Chytridiomycosis in dwarf African frogs Hymenochirus curtipes

Abstract

Chytridiomycosis, resulting from an infection with the fungal agent Batrachochytrium dendrobatidis (Bd), has resulted in widespread population declines in both wild and captive amphibians. The dwarf African frog (DAF) Hymenochirus curtipes is native to central Africa and is commonly sold throughout North America as an aquarium pet species. Here we document fatal chytridiomycosis resulting from cutaneous Bd infections in DAF purchased directly from a pet store and from a historical lethal epizootic occurring at an aquaculture facility in central California, USA, more than 25 yr ago. Histological lesions and PCR-amplified sequence data were consistent with the etiology of Bd. The potential epidemiological relevance of this infection in DAF is discussed. KEY WORDS: Frog · Batrachochytrium dendrobatidis · Bd · Hymenochirus · ChytridiomycosisResale or republication not permitted without written consent of the publisher Dis Aquat Org 114: 69-75, 2015 during the 20th century resulted in worldwide dissemination of the chytridiomycete fungal agent (Weldon et al. 2004). Multiple states in the USA now require a permit to purchase ACF. ACF (X. laevis) in the wild do not demonstrate clinical signs of chytridiomycosis, and sudden die-offs of ACF have not been documented (Weldon et al. 2004). However, subclinical infections with Bd have been well documented in captive Xenopus laevis (Reed et al. 2000). In contrast, Bd infection in the related ACF X. tropicalis can result in anorexia and lethargy, cutaneous pigment changes, loss of the cutaneous slime layer and death (Parker et al. 2002). In a survey of archived specimens of 3 different species of Xenopus from 1879 to 1999, the earliest case of chytridiomycosis was found in a Xenopus laevis frog in 1938 (Weldon et al. 2004). This fungal pathogen apparently existed as a stable endemic infection in southern Africa for at least 23 yr before any Bd-infected specimens ap peared outside of Africa (Weldon et al. 2004).Dwarf African frogs are small aquatic frogs native to central Africa that lack both teeth and a tongue and are completely aquatic. Otto Boettger, one of the dwarf African frog discoverers, originally named them African dwarf clawed frogs in recognition of the small black claws on their hind legs. Since these claws are often lost as the frogs mature, these animals are now more commonly re ferred to as dwarf African frogs. There are currently 4 recognized species of Hymenochirus: H. boulengeri, H. curtipes, H. boettgeri, and H. feae (IUCN Red List of Threatened Species, www.iucnredlist.org). Currently, there is some controversy over the taxonomic status of H. feae. Both H. boettgeri and H. curtipes are commonly sold in the pet trade. As these animals look very similar to one another, the morphological separation between these 2 species can be challenging. In addition, these frogs are capable of interbreeding and forming hy brids; as a result, some breeders feel that the DAF sold in the pet trade are actually a H. boettgeri × H. curtipes hybrid.The peer-reviewe...

Globally invasive genotypes of the amphibian chytrid outcompete an enzootic lineage in coinfections

“…We used the aquatic, western dwarf clawed frog (Hymenochirus curtipes, Pipidae) as the host for this study. Hymenochirus curtipes is tolerant to Bd infection at low levels but may succumb to disease at high pathogen loads [38,39]. Hymenochirus curtipes is also available from commercial suppliers in the aquarium trade, allowing for the iteration of this study by separate research groups.…”

Amphibian chytrid fungus in Africa – realigning hypotheses and the research paradigm

“…Ex situ exposure of Malagasy frogs to Bd GPL has demonstrated extremely high susceptibility and rapid proliferation of infection, although trials were terminated with the onset of humane endpoints before lethality could be determined (Bletz et al , ). Other African species have been found to succumb to lethal infection by Bd , including caecilians, such as Geotrypetes seraphini (from a Bd CAPE strain), as well as dwarf clawed frogs Hymenochirus curtipes (unknown strain) albeit possibly confounded by stress from captivity in these cases (Gower et al , 2013 b ; Murphy et al , ). Research on other amphibian taxa that are possibly susceptible to infection is now needed, especially West African endemic species, and high elevation species of puddle frogs ( Phrynobatrachus spp.…”