Smith H J
Can J Comp Med. 1974 Apr;38(2):185-92.
By placing parasite-free calves in paddocks grazed by infected animals for 18 day periods at various times during the previous season it was shown that eggs of Ostertagia ostertagi, Cooperia oncophora and Nematodirus helvetianus deposited on pastures from early July to October of one year were able to survive in the Maritime area of Canada over winter either as eggs and/or larvae and contribute to residual infections on these pastures the following spring. The greatest deposition and/or survival of those eggs that were shed on pasture occurred in August and September for Cooperia and in September and October for Ostertagia. Greatest deposition of Nematodirus occurred in July and August and relatively few Nematodirus eggs shed in late September or early October were infective early in the next season. The number of generations of worms per year was low, ranging from one to two or perhaps three per year depending on the species. There was a delay in the maturation of many worm eggs. Residual overwintering infections play a significant role in the establishment of initial infections each summer in susceptible stock. These animals recontaminate the pastures leading to the subsequent development of large numbers of infective larvae by late summer and autumn.
通过在前一季的不同时间将未感染寄生虫的犊牛放置在被感染动物放牧过的围场中18天，结果表明，在加拿大沿海地区，一年中7月初至10月沉积在牧场上的奥斯特他线虫、牛古柏线虫和瑞士细颈线虫的卵能够以卵和/或幼虫的形式越冬，并在次年春天导致这些牧场上的残留感染。库柏线虫卵在牧场上的最大沉积和/或存活发生在8月和9月，奥斯特他线虫则在9月和10月。细颈线虫的最大沉积发生在7月和8月，9月下旬或10月初排出的细颈线虫卵在下一季早期感染性相对较低。每年的蠕虫代数较少，根据物种不同，每年从一代到两代，或者可能三代。许多蠕虫卵的成熟存在延迟。残留的越冬感染在每年夏天易感家畜初次感染的建立中起重要作用。这些动物再次污染牧场，导致夏末和秋季大量感染性幼虫的后续发育。
