Bishop R M, Scott I, Gee E K, Rogers C W, Pomroy W E, Mayhew I G
a Institute of Veterinary, Animal and Biomedical Sciences , Massey University , Private Bag 11222, Palmerston North 4442 , New Zealand.
N Z Vet J. 2014 Mar;62(2):91-5. doi: 10.1080/00480169.2013.843146. Epub 2013 Oct 24.
To ascertain whether resistance was present in Parascaris equorum to the macrocyclic lactone anthelmintic ivermectin, using faecal egg count reduction tests.
Thirty-nine foals aged between 11 and 28 weeks on three Thoroughbred stud farms (Farms A; n=20, B; n=5 and C; n=14) were treated with ivermectin (Day 0) and faecal egg counts (FEC) were monitored before and for 21 (Farms A and B) or 14 (Farm C) days after treatment. On Farms A and B, the foals were treated with a macrocyclic lactone/benzimidazole/praziquantel combination on Day 21 and FEC assessed on Day 35. The three farms were all in the Manawatu region in the southern half of New Zealand's North Island.
Of the 39 foals, 15 were not shedding P. equorum eggs on the day they were treated with ivermectin, but all 15 did so post-treatment. The FEC on Farms A and B showed no evidence of a reduction at any time between Day 7 and 21; egg output increased steadily over this period. Following combination treatment FEC were reduced by 94% on farm A and 100% on Farm B. On Farm C, there was a 69% reduction in P. equorum FEC on Day 14. Twelve of the 14 foals on Farm C were shedding strongylid eggs on Day 0 and on Day 14 FEC were reduced by 84%.
Without comparison to untreated control animals, these results do not allow a reliable estimation of the exact level of efficacy of ivermectin against P. equorum, but they nevertheless show that, within the farms studied, ivermectin no longer achieved a complete kill of egg-laying adults and that foals treated with this drug may continue to shed considerable numbers of eggs after treatment. The results also indicate that ivermectin had sub-optimal efficacy against strongylid nematodes on one of the farms.
通过粪便虫卵计数减少试验，确定马副蛔虫对大环内酯类驱虫药伊维菌素是否存在抗性。
对三个纯种种马场（A场；n = 20，B场；n = 5，C场；n = 14）中11至28周龄的39匹小马驹用伊维菌素进行治疗（第0天），并在治疗前及治疗后21天（A场和B场）或14天（C场）监测粪便虫卵计数（FEC）。在A场和B场，小马驹在第21天用大环内酯/苯并咪唑/吡喹酮联合用药治疗，并在第35天评估FEC。这三个马场均位于新西兰北岛南部的马纳瓦图地区。
在39匹小马驹中，15匹在接受伊维菌素治疗当天未排出马副蛔虫卵，但所有15匹在治疗后均排出虫卵。A场和B场的FEC在第7天至21天之间的任何时间均未显示出减少的迹象；在此期间虫卵排出量稳步增加。联合用药治疗后，A场的FEC减少了94%，B场减少了100%。在C场，第14天马副蛔虫FEC减少了69%。C场14匹小马驹中有12匹在第0天排出圆线虫卵，第14天FEC减少了84%。
由于未与未治疗的对照动物进行比较，这些结果无法可靠地估计伊维菌素对马副蛔虫的确切疗效水平，但它们仍表明，在所研究的马场中，伊维菌素不再能完全杀死产卵成虫，用该药物治疗的小马驹在治疗后可能仍会排出大量虫卵。结果还表明，伊维菌素对其中一个马场的圆线虫的疗效欠佳。
