Dorchies P
Ecole Nationale Vétérinaire de Toulouse.
Bull Acad Natl Med. 1997 Apr;181(4):673-83; discussion 683-4.
Oestrus ovis is an agent of a naso-sinusal myiasis of sheep and goats. This infestation is very frequent and induces clinical signs of rhinitis and sinusitis which are sometimes severe. The pathogenic role of this parasite has been explained until now exclusively because of its size, hooks and spines. Some recent studies indicate the involvement of local hypersensitivity with recruitment of numerous mast cells and eosinophils. Histological nasal mucosal tissue section examination from both sheep and goats showed the presence in considerable numbers of eosinophils and mast cells in lambs receiving single doses of artificial infection were twice as many as the number in control group. In animals subjected to multiple artificial infection the serous mast cell population increased 11-folds and that of mucous mast cells by 5-7 folds when compared with non-infected control groups. Similarly, the eosinophil counts were 17, 29 and 58 times greater in nasal septum, turbinates and sinus in infected groups than their control counter mates. The findings hence suggest that single infection is apparently tolerated by the host while massive cellular recruitment characterizes the cellular responses vis à vis multiple exposure. These reactive cells are localized mainly in the chorion layer just beneath the epithelium with only very few cells in the sub-mucosa level. It is, therefore, presumed that these cells are responsible in limiting parasite (larval) populations and in sustaining the hypersensitivity phenomenon at the site of tissue insult during infection. In naturally infected sheep the mean number of mast cells is only twice that present in parasite free animals. This result is remarkably different from that obtained in repeated artificial infections, probably associated to the difference in cellular response between adult sheep and lambs. It may also possibly explained as resulting from the immunodeficiency induced by parasite antigens. Human beings may be accidently infected. Larvae are deposited by adult flies into conjunctival sacs. Clinical signs of this zoonosis indicate that the pathophysiological processus are different than in animals. Examination of such cases did not confirm the existence of an accompanying allergic reaction in the process.
羊狂蝇是绵羊和山羊鼻-鼻窦炎性蝇蛆病的病原体。这种感染非常常见，会引发鼻炎和鼻窦炎的临床症状，有时症状较为严重。迄今为止，一直认为这种寄生虫的致病作用完全是由于其大小、钩和刺。最近的一些研究表明，局部超敏反应与大量肥大细胞和嗜酸性粒细胞的募集有关。对绵羊和山羊的鼻黏膜组织切片进行组织学检查发现，接受单剂量人工感染的羔羊中，嗜酸性粒细胞和肥大细胞数量相当多，是对照组数量的两倍。与未感染的对照组相比，多次人工感染的动物中，浆液性肥大细胞数量增加了11倍，黏液性肥大细胞数量增加了5至7倍。同样，感染组鼻中隔、鼻甲和鼻窦中的嗜酸性粒细胞计数分别比对照组高17倍、29倍和58倍。因此，研究结果表明，单次感染时宿主显然能够耐受，而多次接触时大量细胞募集则是细胞反应的特征。这些反应性细胞主要位于上皮层下方的绒毛层，黏膜下层仅有极少数细胞。因此，可以推测这些细胞负责限制寄生虫（幼虫）数量，并在感染期间维持组织损伤部位的超敏反应现象。在自然感染的绵羊中，肥大细胞的平均数量仅为未感染动物的两倍。这一结果与多次人工感染的结果明显不同，可能与成年绵羊和羔羊细胞反应的差异有关。这也可能是由于寄生虫抗原诱导的免疫缺陷所致。人类可能会意外感染。成虫将幼虫产在结膜囊中。这种人畜共患病的临床症状表明，其病理生理过程与动物不同。对这类病例的检查未证实该过程中存在伴随的过敏反应。
