Abstract: To make clear the area of sheep nasal flies maggots infection and the pathological changes of the disease by performing an infection survey and pathology study of Oestrus ovis in the loess plateau area in Shanxi province in spring and autumn. 307 samples were dissected to check the infection status of nasal flies maggots larvae, while histopathology methods were used to observe pathological changes. And take the infection of sheep nasal mucosa, retropharyngeal lymph nodes, brain and lung histologic examination. 34 cases were detected in 157 sampled cases in spring 22% detection rate; 70 in 150 were detected in autumn 47% detection rate; the average infection rate was 34%. The pathological changes are mainly manifested as follows: nasal mucosa appeared different injury and proliferative inflammation, retropharyngeal lymph node inflammatory cells were infiltrated, and some lungs appeared emphysema, brain tissue edema. Immunohistochemistry results showed that compared with no parasite detected cases, the quantity of IgA secretory cells and IgG secretory cells in parasites detected cases was increased in the retropharyngeal lymph nodes of sheep, especially in lymph node medulla.

Key words: Oestrus ovis; epidemiology; pathology; immunohistochemistry