Amphibian populations are globally declining at an alarming rate, and infectious diseases are among the main causes of their decline. Two micro-parasites, the fungus Batrachochytrium dendrobatidis (Bd) and the virus Ranavirus (RV) have caused mass mortality of amphibians and population declines. Other, less understood epizootics are caused by macro-parasites, such as Trombiculoidea chiggers. Infection with chiggers can affect frog behavior and survival. Furthermore, synergistic effects of co-infection with both macro and micro-parasites may lead to higher morbidity. To better understand these potential synergies, we investigated the presence and co-infection by chiggers, Bd and RV in the endemic frog Tlalocohyla smithii (T. smithii). Co-infection of Bd, RV, and/or chiggers is expected in habitats that are suitable for their co-occurrence; and if infection with one parasite facilitates infection with the others. On the other hand, co-infection could decrease if these parasites were to differ in their micro-environmental requirements (i.e. niche apportionment). A total of 116 frogs of T. smithii were studied during 2014 and 2016 in three streams within the Chamela-Cuixmala Biosphere Reserve in Jalisco, Mexico. Our results show that 31% of the frogs were infected with Trombiculoidea chiggers (Hannemania sp. and Eutrombicula alfreddugesi); Hannemania prevalence increased with air temperature and decreased in sites with high canopies and with water pH values above 8.5 and below 6.7. Bd prevalence was 2.6%, RV prevalence was 0%, and none of the frogs infected with chiggers were co-infected with Bd. Together, this study suggests that chiggers do not facilitate infection with Bd, as these are apportioned in different micro-habitats. Nevertheless, the statistical power to assure this is low. We recommend further epidemiological monitoring of multiple parasites in different geographical locations in order to provide insight on the true hazards, risks and conservation options for amphibian populations.

中文翻译：

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恙螨（螨形目：Trombiculoidea）不会增加地方性矮墨西哥树蛙 Tlalocohyla smithii（无尾：Hylidae）中 Batrachochytrium dendrobatidis 真菌的感染率。

全球两栖动物数量正在以惊人的速度下降，而传染病是其下降的主要原因之一。两种微型寄生虫，真菌 Batrachochytrium dendrobatidis (Bd) 和病毒 Ranavirus (RV)，导致两栖动物大规模死亡和种群数量下降。其他不太了解的动物流行病是由大型寄生虫引起的，例如恙螨。恙螨感染会影响青蛙的行为和生存。此外，宏观和微观寄生虫共同感染的协同效应可能导致更高的发病率。为了更好地了解这些潜在的协同作用，我们研究了恙虫、Bd 和 RV 在特有青蛙 Tlalocohyla smithii (T. smithii) 中的存在和共同感染。在适合 Bd、RV 和/或恙虫共存的栖息地中，预计会出现 Bd、RV 和/或恙虫的共同感染；如果一种寄生虫的感染会促进其他寄生虫的感染。另一方面，如果这些寄生虫的微环境要求（即生态位分配）不同，那么共同感染可能会减少。2014 年和 2016 年，我们对墨西哥哈利斯科州 Chamela-Cuixmala 生物圈保护区内的三个溪流中总共 116 只 T. smithii 青蛙进行了研究。我们的结果表明，31% 的青蛙感染了 Trombiculoidea 恙螨（Hannemania sp. 和 Eutrombicula alfreddugesi）；汉尼曼原虫流行率随着气温的升高而增加，而在树冠高且水 pH 值高于 8.5 和低于 6.7 的地区则降低。Bd 患病率为 2.6%，RV 患病率为 0%，感染恙螨的青蛙均未同时感染 Bd。总之，这项研究表明恙螨不会促进 Bd 感染，因为它们分布在不同的微生境中。然而，确保这一点的统计能力很低。我们建议对不同地理位置的多种寄生虫进行进一步的流行病学监测，以便深入了解两栖动物种群的真正危害、风险和保护方案。