# Parasitism with Protozoa and Monogeneans in Fish from the Natural Waters of Romania

## TL;DR

This study examines parasitism in freshwater fish from two Romanian rivers, identifying various protozoa and monogenean flatworms and their prevalence across fish species.

## Contribution

The study provides new insights into the diversity and distribution of parasites in Romanian freshwater fish ecosystems.

## Key findings

- Trichodina spp. had the highest average parasitism rate at 21%.
- European chub and schneider were found to host the most parasite species (six each).
- The rivers may act as a source of parasites for neighboring countries.

## Abstract

Parasitism by protozoa and monogenean flatworms in freshwater fish from Romania was studied by collecting and examining samples from two major river systems there: 183 fish from 17 species from the Olt River and its tributaries; and 155 fish from 16 species from the Mureș River and its tributary, Târnava Mare. The average rates of parasitism in the samples from the two rivers and their tributaries were as follows: Ichthyiophthirius multifiliis (2%), Trichodina spp. (21%), Apiosoma spp. (18%), Mixobolus spp. (8%), Dactylogyrus spp. (9%), and Gyrodactylus spp. (10%). The number of parasite species varied from one river to another. I. multifiliis was found in only 3 fish species, Trichodina spp. in 13 species, Glosatella spp. in 6 species, and Mixobollus spp., Dactylogyrus spp., and Gyrodactylus spp. in 7 different species each. The highest number of parasite species (six) were identified in the European chub (Squalius cephalus) and schneider (Alburnoides bipunctatus), which seem more susceptible to parasitic infections. The aquatic environment of these rivers may represent a source of parasites for fish from neighboring countries through which these rivers pass.