Experimental infection of self-cured Leiopelma archeyi with the amphibian chytrid Batrachochytrium dendrobatidis

Abstract

The susceptibility of Archey's frog Leiopelma archeyi to Batrachochytrium dendrobatidis (Bd) is unknown, although one large population is thought to have declined sharply due to chytridiomycosis. As primary infection experiments were not permitted in this endangered New Zealand species, 6 wild-caught L. archeyi that naturally cleared infections with Bd while in captivity were exposed again to Bd to assess their immunity. These frogs were from an infected population at Whareorino, which has no known declines. All 6 L. archeyi became reinfected at low intensities, but rapidly self cured, most by 2 wk. Six Litoria ewingii were used as positive controls and developed heavier infections and clinical signs by 3 wk, demonstrating that the zoospore inoculum was virulent. Six negative controls of each species remained uninfected and healthy. Our results show that L. archeyi that have self cured have resistance to chytridiomycosis when exposed. The pattern is consistent with innate or acquired immunity to Bd, and immunological studies are needed to confirm this. KEY WORDS: Leiopelma archeyi · Litoria ewingii · Batrachochytrium dendrobatidis · Chytridiomycosis Resale or republication not permitted without written consent of the publisherContribution to DAO Special 4 'Chytridiomycosis: an emerging disease'

American Bullfrogs (Lithobates catesbeianus) Resist Infection by Multiple Isolates of Batrachochytrium dendrobatidis, Including One Implicated in Wild Mass Mortality

“…The relatively thick epidermis of this species, which allows for rapid skin sloughing and thus shedding of epidermal Bd infection, may contribute to resistance (Greenspan et al 2012a, b). In addition, the complete lack of infection following our second exposure with SL Bd might be partially attributable to primed host defenses that conferred effective resistance to these individuals, all of which had been previously exposed to Bd (Shaw et al 2010;McMahon et al 2014). However, the lack of clinical signs of chytridiomycosis in the American bullfrogs that did become infected indicates tolerance mechanisms also play a role in bullfrogBd interactions, as previous work has suggested (Hanselmann et al 2004;Greenspan et al 2012b).…”

Potential influence of plant chemicals on infectivity of Batrachochytrium dendrobatidis

“…Not all animals appeared to acquire this resistance, but a large proportion of those we treated produced only low or no infection even after treatment with high levels of active zoospores. Resistance to Bd in previously cured Leiopelma archeyi frogs was reported by Shaw et al (2010) and in toads Anaxyrus (Bufo) boreas by Murphy et al (2011), suggesting that acquired resistance against this pathogen is possible, although an attempt to immunize Rana muscosa by injection of killed Bd culture was ineffective (Stice & Briggs 2010). Zoospore load (zsp GE) Fig.…”

Amphibians acquire resistance to live and dead fungus overcoming fungal immunosuppression

“…Surprisingly, there are no published studies that experimentally subjected amphibians to regimes of repeated Bd infection followed by clearance and then tested for an association between the number of previous infections and Bd abundance, immune parameters and behavioural avoidance (ref. 14, but see also 15–22). We hypothesized that, despite Bd -induced immunosuppression 7–9 , effects of repeated exposures to Bd followed by pathogen clearance could include reduced Bd abundance on frog skin, increases in the abundance or efficacy of skin peptides, augmentation of the abundance of responding lymphocyte populations (mediators of Bd resistance 16–18 ), and induction of learned avoidance of Bd.…”