Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
Vet Parasitol. 2011 May 31;178(1-2):48-57. doi: 10.1016/j.vetpar.2010.12.024. Epub 2010 Dec 25.
Twin lambs at pasture with their ewes, were divided into seven groups of 10 lambs. One group of 10 lambs served as a non-infected, untreated control. Five groups of 10 lambs were infected with 10,000 oocysts of Eimeria crandallis and 10,000 oocysts of Eimeria ovinoidalis when they were 3 weeks old (day 21 of the study). This produced a good level of infection with high oocysts production and diarrhoea in the lambs. Fourteen days after the primary, artificial challenge (day 35) four of these groups were treated with oral diclazuril at 0.25, 1.0, 2.0 or 4.0mg/kg. Diclazuril treatment was highly effective, dramatically reducing symptoms of diarrhoea and reducing faecal oocyst output by 79.7%, 97.3%, 99.4% and 99.5% respectively in the treated groups within four days. Two weeks post-treatment, and 28 days after the primary coccidial challenge (day 49 of the study), five groups of lambs were re-challenged with 100,000 oocysts of E. crandallis and 100,000 oocysts of E. ovinoidalis (secondary challenge). A group of lambs which had received neither the primary coccidia infection, nor drug treatment (susceptible controls) were also given the secondary challenge. All lambs given the secondary challenge produced high numbers of coccidia and exhibited varying degrees of diarrhoeic faeces. The lambs, which had previously received the higher doses of diclazuril at 2.0 and 4.0mg/kg, developed clinical signs of coccidiosis. These lambs were completely susceptible despite having received the early primary immunising infection of coccidia on day 21. The effects of the secondary challenge were more severe in the groups dosed with the two highest levels of diclazuril than in the susceptible control lambs, which had presumably been exposed to continued low levels of pasture contamination and had acquired a limited degree of immunity from this exposure. It would appear that treatment at the higher dose levels not only eliminated most of the oocysts from the primary challenge but also adventitious infection derived from the grazing paddocks. In contrast, lambs which had received the two lower drug levels of diclazuril (0.25 and 1.0mg/kg) whilst producing large numbers of oocysts, had only transient diarrhoea following secondary challenge. It was concluded that when used as a metaphylactic treatment, diclazuril works rapidly and is effective within four days of administration. Overall, a single dose of diclazuril at either 0.25-1.0mg/kg appears to be highly effective in the control of coccidiosis in young lambs at pasture whilst allowing the development of protective immunity against subsequent heavy coccidia challenge.
牧场中的两只羔羊与它们的母羊在一起，被分为 7 组，每组 10 只羔羊。一组 10 只羔羊作为未感染、未治疗的对照。当羔羊 3 周大（研究第 21 天）时，将 5 组 10 只羔羊感染 10,000 个艾美耳球虫孢子囊和 10,000 个艾美耳属球虫孢子囊。这导致羔羊出现了良好的感染水平，产生了大量的卵囊和腹泻。原发性人工攻毒后 14 天（第 35 天），其中 4 组用口服地克珠利进行治疗，剂量分别为 0.25、1.0、2.0 或 4.0mg/kg。地克珠利治疗非常有效，在 4 天内分别使治疗组羔羊的腹泻症状显著减轻，粪便卵囊排出量减少 79.7%、97.3%、99.4%和 99.5%。治疗后两周（即原发性球虫攻毒后 28 天，研究第 49 天），5 组羔羊再次用 100,000 个艾美耳球虫孢子囊和 100,000 个艾美耳属球虫孢子囊进行二次攻毒。一组既未接受原发性球虫感染，也未接受药物治疗的羔羊（易感对照）也接受了二次攻毒。所有接受二次攻毒的羔羊均产生了大量球虫，并表现出不同程度的腹泻粪便。以前用 2.0 和 4.0mg/kg 地克珠利高剂量治疗的羔羊出现了球虫病的临床症状。尽管在第 21 天已经接受了早期的原发性球虫免疫感染，但这些羔羊仍然完全易感。与易感对照羔羊相比，用两种最高水平地克珠利治疗的羔羊的二次攻毒效果更为严重，这可能是因为它们一直暴露于牧场污染的低水平中，并从这种暴露中获得了一定程度的免疫力。似乎高剂量治疗不仅消除了原发性攻毒中的大多数卵囊，而且还消除了来自放牧围场的偶然感染。相比之下，接受地克珠利两种较低药物水平（0.25 和 1.0mg/kg）治疗的羔羊在产生大量卵囊后，仅在二次攻毒后出现短暂的腹泻。结论是，作为一种预防治疗，地克珠利在给药后 4 天内快速起效且有效。总的来说，在牧场饲养的羔羊中，单次使用 0.25-1.0mg/kg 的地克珠利似乎非常有效地控制球虫病，同时允许针对随后的严重球虫攻毒产生保护性免疫。
