Bagagli Eduardo, Bosco Sandra M G, Theodoro Raquel Cordeiro, Franco Marcello
Departmento de Microbiologia e Imunologia, Instituto de Biociências, UNESP, Botucatu 18618-000, São Paulo, Brazil.
Infect Genet Evol. 2006 Sep;6(5):344-51. doi: 10.1016/j.meegid.2005.12.002. Epub 2006 Feb 10.
The habitat of the mycelial saprobic form of Paracoccidioides brasiliensis, which produces the infectious propagula, has not been determined and has proven difficult for mycologists to describe. The fungus has been rarely isolated from the environment, the disease has a prolonged latency period and no outbreaks have been reported. These facts have precluded the adoption of preventive measures to avoid infection. The confirmation of natural infections in nine-banded armadillos (Dasypus novemcinctus) with P. brasiliensis, in high frequency and wide geographic distribution, has opened new avenues for the study and understanding of its ecology. Armadillos belong to the order Xenarthra, which has existed in South America ever since the Paleocene Era (65 million years ago), when the South American subcontinent was still a detached land, before the consolidation of what is now known as the American continent. On the other hand, strong molecular evidence suggests that P. brasiliensis and other dimorphic pathogenic fungi--such as Blastomyces dermatitidis, Coccidioides immitis and Histoplasma capsulatum--belong to the family Onygenaceae sensu lato (order Onygenales, Ascomycota), which appeared around 150 million years ago. P. brasiliensis ecology and relation to its human host are probably linked to the fungal evolutionary past, especially its long coexistence with and adaptation to animal hosts other than Homo sapiens, of earlier origin. Instead of being a blind alley, the meaning of parasitism for dimorphic pathogenic fungi should be considered as an open two-way avenue, in which the fungus may return to the environment, therefore contributing to preserve its teleomorphic (sexual) and anamorphic (asexual) forms in a defined and protected natural habitat.
巴西副球孢子菌产生感染性繁殖体的菌丝腐生型的栖息地尚未确定，并且真菌学家已证实很难对其进行描述。该真菌很少从环境中分离得到，这种疾病的潜伏期较长，也没有爆发的报道。这些事实使得无法采取预防措施来避免感染。在九带犰狳（Dasypus novemcinctus）中高频且广泛地确认了巴西副球孢子菌的自然感染，为研究和理解其生态学开辟了新途径。犰狳属于异关节目，自古新世时期（6500万年前）以来就存在于南美洲，当时南美次大陆仍是一块孤立的陆地，在现在所知的美洲大陆合并之前。另一方面，有力的分子证据表明，巴西副球孢子菌和其他双相致病性真菌——如皮炎芽生菌、粗球孢子菌和荚膜组织胞浆菌——属于广义的奥尼翁科（奥尼翁目，子囊菌门），该科大约在1.5亿年前出现。巴西副球孢子菌的生态学及其与人类宿主的关系可能与其真菌进化史有关，特别是它与比智人起源更早的其他动物宿主长期共存并适应的过程。双相致病性真菌的寄生意义不应被视为一条死胡同，而应被视为一条开放的双向通道，在这条通道中，真菌可能回归环境，从而有助于在一个明确且受保护的自然栖息地中保存其有性型（有性）和无性型（无性）形态。
