Examinando por Autor "Azat, Claudio"
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Ítem Accounting for bias in prevalence estimation: The case of a globally emerging pathogen(John Wiley and Sons Inc, 2023-09) Sentenac, Hugo; Valenzuela-Sánchez, Andrés; Haddow-Brown, Natashja; Delgado, Soledad; Azat, Claudio; Cunningham, Andrew A.Accurate quantification of infection parameters is necessary to ensure effective surveillance, investigation and mitigation of infectious diseases. However, hosts and pathogens are often imperfectly observed and key epidemiological parameters, such as infection prevalence, can be biased if this observational uncertainty is not properly accounted for. Here, we evaluated the combined effects of imperfect pathogen detection and host pseudoreplication on the estimation of infection prevalence of the pathogen Batrachochytrium dendrobatidis (Bd) in the southern Darwin's frog (Rhinoderma darwinii). This pathogen causes amphibian chytridiomycosis, a panzootic disease responsible for the greatest documented loss of biodiversity due to an infectious disease. From November 2018 to March 2019, we made 1085 captures of 641 R. darwinii individuals in two areas of Southern Chile. Captured frogs were individually identified to eliminate host pseudoreplication, skin-swabbed twice in sequence, and each swab was analysed in duplicate using a real-time polymerase chain reaction (qPCR) assay to detect Bd. To provide a robust estimate of period prevalence, we used a Bayesian multiscale occupancy model that considers pathogen imperfect detection arising from both sampling and diagnostic testing processes. Finally, using a deterministic matrix population model, we illustrated how the method chosen to estimate prevalence influenced our conclusions regarding the impact of Bd infection on host population trajectories. Our results showed that Bd prevalence could be underestimated by 55% if false negatives and host pseudoreplication were not accounted for. Host pseudoreplication had a greater impact on prevalence underestimation than pathogen imperfect detection in our study. This underestimation in prevalence changed our interpretation of the impacts of Bd infections on our model species, from a nearly stable population using the naïve period prevalence to a declining one using our robust estimate. Synthesis and applications. These results highlight the importance of using robust inferences to inform disease risk assessments and to efficiently allocate limited resources during mitigation strategies of infectious diseases. The methods used here can be applied to a wide range of host–pathogen systems, and will be of interest to both researchers and practitioners aiming to investigate and mitigate the impacts of infectious diseases on free-ranging populations. © 2023 The Authors. Journal of Applied Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.Ítem First case of male alloparental care in amphibians: tadpole stealing in Darwin’s frogs(Inter-Research, 2021) Cabeza-Alfaro, Osvaldo; Valenzuela-Sánchez, Andrés; Alvarado-Rybak, Mario; Serrano, José M.; Azat, ClaudioAll oparental care, i.e. care directed at non-descendant offspring, has rarely been described in amphibians. Rhinoderma darwinii is an Endangered and endemic frog of the tem - perate forests of Chile and Argentina. This species has evolved a unique reproductive strategy whereby males brood their tadpoles within their vocal sacs (known as neomelia). Since 2009, the National Zoo of Chile has developed an ex situ conservation programme for R. darwinii, in which during reproduction, adults are kept in terraria in groups of 2 females with 2 males. In September 2018, one pair engaged in amplexus, with one of the males fertilizing the eggs. Twenty days later, the second male (the alloparent) ingested all of the 8 viable, recently hatched tadpoles, releasing 2 froglets 9 wk later. This unusual behaviour observed in captivity is complemented by observations in the field of male R. darwinii brooding tadpoles of markedly different sizes, possibly reflecting the brooding of tadpoles from different ovipositions. To our knowledge, this is the first documented case of male alloparental care in amphibians and an example of captive breeding programmes contributing important knowledge about the natural history of threatened species. © The authors 2021. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are un - restricted. Authors and original publication must be credited.Ítem Is xenopus laevis introduction linked with Ranavirus incursion, persistence and spread in Chile?(PeerJ Inc., 2023-02) Peñafiel-Ricaurte, Alexandra; Price, Stephen J.; Leung, William T.M.; Alvarado-Rybak, Mario; Espinoza-Zambrano, Andrés; Valdivia, Catalina; Cunningham, Andrew A.; Azat, ClaudioRanaviruses have been associated with amphibian, fish and reptile mortality events worldwide and with amphibian population declines in parts of Europe. Xenopus laevis is a widespread invasive amphibian species in Chile. Recently, Frog virus 3 (FV3), the type species of the Ranavirus genus, was detected in two wild populations of this frog near Santiago in Chile, however, the extent of ranavirus infection in this country remains unknown. To obtain more information about the origin of ranavirus in Chile, its distribution, species affected, and the role of invasive amphibians and freshwater fish in the epidemiology of ranavirus, a surveillance study comprising wild and farmed amphibians and wild fish over a large latitudinal gradient (2,500 km) was carried out in 2015–2017. In total, 1,752 amphibians and 496 fish were tested using a ranavirus-specific qPCR assay, and positive samples were analyzed for virus characterization through whole genome sequencing of viral DNA obtained from infected tissue. Ranavirus was detected at low viral loads in nine of 1,011 X. laevis from four populations in central Chile. No other amphibian or fish species tested were positive for ranavirus, suggesting ranavirus is not threatening native Chilean species yet. Phylogenetic analysis of partial ranavirus sequences showed 100% similarity with FV3. Our results show a restricted range of ranavirus infection in central Chile, coinciding with X. laevis presence, and suggest that FV3 may have entered the country through infected X. laevis, which appears to act as a competent reservoir host, and may contribute to the spread the virus locally as it invades new areas, and globally through the pet trade.Ítem Is Xenopus laevis introduction linked with Ranavirus incursion, persistence and spread in Chile?(2023-02) Peñafiel-Ricaurte, Alexandra; J. Price, Stephen; T.M. Leung, William; Alvarado-Rybak, Mario; Espinoza-Zambrano, Andrés; Valdivia, Catalina; Cunningham, Andrew A.; Azat, ClaudioRanaviruses have been associated with amphibian, fish and reptile mortality events worldwide and with amphibian population declines in parts of Europe. Xenopus laevis is a widespread invasive amphibian species in Chile. Recently, Frog virus 3 (FV3), the type species of the Ranavirus genus, was detected in two wild populations of this frog near Santiago in Chile, however, the extent of ranavirus infection in this country remains unknown. To obtain more information about the origin of ranavirus in Chile, its distribution, species affected, and the role of invasive amphibians and freshwater fish in the epidemiology of ranavirus, a surveillance study comprising wild and farmed amphibians and wild fish over a large latitudinal gradient (2,500 km) was carried out in 2015–2017. In total, 1,752 amphibians and 496 fish were tested using a ranavirus-specific qPCR assay, and positive samples were analyzed for virus characterization through whole genome sequencing of viral DNA obtained from infected tissue. Ranavirus was detected at low viral loads in nine of 1,011 X. laevis from four populations in central Chile. No other amphibian or fish species tested were positive for ranavirus, suggesting ranavirus is not threatening native Chilean species yet. Phylogenetic analysis of partial ranavirus sequences showed 100% similarity with FV3. Our results show a restricted range of ranavirus infection in central Chile, coinciding with X. laevis presence, and suggest that FV3 may have entered the country through infected X. laevis, which appears to act as a competent reservoir host, and may contribute to the spread the virus locally as it invades new areas, and globally through the pet trade. Copyright 2023 Peñafiel-Ricaurte et al.Ítem Ongoing declines for the world’s amphibians in the face of emerging threats(Nature Research, 2023-10) Luedtke, Jennifer A.; Chanson, Janice; Neam, Kelsey; Hobin, Louise; Maciel, Adriano O.; Catenazzi, Alessandro; Borzée, Amaël; Hamidy, Amir; Aowphol, Anchalee; Jean, Anderson; Sosa-Bartuano, Ángel; Fong G, Ansel; de Silva, Anslem; Fouquet, Antoine; Angulo, Ariadne; Kidov, Artem A.; Muñoz Saravia, Arturo; Diesmos, Arvin C.; Tominaga, Atsushi; Shrestha, Biraj; Gratwicke, Brian; Tjaturadi, Burhan; Martínez Rivera, Carlos C.; Vásquez Almazán, Carlos R.; Señaris, Celsa; Chandramouli S.R.; Strüssmann, Christine; Cortez Fernández, Claudia Fabiola; Azat, Claudio; Hoskin, Conrad J.; Hilton-Taylor, Craig; Whyte, Damion L.; Gower, David J.; Olson, Deanna H.; Cisneros-Heredia, Diego F.; Santana, Diego José; Nagombi, Elizah; Najafi-Majd, Elnaz; Quah, Evan S. H.; Bolaños, Federico; Xie, Feng; Brusquetti, Francisco; Álvarez, Francisco S.; Andreone, Franco; Glaw, Frank; Castañeda, Franklin Enrique; Kraus, Fred; Parra-Olea, Gabriela; Chaves, Gerardo; Medina-Rangel, Guido F.; González-Durán, Gustavo; Ortega-Andrade, H. Mauricio; Machado, Iberê F.; Das, Indraneil; Dias, Iuri Ribeiro; Urbina-Cardona, J. Nicolas; Crnobrnja-Isailović, Jelka; Yang, Jian-Huan; Jianping, Jiang; Wangyal, Jigme Tshelthrim; Rowley, Jodi J. L.; Measey, John; Vasudevan, Karthikeyan; Chan, Kin Onn; Gururaja, Kotambylu Vasudeva; Ovaska, Kristiina; Warr, Lauren C.; Canseco-Márquez, Luis; Toledo, Luís Felipe; Díaz, Luis M.; Khan, M. Monirul H.; Meegaskumbura, Madhava; Acevedo, Manuel E.; Napoli, Marcelo Felgueiras; Ponce, Marcos A.; Vaira, Marcos; Lampo, Margarita; Yánez-Muñoz, Mario H.; Scherz, Mark D.; Rödel, Mark-Oliver; Matsui, Masafumi; Fildor, Maxon; Kusrini, Mirza D.; Ahmed, Mohammad Firoz; Rais, Muhammad; Kouamé, N’Goran G.; García, Nieves; Gonwouo, Nono Legrand; Burrowes, Patricia A.; Imbun, Paul Y.; Wagner, Philipp; Kok, Philippe J. R.; Joglar, Rafael L.; Auguste, Renoir J.; Brandão, Reuber Albuquerque; Ibáñez, Roberto; von May, Rudolf; Hedges, S. Blair; Biju S.D.; Ganesh S.R.; Wren, Sally; Das, Sandeep; Flechas, Sandra V.; Ashpole, Sara L.; Robleto-Hernández, Silvia J.; Loader, Simon P.; Incháustegui, Sixto J.; Garg, Sonali; Phimmachak, Soumphthone; Richards, Stephen J.; Slimani, Tahar; Osborne-Naikatini, Tamara; Abreu-Jardim, Tatianne P. F.; Condez, Thais H.; De Carvalho, Thiago R.; Cutajar, Timothy P.; Pierson, Todd W.; Nguyen, Truong Q.; Kaya, Uğur; Yuan, Zhiyong; Long, Barney; Langhammer, Penny; Stuart, Simon N.Systematic assessments of species extinction risk at regular intervals are necessary for informing conservation action1,2. Ongoing developments in taxonomy, threatening processes and research further underscore the need for reassessment3,4. Here we report the findings of the second Global Amphibian Assessment, evaluating 8,011 species for the International Union for Conservation of Nature Red List of Threatened Species. We find that amphibians are the most threatened vertebrate class (40.7% of species are globally threatened). The updated Red List Index shows that the status of amphibians is deteriorating globally, particularly for salamanders and in the Neotropics. Disease and habitat loss drove 91% of status deteriorations between 1980 and 2004. Ongoing and projected climate change effects are now of increasing concern, driving 39% of status deteriorations since 2004, followed by habitat loss (37%). Although signs of species recoveries incentivize immediate conservation action, scaled-up investment is urgently needed to reverse the current trends. © 2023, The Author(s).Ítem Synthesis of Batrachochytrium dendrobatidis infection in South America: amphibian species under risk and areas to focus research and disease mitigation(John Wiley and Sons Inc, 2022-07) Azat, Claudio; Alvarado-Rybak, Mario; Solano-Iguaran, Jaiber J.; Velasco, Aníbal; Valenzuela-Sánchez, Andrés; Flechas, Sandra V.; Peñafiel-Ricaurte, Alexandra; Cunningham, Andrew A.; Bacigalupe, Leonardo D.Amphibian chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), has been recognized as the infectious disease causing the most catastrophic loss of biodiversity known to science, with South America being the most impacted region. We tested whether Bd prevalence is distributed among host taxonomy, ecoregion, conservation status and habitat preference in South America. Here we provide a synthesis on the extent of Bd infection across South America based on 21 648 molecular diagnostic assays, roles of certain species in the epidemiology of Bd and explore its association with the reported amphibian catastrophic declines in the region. We show that Bd is widespread, with a continental prevalence of 23.2%. Its occurrence in the region shows a phylogenetic signal and the probability of infection is determined by ecoregion, preferred habitat and extinction risk hosts' traits. The taxa exhibiting highest Bd occurrence were mostly aquatic amphibians, including Ranidae, Telmatobiidae, Hylodidae, Calyptocephalellidae and Pipidae. Surprisingly, families exhibiting unusually low Bd prevalence included species in which lethal chytridiomycosis and population declines have been described (genera Atelopus, Rhinoderma and Eleutherodactylus). Higher than expected prevalence of Bd occurred mainly in amphibians living in association with mountain environments in the Andes and Atlantic forests, reflecting highly favourable Bd habitats in these areas. Invasive amphibian species (e.g. Lithobates catesbeianus and Xenopus laevis) exhibited high Bd prevalence; thus we suggest using these as sentinels to understand their potential role as reservoirs, vectors or spreaders of Bd that can be subjected to management. Our results guide on the prioritization of conservation actions to prevent further biodiversity loss due to chytridiomycosis in the world's most amphibian diverse region. © 2022 The Authors. Ecography published by John Wiley & Sons Ltd on behalf of Nordic Society Oikos.