# Molecular detection of Ehrlichia chaffeensis in marsh deer (Blastocerus dichotomus) and their parasitic Amblyomma triste ticks in Argentina suggests a local transmission cycle

## TL;DR

Researchers found Ehrlichia chaffeensis in marsh deer and their ticks in Argentina, suggesting a local transmission cycle.

## Contribution

This study provides the first evidence of Ehrlichia chaffeensis transmission in a natural setting involving wild deer and ticks in Argentina.

## Key findings

- Ehrlichia chaffeensis DNA was detected in two marsh deer blood samples.
- The pathogen was also found in the salivary glands of three Amblyomma triste ticks.
- A previously reported genotype was identified through sequencing of specific molecular markers.

## Abstract

Since the first finding of Ehrlichia chaffeensis in the Argentinian marsh deer populations in 2018, we have conducted ongoing surveillance efforts to better understand the ecological and epidemiological dynamics of this zoonotic tick-borne pathogen in the region.

Over a period of 7 years (2018–2024) we analyzed blood and tissue samples from 40 marsh deer (Blastocerus dichotomus) and 13 parasitic Amblyomma triste ticks in the Paraná River Delta, Argentina.

We identified E. chaffeensis DNA in two deer blood samples and in the salivary glands of three A. triste ticks parasitizing one of those deer. The approach used for E. chaffeensis detection in the tick sample ensured that the identified DNA came from an active tick infection, not residual host blood in the gut. After sequencing generic genes (16S ribosomal RNA [rRNA], 23S rRNA and groEl) and the specific E. chaffeensis variable-length polymerase chain reaction target (VLPT) molecular marker, we identified a genotype previously reported in Argentina.

This first-time contemporary detection of zoonotic E. chaffeensis in both a wild vertebrate host and its parasitic generalist ticks in a natural setting, provides direct evidence of a putative transmission cycle in Argentina, highlighting the need of implementing multidisciplinary surveillance systems.

The online version contains electronic supplementary material available at 10.1186/s13071-025-07211-1.