Distribution and ecology of Clostridium botulinum in fish and aquatic environments of a tropical region Original Research Article

The distribution of Clostridium botulinum in sediments and fish from coastal and inland areas of India was investigated. Seventy-one samples of sediments from brackish water/freshwater farms on the west coast and from the seashores of both west and east coasts were analysed. The overall prevalence of C. botulinum in sediments was 21% and the predominant types were types C and D (18%) followed by type A (3%). Sixty-eight samples of wild and farmed shellfish samples from the west coast were examined. Fifteen samples (22%) harboured C. botulinum and the identified C. botulinum types included type C (9%), type D (9%) and type A (4%). Sixty-one samples representing cultivable fish from the west coast and east coast (20), trash fish from the west coast (30) and farmed fish from the west coast (11) were screened and C. botulinum was detected in four (20%), eight (27%) and two (18%) samples, respectively. An overall prevalence of 22% was found in fish. The identified C. botulinum types on the surfaces of wild fish included type D (8%), type C (6%), type A (6%) and type B (2%), whereas the intestine samples harboured types A (4%) and C (2%). In farmed fish, C. botulinum type C was detected in the intestine sample. The present study revealed that C. botulinum types C and D are the predominant types seen in fish and aquatic environments of the tropical Indian subcontinent.