You are likely to develop foodborne botulism when you eat food without cooking it enough to disable the Clostridium botulinum or its toxin. Clostridium botulinum is an 'anaerobic bacterium'(it can only grow in the absence of oxygen).So the growth of the bacteria and the formation of its poison tend to occur in products with low oxygen content and the right combination of storage temperature and preservatives. This happens most often in lightly preserved foods, eg fermented, salted or smoked fish and meat products and in inadequately processed home canned or home bottled low acid foods, eg vegetables.
Attribution: Avallain