Avian botulism and the high prevalence of Clostridium botulinum in the Norflok Broads.

An account is given of a severe outbreak of type C botulism in waterfowl that occurred on the Norfolk Broads during the exceptionally warm summer of 1975. Forty-five mud samples were collected from 22 well distributed aquatic sites representing a considerable proportion of the total number of Broads. All samples except one (ie, 97-8 per cent) were shown to contain Clostridium botulinum and 58 per cent contained more than one type of the organism. Types B, C and E were demonstrated in 62-2 per cent, 51-1 per cent and 60 per cent of samples respectively. Recent surveys, made by identical methods, of aquatic environments in the London area and the Camargue (France) showed prevalences of Cl botulinum of 72-5 per cent and 4-5 per cent respectively. It seems likely that the Norfolk Broads will continue to present a risk to waterfowl from botulism in future hot summers.