Examination of the migration of first instar larvae of the parasite OEstrus ovis (Linne 1761) [Diptera: OEstridae] in the upper respiratory tract of artificially infected lambs and daily measurements of the kinetics of blood eosinophilia and mucosal inflammatory response associated with repeated infection.

Twelve lambs were divided into two groups: Group C control, non-infected, and Group O infected once a week for 5 weeks with OEstrus ovis L1 through the same nostril. The first objective of this experiment was to check whether larvae moving through a given nostril remain in the same side nasal cavity or might to spread in both nasal cavities. It has been observed that larvae invade and spread through the entire nasal cavities. The only possible passage way between both sides is via the choanae and velum palatinum. The second objective was to follow the kinetics of blood eosinophilia. A primary peak in eosinophil numbers was noted 4 days following infection, with a higher peak following the second infection. After that, no major changes were seen. Nevertheless, the numbers of eosinophils were always higher than in control animals until the end of the follow-up. The third objective of the study was an enumeration of reactive cells (mast cells, globule leucocytes, and eosinophils) in the mucosae of the upper and lower respiratory tract after necropsy of the animals of the two groups. As observed in previous experiments, there was a large accumulation of these cells in mucosae of the upper respiratory tract. It was also worth noting a significant accumulation of eosinophils in the tissues of the trachea, bronchae and lungs even though OE. ovis was not present there. This "distant" eosinophilic reaction may have important consequences on patho-physiology of other parasites living in these locations: eosinophils have the potential to kill them even though these cells are not activated by their specific antigens.