Morbidity and mortality of the Critically Endangered Lake Oku clawed frog Xenopus longipes

Abstract

Between 2006 and 2010, recurring morbidity and mortality of the endemic Lake Oku clawed frog Xenopus longipes was observed at its only known locality, Lake Oku, Cameroon. During repeated visits in 2006, 2008, 2009 and 2010, we found large numbers of dead frogs around the lake shore, as well as a higher than expected prevalence of diseased frogs. No significant relationships between disease occurrence and environmental parameters were found, with the exception of a significant but unexplained association between phosphate concentration and disease incidence. Tissue samples from X. longipes collected during 3 field seasons were negative for the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) using a Bd-specific real-time PCR test, although other species of sympatric amphibians were positive for this pathogen. Only 1 of 48 tissue samples from diseased frogs was positive for ranavirus infection using a ranavirus-specific PCR, suggesting that this pathogen is not necessarily the cause of this disease. No evidence of pathogens was found in tissues examined histologically from 10 X. longipes which had been collected and fixed when freshly dead. The cause(s) of the morbidities and mortalities remain(s) unknown, as does their consequence to the population of this Critically Endangered species. Identifying the causative factor(s) of the X. longipes mortality and its impact on the population is crucial for planning conservation actions.

Distribution and Host Range of Ranaviruses

“…that were present in the pond did not die or appear moribund, but ranavirus was documented in the livers of the fi sh (Une et al 2009b ), suggesting interclass transmission. The single case of ranavirus infection in Africa reported by Docherty-Bone et al ( 2013 ) is also likely to be an FV3-like virus. The primers used were those developed for the major capsid protein of FV3, but the PCR products were of poor quality and could not be sequenced (Docherty-Bone et al 2013 ).…”

“…The single case of ranavirus infection in Africa reported by Docherty-Bone et al ( 2013 ) is also likely to be an FV3-like virus. The primers used were those developed for the major capsid protein of FV3, but the PCR products were of poor quality and could not be sequenced (Docherty-Bone et al 2013 ). In general, surveillance data for ranaviruses in Asia and Africa have been slower to accumulate than for North America or Europe, which are essential to understanding the distribution, host range, and threat of ranaviruses.…”

The Amphibians of Mount Oku, Cameroon: an updated species inventory and conservation review

“…The Puddle Frog, Phrynobatrachus njiomock was recently formally described (Zimkus and Gvoždík 2013) but was previously known as Phrynobatrachus sp. 11 (sensu Amiet 1978) – this frog has also been referred to as Phrynobatrachus cf. steindachneri (Doherty-Bone et al 2008, 2013b) and resembles Phrynobatrachus steindachneri and Phrynobatrachus jimzimkusi which also occur on Mt Oku. This species is mostly restricted to the forest adjacent to Lake Oku, with some individuals found towards the summit.…”

“…An enigmatic disease has been observed in the Lake Oku Clawed Frog ( Xenopus longipes ) since 2006, where many frogs have been found with lesions and necrotic limbs, but with the agent still unidentified (Blackburn et al 2010a; Doherty-Bone et al 2013b). Ranavirus has been found in one of these clinical specimens, but its presence needs to be verified and impacts on Cameroonian amphibians assessed.…”

Imunobiológicos para o diagnóstico laboratorial de ranavirose: clonagem e expressão do gene MCP de isolado brasileiro de >i<Ranavirus>/i< e produção de anticorpos policlonais anti-proteína MCP recombinante

“…Em anfíbios, diversas infecções por ranaviroses já foram identificadas em animais selvagens e cultivados na Ásia, Américas, Oceania, África e Europa, sendo um dos responsáveis principais pelo declínio mundial dos anuros na natureza (ALENCAR, 2016;CULLEN;OWENS, 2002;CUNNINGHAM et al, 1996;DOCHERTY-BONE et al, 2013;DUFFUS et al, 2017;FOX et al, 2006;GALLI et al, 2006;MAZZONI et al, 2009;OLIVEIRA, 2020;WOLF et al, 1968;ZHANG et al, 2001;ZUPANOVIC et al, 1998). Em salamandras, ocorrências foram registadas na América do Norte e Ásia (BOLLINGER et al, 1999;DOCHERTY et al, 2003;ZHOU et al 2013); e em répteis na Europa, América do Norte, Ásia e Austrália (CHEN;ZHENG;JIANG, 1999;DE VOE et al, 2004;HYATT et al, 2002, HUANG et al, 2009MARSCHANG et al, 1999;WINZELER et al, 2015).…”