An 18 year old male presented with acute onset descending paralysis of 3 days duration. There is also a history of blurring of vision for the same duration. On examination, the patient has quadriparesis with areflexia. Both the pupils are non-reactive. The most probable diagnosis is:
Diagnosis of botulism should be considered in patient with symmetric descending paralysis with bilateral cranial neuropathies in addition of following features:

Absent fever
Patient remains responsive
Heart rate normal or slow
Sensory deficit doesn’t occur except for blurred vision.

Remember: Neurologic signs and symptom of botulism:

Dysphagia
Dry mouth
Diplopia
Dysarthria
Upper limb weakness
Lower limb weakness
Blurred vision
Dyspnea
Poliomyelitis
Botulism
Diphtheria
Porphyria