Shaw D J, Vercruysse J, Claerebout E, Agneessens J, Dorny P
Department of Parasitology, Faculty of Veterinary Medicine, University of Gent, Merelbeke, Belgium.
Vet Parasitol. 1997 Apr;69(1-2):103-16. doi: 10.1016/s0304-4017(96)01105-3.
Comparative analyses of the patterns of gastrointestinal nematode infections of first-grazing season cattle in Belgium are presented. The analysis involves 17 studies covering a 10 year period on 13 different farms in Flanders, Belgium. In all studies the calves were divided into an untreated control group, and one or two groups treated with chemoprophylactic systems. Two general infection levels emerged-'sub-clinical' (14 studies) and 'clinical' (three studies). The 'sub-clinical' infections were characterised by no clinical signs of parasitic gastroenteritis in the untreated control groups. Mean faecal egg counts remained low (less than 200), maximum pepsinogen levels only reached about 3500 mU tyrosine, and very small reductions in overall daily weight gain were observed compared with calves given chemoprophylaxis (less than 40 g day-1). Based on these results, on these 'sub-clinical' farms, chemoprophylaxis may not have been needed. In contrast, multiple salvage treatments of the control calf groups were required in the 'clinical' infections. Even with these salvage treatments mean faecal egg counts were high (more than 300), maximum pepsinogen levels were over 5500 mU tyrosine and there was a very large reduction in overall daily weight gain (more than 300 g day-1). However, it was not possible to predict either at turnout, or during the first month afterwards whether an infection on a particular farm would develop into a 'clinical' infestation. With the present data this prediction was possible from 8 weeks (Day 56) onwards, based on faecal egg counts and pasture larval contamination. It was also possible to predict using serum pepsinogen levels on Day 84. Therefore, one possible strategy for the effective control of gastrointestinal nematode infections of calves in temperate regions would be to evaluate faecal egg counts 2 months after turnout, and then only start treatment (i.e. metaphylaxis) if required.
本文对比利时首个放牧季节牛群的胃肠道线虫感染模式进行了比较分析。该分析涉及17项研究，涵盖了比利时弗拉芒地区13个不同农场的10年时间。在所有研究中，犊牛被分为未处理的对照组，以及一个或两个接受化学预防系统处理的组。出现了两种一般感染水平——“亚临床”（14项研究）和“临床”（3项研究）。“亚临床”感染的特征是未处理的对照组没有寄生性胃肠炎的临床症状。平均粪便虫卵计数保持较低水平（低于200），最大胃蛋白酶原水平仅达到约3500 mU酪氨酸，与接受化学预防的犊牛相比，总体日增重的降低非常小（低于40克/天）。基于这些结果，在这些“亚临床”农场，可能不需要进行化学预防。相比之下，在“临床”感染中，需要对对照组犊牛进行多次挽救性治疗。即使进行了这些挽救性治疗，平均粪便虫卵计数仍然很高（超过300），最大胃蛋白酶原水平超过5500 mU酪氨酸，总体日增重有非常大的降低（超过300克/天）。然而，在放牧开始时或之后的第一个月内，无法预测特定农场的感染是否会发展为“临床”感染。根据目前的数据，从第8周（第56天）起，根据粪便虫卵计数和牧场幼虫污染情况可以进行这种预测。在第84天使用血清胃蛋白酶原水平也可以进行预测。因此，在温带地区有效控制犊牛胃肠道线虫感染的一种可能策略是在放牧开始2个月后评估粪便虫卵计数，然后仅在需要时开始治疗（即群体预防）。
