Department of Animal Health. Faculty of Veterinary Medicine. Miguel Servet, 177. 50013 Zaragoza, Spain; Group of Research on Emerging Zoonoses, Instituto Agroalimentario de Aragón (IA2), 50013 Zaragoza, Spain.
Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, Av. Prof. Orlando Marques de Paiva, 87, Cidade Universitária. São Paulo, SP, 05508-270, Brazil.
Ticks Tick Borne Dis. 2021 Sep;12(5):101754. doi: 10.1016/j.ttbdis.2021.101754. Epub 2021 Jun 4.
This study addresses a meta-analysis of the distribution of Rickettsia spp. in the Neotropical region, as well as their associations with ticks and vertebrates. A total of 219 published reports on Rickettsia in ticks in the target region were compiled, providing 599 records of 31 species of Rickettsia recorded in 50 species of Ixodidae. The aim is to capture the phylogenetic relationships between rickettsiae and the ticks carrying them in the target region, with a focus on the co-speciation ticks-rickettsiae. We compared the phylogeny of ticks, the records of rickettsiae, the environmental gradients colonized by ticks and the effect of the phylogenetic composition of vertebrates feeding ticks on the detection of Rickettsia in ticks. Results show that differences in rickettsial composition in ticks do not depend on the vertebrate's blood-source. This is the first time this result is demonstrated. This study pinpoints that some Neotropical rickettsial organisms are associated with well-defined phylogenetical clusters of ticks. Secondarily, and probably only in a few cases, rickettsiae share species of phylogenetically distant ticks distributed along a gradient of environmental traits in which the ticks overlap (i.e., the different strains of Rickettsia parkeri sensu lato). We outline the importance of some ticks that share hosts and habitat: these ticks may act as "bridges" for the circulation of rickettsial species. There are also many species of Rickettsia that have been detected so far in only one tick species, pointing to a tight relationship or to the lack of data preventing conclusions about the detection of these bacteria in other ticks. Two species, namely Rickettsia amblyommatis and Rickettsia bellii have been recorded in the majority of ticks in the region (mainly Amblyomma spp.) and seem to be not associated with definite tick species because they may be an essential symbiont of the ticks. We conclude that an adequate analysis of rickettsiae-ticks-habitat is necessary to address the human health issues derived from the infections by rickettsiae.
本研究对新热带地区立克次体的分布及其与蜱和脊椎动物的关系进行了荟萃分析。共汇编了 219 篇关于目标地区蜱中立克次体的已发表报告，提供了在 50 种壁虱科中记录的 31 种立克次体的 599 个记录。目的是捕捉目标地区携带立克次体的蜱和携带它们的蜱之间的系统发育关系，重点是共进化的蜱-立克次体。我们比较了蜱的系统发育、立克次体的记录、蜱所定殖的环境梯度以及以蜱为食的脊椎动物的系统发育组成对立克次体在蜱中的检测的影响。结果表明，蜱中立克次体的组成差异不取决于脊椎动物的血液来源。这是首次证明这一结果。本研究指出，一些新热带立克次体生物与蜱的明确系统发育聚类有关。其次，可能只有在少数情况下，立克次体与沿环境特征梯度分布的亲缘关系较远的蜱种共享物种，而这些蜱种重叠（即，不同株的立氏立克次体 sensu lato）。我们概述了一些共享宿主和栖息地的蜱的重要性：这些蜱可能是立克次体物种循环的“桥梁”。迄今为止，还有许多种立克次体仅在一种蜱中被检测到，这表明它们与蜱之间存在紧密的关系，或者缺乏数据，无法得出关于在其他蜱中检测到这些细菌的结论。两种物种，即 Rickettsia amblyommatis 和 Rickettsia bellii，已在该地区的大多数蜱中记录（主要是 Amblyomma spp.），并且似乎与明确的蜱种没有关联，因为它们可能是蜱的必需共生体。我们的结论是，需要对立克次体-蜱-栖息地进行充分分析，以解决由立克次体感染引起的人类健康问题。
