Gasbarre Louis C, Ballweber Lora R, Stromberg Bert E, Dargatz David A, Rodriguez Judy M, Kopral Christine A, Zarlenga Dante S
USDA, ARS, Bovine Functional Genomics Lab, Beltsville, Maryland (Gasbarre); Colorado State University, Veterinary Diagnostic Laboratory, Fort Collins, Colorado (Ballweber); College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota (Stromberg); USDA, APHIS, VS Centers for Epidemiology and Animal Health, Fort Collins, Colorado (Dargatz, Rodriguez, Kopral); and USDA, ARS, Animal Parasitic Diseases Lab, Beltsville, Maryland, USA (Zarlenga).
Can J Vet Res. 2015 Oct;79(4):296-302.
During the United States Department of Agriculture (USDA) National Animal Health Monitoring System's (NAHMS) 2007-2008 beef study, producers from 24 states were offered the opportunity to evaluate their animals for internal parasites and for overall responses to treatment with anthelmintics. A lapse of 45 d was required between initial sampling and any previous treatments. Choice of anthelmintic (oral benzimidazoles, and both injectable and pour-on endectocides) was at the discretion of the producer so as not to alter the local control programs. Fresh fecal samples were collected from 20 animals, or from the entire group if less than 20, then randomly assigned to 1 of 3 participating laboratories for examination. Analyses consisted of double centrifugation flotation followed by enumeration of strongyle, Nematodirus, and Trichuris eggs (the presence of coccidian oocysts and tapeworm eggs was also noted). Where strongyle eggs per gram (epg) exceeded 30, aliquots from 2 to 6 animals were pooled for egg isolation and polymerase chain reaction (PCR) analysis for the presence of Ostertagia, Cooperia, Haemonchus, Oesophagostomum, and Trichostrongylus. Results from 72 producers (19 States) indicated that fecal egg count reductions were < 90% in 1/3 of the operations. All operations exhibiting less than a 90% reduction had used pour-on macrocyclic lactones as the anthelmintic treatment. While some of these less than expected reductions could have been the result of improper drug application, PCR analyses of the parasite populations surviving treatment, coupled with follow-up studies at a limited number of sites, indicated that less than expected reductions were most likely due to anthelmintic resistance in Cooperia spp. and possibly Haemonchus spp.
在美国农业部（USDA）国家动物健康监测系统（NAHMS）2007 - 2008年的牛肉研究中，来自24个州的养殖者有机会对其动物进行体内寄生虫评估以及评估驱虫药治疗的整体效果。初始采样与之前的任何治疗之间需间隔45天。驱虫药（口服苯并咪唑类，以及注射用和浇泼用的体内外寄生虫驱虫剂）的选择由养殖者自行决定，以免改变当地的防控方案。从20只动物身上采集新鲜粪便样本，如果动物数量少于20只，则从整个群体中采集，然后随机分配到3个参与实验室中的1个进行检测。分析包括双重离心浮选，随后对圆线虫、细颈线虫和鞭虫虫卵进行计数（同时也记录球虫卵囊和绦虫卵的存在情况）。当每克粪便中的圆线虫虫卵数（epg）超过30时，将2至6只动物的等分样本混合用于虫卵分离和聚合酶链反应（PCR）分析，以检测奥斯特他线虫、古柏线虫、血矛线虫、食道口线虫和毛圆线虫的存在情况。来自72位养殖者（19个州）的结果表明，在三分之一的养殖场中，粪便虫卵计数减少率低于90%。所有虫卵计数减少率低于90%的养殖场都使用浇泼用大环内酯类药物作为驱虫治疗。虽然这些低于预期的减少率部分可能是由于药物使用不当造成的，但对治疗后存活的寄生虫种群进行的PCR分析，以及在有限数量地点进行的后续研究表明，低于预期的减少率很可能是由于古柏属线虫以及可能还有血矛属线虫产生了驱虫药抗性。
