In the lawsuit filed Monday, Anthony Franz said he ordered salmon salad for lunch from Shaw's Crab House in 2006 and fell violently ill. He later passed the giant parasite, which a pathologist determined came from undercooked fish, such as salmon.
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.