has driven pop­u­la­tion de­clines of 501 am­phib­ian species; 90 of these are now ex­tinct. The dis­ease is caused by two fun­gal pathogens, Ba­tra­chochytriu­m den­dro­ba­tidis (Bd), dis­cov­ered in the 1980s, and the more re­cently dis­cov­ered Ba­tra­chochytriu­m sala­man­drivo­rans (Bsal) – a strain par­tic­u­larly dam­ag­ing to sala­man­ders. With the num­ber of Euro­pean sala­man­ders in­fected with Bsal in­creas­ing, her­petol­o­gists are work­ing to pre­vent its in­tro­duc­tion to sala­man­der stronghold­s in the USA.

Bsal was first iso­lated in 2012 from a fire sala­man­der in the Bun­der­bos re­gion of the Nether­lands, where the pop­u­la­tion had been mys­te­ri­ously de­clin­ing since 2010. In less than six months, the dis­ease caused a 99.9 per cent drop in fire sala­man­der pop­u­la­tions in the Nether­lands, be­fore spread­ing to Ger­many, Bel­gium and Spain.

In 2014, epi­demi­ol­o­gists at the Univer­sity of Ghent, led by An Mar­tel, showed that Bsal had prob­a­bly co­e­volved with Asian sala­man­ders for gen­er­a­tions, but was in­tro­duced to sus­cep­ti­ble Euro­pean pop­u­la­tions through the pet trade. ‘The sixth mass ex­tinc­tion is threat­en­ing sala­man­ders and it’s hap­pen­ing be­cause of hu­mans and our ef­fects,’ says world sala­man­der ex­pert Vance Vre­den­burg. He ex­plains that pet own­ers can act ir­re­spon­si­bly, al­beit with the best in­ten­tions. ‘When peo­ple move out, or get tired of look­ing af­ter sala­man­ders, they some­times re­lease them into the wild. If in­fected in­di­vid­u­als break out, they can spread dis­ease-caus­ing micro­organ­isms.’

Large de­clines of sala­man­der di­ver­sity would dis­rupt ecosys­tems. Sala­man­ders reg­u­late food webs be­tween aquatic and ter­res­trial sys­tems; as mid-level preda­tors, they con­trol graz­ers and in­sects; their bur­row­ing helps con­trib­ute to soil qual­ity, pro­vid­ing ter­tiary con­sumers with en­ergy and nu­tri­ents. North Amer­ica hosts 48 per cent of the world’s 676 sala­man­der species. Al­though Bsal is yet to be de­tected on the con­ti­nent, epi­demi­ol­o­gists fear that the in­ter­na­tional pet trade could im­peril this strong­hold of sala­man­der bio­di­ver­sity. Be­tween 2010 and 2014, 779,002 sala­man­ders ar­rived in the

USA from Asia through ports in Los An­ge­les, Tampa, New York, At­lanta and San Fran­cisco.

Bsal is ex­tremely dif­fi­cult to erad­i­cate in wild pop­u­la­tions. Preven­tion is a more vi­able op­tion. De­spite the high num­ber of species threat­ened, sci­en­tists re­main op­ti­mistic. ‘As sci­en­tists, we’re hope­ful be­cause we’ve iden­ti­fied

Bsal be­fore it has spread to the US pop­u­la­tions,’ says Vre­den­burg. US leg­is­la­tion has been drafted quickly: the US Fish and Wildlife Ser­vice im­posed a mora­to­rium on the im­por­ta­tion of

201 species of sala­man­ders to the USA, ef­fec­tive from Jan­uary 2016. Switzer­land and Hun­gary have al­ready banned im­ports. In 2018, the EU an­nounced an­i­mal-health pro­tec­tion mea­sures for in­ter­nal trade, in­clud­ing en­forced Bsal test­ing, quar­an­tines and other biose­cu­rity mea­sures.

Yet, sci­en­tists still want to see a more sub­stan­tial in­ter­na­tional ef­fort. ‘We re­ally need a World Health Or­ga­ni­za­tion for wildlife dis­eases. CITES is only for traded or en­dan­gered and pro­tected species,’ says Vre­den­burg. He’s hop­ing that the world has de­vel­oped a newfound recog­ni­tion of the im­por­tance of epi­demi­ol­ogy. ‘The Covid-19 pan­demic in hu­mans is a poignant ex­am­ple of why we need an in­ter­na­tional body to pro­vide stan­dard­ised guid­ance on wildlife dis­eases. Coun­tries can’t solve pan­demics alone; col­lab­o­ra­tion is es­sen­tial.’

Once thought to be born in fires, the fire sala­man­der is Europe’s best known sala­man­der species

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