What Do Worms in Tuna Look Like? A Helpful Guide

Tuna is one of the most popular fish consumed around the world. It’s prized for its delicious flavor and high nutritional content However, tuna is often eaten raw in dishes like sushi and ceviche which has led some to wonder – can tuna harbor parasitic worms? And if so, what do worms in tuna look like?

Let’s dive in and find out what types of worms can be found in tuna and how to identify them. We’ll also cover proper handling and prep methods to avoid potential issues.

Types of Worms in Tuna

There are a few main parasitic worms that can infect tuna fish

• Anisakis – Also called herring worm or whale worm. Nematode roundworms around 2 cm long. Can cause anisakiasis when ingested.

• Pseudoterranova – Type of roundworm or cod worm up to 5cm long. A common tuna parasite. May cause abdominal symptoms if eaten.

• Eustoma rotundatum – Tiny nematode worm less than 1 cm long. Generally benign if ingested.

• Hysterothylacium – Thin nematodes 1-3 cm long found in intestines and flesh. Not harmful to humans if eaten.

• Diphyllobothrium – Rare tapeworm in tuna which can infect humans if larva eaten. Causes diphyllobothriasis.

The most common tuna worms are Anisakidae roundworms, particularly Anisakis and Pseudoterranova species. Heavy infections may be visible, but light infections can easily go unnoticed.

What Do Tuna Worms Look Like?

Here’s how to identify the appearance of worms in tuna:

• Anisakis – Look like thin, cream-colored threads emerging from flesh. Often in coiled shape.

• Pseudoterranova – Slightly thicker roundworms with dark intestine visible inside body.

• Eustoma – Tiny white nematode larvae. Hard to see without microscope.

• Hysterothylacium – Very thin small worms attached to internal organs.

• Diphyllobothrium – Long segmented tapeworm with bulge on one end. Uncommon.

Unless heavily infected, most tuna worms are hard to notice by eye. Microscopic analysis is best for detection. Unusual lumps, bumps or holes in the flesh can indicate worms. Freezing can also kill worms, causing visible cysts.

Where Do Tuna Worms Come From?

Wild tuna pick up parasitic worms during their lifecycle by:

• Consuming smaller infected fish which contain worm larvae.

• Filter feeding on plankton containing worm eggs.

• Migrating through larva-contaminated waters.

Farmed tuna are less prone to worms when properly managed. Worm larvae can’t easily spread from fish to fish in controlled aquaculture.

Once inside a tuna, the worms burrow into the muscle tissue where they can survive for years until ingested by other predators like marine mammals or humans.

How to Tell If Tuna Has Worms

It can be challenging to detect worms in tuna meat, but here are some tips:

• Carefully examine flesh for visible worms which may look like threads emerging from meat.

• Look for small lumps or bumps under the skin which could be enclosed cysts.

• Spotting holes or lines in the flesh can indicate worm tunnels.

• Unusually soft or mushy meat consistency could mean heavy infection.

• Microscopic analysis or candling can help identify larvae not visible to the naked eye.

• Blood meat around internal organs likely indicates presence of worms.

If concerned about parasites, ensure tuna is frozen to appropriate temperatures and cooked thoroughly before consuming.

Can Humans Get Worms from Eating Tuna?

Eating undercooked or raw tuna can potentially transmit parasitic worms, though risks are generally low. Two main concerns:

• Anisakiasis – Anisakis worm larvae attach to gut lining causing nausea, cramps, and fever if eaten alive.

• Pseudoterranovosis – Usually mild illness causing abdominal pain, diarrhea, vomiting. Rarely serious.

Proper freezing or cooking tuna can kill any worms present and make it safe to eat. Symptoms may still occur from dead worms but are not infectious.

Overall, the occurrence of infectious tuna worms in commercial fish is very low due to modern freezing practices.

How To Kill Worms in Tuna

To eliminate any potential worms in tuna, there are two easy methods:

• Freezing – Store tuna at -4°F (-20°C) or below for 7 days to kill any parasites present.

• Cooking – Heating tuna to an internal temperature of 145°F (63°C) kills worms. Tuna turns opaque and flaky when fully cooked.

Other tips:

• Check with your fish supplier or restaurant that tuna was properly frozen before being served raw.

• Avoid cross-contamination by separating raw and cooked seafood in the kitchen.

• Discard any tuna with an unusual odor or appearance.

Following safe handling procedures minimizes any risk of contracting tuna worms.

Can Canned Tuna Have Worms?

Properly processed canned tuna is generally safe from infectious worm parasites. During manufacturing:

• Tuna is first frozen to kill any worms present.

• The processing temperatures used to cook and can tuna also destroy parasites.

• Canning prevents any new worm contamination of the cooked fish.

Unless cans are damaged, commercially canned tuna has virtually zero risk of containing harmful worms. The fish is pre-treated before sealing in the can to ensure safety.

The Takeaway

While the idea of worms in fish may be unpleasant, the reality is that modern freezing and handling practices make tuna very safe to consume. Parasitic infections from tuna are extremely rare, particularly from cooked or canned products. Practice basic seafood safety when preparing raw tuna at home. And don’t let concerns over worms stop you from enjoying the nutritional benefits of tuna!