Thomsen L E, Mejer H, Wendt S, Roepstorff A, Hindsbo O
Department of Veterinary Microbiology, Danish Centre for Experimental Parasitology, The Royal Veterinary and Agricultural University, Dyrlaegevej 100, DK-1870 Frederiksberg C, Denmark.
Vet Parasitol. 2001 Aug 1;99(2):129-46. doi: 10.1016/s0304-4017(01)00454-x.
This study was made to elucidate the transmission of nematode infections in outdoor pigs at different stocking rates during two consecutive seasons. Five pigs (Group 1A) inoculated with low doses of Oesophagostomum dentatum, Ascaris suum, and Trichuris suis and five helminth-naïve pigs (Group 1B) were turned out together in June 1996 on each of four pastures at stocking rates of 100, 240 (two pastures) and 576m(2) per pig, respectively. The pigs were slaughtered in early October, and pasture infectivity was subsequently measured using helminth-naïve tracer pigs (Tracer). In 1997, 10 helminth-naïve pigs were turned out on each pasture in May (Group 2) and again in August (Group 3), and allowed to graze for 12 weeks. The percentage of grass cover was reduced considerably at the high stocking rate in comparison to the other stocking rates. Transmission of all three helminths was observed on all pastures. In 1996, the O. dentatum faecal egg counts and worm burdens were significantly higher in pigs at the high stocking rate compared to pigs at the other stocking rates. O. dentatum did not survive the winter and pigs of Group 2 were inoculated with 3000 larvae each to reintroduce this parasite. Ascaris suum ELISA values and worm counts were highest at the high stocking rate in 1997 (Group 3). Transmission of T. suis was not significantly influenced by stocking rate. The results indicate that transmission of O. dentatum, and to some extent A. suum is influenced by stocking rate. However, both A. suum and T. suis eggs are still expected to constitute a high risk of infection on intensively used pastures where eggs may accumulate for years. The relationship between host density and helminth transmission seems more complex for grazing/rooting pigs than for grazing ruminants. This may be due to the differences in behaviour of the animals and the resulting differences in microclimate of the developing eggs/larvae.
本研究旨在阐明连续两个季节不同饲养密度下户外猪体内线虫感染的传播情况。1996年6月，将5头接种低剂量齿食道口线虫、猪蛔虫和猪鞭虫的猪（1A组）与5头未感染蠕虫的猪（1B组）分别以每头猪100、240（两个牧场）和576平方米的饲养密度放入四个牧场中。10月初将猪屠宰，随后使用未感染蠕虫的示踪猪（Tracer）测量牧场的感染性。1997年5月（2组）和8月（3组）在每个牧场分别放入10头未感染蠕虫的猪，让它们放牧12周。与其他饲养密度相比，高饲养密度下的草地覆盖率大幅降低。在所有牧场都观察到了三种蠕虫的传播。1996年，高饲养密度下猪的齿食道口线虫粪便虫卵计数和虫负荷显著高于其他饲养密度下的猪。齿食道口线虫无法越冬，给2组的猪每头接种3000条幼虫以重新引入这种寄生虫。1997年猪蛔虫ELISA值和虫数在高饲养密度下最高（3组）。猪鞭虫的传播未受饲养密度的显著影响。结果表明，齿食道口线虫的传播以及在一定程度上猪蛔虫的传播受饲养密度影响。然而，在集约化使用的牧场中，猪蛔虫和猪鞭虫的虫卵仍可能构成高感染风险，因为虫卵可能会累积数年。对于放牧/拱地的猪而言，宿主密度与蠕虫传播之间的关系似乎比放牧反刍动物更为复杂。这可能是由于动物行为的差异以及由此导致的发育中虫卵/幼虫微气候的差异。
