Botulism is caused by botulinum toxin, a poison produced by the bacterium Clostridium botulinum. The organism is common in the soil and aquatic sediments and can survive in these environments as a resistant spore.
The 3 main types of botulism are:
intestinal botulism (which is due to proliferation of the organism in the gut)
Symptoms often begin with blurred or double vision and difficulty in swallowing and speaking. In foodborne botulism there may also be diarrhoea and vomiting. The disease can progress to a more generalised paralysis that includes the arms, legs, trunk and respiratory muscles.
Most cases make a full recovery, but the recovery period can be many months.The disease can be fatal in 5 to 10% of cases.
More information about botulism is available on NHS Choices.