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

## TL;DR

A new type of Anaplasma phagocytophilum bacteria was found in ticks in Uruguay, suggesting local transmission and expanding understanding of the species in South America.

## Contribution

The discovery and genetic characterization of a novel A. phagocytophilum ecotype (VI) in Uruguay, the second in South America.

## Key findings

- Anaplasma spp. DNA was detected in five Ixodes fuscipes nymphs from Uruguay.
- Phylogenetic analysis confirmed a novel ecotype (VI) within the A. phagocytophilum clade.
- The new ecotype is closely related to ecotype III and V, suggesting local host involvement in its transmission.

## Abstract

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.

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.

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.

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.

The online version contains supplementary material available at 10.1186/s13071-025-07226-8.