Effect of season and temperature on mortality in amphibians due to chytridiomycosis

Berger, Lee; Speare, Rick; Hines, HB; Marantelli, Gerry; Hyatt, AD; McDonald, K.R.; Skerratt, Lee F.; Olsen, Veronica; Clarke, John Mason; Gillespie, Graeme R.; Mahony, MJ; Sheppard, N.; Williams, Craig R.; Tyler, MJ

doi:10.1111/j.1751-0813.2004.tb11137.x

Cited by 344 publications

(407 citation statements)

References 27 publications

(34 reference statements)

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“…Our finding that disruption of the epidermal cell maturation cycle was mild and localized in bullfrogs, a low-mortality-risk species for chytridiomycosis, and more severe in wood frogs, a high-mortalityrisk species for chy tri diomycosis (at least at some life stages under laboratory conditions), supports previous work (Daszak et al 2004, Berger et al 2005). Abnormal molting is a clinical sign of chytridiomycosis that could be beneficial, by ridding animals of infected skin layers (Davidson et al 2003, Berger et al 2004), or detrimental, by impeding water and electrolyte transport (Voy les et al 2011). Bullfrogs may slough rapidly during experimental inoculations with Bd (Greenspan et al 2012).…”

Section: Discussionmentioning

confidence: 99%

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

Greenspan¹,

Longcore²,

Calhoun³

2012

Dis. Aquat. Org.

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The chytridiomycete fungus Batrachochytrium dendrobatidis (Bd) colonizes mouthparts of amphibian larvae and superficial epidermis of post-metamorphic amphibians, causing the disease chytridiomycosis. Fungal growth within host cells has been documented by light and transmission electron microscopy; however, entry of the fungus into host cells has not. Our objective was to document how Bd enters host cells in the wood frog Lithobates sylvaticus, a species at high mortality risk for chytridiomycosis, and the bullfrog L. catesbeianus, a species at low mortality risk for chytridiomycosis. We inoculated frogs and documented infection with transmission electron microscopy. Zoospores encysted on the skin surface and produced morphologically similar germination tubes in both host species that penetrated host cell membranes and enabled transfer of zoospore contents into host cells. Documenting fungal and epidermal ultrastructure during host invasion furthers our understanding of Bd development and the pathogenesis of chytridiomycosis. KEY WORDS: Chytridiomycosis · Morphology · Transmission electron microscopy · Lithobates catesbeianus · Lithobates sylvaticus Resale or republication not permitted without written consent of the publisherDis 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).The asexual life cycle of Bd consists of a motile zoospore stage and a stationary thallus stage (Berger et al. 2005). Zoospores are flagellated and are not bounded by a cell wall. After a motile period, usually lasting ≤24 h, a zoospore encysts (i.e. attaches to a substrate, retracts the flagellum, and forms a wall of chitin around the spore body). Morphology after encystment depends on substrate type. On nutrient media, an encysted zoospore develops into a single or colonial (internally divided) zoosporangium (endogenous growth); root-like rhizoids originating from 1 or more points on the zoosporangium may be numerous . In an amphibian host, cellular contents of a superficially encysted zoospore leave the cyst and enter a host cell (exogenous growth), inside which a single or colonial zoosporangium develops; rhizoids are usually less abundant than on nutrient media (Berger et al. 2005). The specifics of amphibian host invasion by Bd (i.e. the morphological process by which zoospore contents are transferred from a cyst into a host cell) have not been reported. In other chytrid species with known developmental morphologies (saprophytes and patho gens of plants, algae, protists, and invertebrates), endobiotic (i.e. intracellular) growth of a thallus is initiated when a protrusion of the zoospore cyst wall e...

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Section: Discussionmentioning

confidence: 99%

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

Greenspan¹,

Longcore²,

Calhoun³

2012

Dis. Aquat. Org.

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“…Other breeding sites included a temporary stream, a pond, and an underground water tank. Because Bd prevalence can be influenced by temperature (Berger et al, 2004), we recorded water temperature at all sites sampled for larvae by holding a mercury-filled thermometer in the middle of the water column for 60 sec.…”

Section: Study Sitesmentioning

confidence: 99%

Prevalence of Batrachochytrium Dendrobatidis in Agalychnis Moreletii (Hylidae) of El Salvador and Association With Larval Jaw Sheath Depigmentation

Lawson

Jones

Komar³

et al. 2011

Journal of Wildlife Diseases

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ABSTRACT:Amphibian populations around the world have been declining at an alarming rate due to factors such as habitat destruction, pollution, and infectious diseases. Between May and July 2008, we investigated a fungal pathogen in the critically endangered Morelet's treefrog (Agalychnis moreletii) at sites in El Salvador. Larvae were screened with a hand lens for indications of infection with Batrachochytrium dendrobatidis (Bd), a fungus that can cause lethal chytridiomycosis in amphibians. Subsets of inspected tadpoles were preserved for analysis by polymerase chain reaction to determine the effectiveness of hand lens screening for presence of Bd and to estimate infection prevalence at various sites. Because individuals with signs of infection were preferentially included, we used a novel method to generate unbiased estimates of infection prevalence from these biased samples. External mouthpart deformities, identified with a hand lens, successfully predicted Bd infection across a large spatial scale. Two of 13 sites sampled had high ($89%) estimated prevalence, whereas little or no Bd was detected at the remaining sites. Although it appears that A. moreletii populations in this region are not suffering rapid declines due to Bd, further monitoring is required to determine the extent to which these populations are stably coexisting with the pathogen.

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“…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 .…”

Section: Abstract: Batrachochytrium Dendrobatidis · Amphibian Chytrimentioning

confidence: 99%

“…One potential mechanism for this is the persistence and growth of Batrachochytrium dendrobatidis in tadpoles and adults that do not die from infection (Berger et al 1998, 1999. The broad host range of B. dendrobatidis also provides a reservoir of infection, enabling the species most susceptible to chytridiomycosis to be driven to extinction (Berger et al 2004). An alternative source of infection that could facilitate extinction is the persistence of free-living stages , Godfray et al 1999.…”

Section: Abstract: Batrachochytrium Dendrobatidis · Amphibian Chytrimentioning

confidence: 99%

“…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 .…”

Section: Retreat Sites Of Rain Forest Stream Frogs Are Not a Reservoimentioning

confidence: 99%

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

Rowley¹,

Skerratt²,

Alford³

et al. 2007

Dis. Aquat. Org.

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Chytridiomycosis is a potentially fatal disease of amphibians caused by Batrachochytrium dendrobatidis, and is implicated in declines and extinctions of amphibian populations and species around the world. To cause local host extinction, a disease organism must persist at low host densities. One mechanism that could facilitate this is the ability to persist in the environment. In the laboratory, B. dendrobatidis spreads by both frog-to-frog and environment-to-frog transmission, and can persist on a number of biotic substrates. In the field, B. dendrobatidis has been detected on environmental samples taken during an epidemic, but it is not known if it persists in the environment when endemic. Retreat sites of 2 species of Australian rain forest stream frogs Litoria lesueuri and L. nannotis were sampled 0 to 3 d after occupation during the wet and dry seasons in northern Queensland, Australia, where chytridiomycosis has been endemic for at least 10 yr. The intensity and prevalence of infection in frogs during sampling were comparatively low compared with epidemics. Diagnostic quantitative polymerase chain reaction did not detect B. dendrobatidis in any retreat site samples. It thus appears that retreat sites are not a major environmental source of infection when B. dendrobatidis occurs at low prevalence and intensity on frogs. This suggests that control efforts may not need to eliminate the organism from the environment, at least when prevalence and intensity of infection are low in frogs. Simply treating hosts may be effective at controlling the disease in the wild. KEY WORDS: Batrachochytrium dendrobatidis · Amphibian chytrid fungus · Chytridiomycosis · Environmental reservoir · Disease transmission · FrogsResale or republication not permitted without written consent of the publisher Dis Aquat Org 74: 7-12, 2007 B. 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 .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. One potential mechanism for this is the persistence and growth of Batrachochytrium dendrobatidis in tadpoles and adults that do not die from infection (Berger et al. 1998, 1999. The broad host range of B. dendrobatidis also provides a reservoir of infection, enabling the species most susceptib...

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Effect of season and temperature on mortality in amphibians due to chytridiomycosis

Abstract: Chytridiomycosis is a major cause of mortality in free-living and captive amphibians in Australia and mortality rate increases at lower temperatures.

Cited by 344 publications

References 27 publications

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

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

Prevalence of Batrachochytrium Dendrobatidis in Agalychnis Moreletii (Hylidae) of El Salvador and Association With Larval Jaw Sheath Depigmentation

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

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