Dever M L, Kahn L P, Doyle E K, Walkden-Brown S W
School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia; CRC for Sheep Industry Innovation, CJ Hawkins Homestead, University of New England, Armidale, NSW 2351, Australia.
School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia.
Vet Parasitol. 2016 Jan 30;216:23-32. doi: 10.1016/j.vetpar.2015.11.017. Epub 2015 Dec 2.
The hypothesis tested in this experiment was that Trichostrongylus colubriformis infection would reduce growth rates of grazing meat-breed lambs; however production loss would be reduced by suppression of the host immune response. The experiment had a 3×2 factorial design using 6-7 month old meat-breed lambs which remained uninfected or infected (IFY) with 2000 or 4000 T. colubriformis L3/week for 12 weeks and were immunosuppressed (SUPY) using methylprednisolone acetate once weekly or remained non-immunosuppressed (SUPN). Immunosuppression increased worm egg counts (WEC) of infected lambs (SUPY 2421 eggs per gram (epg), SUPN 1154 epg on day 84, p<0.05) and T. colubriformis burdens (p<0.05-0.10) and reduced circulating eosinophils (p<0.05 on days 11, 42, 56 and 84) and intestinal total antibody titres (p<0.02). There was a significant (p<0.05) interaction between the main effects of infection and immunosuppression with infection having a larger negative effect on the liveweight of non-immunosuppressed lambs. The immunological response of the host to T. colubriformis infection accounted for 75% of the overall cost of infection (3.1kg) with the majority of this cost occurring during the first 35 days of infection. In contrast, most of the cost associated with the direct effect of infection occurred after day 35. These results confirm in grazing meat-breed lambs that the host's immunological response to T. colubriformis infection is the major component of production loss.
本实验所检验的假设是，蛇形毛圆线虫感染会降低肉用品种放牧羔羊的生长速度；然而，通过抑制宿主免疫反应可减少生产损失。实验采用3×2析因设计，使用6至7月龄的肉用品种羔羊，这些羔羊保持未感染状态，或每周感染2000或4000条蛇形毛圆线虫第三期幼虫（L3），持续12周，并每周一次使用醋酸甲泼尼龙进行免疫抑制（SUPY），或保持非免疫抑制状态（SUPN）。免疫抑制增加了感染羔羊的虫卵计数（WEC）（第84天，SUPY为每克2421个虫卵（epg），SUPN为1154 epg，p<0.05）和蛇形毛圆线虫负荷（p<0.05至0.10），并减少了循环嗜酸性粒细胞（第11、42、56和84天，p<0.05）和肠道总抗体滴度（p<0.02）。感染和免疫抑制的主要效应之间存在显著（p<0.05）交互作用，感染对非免疫抑制羔羊的体重有更大的负面影响。宿主对蛇形毛圆线虫感染的免疫反应占感染总成本（3.1千克）的75%，其中大部分成本发生在感染的前35天。相比之下，与感染直接效应相关的大部分成本发生在第35天之后。这些结果证实，在肉用品种放牧羔羊中，宿主对蛇形毛圆线虫感染的免疫反应是生产损失的主要组成部分。
