Background Anaplasma phagocytophilum is a complex of tick-borne bacteria of medical and veterinary relevance, whose eco-epidemiology is well characterized in the Northern Hemisphere but remains poorly understood in South America. Here, we report in Uruguay the detection and genetic characterization of a novel A. phagocytophilum ecotype in South America. Methods Questing Ixodes fuscipes, the only member of the Ixodes ricinus complex in the country, were collected in five localities in Uruguay, and the presence of Anaplasma spp. DNA was assessed using PCR to amplify fragments of the 16S ribosomal RNA (rrs), gltA and groEL genes. Results A total of 223 Ixodes fuscipes ticks were collected between 2017 and 2022 in five localities. PCR screening and subsequent sequencing identified Anaplasma spp. DNA in five nymphs from the Rivera and Tacuarembó departments. Phylogenetic analyses of rrs, gltA and groEL sequences of this bacteria confirmed the placement within the A. phagocytophilum clade. In particular, groEL-based phylogenies showed that Uruguayan sequences form a distinct and well-supported lineage, grouping with ecotype V (strain Patagonia) and being closely related to ecotype III. Pairwise genetic distance analyses of groEL sequences further supported the recognition of this lineage as a novel ecotype (ecotype VI). The detection of positive nymphs suggests acquisition from local vertebrate hosts, and the phylogenetic relationship among ecotypes III, V and VI, together with host records for immature and adult I. fuscipes, point to a potential role for small mammals, birds or cervids in maintaining the enzootic cycle of A. phagocytophilum strain “Uruguay.” Although vector competence of I. fuscipes remains to be determined, these findings provide preliminary evidence of the potential involvement of this tick species in local transmission and represent the second characterization of an A. phagocytophilum ecotype in South America. Conclusions Anaplasma phagocytophilum is reported for the first time in Uruguay. The recognition of this new ecotype (VI) expands regional knowledge and underscores the influence of local host–vector assemblages in shaping A. phagocytophilum diversity. Broader host–vector surveys are needed to clarify its ecology, transmission dynamics and potential epidemiological implications in the region. Graphical Abstract

A novel ecotype of Anaplasma phagocytophilum complex in questing Ixodes fuscipes ticks

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2026年2月9日

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María L. Félix,
Adriana Santodomingo,
Richard Thomas,
Diego Queirolo,
Sebastián Muñoz-Leal,
José M. Venzal

摘要

Background

Anaplasma phagocytophilum is a complex of tick-borne bacteria of medical and veterinary relevance, whose eco-epidemiology is well characterized in the Northern Hemisphere but remains poorly understood in South America. Here, we report in Uruguay the detection and genetic characterization of a novel A. phagocytophilum ecotype in South America.

Methods

Questing Ixodes fuscipes, the only member of the Ixodes ricinus complex in the country, were collected in five localities in Uruguay, and the presence of Anaplasma spp. DNA was assessed using PCR to amplify fragments of the 16S ribosomal RNA (rrs), gltA and groEL genes.

Results

A total of 223 Ixodes fuscipes ticks were collected between 2017 and 2022 in five localities. PCR screening and subsequent sequencing identified Anaplasma spp. DNA in five nymphs from the Rivera and Tacuarembó departments. Phylogenetic analyses of rrs, gltA and groEL sequences of this bacteria confirmed the placement within the A. phagocytophilum clade. In particular, groEL-based phylogenies showed that Uruguayan sequences form a distinct and well-supported lineage, grouping with ecotype V (strain Patagonia) and being closely related to ecotype III. Pairwise genetic distance analyses of groEL sequences further supported the recognition of this lineage as a novel ecotype (ecotype VI). The detection of positive nymphs suggests acquisition from local vertebrate hosts, and the phylogenetic relationship among ecotypes III, V and VI, together with host records for immature and adult I. fuscipes, point to a potential role for small mammals, birds or cervids in maintaining the enzootic cycle of A. phagocytophilum strain “Uruguay.” Although vector competence of I. fuscipes remains to be determined, these findings provide preliminary evidence of the potential involvement of this tick species in local transmission and represent the second characterization of an A. phagocytophilum ecotype in South America.

Conclusions

Anaplasma phagocytophilum is reported for the first time in Uruguay. The recognition of this new ecotype (VI) expands regional knowledge and underscores the influence of local host–vector assemblages in shaping A. phagocytophilum diversity. Broader host–vector surveys are needed to clarify its ecology, transmission dynamics and potential epidemiological implications in the region.

Graphical Abstract