Epidemiology, chronobiology and taxonomic updates of Rhinoestrus spp. infestation in horses of Sardinia Isle, Western Mediterranean (Italy).

From January to December 2008, 265 horses slaughtered in Sardinia (Italy) were examined for the presence of Rhinoestrus spp. (Diptera: Oestridae) through the examination of the nasal cavities and pharynges. Larvae were detected in 49% of the horses, with a mean intensity of infestation of 16.09 and abundance of 7.95. A total of 2108 larvae were collected, 66% of which were classified in first instar (L1), 22% in second instar (L2) and 12% in third instar (L3). The most frequent localization of larvae was the ethmoid, while the less one the larynx. According to the dynamics of Rhinoestrus larval stages, three periods in the chronobiology can be considered, the diapause (September-February) characterized by an absolute prevalence of first larval stage; the active phase of the endogenous phase (February-September) with an increase in the percentages of L2 and L3, and the exit phase (May-September), pointed by a further increase of L1. Morphological examination of L3 larvae revealed the presence of the Rhinoestrus purpureus features in 8% of the examined larvae, of 8% of the Rhinoestrus usbekistanicus features, while in 84% of the larvae were evidenced intermediate features. Contrastingly biomolecular analysis of the COI gene of the larvae evidenced uniformity at genetic level, confirming the presence of a unique species in the Mediterranean area. The results of the present paper, reveal the wide diffusion of rhinoestrosis among Sardinian horses, and suggest the need for applying appropriate control measures. Chemotherapy should be very useful if administered during the diapause period, for reducing the presence of L1 stages and interrupting thus the life cycle of this myiasis.