# First report of Taenia arctos (Cestoda: Taeniidae) from brown bears (Ursus arctos) in Romania

## TL;DR

This study reports the first detection of the tapeworm Taenia arctos in brown bears in Romania, expanding its known geographic range.

## Contribution

The first molecular confirmation of Taenia arctos in brown bears in southeastern Europe.

## Key findings

- Taenia arctos was identified in one of 91 brown bear samples from Romania.
- This is the first molecularly confirmed case of T. arctos in southeastern Europe.
- The presence suggests possible trophic interactions supporting T. arctos' life cycle in the region.

## Abstract

The brown bear (Ursus arctos) is an apex predator with significant ecological importance and serves as a valuable indicator species for monitoring parasitic burdens in forest ecosystems. Owing to its complex ecology and varied diet, this species may play a key role in the life cycle of numerous pathogens, including cestodes of the genus Taenia, such as the recently described Taenia arctos. Among the potential intermediate hosts for T. arctos is the moose (Alces alces), a species sporadically present in northern Romania, where its habitat may overlap with that of U. arctos. In this context, the present study aimed to identify and molecularly characterize cestodes isolated from the small intestines of U. arctos.

Between May 2022 and December 2024, small intestines from 91 U. arctos individuals were collected across 16 counties in Romania. Biological samples were preserved by freezing and analyzed using both classical methods (macroscopic and microscopic examination) and molecular biology techniques (through amplification and sequencing of mitochondrial gene fragments, cox1 and 12S rRNA).

Out of the 91 samples analyzed, only 1 specimen tested positive for an adult cestode (prevalence 1.1%). Genetic analysis confirmed its identification as T. arctos, a species not previously reported in Romania.

This study represents the first molecular identification of T. arctos in U. arctos in southeastern Europe, thereby extending the known geographic range of the parasite. The findings may indicate that trophic interactions compatible with the life cycle of T. arctos occur in this area, although the evidence is limited to a single detection.