Batrachochytrium Dendrobatidis in Amphibians Confiscated from Illegal Wildlife Trade and Used in an Ex Situ Breeding Program in Brazil
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Vol. 98: 171–175, 2012 DISEASES OF AQUATIC ORGANISMS Published March 20 doi: 10.3354/dao02426 Dis Aquat Org NOTE Batrachochytrium dendrobatidis in amphibians confiscated from illegal wildlife trade and used in an ex situ breeding program in Brazil C. D. De Paula1,*, E. C. Pacífico-Assis2, J. L. Catão-Dias1 1Departamento de Patologia, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, SP, Brazil 2Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil ABSTRACT: This paper describes an outbreak of chytridiomycosis affecting a group of Dendro- bates tinctorius, a Neotropical anuran species, confiscated from the illegal wildlife trade and housed in a private zoo in Brazil as part of an ex situ breeding program. We examined histological sections of the skin of 30 D. tinctorius and 20 Adelphobates galactonotus individuals. Twenty D. tinctorius (66.7%) and none of the A. galactonotus were positive for Batrachochytrium dendroba- tidis (Bd). Multiple development stages of Bd infection were observed. The reasons for the inter- specific difference in the rate of infection could not be determined, and further studies are advised. Because the examined population consisted of confiscated frogs, detailed epidemiologi- cal aspects could not be investigated, and the source of the fungus remains uncertain. The exis- tence of ex situ amphibian populations is important for protecting species at higher risk in the wild, and ex situ amphibian conservation and breeding programs in Brazil may be established using confiscated frogs as founders. However, this paper alerts these programs to the urgency of strict quarantine procedures to prevent the introduction of potential pathogens, particularly Bd, into ex situ conservation programs. KEY WORDS: Chytridiomycosis · Dendrobates tinctorius · Neotropical anuran · Brazil Resale or republication not permitted without written consent of the publisher INTRODUCTION species in the International Union for Conservation of Nature (IUCN) Red List (IUCN 2008), and the Brazil- Dramatic declines among amphibian populations ian government lists 16 species as threatened, 1 spe- worldwide have occurred in recent decades (Stuart cies as extinct and 90 species as data deficient (Had- et al. 2004). Many causes have been suggested, dad 2008). There is insufficient information to including habitat loss, invasive species, overexploita- evaluate the conservation status of more than 10% of tion, climate change, environmental contaminants the Brazilian amphibians and a general lack of infor- and infectious diseases (Gardner 2001, Blaustein & mation about the species that are either threatened Kiesecker 2002, Stuart et al. 2004). Brazil has the or data deficient (Pistoni & Toledo 2010). world’s greatest amphibian diversity with more than Chytridiomycosis, which is caused by the chytrid 860 species, most of which were described in the last fungus Batrachochytrium dendrobatidis (Bd), is a 40 yr (SBH 2010). There are few reports of amphibian devastating emerging infectious disease that infects population declines in Brazil, and most involve high- a high diversity of amphibian species and is consid- altitude species (Eterovick et al. 2005, Silvano & ered responsible for massive amphibian declines and Segalla 2005). There are 116 Brazilian amphibian extinctions. It has been reported in wild populations *Email: [email protected] © Inter-Research 2012 · www.int-res.com 172 Dis Aquat Org 98: 171–175, 2012 in several regions throughout the world, including an important strategy for responding to the amphibian South America (Daszak et al. 2003, Morehouse et al. conservation crisis. In this scenario, zoological insti - 2003, Lips et al. 2005, Lips et al. 2006). The first evi- tutions may play an important role in preventing dence of infection in wild frogs in Brazil was reported the spread of the disease throughout captive facilities in Hylodes magalhaesi, a leptodactylid from the as well as in disease surveillance, research, and Atlantic Rain Forest (Carnaval et al. 2005). Later in - captive breeding and reintroduction programs (Gas- vestigations revealed that Bd was broadly distributed con et al. 2007). This paper describes an outbreak of in that biome, infecting another 5 species (Carnaval chytridiomycosis affecting a group of Dendrobates et al. 2006, Toledo et al. 2006). It has also been de - tinctorius, a Neotropical anuran species, that origi- scribed in farmed, captive Lithobates catesbeianus in nated from an illegal trade apprehension and were Brazil (Schloegel et al. 2010). subsequently housed in a private zoo in Brazil. Impli- Bd is a member of the Phylum Chytridiomycota and cations for in situ and ex situ conservation programs the first chytrid fungus to be recognized as a parasite are briefly discussed. of the Phylum Vertebrata (Berger et al. 1998). It infects keratinized cells in amphibians (the mouth- parts of larvae and the epidermis of adults) and leads CASE REPORT to hyperkeratosis (Pessier et al. 1999). The pathogen- esis of Bd is controversial; however, Voyles et al. We examined formalin-fixed specimens of 30 Den- (2009) demonstrated that electrolytic transport in the drobates tinctorius and 20 Adelphobates galactono- skin was inhibited by >50%, plasma sodium and tus that had died between 2005 and 2009 in a private potassium concentrations were reduced, and asys- zoo in São Paulo State, Brazil. Some animals died tolic cardiac arrest resulted in death in diseased without previous clinical signs, while others pre- green tree frogs Litorea caerulea. Because the skin is sented progressive emaciation. The animals were critical for amphibian homeostasis, disruption of received from local authorities after an illegal trade cutaneous function may cause morbidity and mortal- apprehension and were housed off-exhibit in the ity in a wide range of amphibians. same room and in close proximity to each other in The diagnosis of Bd can be obtained through several glass vivaria. Additional information regard- histopathological demonstration of the zoospore in ing shipment conditions was not available. Room the epidermis of infected anurans (Pessier et al. temperature was maintained at approximately 25°C, 1999). Variable amounts of keratin may closely sur- and the relative humidity ranged from 60 to 80%. round the organism (Berger et al. 2000). The main The vivaria had an expanded clay substrate with histopathological change in the skin is mild to moder- plants and coconut shells to provide shelter. The ate hyperkeratosis. Irregular hyperplasia may be dead animals were fixed in 10% formalin and sub- present, as well as mild focal necrosis of the epider- mitted for histo pathological examination at the Labo- mal cells. Occasional ulcerations can be seen and are ratório de Patologia Comparada de Animais Sel- generally associated with secondary bacterial infec- vagens — Departamento de Patologia, Faculdade de tion. Inflammation is an inconsistent finding. There is Medicina Veterinária e Zootecnia — Universidade de extensive involvement of the ventral skin and toes São Paulo, Brazil. Skin sections from the digits of the (Pessier et al. 1999, Berger et al. 2000, 2005). Other front and rear limbs and from the lower abdomen diagnostic methods include immunohistochemistry were embedded in paraffin, cut into 5 μm sections, (Van Ells et al. 2003), electron microscopy (Berger et stained with hematoxylin and eosin (H & E) and then al. 2002), conventional PCR (Annis et al. 2004) and examined under light microscopy. Attempts to ex - real-time PCR (Boyle et al. 2004). tract DNA for molecular diagnosis of Bd infection by Despite the threats to its rich amphibian diversity, conventional PCR were performed using the Invitro- Brazil has very few captive populations or ex situ con- gen Pure Link Genomic DNA kit according to the servation programs involving these vertebrates. This manufacturer’s recommendations. Complementary situation may change rapidly because several species microbiological exams were not performed because are facing threats that cannot be solved solely with the carcasses were already in formalin solution when the in situ conservation strategies currently available. they were received. The existence of ex situ amphibian populations is im- Twenty Dendrobates tinctorius (66.7%) and none portant to protect species that are at higher risk in the of the Adelphobates galactonotus (0%) were positive wild until the threats can be reduced, and the estab- for Bd based on histological diagnosis. Various devel- lishment of captive breeding facilities is considered opment stages of Bd infection were observed within De Paula et al.: Bd infection in confiscated amphibians in Brazil 173 the stratum corneum, including zoosporangia with been detected in the ex situ population, and the fun- zoospores and empty zoosporangia with internal sep- gus was accidentally introduced to the wild population tation (Fig. 1). Hyperkeratosis was also observed, but (Walker et al. 2008). Situations like this reinforce the no inflammatory response was seen in the epidermis need to strictly follow the IUCN guidelines for captive or in the underlying dermis. Attempts to extract DNA breeding and reintroduction projects (IUCN 1998). were unsuccessful. In Brazil, Bd has already been identified in asymp- tomatic captive North American bullfrogs Lithobates catesbeianus, with an overall prevalence of 78.5%. DISCUSSION Recent studies showed a marked similarity in Latin American Bd isolates from captive