Descriptive study of an avian pox outbreak in wild red-legged partridges (Alectoris rufa) in Spain

This study describes the dynamics and epidemiology of an outbreak of avian pox in free-living, red-legged partridges (Alectoris rufa) in southern Spain. Between March 2000 and January 2001, 115 free-living, red-legged partridges (70 juveniles, 45 adults) were captured and radio-tagged. This, together with the necropsy of 44 carcasses (10 juveniles, 34 adults) found in the study area, and the inspection of 108 shot birds (74 juveniles, 34 adults) after a hunting drive in October, permitted a close monitoring of the course of the disease. Forty-one per cent of radio-tagged juveniles but none of 45 radio-tagged adults showed pox-like lesions at the time of capture, recapture, or necropsy. At least 40% of the juveniles that survived into the hunting season, but only 2.9% of the adults inspected at the same time, showed lesions suggestive of infection with avian poxvirus. The survival of juveniles during the peak of the outbreak was much lower than that of the adults, but we found no significant differences between the survival probabilities of juvenile partridges with and without pox-like lesions. Nevertheless, some birds may have developed lesions after their capture. The occurrence and course of the disease in a managed area with intense predator control underlines the need for studies on the combined influence of diseases and predators on population dynamics. Also the need for early detection of diseases for the management of game species is emphasized.