绵羊胃肠道线虫季节动态的研究

本文采用粪便幼虫培养法和剖检过筛法研究了绵羊胃肠道线虫的季节动态.结果表明:成年羊胃肠道线虫的卵排出量或成虫寄生量4～6月出现一次明显的高峰,8、9月又出现一次较小的升高,一年的其它月份很低.羔羊粪便中最早检获虫卵是在7月上旬,8月下旬排卵量达高峰,此后,虫卵排出量相当低.剖检成年羊体内,捻转血矛线虫受阻幼虫百分率1～6月逐渐下降,7～12月逐渐上升,受阻率最高的是12月下旬.放牧地幼虫检查发现,感染性幼虫夏末秋初出现一次高峰,到翌年3、4月仍可检到少量的毛圆线虫幼虫.越冬试验证明,毛圆线虫的感染性幼虫能越冬.本文还提出了适合黑龙江省特点的有效防治措施的建议.

STUDIES ON THE SEASONAL INCIDENCE OF GASTRO-INTESTINAL NEMATODES IN SHEEP

The seasonal incidence of the gastro-intestinal nematodes of sheep was studied in Zhaodong county, Heilongjiang province. Results showed that the egg outputs or worm burdens of gastro-intestinal nematodes in adults rise highly from April to June in a Spring Rise, while another rise occurs in August and September. However, in summer and winter, egg counts and worm burdens are very low. Infective larvae were first found in lamb faeces incubated in early July and the peak of the egg outputs appeared in late August From then on, only a few larvae were found in the faeces. The percentage of the inhibited larvae of Haemoncus contortus decreased gradually from July to December gradually. In late December, up to 99.73% of the H. contortus population consisted of early fourth stage larvae (EL_4). The percentage of the inhibited larvae of Trichostrongylus spp. was much lower than that of H. contortus and its highest inhibited rate did not exceed 20%, as found in early October. Larva examination showed that infective larvae on herbage reached their peak in late September, and even in March and April of the next year a few infective larvae of Trichostrongylus spp. were still found. It was also found that eggs of H. contortus, Bunostomun sp., Oesophagostomun spp. and Trichostrongylus spp, can not overwinter on pasture whereas the infective larvae of Trichostrongylus spp. can. The results of these trials were discussed in detail and it was suggested that the optimal time of anthelmintic treatment be late December or early January.