Roepstorff A, Murrell K D
Danish Centre for Experimental Parasitology, Royal Veterinary and Agricultural University, Frederiksberg C, Copenhagen, Denmark.
Int J Parasitol. 1997 May;27(5):553-62. doi: 10.1016/s0020-7519(97)00023-4.
An increase in alternative outdoor pig production systems is occurring in Denmark, and this study was designed to elucidate the transmission patterns of Oesophagostomum dentatum and Hyostrongylus rubidus in pigs allowed to graze continuously on a pasture. A group of pigs was turned out in May 1993 (Year 1 of the study) and subsequently inoculated with low numbers of both helminths. These pigs were followed parasitologically until October by serial necropsy and sampling of faeces, grass and soil. A non-inoculated group of pigs was similarly followed on the same pasture in Year 2 (1994). Pasture infectivity was measured using helminth-naïve tracer pigs during all seasons. The pasture vegetation was rapidly destroyed by the pigs, resulting in a dirt lot by the autumn of Year 2. The area was soon contaminated with eggs, resulting in heavy pasture infectivity and increasing worm burdens in late summer; then the numbers of larvae declined markedly. In May of Year 2, newly exposed pigs became only lightly infected (mostly O. dentatum), and no transmission was observed in July-August of Year 2, probably due to an unusually dry summer and a lack of protecting vegetation. The results indicate that both O. dentatum and H. rubidus are very sensitive to environmental factors, because significant transmission occurred only under the most favourable conditions (summer combined with protecting vegetation as in Year 1). Transmission was severely reduced during the low temperatures experienced in the winter between Years 1 and 2 and during the dry summer of Year 2, when vegetation was lacking. Continuous grazing actually reduced transmission of O. dentatum and H. rubidus because of the reduction in vegetation. This, however, is not a desirable alternative farming system, because of its adverse environmental effects. This environmental impact may be mitigated by employment of a pasture rotation system in place of continuous grazing.
丹麦正在增加替代性户外养猪生产系统，本研究旨在阐明在牧场上持续放牧的猪中齿食道口线虫和红色猪圆线虫的传播模式。1993年5月（研究的第1年）放出一组猪，随后接种少量的这两种蠕虫。通过连续剖检以及对粪便、草和土壤进行采样，对这些猪进行寄生虫学跟踪，直至10月。在第2年（1994年），在同一牧场上对一组未接种的猪进行类似的跟踪。在所有季节使用未感染蠕虫的示踪猪来测量牧场的感染性。猪很快就把牧场植被破坏了，到第2年秋天形成了一个脏污的场地。该区域很快被虫卵污染，导致夏末牧场感染性增强且蠕虫负荷增加；然后幼虫数量显著下降。在第2年5月，新接触的猪仅受到轻度感染（主要是齿食道口线虫），在第2年7 - 8月未观察到传播，可能是由于夏季异常干燥且缺乏保护性植被。结果表明，齿食道口线虫和红色猪圆线虫对环境因素都非常敏感，因为只有在最有利的条件下（如第1年夏季与保护性植被相结合）才会发生显著传播。在第1年和第2年之间的冬季低温期间以及第2年植被缺乏的干燥夏季，传播严重减少。由于植被减少，持续放牧实际上减少了齿食道口线虫和红色猪圆线虫的传播。然而，这并不是一个理想的替代养殖系统，因为它会产生不利的环境影响。采用轮牧系统代替持续放牧可能会减轻这种环境影响。
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