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Reasons for performing study Anthelmintic resistance in equine gastrointestinal nematodes is a threat to equine health and welfare. Detailed knowledge of anthelmintic use and parasite control methods is a prerequisite to identification of potential risk factors for resistance. Objectives To identify parasite control practices employed by equine owners in Scotland and investigate management factors associated with anthelmintic resistance. Study design Questionnaire study of equine parasite control in Scotland. Methods Questionnaires were available electronically, distributed at a conference and mailed to clients. Key areas explored included general background, grazing management, anthelmintic treatment practices and use of diagnostic tests. Results A total of 193 responses detailing information on parasite control programmes of 993 equids were analysed. Moxidectin ( MOX) and ivermectin or related combination products were the most commonly administered anthelmintics in the preceding 12 months. Treatments licensed for use against cyathostomin encysted larvae and tapeworms were administered by 80% and 90% of respondents, respectively. This was often achieved through indiscriminate use of MOX and MOX-praziquantel products. Faecal egg count ( FEC) analysis had been performed on 62% of yards and regular use of FECs reduced annual anthelmintic treatment frequency. Veterinarians had the greatest influence on control practices. While 40% of respondents believed that they practised targeted dosing, this was not associated with delaying treatment beyond the egg reappearance period of the anthelmintic used. Conclusions Responses indicated increasing veterinary involvement and use of FECs. The majority of respondents administered anthelmintics licensed against cyathostomin encysted larvae and tapeworms. However, responses suggested that owners did not understand the definition of 'targeted' dosing regimens. Potential relevance The high frequency of MOX use represents a potential risk factor for macrocyclic lactone resistance. As veterinarians were the most influential factor in anthelmintic choice, awareness of macrocyclic lactone resistance and potential risk factors for its development and spread should be incorporated into client advice. [ABSTRACT FROM AUTHOR]

Reasons for performing study Cyathostomins comprise 50 helminth species, considered the most problematic equine endoparasites. Three classes of anthelmintic are currently licensed for their control, namely the benzimidazoles (fenbendazole), tetrahydropyrimidines (pyrantel) and macrocyclic lactones (ivermectin and moxidectin). Anthelmintic resistance in cyathostomins is common. With no new classes expected in the near future, it is essential to determine the efficacy of the available anthelmintics to inform future control programmes. Objectives To determine the efficacy of all 3 anthelmintic classes against strongyles in equids on livery yards in east and central Scotland. Study design Anthelmintic efficacy testing using the faecal egg count reduction test (FECRT). Methods FECRTs were performed on equids with initial strongyle faecal egg counts ( FECs) of ≥50 eggs per gram. Efficacy was determined by comparing pretreatment (Day 0) and 14 days post treatment (Day 14) FECs. The following chemicals were tested: fenbendazole, pyrantel, ivermectin and moxidectin. Group arithmetic mean FECR of >90% for fenbendazole and pyrantel, and >95% for ivermectin and moxidectin, represented efficacy, whereas lower mean FECR indicated potential resistance. Results A total of 447 FECRTs were performed on 15 yards, as follows (the numbers in parentheses represent the number of yards each anthelmintic was tested on): 55 equids (7 yards) fenbendazole, 111 (8 yards) pyrantel, 163 (13 yards) ivermectin and 118 (10 yards) moxidectin. Fenbendazole resistance was documented on all yards (range of mean FECR, 15.8-83.4%), whereas pyrantel (90.4-99.6%), ivermectin (99.5-100%) and moxidectin (99.4-100%) treatment had acceptable efficacy. Conclusions Reduced efficacy of fenbendazole was widespread, whereas >90% efficacy was found after pyrantel, and >95% efficacy after ivermectin and moxidectin. Overall, efficacies were higher than reported previously in Europe and the USA, potentially reflecting differences in management and anthelmintic use on the yards surveyed. Potential relevance The use of fenbendazole for strongyle control in Scotland should be questioned. Targeted use of pyrantel should be encouraged to reduce reliance on macrocyclic lactones. Further work to correlate management practices with the presence of anthelmintic resistance is warranted. The Summary is available in Chinese - see Supporting information. [ABSTRACT FROM AUTHOR]

See the original clinical commentary by K. J Pickles and correspondence by S. Devereux. [ABSTRACT FROM AUTHOR]