Descriptive epidemiology of a scabies epidemic in chamois in the Dolomite Alps, Italy

In 1995, the hitherto Sarcoptes-free alpine chamois (Rupicapra rupicapra) of the Dolomite Alps (Italy) were affected by scabies for the first time after the spread of the disease from a neighbouring focus in Austria. Since then, four Agencies cooperated to warrant monitoring of the spatial and temporal progress of the outbreak and further active surveillance was carried out within an intensive study area. In ten years, 15 meta-populations numbering 10,000 chamois and 210,000 ha were encompassed with a maximum distance of 55 km from the index case. "Oil spot" advancement of the epidemic was observed together with "jumps" of 9 to 20 km followed by spreading of the infection to the intervening population units. Demographic decline of the four meta-populations so far affected for a minimum of six years ranged between 49 and 77% (x = 62.5 +/- 13.5), whereas similar post-epidemic densities of 1.1 to 1.7 heads/100 ha (x = 1.5 +/- 0.27) were recorded. Contiguous resistant and sensitive herds with similar pre-epidemic density were detected on a smaller population scale, suggesting complementary mechanisms intervening besides density-dependence as determinants of the outbreak outcome. No sex or age class showed a higher sensitivity to scabies out of a sample of 1,696 infected chamois. A peak prevalence of free-ranging chamois bearing overt scabietic lesions was observed in January and February. Cases were only sporadically diagnosed in other sympatrc wild ruminants (Cervus elaphus, Capreolus capreolus and Ovis gmelini musimon), whereas all four alpine ibex (Capra ibex ibex) herds living in the surveyed area suffered from scabies-induced decline.