Experimental Transmission of Cutaneous Chytridiomycosis in Dendrobatid Frogs

Abstract

In a series of three experiments during March-October, 1998, two species of captivebred poison dart frogs (Dendrobates tinctorius and D. auratus) were exposed to Batrachochytrium dendrobatidis, a recently-described chytridiomycete fungus (chytrid) that was originally isolated from a blue poison dart frog (D. azureus). All frogs exposed to the chytrids developed a fatal skin disease, whereas none of the control frogs developed skin lesions. The most consistent clinical sign in chytrid-exposed frogs was excessive shedding of skin. Gross lesions were subtle, usually affected the legs and ventrum, and consisted of mild skin thickening and discoloration. Microscopic examination of shed skin pieces and/or skin imprints demonstrated the presence of chytrids and was used for ante mortem and post mortem confirmation of chytrid infection. Histologically, there was epidermal hyperkeratosis, hyperplasia, and hypertrophy associated with low to moderate numbers of chytrids in the keratinized layers. These experiments demonstrated that Batrachochytrium dendrobatidis can be a fatal pathogen in poison dart frogs. The experimentally-induced disease in these frogs resembled cases of cutaneous chytridiomycosis that have recently been described in several other species of captive and wild amphibians.

Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community

“…Chytridiomycosis lesions were diffuse to multifocally extensive, especially on skin sections from the ventral body. These lesions were significantly more severe than the relatively minimal focal lesions described in infected, but apparently healthy, bullfrogs (12) and were of a level consistent with those associated with mortality in natural and experimental infections (13). Molecular analyses of tissue collected from 38 individuals of 11 species were negative for ranavirus (A. Picco, personal communication).…”

Host invasion by Batrachochytrium dendrobatidis: fungal and epidermal ultrastructure in model anurans

“…Dis Aquat Org 100: [201][202][203][204][205][206][207][208][209][210] 2012 scopically, excessive skin sloughing, lethargy, anorexia, loss of righting reflex, and abnormal posture may be observed (Nichols et al 2001, Daszak et al 2004) but often not until immediately before death (Bradley et al 2002, Parker et al 2002. Proximate cause of death is inhibition of electrolyte transport across epidermis and subsequent disruption of cardiac electrical activity (Voyles et al 2009).…”

Retreat sites of rain forest stream frogs are not a reservoir for Batrachochytrium dendrobatidis in northern Queensland, Australia

“…dendrobatidis is the only chytrid known to cause disease in vertebrate hosts (Berger et al 1998), presumably breaking down keratin that occurs in the epidermis of adult amphibians and the mouthparts of larval anurans. Chytridiomycosis can cause rapid mortality (Nichols et al 2001), with infected frogs of susceptible species dying within 3 wk of infection in the laboratory (Berger et al 1998(Berger et al , 2004. In the laboratory, the disease is highly contagious (Nichols et al 2001), spreading within and among individuals via motile, waterborne zoospores .…”

“…Chytridiomycosis can cause rapid mortality (Nichols et al 2001), with infected frogs of susceptible species dying within 3 wk of infection in the laboratory (Berger et al 1998(Berger et al , 2004. In the laboratory, the disease is highly contagious (Nichols et al 2001), spreading within and among individuals via motile, waterborne zoospores .…”

“…Chytridiomycosis can cause rapid mortality (Nichols et al 2001), with infected frogs of susceptible species dying within 3 wk of infection in the laboratory (Berger et al 1998(Berger et al , 2004. In the laboratory, the disease is highly contagious (Nichols et al 2001), spreading within and among individuals via motile, waterborne zoospores .One of the unusual aspects of chytridiomycosis is that it drives many host species to local extinction during outbreaks (Berger et al 1998, Lips et al 2006. For a pathogen to cause local host extinction it must be capable of persisting and infecting new hosts even at very low host population densities (Anderson & May 1986, Dobson & May 1986.…”