Shutt D A, Smith A I, Wallace C A, Connell R, Fell L R
Department of Agriculture, Hawkesbury Agricultural Research Unit, Richmond, N.S.W.
Aust J Biol Sci. 1988;41(3):297-301. doi: 10.1071/bi9880297.
Cutaneous myiasis in sheep arising from the activity of Lucilia cuprina larvae can result in significant physiological changes in susceptible animals. The stress imposed on the pituitary-adrenal axis of the sheep in response to myiasis and acute restraint is the subject of this investigation. Merino wethers were exposed to handling restraint, and blood sampling, during examination for blowfly strike; where necessary, they were treated for cutaneous myiasis. Significant changes in the plasma concentrations of immunoreactive beta-endorphin (beta-EP), ACTH and cortisol were found in sheep with extensive myiasis, as compared with unstruck sheep or those with only localized myiasis. In five susceptible sheep with extensive cutaneous myiasis, mean plasma levels of beta-EP, ACTH and cortisol were 307 +/- 71 pg ml-1, 953 +/- 58 pg ml-1 and 232 +/- 46 nmol l-1 respectively, compared with 818 +/- 89 pg ml-1, 641 +/- 41 pg ml-1 and 107 +/- 17 nmol l-1 in six unstruck sheep handled similarly. Whereas significant increases in plasma ACTH and cortisol can result from pituitary-adrenal responses to acute emotional or surgical stress, and are usually accompanied by a concomitant release of beta-EP from the pituitary, the present findings indicate a marked reduction in beta-EP levels and a significant increase in ACTH and cortisol in sheep following blowfly strike and acute handling restraint. This result suggests that cutaneous myiasis in susceptible sheep can alter the pituitary-adrenal response to acute restraint stress, and this could occur either by an alteration of precursor processing in the pituitary or by the selective release of ACTH.
由铜绿蝇幼虫活动引起的绵羊皮肤蝇蛆病可导致易感动物出现显著的生理变化。本研究的主题是绵羊在应对蝇蛆病和急性束缚时垂体 - 肾上腺轴所承受的应激。美利奴阉羊在检查羊蝇侵袭时接受处理束缚和采血；必要时，对它们进行皮肤蝇蛆病治疗。与未受侵袭的绵羊或仅有局部蝇蛆病的绵羊相比，患有广泛蝇蛆病的绵羊血浆中免疫反应性β - 内啡肽（β - EP）、促肾上腺皮质激素（ACTH）和皮质醇的浓度有显著变化。在五只患有广泛皮肤蝇蛆病的易感绵羊中，β - EP、ACTH和皮质醇的平均血浆水平分别为307±71 pg/ml、953±58 pg/ml和232±46 nmol/L，而在六只同样接受处理的未受侵袭绵羊中，其水平分别为818±89 pg/ml、641±41 pg/ml和107±17 nmol/L。虽然垂体 - 肾上腺对急性情绪或手术应激的反应可导致血浆ACTH和皮质醇显著增加，且通常伴随着垂体释放β - EP，但目前的研究结果表明，在羊蝇侵袭和急性处理束缚后，绵羊的β - EP水平显著降低，ACTH和皮质醇显著增加。这一结果表明，易感绵羊的皮肤蝇蛆病可改变垂体 - 肾上腺对急性束缚应激的反应，这可能是由于垂体前体加工的改变或ACTH的选择性释放所致。
