Roepstorff A, Bjørn H, Nansen P, Barnes E H, Christensen C M
Danish Centre for Experimental Parasitology, Royal Veterinary and Agricultural University, Frederiksberg, Copenhagen, Denmark.
Int J Parasitol. 1996 Apr;26(4):399-408. doi: 10.1016/0020-7519(96)00006-9.
This paper describes the worm populations in pigs experimentally infected by trickle infections with different dose levels of the nodular worm, Oesophagostomum dentatum. Four groups each of 20 helminth naïve pigs, 10-12 weeks old, were inoculated with 0 (group 1), 100 (group 2), 1000 (group 3), or 10,000 (group 4) infective larvae twice weekly, and the pigs were killed after 10-13 weeks. No overt clinical signs were observed, and only group 4 had slightly lower food conversion rate (P < 0.05) than the controls. Faecal egg counts revealed that the nodular worms in pigs of groups 2 and 3 had a short prepatent period (3-4 1/2 weeks) and a fairly stable egg output, while the worms in the pigs of group 4 had prepatent periods of 3-10 weeks and low, unstable egg excretion. The mean worm burdens increased with the dose rate (group 2: 929 worms; group 3: 7467 worms; group 4: 19,847 worms), but detailed analyses of the worm populations from 10 pigs from each of the infected groups revealed a clear dose-dependency in worm recovery, percentage adult worms, worm lengths and female fecundity, as all these measures declined significantly with increasing dose level. The adult worms seemed to be shorter and less fertile when they were located posteriorly to their predilection site, and especially in group 4 many stunted infertile adults measuring only 2-5 mm were found in the posterior half of the colon, but there were no indications of worm expulsion. Superimposed on the main experiment was a cohort study in which 4 pigs of group 3 were given a single dose of 1000 pyrantel resistant larvae at day 56 (all other larvae were pyrantel sensitive), treated with 28 mg pyrantel per kg body weight at day 85 and killed at day 90. Appropriate control groups were included. The mean establishment of the cohort was similar to previously uninfected controls, but between-animal variation was much higher in the trickle infected group.
本文描述了通过不同剂量水平的结节虫——齿状食道口线虫进行持续感染实验感染猪的蠕虫种群情况。将四组每组20头10 - 12周龄未感染蠕虫的猪，分别每周两次接种0（第1组）、100（第2组）、1000（第3组）或10000（第4组）条感染性幼虫，10 - 13周后将猪处死。未观察到明显的临床症状，只有第4组的食物转化率略低于对照组（P < 0.05）。粪便虫卵计数显示，第2组和第3组猪体内的结节虫潜伏期较短（3 - 4.5周）且产卵量相当稳定，而第4组猪体内的蠕虫潜伏期为3 - 10周，且排虫卵量少且不稳定。平均蠕虫负荷随剂量率增加而增加（第2组：929条蠕虫；第3组：7467条蠕虫；第4组：19847条蠕虫），但对每个感染组的10头猪的蠕虫种群进行详细分析发现，蠕虫回收率、成虫百分比、蠕虫长度和雌虫繁殖力存在明显的剂量依赖性，因为随着剂量水平的增加，所有这些指标均显著下降。当成虫位于其偏好部位后方时，似乎较短且繁殖力较低，特别是在第4组中，在结肠后半部发现许多发育不良的不育成虫，长度仅为2 - 5毫米，但没有蠕虫排出的迹象。在主要实验之上进行了一项队列研究，其中第3组的4头猪在第56天接种1000条对吡喹酮耐药的幼虫（所有其他幼虫对吡喹酮敏感），在第85天以每千克体重28毫克吡喹酮进行治疗，并在第90天处死。纳入了适当的对照组。该队列的平均定植情况与先前未感染的对照组相似，但在持续感染组中动物个体间的差异要高得多。
