COMPARATIVE PHYSIOPATHOLOGY OF ESTRUS-OVI S (LINNE 1761) MYIASIS IN MAN AND ANIMALS

Oestrus ovis is an agent of a naso-sinusal myiasis of sheep and goats. This infestation is very frequent and induces clinical signs of rhini tis and sinusitis which are sometimes severe. The pathogenic role of t his parasite has been explained until now exclusively because of its s ize, hooks and spines. Some recent studies indicate the involvement of local hypersensitivity with recruitement of numerous mast cells and e osinophils. Histological nasal mucosal tissue section examination from both sheep and goats showed the presence in considerable numbers of e osinophils and mast cells in lambs receiving single doses of artificia l infection were twice as many, as the number in control group. In ani mals subjected to multiple artificial infection the serous mast cell p opulation increased 11-folds and that of mucous mast cells by 5-7 fold s when compared with non-infected control groups. Similarly, the eosin ophil counts were 17, 29 and 58 times greater in nasal septum, turbina tes and sinus in infected groups than their control conter mates. The findings hence suggest that single infection is apparently tolerated b y the host while massive cellular recruitement characterizes the cellu lar responses vis Li vis multiple exposure. These reactive cells are l ocalized mainly in the chorion layer just beneath the epithelium with only very few cells in the sub-mucosa level. It is, therefore, presume d that these cells are responsible in limiting parasite (larval) popul ations and in sustaining the hypersensitivity phenomenon at the site o f tissue insult during infection. In naturally infected sheep the mean number of mast cells is only twice that present in parasite free anim als. This result is remarkably different from that obtained in repeate d artificial infections, probably associated to the difference in cell ular response between adult sheep and lambs. It may also possibly expl ained as resulting from the immunodeficiency induced by parasite antig ens.Human beings may be accidently infected Lai vm are deposited by ad ult flies into cunjunctival sacs. Clinical signs of this zoonosis indi cate that the pathophysiological processus are different than in anima ls. Examination of such cases did not confirm the existence of an acco mpanying allergic reaction in the process.