# Evaluation of Different Benzimidazole Formulations Against Sheep Naturally Infected with Fasciola hepatica and Anthelmintic Resistance Analysis

## TL;DR

This study tests the effectiveness of benzimidazole drugs against liver fluke in sheep and highlights growing resistance to these treatments.

## Contribution

The study applies a new classification framework for Fasciola hepatica resistance detection for the first time.

## Key findings

- Resistance to benzimidazole drugs is increasing in Fasciola hepatica-infected sheep.
- Standardized resistance detection methods are urgently needed for effective treatment.
- Fenbendazole and oxfendazole were tested as potential alternatives to albendazole and triclabendazole.

## Abstract

Fasciola infection is now a widely known parasitic disease that affects animals and humans, causing significant losses in livestock production worldwide. Its control depends mainly on a few antiparasitic drugs, such as albendazole and triclabendazole. The aim of this study was to evaluate the efficacy of these drugs in a flock of sheep in northwestern Spain infected with the species Fasciola hepatica, while also testing other drugs from the same family as an alternative to these treatments and comparing the results using different analysis methods. Thanks to this comparison, which was carried out using a technique that counts the eggs eliminated in the animals’ faeces at different times, it was possible to demonstrate that resistance to antiparasitic drugs is a growing problem in the treatment of fasciolosis, as well as the urgent need to standardize the methods currently used to detect such resistance.

Fasciola infection, which is widely distributed and has a major impact on livestock production, is emerging as a significant zoonotic parasitic disease affecting both human and animal health worldwide. The main control strategy currently relies on a limited number of anthelmintic drugs, especially benzimidazoles such as albendazole and triclabendazole. The aim of this study was to evaluate the efficacy of albendazole and triclabendazole in a sheep flock in northwestern Spain naturally infected with F. hepatica and to test fenbendazole and oxfendazole as alternative formulations. For this purpose, a faecal egg count reduction test (FECRT) was conducted applying various statistical methods based on the guidelines used for gastrointestinal nematodes. This study represents the first application of the new classification framework for F. hepatica, emphasizing the urgent need for standardized resistance detection protocols for this parasite and underlining the growing challenge of anthelmintic resistance in the treatment of fasciolosis.