Waghorn T S, Reynecke D P, Oliver A-M B, Miller C M, Vlassoff A, Koolaard J P, Leathwick D M
AgResearch Grasslands, Private Bag 11008, Palmerston North 4442, New Zealand.
N Z Vet J. 2011 Nov;59(6):279-86. doi: 10.1080/00480169.2011.610279.
To describe the seasonal pattern of development of third-stage infective larvae (L3) from eggs of Teladorsagia (=Ostertagia) circumcincta, Trichostrongylus colubriformis and Haemonchus contortus on pasture in the North Island of New Zealand.
Sheep faeces containing known numbers of eggs of all three nematode species were deposited on, or buried in, pasture plots at three sites, viz coastal Manawatu, Upper Hutt Valley, and East Cape hill country. Development was measured by recovering L3 from faeces, herbage and soil 28-31 days after deposition on 13-18 occasions, between January 2005 and July 2006. Analysis of the number of larvae recovered used a mixed model including number of eggs deposited, weight of faeces recovered (an assumed indicator of earthworm activity), site, contamination date, and position of deposited faeces, i.e. on the surface or buried.
There was a significant effect of contamination date on development of all three species, with maximum numbers of L3 developing between late spring (November) and early autumn (March), and minimum numbers in June and July. There were large differences between species, with H. contortus exhibiting a long period (April to October) where development was close to zero, whereas T. circumcincta developed to some extent all year round. Development of T. colubriformis was intermediate between the other two species. Burying faeces containing nematode eggs increased the number of L3 recovered compared with surface deposition (p ≤ 0.001), although there were a small number of exceptions involving only T. colubriformis. The weight of faeces recovered at harvest, which was assumed to be an indication of earthworm activity, was correlated with the number of L3 recovered for all species (p<0.001). In a separate analysis, earthworms were assumed to have been active if <5 g faeces remained at harvest. Where this occurred, the number of L3 of T. colubriformis and T.circumcincta recovered was reduced by 56% and 58%, respectively (p<0.001).
A marked seasonal pattern of development was observed for all three species, with the most larvae developing in spring-early autumn and the least in winter. This seasonal pattern was most pronounced in H. contortus and least obvious in T. circumcincta. Burying faeces containing eggs generally resulted in more L3 being recovered, whilst the apparent activity of earthworms resulted in fewer larvae being recovered.
描述新西兰北岛牧场中土生奥斯特他线虫（=环形泰勒虫）、蛇形毛圆线虫和捻转血矛线虫虫卵发育至第三期感染性幼虫（L3）的季节性模式。
将含有已知数量的上述三种线虫虫卵的羊粪便放置或埋入三个地点的牧场地块中，即沿海的马纳瓦图、上哈特谷和东开普山地。于2005年1月至2006年7月期间，在13 - 18个不同时间点，于粪便放置28 - 31天后，从粪便、牧草和土壤中回收L3以测定发育情况。对回收的幼虫数量进行分析时使用了混合模型，该模型包括所放置的虫卵数量、回收的粪便重量（假定为蚯蚓活动的指标）、地点、污染日期以及所放置粪便的位置，即放置在地表还是埋入地下。
污染日期对所有三种线虫的发育均有显著影响，L3的最大数量出现在晚春（11月）至初秋（3月）之间，而在6月和7月数量最少。不同线虫种类之间存在很大差异，捻转血矛线虫在较长时期（4月至10月）内发育接近零，而环形泰勒虫全年都有一定程度的发育。蛇形毛圆线虫的发育情况介于其他两种线虫之间。与地表放置相比，掩埋含有线虫虫卵的粪便可增加回收的L3数量（p≤0.001），不过有少数仅涉及蛇形毛圆线虫的例外情况。收获时回收的粪便重量（假定为蚯蚓活动的指标）与所有线虫种类回收的L3数量相关（p<0.001）。在另一项分析中，如果收获时剩余粪便<5克，则假定蚯蚓有活动。当出现这种情况时，回收的蛇形毛圆线虫和环形泰勒虫的L3数量分别减少了56%和58%（p<0.001）。
观察到所有三种线虫均有明显的季节性发育模式，春季至初秋发育的幼虫最多，冬季最少。这种季节性模式在捻转血矛线虫中最为明显，在环形泰勒虫中最不明显。掩埋含有虫卵的粪便通常会回收更多的L3，而蚯蚓的明显活动则会导致回收的幼虫数量减少。
