Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
PLoS One. 2011 May 11;6(5):e19688. doi: 10.1371/journal.pone.0019688.
Most of the species of fungi that cause disease in mammals, including Cryptococcus neoformans var. grubii (serotype A), are exogenous and non-contagious. Cryptococcus neoformans var. grubii is associated worldwide with avian and arboreal habitats. This airborne, opportunistic pathogen is profoundly neurotropic and the leading cause of fungal meningitis. Patients with HIV/AIDS have been ravaged by cryptococcosis--an estimated one million new cases occur each year, and mortality approaches 50%. Using phylogenetic and population genetic analyses, we present evidence that C. neoformans var. grubii may have evolved from a diverse population in southern Africa. Our ecological studies support the hypothesis that a few of these strains acquired a new environmental reservoir, the excreta of feral pigeons (Columba livia), and were globally dispersed by the migration of birds and humans. This investigation also discovered a novel arboreal reservoir for highly diverse strains of C. neoformans var. grubii that are restricted to southern Africa, the mopane tree (Colophospermum mopane). This finding may have significant public health implications because these primal strains have optimal potential for evolution and because mopane trees contribute to the local economy as a source of timber, folkloric remedies and the edible mopane worm.
引起哺乳动物疾病的大多数真菌物种，包括新型隐球菌变种（血清型 A），都是外生的且不具传染性的。新型隐球菌变种与鸟类和树木栖息地在世界范围内相关。这种空气传播的、机会性的病原体对神经具有很强的亲嗜性，是真菌性脑膜炎的主要病因。艾滋病病毒/艾滋病患者深受隐球菌病的困扰——估计每年新发病例约有 100 万例，死亡率接近 50%。通过系统发育和种群遗传学分析，我们提供的证据表明，新型隐球菌变种可能是从南部非洲的一个多样化种群中进化而来的。我们的生态研究支持了这样一种假说，即其中一些菌株获得了一个新的环境储库，即野鸽（Columba livia）的排泄物，并通过鸟类和人类的迁徙在全球范围内传播。这项调查还发现了一个新型的树木储库，用于储存高度多样化的新型隐球菌变种，这些变种仅限于南部非洲，即马蓬树（Colophospermum mopane）。这一发现可能具有重要的公共卫生意义，因为这些原始菌株具有最佳的进化潜力，而且马蓬树作为木材、民间疗法和可食用的马蓬虫的来源，对当地经济有贡献。
