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CHE WELDON

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INDIAN AGRICULTURAL RESEARCH INSTITUTE, NEW DELHI, INDIA

Alex Mauricio Jimenez-Ortega

Universidad Tecnológica del Chocó

Armando Marques-Guedes

UNL - New University of Lisbon

UPM - Universiti Putra Malaysia

Dr. Mohd. Javed Ansari

King Saud University

Shailesh K Tiwari

Indian Council of Agricultural Research

Dr. Eluvathingal Antony Jayson

Kerala Forest Research Institute

Alejandro Valenzuela

Universidad Nacional de Tierra del Fuego

Joseph Shalhoub

Imperial College London

André Ricardo Ribas Freitas

Centro de Pesquisas em Odontologia Sao Leopoldo Mandic

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Papers by CHE WELDON

Prey items count data from laboratory feeding experiment

File include data on the number of prey items consumed through time in a laboratory feeding exper... more

Culex egg raft distribution in mesocosm experiment

File include data on the distribution of Culex egg rafts between treatments. The data was collect... more File include data on the distribution of Culex egg rafts between treatments. The data was collected in an oviposition habitat selection outdoor mesocosm experiment. Columns A-C describe the treatment code. Columns E-F describe the distribution of treatments among experimental tubs. Columns I-K describe the number of egg rafts deposited per day in each of the experimental tubs

Data from: Testing the link between perceived and actual risk of predation: mosquito oviposition site selection and egg predation by native and introduced fish

Origin of the Amphibian Fungus

The sudden appearance of chytridiomycosis, the cause of amphibian deaths and population declines ... more The sudden appearance of chytridiomycosis, the cause of amphibian deaths and population declines in several continents, suggests that its etiologic agent, the amphibian chytrid Batrachochythum dendrobatidis. was introduced into the affected regions. However, the origin of this virulent pathogen is unknown. A survey Vi'as conducted of 697 archived specimens of 3 species of Xenopus collected from 1879 to 1999 in southern Africa in which the histologic features of the interdigital webbing were analyzed. The earliest case of chytridiomycosis found was in a Xenopus laevis frog in 1938, and overall prevalence was 2.7%. The prevalence showed no significant differences between species, regions, season, or time period. Chytridiomycosis was a stable endemic infection in southern Africa for 23 years before any positive specimen was found outside Africa. We propose that Africa is the origin of the amphibian chytrid and that the international trade in X. laevis that began in the mid-1930s wa...

A series of terribly unfortunate events: How environment and infection synergized to cause the Kihansi spray toad extinction

Outbreaks of emerging infectious diseases are trained by local biotic and abiotic factors, with h... more Outbreaks of emerging infectious diseases are trained by local biotic and abiotic factors, with host declines occurring when conditions favour the pathogen. Extinction of the Tanzanian Kihansi spray toad (Nectophrynoides asperginis) in 2004 was contemporaneous with the construction of a dam, implicating habitat modification in the loss of this species. However, high burdens of a globally emerging infection, Batrachochytrium dendrobatidis (Bd) were synchronously observed implicating infectious disease in this toads extinction. Here, by shotgun sequencing skin DNA from archived toad mortalities and assembling chytrid mitogenomes, we prove this outbreak was caused by the BdCAPE lineage and not the panzootic lineage BdGPL that is widely associated with global amphibian extinctions. Molecular dating showed an invasion of BdCAPE across Southern Africa overlapping with the timing of the extinction event. However, post-outbreak surveillance of conspecific species inhabiting this mountainous...

A case study in canine detection of giant bullfrog scent

Journal of Vertebrate Biology, 2021

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more

Response to Comment on “Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity”

Science, 2020

Lambert et al . question our retrospective and holistic epidemiological assessment of the role of... more Lambert et al . question our retrospective and holistic epidemiological assessment of the role of chytridiomycosis in amphibian declines. Their alternative assessment is narrow and provides an incomplete evaluation of evidence. Adopting this approach limits understanding of infectious disease impacts and hampers conservation efforts. We reaffirm that our study provides unambiguous evidence that chytridiomycosis has affected at least 501 amphibian species.

Disease driven extinction in the wild of the Kihansi spray toad (Nectophrynoides asperginis)

The Kihansi spray toad, Nectophrynoides asperginis, became extinct in the wild despite population... more The Kihansi spray toad, Nectophrynoides asperginis, became extinct in the wild despite population monitoring and conservation management of its habitat in the Kihansi gorge, Tanzania. Anecdotal evidence has indicated human induced habitat modification, predators, pesticides and disease as possible causes of a rapid population decline and the species extirpation. Here, we systematically investigate the role of disease in the extinction event of the wild toad population. The amphibian chytrid fungus, Batrachochytrium dendrobatidis, was detected in spray toads that died during the extinction event and subsequently in other amphibian species in Kihansi Gorge and the adjacent Udagaji Gorge, but not in any toads collected prior to this. Following the population decline, the remnant spray toad population gradually disappeared over a nine-month period. We demonstrate how demographic and behavioral attributes predisposed the spray toads to chytridiomycosis, due to B. dendrobatidis infection,...

Development and worldwide use of non-lethal, and minimal population-level impact, protocols for the isolation of amphibian chytrid fungi

Scientific reports, Jan 17, 2018

Parasitic chytrid fungi have emerged as a significant threat to amphibian species worldwide, nece... more Parasitic chytrid fungi have emerged as a significant threat to amphibian species worldwide, necessitating the development of techniques to isolate these pathogens into culture for research purposes. However, early methods of isolating chytrids from their hosts relied on killing amphibians. We modified a pre-existing protocol for isolating chytrids from infected animals to use toe clips and biopsies from toe webbing rather than euthanizing hosts, and distributed the protocol to researchers as part of the BiodivERsA project RACE; here called the RML protocol. In tandem, we developed a lethal procedure for isolating chytrids from tadpole mouthparts. Reviewing a database of use a decade after their inception, we find that these methods have been applied across 5 continents, 23 countries and in 62 amphibian species. Isolation of chytrids by the non-lethal RML protocol occured in 18% of attempts with 207 fungal isolates and three species of chytrid being recovered. Isolation of chytrids ...

Estimating Herd Immunity to Amphibian Chytridiomycosis in Madagascar Based on the Defensive Function of Amphibian Skin Bacteria

Frontiers in Microbiology, 2017

For decades, Amphibians have been globally threatened by the still expanding infectious disease, ... more For decades, Amphibians have been globally threatened by the still expanding infectious disease, chytridiomycosis. Madagascar is an amphibian biodiversity hotspot where Batrachochytrium dendrobatidis (Bd) has only recently been detected. While no Bd-associated population declines have been reported, the risk of declines is high when invasive virulent lineages become involved. Cutaneous bacteria contribute to host innate immunity by providing defense against pathogens for numerous animals, including amphibians. Little is known, however, about the cutaneous bacterial residents of Malagasy amphibians and the functional capacity they have against Bd. We cultured 3179 skin bacterial isolates from over 90 frog species across Madagascar, identified them via Sanger sequencing of approximately 700 bp of the 16S rRNA gene, and characterized their functional capacity against Bd. A subset of isolates was also tested against multiple Bd genotypes. In addition, we applied the concept of herd immunity to estimate Bd-associated risk for amphibian communities across Madagascar based on bacterial antifungal activity. We found that multiple bacterial isolates (39% of all isolates) cultured from the skin of Malagasy frogs were able to inhibit Bd. Mean inhibition was weakly correlated with bacterial phylogeny, and certain taxonomic groups appear to have a high proportion of inhibitory isolates, such as the Enterobacteriaceae, Pseudomonadaceae, and Xanthamonadaceae (84, 80, and 75% respectively). Functional capacity of bacteria against Bd varied among Bd genotypes; however, there were some bacteria that showed broad spectrum inhibition against all tested Bd genotypes, suggesting that these bacteria would be good candidates for probiotic therapies. We estimated Bd-associated risk for sampled amphibian communities based on the concept of herd immunity. Multiple amphibian communities, including those in the amphibian diversity hotspots, Andasibe and Ranomafana, were estimated to be below the 80% herd immunity threshold, suggesting they may be at higher risk to chytridiomycosis if a lethal Bd genotype Bletz et al. Antifungal Skin Bacteria from Madagascar Amphibians emerges in Madagascar. While this predictive approach rests on multiple assumptions, and incorporates only one component of hosts' defense against Bd, their culturable cutaneous bacterial defense, it can serve as a foundation for continued research on Bd-associated risk for the endemic frogs of Madagascar.

Mitigating amphibian chytridiomycoses in nature

Philosophical Transactions of the Royal Society B: Biological Sciences, 2016

Amphibians across the planet face the threat of population decline and extirpation caused by the ... more Amphibians across the planet face the threat of population decline and extirpation caused by the disease chytridiomycosis. Despite consensus that the fungal pathogens responsible for the disease are conservation issues, strategies to mitigate their impacts in the natural world are, at best, nascent. Reducing risk associated with the movement of amphibians, non-amphibian vectors and other sources of infection remains the first line of defence and a primary objective when mitigating the threat of disease in wildlife. Amphibian-associated chytridiomycete fungi and chytridiomycosis are already widespread, though, and we therefore focus on discussing options for mitigating the threats once disease emergence has occurred in wild amphibian populations. All strategies have shortcomings that need to be overcome before implementation, including stronger efforts towards understanding and addressing ethical and legal considerations. Even if these issues can be dealt with, all currently availabl...

Frogs of the Vredefort Dome World Heritage Site

Consistency of Published Results on the Pathogen Batrachochytrium dendrobatidis in Madagascar: Formal Comment on Kolby et al. Rapid Response to Evaluate the Presence of Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) and Ranavirus in Wild Amphibian Populations in Madagascar

PLOS ONE, 2015

Batrachochytrium dendrobatidis (Bd) and ranavirus in Madagascar, presents results for 508 amphibi... more Batrachochytrium dendrobatidis (Bd) and ranavirus in Madagascar, presents results for 508 amphibian specimens and 68 water bodies sampled during a 2-month period of the 2013-14 wet season. Kolby et al. [1] did not detect Bd in any of the samples, presenting evidence that add to our understanding of Bd dynamics in Madagascar. Earlier in 2015, we published "Widespread presence of the pathogenic fungus

Field Guide to the Frogs and Toads of the Vredefort Dome World Heritage Site

The use of diatoms in the conservation management of Hewitt’s Ghost frog

Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie, 2014

Widespread presence of the pathogenic fungus Batrachochytrium dendrobatidis in wild amphibian communities in Madagascar

Scientific reports, Jan 26, 2015

Amphibian chytridiomycosis, an emerging infectious disease caused by the fungus Batrachochytrium ... more Amphibian chytridiomycosis, an emerging infectious disease caused by the fungus Batrachochytrium dendrobatidis (Bd), has been a significant driver of amphibian declines. While globally widespread, Bd had not yet been reported from within Madagascar. We document surveys conducted across the country between 2005 and 2014, showing Bd's first record in 2010. Subsequently, Bd was detected in multiple areas, with prevalence reaching up to 100%. Detection of Bd appears to be associated with mid to high elevation sites and to have a seasonal pattern, with greater detectability during the dry season. Lineage-based PCR was performed on a subset of samples. While some did not amplify with any lineage probe, when a positive signal was observed, samples were most similar to the Global Panzootic Lineage (BdGPL). These results may suggest that Bd arrived recently, but do not exclude the existence of a previously undetected endemic Bd genotype. Representatives of all native anuran families have...

Responses To This Article

Aspects of the biology and biogeography of chelonian polystomes

Die gebruik van diatome vir die bewaringsbestuur van Hewitt se spookpadda: referaatopsomming

Kosakovsky Pond, SL, Shahar-Golan, R., Henk, DA, Fisher, MC (2011): Multiple emergences of genetically diverse amphibian-infecting chytrids include a globalized hypervirulent recombinant lineage

Prey items count data from laboratory feeding experiment

File include data on the number of prey items consumed through time in a laboratory feeding exper... more

Culex egg raft distribution in mesocosm experiment

File include data on the distribution of Culex egg rafts between treatments. The data was collect... more File include data on the distribution of Culex egg rafts between treatments. The data was collected in an oviposition habitat selection outdoor mesocosm experiment. Columns A-C describe the treatment code. Columns E-F describe the distribution of treatments among experimental tubs. Columns I-K describe the number of egg rafts deposited per day in each of the experimental tubs

Data from: Testing the link between perceived and actual risk of predation: mosquito oviposition site selection and egg predation by native and introduced fish

Origin of the Amphibian Fungus

The sudden appearance of chytridiomycosis, the cause of amphibian deaths and population declines ... more The sudden appearance of chytridiomycosis, the cause of amphibian deaths and population declines in several continents, suggests that its etiologic agent, the amphibian chytrid Batrachochythum dendrobatidis. was introduced into the affected regions. However, the origin of this virulent pathogen is unknown. A survey Vi'as conducted of 697 archived specimens of 3 species of Xenopus collected from 1879 to 1999 in southern Africa in which the histologic features of the interdigital webbing were analyzed. The earliest case of chytridiomycosis found was in a Xenopus laevis frog in 1938, and overall prevalence was 2.7%. The prevalence showed no significant differences between species, regions, season, or time period. Chytridiomycosis was a stable endemic infection in southern Africa for 23 years before any positive specimen was found outside Africa. We propose that Africa is the origin of the amphibian chytrid and that the international trade in X. laevis that began in the mid-1930s wa...

A series of terribly unfortunate events: How environment and infection synergized to cause the Kihansi spray toad extinction

Outbreaks of emerging infectious diseases are trained by local biotic and abiotic factors, with h... more Outbreaks of emerging infectious diseases are trained by local biotic and abiotic factors, with host declines occurring when conditions favour the pathogen. Extinction of the Tanzanian Kihansi spray toad (Nectophrynoides asperginis) in 2004 was contemporaneous with the construction of a dam, implicating habitat modification in the loss of this species. However, high burdens of a globally emerging infection, Batrachochytrium dendrobatidis (Bd) were synchronously observed implicating infectious disease in this toads extinction. Here, by shotgun sequencing skin DNA from archived toad mortalities and assembling chytrid mitogenomes, we prove this outbreak was caused by the BdCAPE lineage and not the panzootic lineage BdGPL that is widely associated with global amphibian extinctions. Molecular dating showed an invasion of BdCAPE across Southern Africa overlapping with the timing of the extinction event. However, post-outbreak surveillance of conspecific species inhabiting this mountainous...

A case study in canine detection of giant bullfrog scent

Journal of Vertebrate Biology, 2021

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more

Response to Comment on “Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity”

Science, 2020

Lambert et al . question our retrospective and holistic epidemiological assessment of the role of... more Lambert et al . question our retrospective and holistic epidemiological assessment of the role of chytridiomycosis in amphibian declines. Their alternative assessment is narrow and provides an incomplete evaluation of evidence. Adopting this approach limits understanding of infectious disease impacts and hampers conservation efforts. We reaffirm that our study provides unambiguous evidence that chytridiomycosis has affected at least 501 amphibian species.

Disease driven extinction in the wild of the Kihansi spray toad (Nectophrynoides asperginis)

The Kihansi spray toad, Nectophrynoides asperginis, became extinct in the wild despite population... more The Kihansi spray toad, Nectophrynoides asperginis, became extinct in the wild despite population monitoring and conservation management of its habitat in the Kihansi gorge, Tanzania. Anecdotal evidence has indicated human induced habitat modification, predators, pesticides and disease as possible causes of a rapid population decline and the species extirpation. Here, we systematically investigate the role of disease in the extinction event of the wild toad population. The amphibian chytrid fungus, Batrachochytrium dendrobatidis, was detected in spray toads that died during the extinction event and subsequently in other amphibian species in Kihansi Gorge and the adjacent Udagaji Gorge, but not in any toads collected prior to this. Following the population decline, the remnant spray toad population gradually disappeared over a nine-month period. We demonstrate how demographic and behavioral attributes predisposed the spray toads to chytridiomycosis, due to B. dendrobatidis infection,...

Development and worldwide use of non-lethal, and minimal population-level impact, protocols for the isolation of amphibian chytrid fungi

Scientific reports, Jan 17, 2018

Parasitic chytrid fungi have emerged as a significant threat to amphibian species worldwide, nece... more Parasitic chytrid fungi have emerged as a significant threat to amphibian species worldwide, necessitating the development of techniques to isolate these pathogens into culture for research purposes. However, early methods of isolating chytrids from their hosts relied on killing amphibians. We modified a pre-existing protocol for isolating chytrids from infected animals to use toe clips and biopsies from toe webbing rather than euthanizing hosts, and distributed the protocol to researchers as part of the BiodivERsA project RACE; here called the RML protocol. In tandem, we developed a lethal procedure for isolating chytrids from tadpole mouthparts. Reviewing a database of use a decade after their inception, we find that these methods have been applied across 5 continents, 23 countries and in 62 amphibian species. Isolation of chytrids by the non-lethal RML protocol occured in 18% of attempts with 207 fungal isolates and three species of chytrid being recovered. Isolation of chytrids ...

Estimating Herd Immunity to Amphibian Chytridiomycosis in Madagascar Based on the Defensive Function of Amphibian Skin Bacteria

Frontiers in Microbiology, 2017

For decades, Amphibians have been globally threatened by the still expanding infectious disease, ... more For decades, Amphibians have been globally threatened by the still expanding infectious disease, chytridiomycosis. Madagascar is an amphibian biodiversity hotspot where Batrachochytrium dendrobatidis (Bd) has only recently been detected. While no Bd-associated population declines have been reported, the risk of declines is high when invasive virulent lineages become involved. Cutaneous bacteria contribute to host innate immunity by providing defense against pathogens for numerous animals, including amphibians. Little is known, however, about the cutaneous bacterial residents of Malagasy amphibians and the functional capacity they have against Bd. We cultured 3179 skin bacterial isolates from over 90 frog species across Madagascar, identified them via Sanger sequencing of approximately 700 bp of the 16S rRNA gene, and characterized their functional capacity against Bd. A subset of isolates was also tested against multiple Bd genotypes. In addition, we applied the concept of herd immunity to estimate Bd-associated risk for amphibian communities across Madagascar based on bacterial antifungal activity. We found that multiple bacterial isolates (39% of all isolates) cultured from the skin of Malagasy frogs were able to inhibit Bd. Mean inhibition was weakly correlated with bacterial phylogeny, and certain taxonomic groups appear to have a high proportion of inhibitory isolates, such as the Enterobacteriaceae, Pseudomonadaceae, and Xanthamonadaceae (84, 80, and 75% respectively). Functional capacity of bacteria against Bd varied among Bd genotypes; however, there were some bacteria that showed broad spectrum inhibition against all tested Bd genotypes, suggesting that these bacteria would be good candidates for probiotic therapies. We estimated Bd-associated risk for sampled amphibian communities based on the concept of herd immunity. Multiple amphibian communities, including those in the amphibian diversity hotspots, Andasibe and Ranomafana, were estimated to be below the 80% herd immunity threshold, suggesting they may be at higher risk to chytridiomycosis if a lethal Bd genotype Bletz et al. Antifungal Skin Bacteria from Madagascar Amphibians emerges in Madagascar. While this predictive approach rests on multiple assumptions, and incorporates only one component of hosts' defense against Bd, their culturable cutaneous bacterial defense, it can serve as a foundation for continued research on Bd-associated risk for the endemic frogs of Madagascar.

Mitigating amphibian chytridiomycoses in nature

Philosophical Transactions of the Royal Society B: Biological Sciences, 2016

Amphibians across the planet face the threat of population decline and extirpation caused by the ... more Amphibians across the planet face the threat of population decline and extirpation caused by the disease chytridiomycosis. Despite consensus that the fungal pathogens responsible for the disease are conservation issues, strategies to mitigate their impacts in the natural world are, at best, nascent. Reducing risk associated with the movement of amphibians, non-amphibian vectors and other sources of infection remains the first line of defence and a primary objective when mitigating the threat of disease in wildlife. Amphibian-associated chytridiomycete fungi and chytridiomycosis are already widespread, though, and we therefore focus on discussing options for mitigating the threats once disease emergence has occurred in wild amphibian populations. All strategies have shortcomings that need to be overcome before implementation, including stronger efforts towards understanding and addressing ethical and legal considerations. Even if these issues can be dealt with, all currently availabl...

Frogs of the Vredefort Dome World Heritage Site

Consistency of Published Results on the Pathogen Batrachochytrium dendrobatidis in Madagascar: Formal Comment on Kolby et al. Rapid Response to Evaluate the Presence of Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) and Ranavirus in Wild Amphibian Populations in Madagascar

PLOS ONE, 2015

Batrachochytrium dendrobatidis (Bd) and ranavirus in Madagascar, presents results for 508 amphibi... more Batrachochytrium dendrobatidis (Bd) and ranavirus in Madagascar, presents results for 508 amphibian specimens and 68 water bodies sampled during a 2-month period of the 2013-14 wet season. Kolby et al. [1] did not detect Bd in any of the samples, presenting evidence that add to our understanding of Bd dynamics in Madagascar. Earlier in 2015, we published "Widespread presence of the pathogenic fungus

Field Guide to the Frogs and Toads of the Vredefort Dome World Heritage Site

The use of diatoms in the conservation management of Hewitt’s Ghost frog

Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie, 2014

Widespread presence of the pathogenic fungus Batrachochytrium dendrobatidis in wild amphibian communities in Madagascar

Scientific reports, Jan 26, 2015

Amphibian chytridiomycosis, an emerging infectious disease caused by the fungus Batrachochytrium ... more Amphibian chytridiomycosis, an emerging infectious disease caused by the fungus Batrachochytrium dendrobatidis (Bd), has been a significant driver of amphibian declines. While globally widespread, Bd had not yet been reported from within Madagascar. We document surveys conducted across the country between 2005 and 2014, showing Bd's first record in 2010. Subsequently, Bd was detected in multiple areas, with prevalence reaching up to 100%. Detection of Bd appears to be associated with mid to high elevation sites and to have a seasonal pattern, with greater detectability during the dry season. Lineage-based PCR was performed on a subset of samples. While some did not amplify with any lineage probe, when a positive signal was observed, samples were most similar to the Global Panzootic Lineage (BdGPL). These results may suggest that Bd arrived recently, but do not exclude the existence of a previously undetected endemic Bd genotype. Representatives of all native anuran families have...

Responses To This Article

Aspects of the biology and biogeography of chelonian polystomes

Die gebruik van diatome vir die bewaringsbestuur van Hewitt se spookpadda: referaatopsomming

Kosakovsky Pond, SL, Shahar-Golan, R., Henk, DA, Fisher, MC (2011): Multiple emergences of genetically diverse amphibian-infecting chytrids include a globalized hypervirulent recombinant lineage