Van Wyk J A, Stenson M O, Van der Merwe J S, Vorster R J, Viljoen P G
Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa.
Onderstepoort J Vet Res. 1999 Dec;66(4):273-84.
Surveys to determine the prevalence and degree of resistance of Haemonchus spp. of sheep and goats to the available anthelmintics in South Africa indicate that small ruminant production is entering a crisis situation. Three surveys employing the faecal egg count reduction (FECR) test to determine resistance were conducted in some of the main sheep-producing areas in the summer rainfall region of South Africa, where H. contortus is the principal worm species in sheep. After analyzing the data recorded in the surveys by six different methods, including the RESO test at two different levels of confidence, the results obtained in the least stringent one (geometric mean reduction of the worm egg counts of drenched, vs untreated group of sheep) are reported in this paper, so that if any bias was obtained it would be in the favour of the anthelmintic. In Mpumalanga and KwaZulu-Natal there was anthelmintic resistance in Haemonchus spp. on all the 52 farms surveyed. Sixteen percent of the strains of H. contortus were < 60% susceptible to three of the four anthelmintics tested, and 8% of the strains were < 40% susceptible to all four of the anthelmintics. FECR tests of sheep in six localities in the Lebowa district of Northern Province indicated that even in previously disadvantaged communities where anthelmintic treatment is less intensive, anthelmintic resistance is developing, and is possibly at the level at which the situation on commercial sheep and goat farms in South Africa was 25 years ago. From the data it appears that the level of anthelmintic resistance of H. contortus in South Africa is possibly the highest that has so far been recorded in the world and that strains of it are emerging that may soon not be controllable by treatment with any of the existing anthelmintics. Farmers in the summer rainfall region, if not the whole country, must be alerted to the immediate need for testing the parasite burdens of their sheep for susceptibility to preparations in all four groups of anthelmintic compounds currently available. Alternative methods of integrated worm control, including biological, must be sought and implemented with urgency, to reduce further selection for resistance and to induce reversion of the resistance that has already developed.
旨在确定南非绵羊和山羊体内捻转血矛线虫对现有驱虫药的耐药率和耐药程度的调查表明，小反刍动物生产正进入危机状态。在南非夏季降雨区的一些主要绵羊产区开展了三项采用粪便虫卵计数减少率（FECR）试验来确定耐药性的调查，其中捻转血矛线虫是绵羊体内的主要蠕虫种类。通过六种不同方法（包括在两个不同置信水平下进行的RESO试验）对调查记录的数据进行分析后，本文报告了在最宽松的方法（用药组与未用药组绵羊的虫卵计数几何平均减少率）中获得的结果，这样如果存在任何偏差，也是有利于驱虫药的。在姆普马兰加省和夸祖鲁 - 纳塔尔省，接受调查的所有52个农场的捻转血矛线虫均存在驱虫药耐药性。在接受测试的四种驱虫药中，16%的捻转血矛线虫菌株对其中三种药物的敏感性低于60%，8%的菌株对所有四种药物的敏感性低于40%。在北省勒博瓦区六个地点对绵羊进行的FECR试验表明，即使在驱虫药使用强度较低的以前处境不利的社区，驱虫药耐药性也在发展，而且可能处于25年前南非商业绵羊和山羊农场的情况水平。从数据来看，南非捻转血矛线虫的驱虫药耐药水平可能是迄今为止世界上有记录以来最高的，并且正在出现一些菌株，可能很快就无法用任何现有驱虫药进行控制。必须提醒夏季降雨区的农民，即使不是全国的农民，也迫切需要检测其绵羊体内寄生虫负荷对目前可用的所有四类驱虫化合物制剂的敏感性。必须紧急寻求并实施包括生物方法在内的综合蠕虫控制替代方法，以减少对耐药性的进一步选择，并促使已经产生的耐药性发生逆转。
