Franz's lawsuit seeks $100,000 from Shaw's and its parent company, Lettuce Entertain You Enterprises, contending the restaurant's staff was negligent in serving him improperly cooked fish.
But Carrol Symank, vice president of food safety for Lettuce Entertain You, said the tapeworm didn't come from Shaw's.
"We have done a thorough investigation and we're confident the restaurant is not the source," he said.
According to the Web site mayoclinic.com, tapeworms can measure up to 50 feet long.
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