{"title":"Anthelmintic resistance in gastrointestinal nematodes of cattle owned by smallholders in Southern Chile","authors":"D. Tapia-Escárate, J. Paredes, J. Sanhueza","doi":"10.1016/j.vprsr.2025.101320","DOIUrl":null,"url":null,"abstract":"<div><div>Helminth infections present a significant challenge to rural and indigenous smallholders. In a municipality of Los Lagos Region, Chile, ivermectin has been the preferred method of anthelmintic control in cattle, but its efficacy against gastrointestinal nematodes after years of usage had not been evaluated. In the spring of 2021, 30 smallholder cattle farmers and 128 bovines were selected using a one stage cluster sampling. During the first visit, fecal samples were collected, and animals were treated with subcutaneous ivermectin (0.2 mg/kg). Samples were sent to the Parasitology Laboratory of the Universidad Católica de Temuco. Fourteen days after the first sampling, a second fecal sample was taken from the same animals. Fecal eggs count (FEC) was performed in a Whitlock universal chamber. Animals with initial FECs ≤100 eggs per gram (epg) were excluded from the FEC reduction test (FECRT). The classification of resistance, suspected resistance, or susceptibility was established based on the guidelines provided by Denwood et al. (2023) and the WAAVP (2023). Among the 128 animals sampled and treated in the first sampling, 61 (47.7 %) had FEC ≥100 epg, with 85.2 % being ≤18-month-old. Considering animals with initial FEC ≥100, the mean farm adjusted FECR percentage was 55.0 % (95 % CI 34.3 % - 87.9 %) and the treatment failed to reduce the egg count per gram by more than 95 % in 65.6 % of the animals sampled. Additionally, animals ≥18-month-old had 48 times higher odds of achieving a 95 % FECR percentage than animals <6 month-old. This study provides evidence of gastrointestinal nematode's resistance to subcutaneous ivermectin treatment in smallholders' cattle in a municipality of Los Lagos region, Chile.</div></div>","PeriodicalId":23600,"journal":{"name":"Veterinary parasitology, regional studies and reports","volume":"64 ","pages":"Article 101320"},"PeriodicalIF":1.4000,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Veterinary parasitology, regional studies and reports","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S2405939025001285","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"PARASITOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Helminth infections present a significant challenge to rural and indigenous smallholders. In a municipality of Los Lagos Region, Chile, ivermectin has been the preferred method of anthelmintic control in cattle, but its efficacy against gastrointestinal nematodes after years of usage had not been evaluated. In the spring of 2021, 30 smallholder cattle farmers and 128 bovines were selected using a one stage cluster sampling. During the first visit, fecal samples were collected, and animals were treated with subcutaneous ivermectin (0.2 mg/kg). Samples were sent to the Parasitology Laboratory of the Universidad Católica de Temuco. Fourteen days after the first sampling, a second fecal sample was taken from the same animals. Fecal eggs count (FEC) was performed in a Whitlock universal chamber. Animals with initial FECs ≤100 eggs per gram (epg) were excluded from the FEC reduction test (FECRT). The classification of resistance, suspected resistance, or susceptibility was established based on the guidelines provided by Denwood et al. (2023) and the WAAVP (2023). Among the 128 animals sampled and treated in the first sampling, 61 (47.7 %) had FEC ≥100 epg, with 85.2 % being ≤18-month-old. Considering animals with initial FEC ≥100, the mean farm adjusted FECR percentage was 55.0 % (95 % CI 34.3 % - 87.9 %) and the treatment failed to reduce the egg count per gram by more than 95 % in 65.6 % of the animals sampled. Additionally, animals ≥18-month-old had 48 times higher odds of achieving a 95 % FECR percentage than animals <6 month-old. This study provides evidence of gastrointestinal nematode's resistance to subcutaneous ivermectin treatment in smallholders' cattle in a municipality of Los Lagos region, Chile.
期刊介绍:
Veterinary Parasitology: Regional Studies and Reports focuses on aspects of veterinary parasitology that are of regional concern, which is especially important in this era of climate change and the rapid and often unconstrained travel of people and animals. Relative to regions, this journal will accept papers of the highest quality dealing with all aspects of disease prevention, pathology, treatment, epidemiology, and control of parasites within the field of veterinary medicine. Also, case reports will be considered as they add to information related to local disease and its control; such papers must be concise and represent appropriate medical intervention. Papers on veterinary parasitology from wildlife species are acceptable, but only if they relate to the practice of veterinary medicine. Studies on vector-borne bacterial and viral agents are suitable, but only if the paper deals with vector transmission of these organisms to domesticated animals. Studies dealing with parasite control by means of natural products, both in vivo and in vitro, are more suited for one of the many journals that now specialize in papers of this type. However, due to the regional nature of much of this research, submissions may be considered based upon a case being made by the author(s) to the Editor. Circumstances relating to animal experimentation must meet the International Guiding Principles for Biomedical Research Involving Animals as issued by the Council for International Organizations of Medical Sciences (obtainable from: Executive Secretary C.I.O.M.S., c/o W.H.O., Via Appia, CH-1211 Geneva 27, Switzerland).