{"id":16746,"date":"2012-09-03T19:29:09","date_gmt":"2012-09-03T22:29:09","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/?p=16746"},"modified":"2016-05-24T13:25:52","modified_gmt":"2016-05-24T16:25:52","slug":"the-exterminator-of-amphibians","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/the-exterminator-of-amphibians\/","title":{"rendered":"The exterminator of amphibians"},"content":{"rendered":"
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Fabio Colombini<\/span>Dendrobates tinctorius<\/em>, colorful and sensitiveFabio Colombini<\/span><\/p><\/div>\n

An unexpected deviation from the route proved just how harmful the fungus Batrachochytrium dendrobatidis<\/em> (or Bd) can be for Brazilian amphibians. In June 2006, C\u00e1tia Dejuste de Paula was looking for parasites and microorganisms in amphibians for her PhD research at the School of Veterinary Medicine at the University of S\u00e3o Paulo (USP) when a request arrived for her to examine the possible cause of death of two different species of 50 amphibians \u00a0in a private zoo in the S\u00e3o Paulo State .<\/p>\n

After weighing up all other possibilities the conclusion that she, Jos\u00e9 Luiz Cat\u00e3o Dias (associate coordinator of USP\u2019s Laboratory of Compared Wild Animals Pathology – Lapcom), and collaborators from the United States reached is that Bd must have been responsible for the death of a large part of the animals examined. This is a direct indication, perhaps for the first time, of the lethal nature of this fungus in Brazil. For years Bd has been associated with the reduction (at times, elimination) of populations of toads and frogs worldwide; Brazilian species seemed immune to this microorganism.<\/p>\n

This episode is evidence, and perhaps the first evidence, that animal traffic may favor the dissemination of fungi in amphibians kept in captivity, since the toads had been apprehended before being sent to a private zoo with the authorization of federal government bodies. Detailed in the journal, Diseases of Aquatic Organisms, the study suggests the possibility of contagion between animals kept in captivity, reinforcing the need for preventive measures, such as quarantine and being bathed in antifungal substances.<\/p>\n

It is also a clear indication that some species are sensitive to the fungus, while others seem to be resistant. \u2028C\u00e1tia detected the fungus in various stages of development on the skin of 20 of the 30 Dendrobates tinctorius<\/em>, or dyed dart frog, a colored frog with a mottled black skin with green or blue spots, albeit poisonous. However, there were no signs of the fungus on any of the 20 animals of the other species, Adelphobates galactonotus<\/em>, also colored and poisonous, which must have died for some other reason.<\/p>\n

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LUIS FELIPE TOLEDO<\/span>Adelphobates galactonotus<\/em> is indifferent to the devastating Bd fungusLUIS FELIPE TOLEDO<\/span><\/p><\/div>\n

It was already known that some species may be resistant to the fungus, but this capacity has not yet been seen as clearly as with Adelphobates galactonotus<\/em>. The large-bodied American bullfrogs (Lithobates catesbianus<\/em>), which can reach 20 centimeters in length and weigh 1.5 kg., are generally green or brown in color, is usually \u00a0the most quoted species as an example of peaceful coexistence with the microorganism, and is now being considered as a possible transmitter to other species, the researchers warn.<\/p>\n

Imported since the 1930s from the United States to be bred commercially, but abandoned after few people showed any interest in buying the skin and meat, the bullfrog spread throughout the country, since it multiplies easily and adapts to both moist and dry environments. Nevertheless, it is not the only involuntary carrier of fungi. In December 2011, in Diseases of Aquatic Organisms, researchers from McGill University in Canada warned that lizards and snakes were transmitters of this organism, thus helping to spread it.<\/p>\n

\u201cAlthough it can be an animal parasite, Bd does not need them as hosts, because it can live on organic material in aquatic environments, like other fungi that survive in the soil, on tree bark or in decaying leaves,\u201d comments Selene Dall\u2019Acqua Coutinho, a professor from Paulista University (Unip) who has been working with fungi for 30 years and who carried out the molecular biology analyses that complemented the examinations of C\u00e1tia and Cat\u00e3o. \u201cBd is probably widely disseminated in the environment.\u201d<\/p>\n

This is what C\u00e1tia, currently a researcher with the Wildlife Conservation Society in Brazil, observed: \u201cWherever you look for the fungus you find it.\u201d In her PhD, concluded in 2011, she looked for microorganisms and parasites in 120 animals of 33 different species of toads and frogs collected in the Boraceia biological station, a humid forest area covering 100 hectares that belongs to USP, in the municipality of Sales\u00f3polis. She found parasites \u2013 mainly in the intestine \u2013 in almost half (55) the animals she examined. The most common microorganism found in 22 toads (19.1% of the total) was the Bd, identified by means of microscopic and DNA examinations from a sample provided by Alan Pessier, from the San Diego Zoo, in California.<\/p>\n

Fewer toads in the wild<\/strong>
\n\u201cWe saw the fungus but the animals seemed healthy, without skin lesions or alterations,\u201d says C\u00e1tia. Neither she nor the other researchers found sick amphibians in Boraceia or in other places, but they observed that the diversity of species and number of amphibians were smaller than a few years ago. Bd<\/em> sticks to the fine, moist skin of the amphibians and, as the researchers in the United States and Australia indicated in 2009, changes the balance of muscle electrolytes (ions), making some animal species die suddenly from cardiac arrest.<\/p>\n

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Catia Dejuste de Paula and Luiz Cat\u00e3o-Dias \/ USP <\/span>The arrows indicate the fungus on a toad\u2019s skin: infected animals show no signs of being sickCatia Dejuste de Paula and Luiz Cat\u00e3o-Dias \/ USP <\/span><\/p><\/div>\n

A biologist and professor at USP, Miguel Urbano Trefaut Rodrigues says that years ago toads of the genus Hylodes<\/em> were common in the Capara\u00f3 National Park, on the border between the states of Esp\u00edrito Santo and Minas Gerais. Last year he walked around there and noted that they had disappeared: \u201cI was shocked.\u201d Toads of the genus Allobates <\/em>have also grown scarcer in the forests of Esp\u00edrito Santo and Rio de Janeiro. \u201cA Dendrobatidae<\/em>, Anomaloglossus<\/em>, was abundant in the Tepequ\u00e9m Hills in Roraima; we used to see 10, 20 beside waterfalls. Now there are none.\u201d<\/p>\n

In 2005, after examining 96 toads of 25 species collected at 10 different points in the Atlantic rainforest, Ana Carnaval from the University of California in Berkeley, Rodrigues, his students and biologists from the University of Costa Rica and Rio de Janeiro significantly expanded the geographic area of the spread of the fungus, which they concluded can live at altitudes that vary from 100 to 2,400 meters. In January of this year, a North American team from Cornell University, in collaboration with researchers from Paulista State University (Unesp) and the State University of Campinas (Unicamp) indicated that the fungus may live in a variety of environments and also at low altitudes in the Atlantic rainforest. All they can do for the time being is to follow the traces of the fungus, since it is difficult to cultivate this organism in a laboratory to study its behavior in detail.<\/p>\n

\u201cThe amphibian species that are disappearing live in preserved areas in Brazil, Central America and Oceania, where there are no dirty or polluted streams that could be fatal,\u201d says Cat\u00e3o. Brazil is one of the countries with the biggest diversity of amphibians, with almost 900 species already identified, of which 16 are considered to be threatened with extinction and one is already extinct. The reduction in the populations of amphibians could mean an increase in populations of the insects that transmit diseases such as dengue fever, malaria and yellow fever, \u201cconsidering merely an anthropocentric view,\u201d says Cat\u00e3o. In broader terms, it could make the survival of other animals, such as birds and reptiles that feed on toads and frogs, difficult.<\/p>\n

According to Cat\u00e3o, the fungus is one of the causes of the mass extinction of amphibians, which is equivalent to others that have occurred in the history of the Earth, although it is not the only responsible factor: \u201cWe have to keep an open mind to other possible causes.\u201d The main ones are the loss or reduction of the habitat and the proliferation of other parasites, such as the ranavirus, a viral group that is lethal to tadpoles, which are normally resistant to the fungus.<\/p>\n

\u201cFungi are opportunistic and advance more easily when the hosts are under stress or some type of environmental pressure,\u201d comments Selene, offering a similar human example: candidiasis, which manifests itself when the organism\u2019s defenses are weakened. She believes that Bd<\/em> is not yet as well adapted to the different environments as the dermatophyte fungi that cause mycoses in animals and people and spread through domestic environments.<\/p>\n

Last year a veterinary student at Unip, S\u00e2ndara Pimentel Sguario, isolated colonies of fungi of another species, Mycroscoporum canis<\/em>, in a cat that her boyfriend had left with her and that she kept in her bedroom. Selene suggested to her student to collect samples of material not only from the cat but also from the rug, the bed, her computer chair, and the entire bedroom. It turned out that these contained the same fungus that had infested the cat. \u201cI\u2019ve not yet read anything that indicates that Bd<\/em> can infect people or other mammals,\u201d says Selene. \u201cFrom an evolutionary perspective it will perhaps take time before it affects people, or maybe it never will.\u201d<\/p>\n

The Project<\/strong>
\nCompared pathology of selected infections of anuran amphibians that live in the wild in the Atlantic rainforest biome: prospective and retrospective study (n\u00ba 2009\/52638-3<\/a>);\u00a0Modality\u00a0<\/strong>Regular Research Project Funding; Coordinator\u00a0<\/strong>Jos\u00e9 Luiz Cat\u00e3o Dias \u2013 FMVZ\/USP;\u00a0Investment\u00a0<\/strong>R$ 47,371.09<\/p>\n

Scientific articles
\n<\/em>DE PAULA, C.D. et al<\/em>. Batrachochytrium dendrobatidis <\/em>in illegal wildlife trade confiscated amphibians used in ex situ<\/em> breeding program \u2028in Brazil<\/a>. Diseases of Aquatic Organisms.<\/strong> v. 98, n.2, p. 171-75. 2012.
\nGR\u00dcNDLER, M.C. et al<\/em>. Interaction between breeding habitat and elevation affects prevalence but not infection intensity of Batrachochytrium dendrobatidis <\/em>in Brazilian anuran assemblages<\/a>. Diseases of Aquatic Organisms.<\/strong> v. 97, n. 3, \u2028p. 173-84. 2012.
\nCARNAVAL, A.C.O.Q. et al<\/em>. Amphibian chytrid fungus broadly distributed in the Brazilian Atlantic rain forest<\/a>. EcoHealth.<\/strong> v. 3, n. 1, p. 41-48. 2006.<\/p>\n","protected":false},"excerpt":{"rendered":"Animal trafficking may spread lethal fungus for toads and frogs\r\n","protected":false},"author":17,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[159],"tags":[209,266],"coauthors":[5968],"class_list":["post-16746","post","type-post","status-publish","format-standard","hentry","category-science","tag-biology","tag-zoology"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/16746","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/17"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=16746"}],"version-history":[{"count":0,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/16746\/revisions"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=16746"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=16746"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=16746"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=16746"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}