Implications of botulism outbreaks in gulls (Larus ridibundus) on the Watershed Management of Lake Kinneret (Israel)

Lake Kinneret (Israel), which currently supplies 30% of the national water demands (of which 50% is for domestic purposes), is also utilized for commercial fishery, recreation, and tourism. The measures taken to prevent pollution include, among others, sewage and fish pond waste removal, and burial of industrial and household solid wastes at established garbage dumps. On January 13, 1985, hundreds of dead and moribund gulls (Larus ridibundus) were observed on the shoreline and water surface at the northwest part of the lake, and around the northern garbage dump site. Sick birds exhibited signs that the nervous system was involved, i.e., paralysis of the wings and of the feet, and limberneck. Routine analyses ruled out the possibility that the poisoning was due to pesticides or an infective agent. Botulism intoxication was suspected and type C‐botulism toxin was identified in the serum of moribund birds. This is the first record of a botulism outbreak in waterfowl in Israel. The total mortality was approximately 3000–4000 gulls, of which 1200 dead birds were collected and burnt. Investigations revealed that at a garbage dump situated in the vicinity of the lake, waste products of a chicken slaughter house were not buried as required by formal regulations. Examination of lake water, sediments, and vegetations for possible contamination by botulism toxin were negative. The implications of the outbreak on the environment are discussed.