Emergency oral rabies vaccination of foxes in Italy in 2009-2010: identification of residual rabies foci at higher altitudes in the Alps

Following a resurgence of fox rabies in northeastern Italy in 2008-2009, two emergency oral rabies vaccination (ORV) campaigns were performed in the Alpine mountain ranges in 2009 and 2010 using aerial distribution to prevent the disease from spreading further inland. Vaccine baits were distributed only below the freezing point altitude, 1000 m above sea level (a.s.l.) in December 2009-January 2010 and 1500 m a.s.l. in April-May 2010, to avoid repeated freeze-thaw cycles. Spatial analysis unexpectedly identified fox rabies hotspots above the threshold altitudes, probably representing local residual rabies foci which may have contributed to maintaining the infectious cycle in areas not vaccinated at higher altitudes. Based on the results obtained, in May 2010, the second ORV campaign was extended to include threshold altitudes of up to 2300 m a.s.l. to eliminate residual foci. The observations made may help in the formulation of ORV strategies in countries sharing similar topographical features.