Epidemiology and control of sheep nasal bot (Oestrus ovis)

Live cycle of Oestrus ovis is very surprising: larvae accumulate nutriments for pupariation, emergence of adults, mating, looking for Suitable host for larviposition and larvae-laying. Adults assume only extension of infection and reproduction. The nutrition is in charge of larvae. Recent epidemiological data have clearly shown what are the periods of risk of infection, then it is easier to use drugs with more or less residual antiparasitic activity. In Northern Mediterranean regions, sheep has to be treated twice during the summer. The first one is therapeutic using closantel in the summer (July-August), it is repeated two months later. This protocol is very efficient and each treatment allows a 4 to 6 weeks protection. In Southern Mediterranean region, control is more difficult due to permanent activity of flies infecting animals nearly all around the year. As risks of infection are permanent, treatments have to be repeated regularly; The residual activity of closantel allows to have a long period between treatments, macrocyclic lactones don't have so long residual activity (injectable ivermectin) or this efficacy is not known (doramectin and moxidectin) or not existing (oral ivermectin). Nevertheless, these drugs have a broader spectrum of activity mainly on gastro-intestinal and respiratory helminths. Finally, as for other parsitic infections, control of aestrosis has to be adapted to local climatic and biological conditions in order to be the most efficient.