The 5cm long worm, which had a red tip, was still wriggling when Kyreen Fields made the unwelcome discovery in the £2.74 breaded haddock package.
A spokeswoman for the retailer told FoodManufacture.co.uk: “The customer has returned the fish and our team are looking into it.
‘Apologise for any inconvenience’
“The store has also given the customer a full refund to apologise for any inconvenience caused.”
The 69-year old shopper told the Mirror: “It is horrible. I’ll never eat fish again.
“At my age that is all I eat because I don’t eat meat but I haven’t been able to eat much of anything since seeing the worm.”
Fields bought the fish on Easter Sunday and was about to cook it when she spotted the live worm.
What type of worm
Meanwhile, the retailer is probing what type of worm contaminated the fish and how it gained access to the packaging.
Seafood Health Facts confirmed there are two types of parasitic worms that can infect humans: Anisakiasis and Tapeworm infections.
Anisakiasis is caused by ingesting the larvae of several types of roundworm, which are found in saltwater fish such as cod, plaice, halibut, rockfish, herring, pollock, sea bass and flounder.
Tapeworm infections occur after ingesting the larvae of diphyllobothrium. The larvae is found in freshwater fish such as pike, perch and anadromous (fresh-saltwater) fish such as salmon.
There was no suggestion either type of worm was discovered by the Lanarkshire shopper.
Meanwhile, read our list of unexpected discoveries in food products ranging from other fish products to baby food and from bananas to tinned tomatoes in the box below.
Venomous spiders and cocaine were just two of the items which shocked shoppers and retail staff.
- Photograph courtesy of the Scottish Daily Record.
Unexpected discoveries in food products
- Baby food recalled due to moth larvae, November 2015
- Aldi probes dead caterpillar in tomato tin, July 2015
- Tesco worker finds cocaine in bananas, July 2015
- Morrisons’ shopper finds tongue-eating parasite in fish, November 2014
- Venomous spider strikes again, in Waitrose bananas, October 2014