Emergence of amphibian chytridiomycosis in Britain
Emergence of amphibian chytridiomycosis in Britain
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DOI：
10.1136/vr.157.13.386
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发表时间：
2005-09-24
影响因子：
2.2
通讯作者：
Fisher, MC
中科院分区：
文献类型：
--
作者：
Cunningham, AA;Garner, TWJ;Fisher, MC
皮肤壶菌病是两栖动物的一种真菌病，被认为是当代两栖动物种群数量下降的主要原因之一（Daszak等人2003年，Stuart等人2004年）。病原体水蛭壶菌（Batrachochytrium dendroatidis）可能具有高度致病性，在一些两栖动物物种的蜕变后生命阶段造成高达90%至100%的死亡率（Scott 1993年，Daszak等人1999年），而其他两栖动物物种在感染这种真菌后似乎对疾病具有抵抗力（Daszak等人2004年，Weldon等人2004年）。树线虫B具有低宿主特异性，在五大洲感染至少14科和100多种两栖动物。壶菌病的爆发导致了许多这些物种的种群数量严重下降和局部灭绝，并且有人假设该疾病导致了一些物种的完全灭绝（Daszak等人，2003年）。该病的临床症状包括嗜睡、翻正反射丧失和姿势异常。肉眼病变通常不明显，但有报道称手指和腹侧皮肤表皮脱落、表皮溃疡和发红（充血）增加（Daszak等人1999年，Berger等人2000年）。由壶菌引起的两栖动物种群数量下降的主要假设是原始宿主种群暴露于新引入的病原体，尽管其他假设，如先前存在的宿主-病原体关系的变化，尚未被排除（Cunningham等人2003年，Weldon等人2004年）。北美牛蛙（Rana catesbeiana）通常不受树线虫B感染的影响（Daszak等人2004年），有人推测该物种可能作为运输宿主，将感染引入新的地区和新的宿主物种和种群（Mazzoni等人2003年）。类似的情况可能发生在非洲爪蛙（Xenopus种）（Weldon等人2004年）和甘蔗蟾蜍（Bufo marinus）（Daszak等人1999年）身上。两栖动物壶菌病与相关的死亡率和种群数量下降有关，最早是在中美洲和澳大利亚同时发现的（Berger等，1998年）。回顾性病理分析表明，至少有一些发生在20世纪70年代和80年代的两栖动物种群数量下降，以前被归因于其他原因，更有可能是由壶菌病引起的（Berger等人1998年，Green和Kagarise-Sherman 2001年）。最近，壶菌病在欧洲大陆出现；自1997年以来，由于树突B感染，西班牙中部每年都会发生大规模死亡事件和助产士蟾蜍（Alytes产科）的灭绝（J. Bosch， M. Fisher, SF Walker，未发表的观察结果）。最近，在西班牙其他地区和其他物种中发现了这种疾病，包括火蜥蜴（Salamandra Salamandra），由于壶菌病，最近在西班牙中部发生了大规模死亡和种群减少（J. Bosch, SF Walker, MC Fisher，未发表的观察结果）。此外，在野生两栖动物中也检测到树突B
CUTANEOUS chytridiomycosis is a fungal disease of amphibians that is considered to be one of the main causes of contemporary amphibian population declines (Daszak and others 2003, Stuart and others 2004). The causative agent, Batrachochytrium dendrobatidis, can be highly pathogenic, causing up to 90 to 100 per cent mortality in the postmetamorphic life stages of some amphibian species (Scott 1993, Daszak and others 1999), while other amphibian species appear to be resistant to disease when infected with this fungus (Daszak and others 2004, Weldon and others 2004). B dendrobatidis has low host specificity, infecting at least 14 families and over 100 species of amphibian on five continents. Outbreaks of chytridiomycosis have caused severe population declines and local extinctions in many of these species, and it has been hypothesised that the disease has caused the total extinction of some species (Daszak and others 2003). Clinical signs of the disease include lethargy, loss of the righting reflex and abnormal posture. Gross lesions are usually not apparent, but increased epidermal sloughing, epidermal ulceration and reddening (hyperaemia) of the digital and ventral skin have been reported (Daszak and others 1999, Berger and others 2000).The primary hypothesis for the emergence of amphibian population declines caused by chytrid fungus is the exposure of naive host populations to a newly introduced pathogen, although other hypotheses, such as a change in a pre-existing host-pathogen relationship, have not yet been discounted (Cunningham and others 2003, Weldon and others 2004). The North American bullfrog (Rana catesbeiana) is generally unaffected by B dendrobatidis infection (Daszak and others 2004) and there has been speculation that this species might act as a transport host, introducing the infection to new areas and to new host species and populations (Mazzoni and others 2003). A similar situation might occur with African clawed frogs (Xenopus species)(Weldon and others 2004) and cane toads (Bufo marinus)(Daszak and others 1999). Amphibian chytridiomycosis, with associated mortalities and population declines, was first described contemporaneously from Central America and Australia (Berger and others 1998). Retrospective pathological analyses have shown that at least some of the amphibian population declines that occurred in the 1970s and 1980s, and which were previously ascribed to other causes, were more likely to have been caused by chytridiomycosis (Berger and others 1998, Green and Kagarise-Sherman 2001). Recently, chytridiomycosis has emerged in continental Europe; since 1997, annual mass mortality incidents and extirpations of midwife toads (Alytes obstetricans) have occurred in central Spain due to B dendrobatidis infection (J. Bosch, M. Fisher, SF Walker, unpublished observations). More recently, the disease has been found in other areas of Spain and in other species, including salamanders (Salamandra salamandra), which have recently been undergoing mass mortalities and population declines in central Spain due to chytridiomycosis (J. Bosch, SF Walker, MC Fisher, unpublished observations). Furthermore, B dendrobatidis has been detected in wild amphibians