School of Zoology, University of Tasmania, Private Bag 5, Hobart, Tasmania 7001, Australia.
Conserv Biol. 2012 Feb;26(1):124-34. doi: 10.1111/j.1523-1739.2011.01747.x. Epub 2011 Oct 6.
Pathogen-driven declines in animal populations are increasingly regarded as a major conservation issue. The Tasmanian devil (Sarcophilus harrisii) is threatened with extinction by devil facial tumor disease, a unique transmissible cancer. The disease is transmitted through direct transfer of tumor cells, which is possible because the genetic diversity of Tasmanian devils is low, particularly in the major histocompatibility complex genes of the immune system. The far northwest of Tasmania now holds the last remaining disease-free wild devil populations. The recent discovery of unique major histocompatibility complex genotypes in the northwestern region of Tasmania has raised the possibility that some animals may be resilient to the disease. We examined the differences in the epidemiology and population effects of devil facial tumor disease at 3 well-studied affected sites in eastern Tasmania and 1 in western Tasmania (West Pencil Pine). In contrast to the 3 eastern sites, there has been no rapid increase in disease prevalence or evidence of population decline at West Pencil Pine. Moreover, this is the only onsite at which the population age structure has remained unaltered 4 years after the first detection of disease. The most plausible explanations for the substantial differences in population effects and epidemiology of the disease between eastern and western sites are geographic differences in genotypes or phenotypes of devils and functional differences between tumor strains in the 2 regions. We suggest that conservation efforts focus on identifying whether either or both these explanations are correct and then, if resistance alleles exist, to attempt to spread the resistant alleles into affected populations. Such assisted selection has rarely been attempted for the management of wildlife diseases, but it may be widely applicable.
病原体导致的动物种群数量下降正日益被视为一个主要的保护问题。塔斯马尼亚恶魔（Sarcophilus harrisii）正受到恶魔面部肿瘤病的威胁，这是一种独特的传染性癌症。这种疾病是通过肿瘤细胞的直接转移传播的，这是可能的，因为塔斯马尼亚恶魔的遗传多样性很低，特别是在免疫系统的主要组织相容性复合体基因中。塔斯马尼亚州的最西北现在拥有最后剩余的无疾病野生恶魔种群。最近在塔斯马尼亚州西北部发现了独特的主要组织相容性复合体基因型，这增加了一些动物可能对这种疾病具有抵抗力的可能性。我们在塔斯马尼亚州东部的 3 个研究充分的受影响地点和 1 个在塔斯马尼亚州西部（西铅笔松）的地点，研究了恶魔面部肿瘤病的流行病学和种群效应差异。与 3 个东部地点相比，在西部铅笔松没有疾病流行率的快速增加或种群减少的证据。此外，这是唯一在疾病首次发现后 4 年内种群年龄结构保持不变的现场。造成疾病在东部和西部种群效应和流行病学方面存在显著差异的最合理解释是，恶魔的基因型或表型以及 2 个地区肿瘤株之间的功能差异在地理上存在差异。我们建议，保护工作的重点是确定这两种解释是否正确，如果存在抗性等位基因，则尝试将抗性等位基因传播到受影响的种群中。这种辅助选择很少用于野生动物疾病的管理，但它可能具有广泛的适用性。
