Treatment against helminths in Norwegian sheep: a questionnaire-based survey.

Maiken Gravdal,Johan Höglund,Snorre Stuen,Kristoffer R Tysnes,Christophe Chartier,Lucy J Robertson

doi:10.1051/parasite/2021061

Abstract

A questionnaire was distributed to 5487 farmers throughout Norway in order to obtain information about management practices regarding helminth infections in sheep. In addition, the farmers' perceptions of helminths and anthelmintic efficacy were investigated. Most farmers (80%) treated prophylactically against nematodes, and 24% also used prophylactic treatment against Fasciola hepatica. Overall, few farmers (11%) used parasitological analysis as a tool to assess the timing of treatment, but rather based it on other factors such as previous experience (70%). In the surveyed sheep flocks, the use of benzimidazoles was reduced from 2018 (52%) to 2019 (47%) (p<0.01), whereas the use of macrocyclic lactones increased from 2017 (23%) to 2019 (36%) (p<0.001). Poor anthelmintic efficacy was suspected by 10% of the farmers, and 11% reported that helminths were an increasing problem in their flocks. The majority of farmers (72%) considered their veterinarian as the most important advisor for treatment of parasites, but reported a high level of uncertainty regarding which parasites were present in their flocks, with unknown status most frequently reported for Haemonchus contortus (71.5%). This is probably related to the fact that very few farmers (15%) regularly test their animals for parasites. The present study provides up-to-date information on treatment practices for helminths in Norwegian sheep flocks.

Highlights

Gastrointestinal nematodes (GINs) and the common liver fluke (Fasciola hepatica) are important helminths that can cause clinical and subclinical disease, as well as economic losses, in small ruminant production [8]
The results suggested that, at that time, more than 90% of the sheep flocks in Norway could be at risk of underdosing when administrating anthelmintics
A total of 1378 sheep farmers responded to the questionnaire survey, resulting in a response rate of 25%

Summary

Introduction

Gastrointestinal nematodes (GINs) and the common liver fluke (Fasciola hepatica) are important helminths that can cause clinical and subclinical disease, as well as economic losses, in small ruminant production [8]. These infections have a crucial impact on animal welfare in the global ruminant livestock industry [31]. Anthelmintic resistance (AR) is an emerging threat to the productivity and welfare of sheep in many parts of the world [26, 41], and is recognized as a widespread and increasing challenge in Europe [4, 39] This has a major economic impact due both to lost production, as well as costs of anthelmintic drugs that may not be effective [8]. These include high frequency of treatment, using the doseand-move strategy, absence of rotation between anthelmintic classes, introduction of animals carrying resistant parasites to the flock, under-dosing with anthelmintics, and blanket nontargeted treatments [6, 9, 10, 19, 28, 40, 42, 49, 51]

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