Flukes (Black, Yellow, and White Grubs, Eye Flukes)


Commonly Infected Wildlife

Fish. The most commonly affected species are

  • Sunfish, bass, crappie, and yellow perch (black grubs)
  • Catfish, bass, bluegill, perch, and sunfish (yellow grubs)
  • Bluegill and crappie (white grubs)
  • Trout and many other fish species (eye flukes)

Is This Animal Infected?

Black grubs (also called “black spot disease”) causes the skin, fins, and flesh of affected fish to appear “peppered.”

Yellow grubs encysting in the flesh do not cause blackening and appear light yellow.

White grubs are found in the liver, kidney, and heart and do not affect the flesh.

Eye flukes cause cataracts and blindness in fish, and the fish are typically dark and in poor condition.

Fish Flukes
Oregon Department of Fish and Wildlife, Fish Health Section

Can I Get It?

No. There is no known risk of fluke infections to humans from U.S. freshwater game fish.

How Bad Can It Get?

Humans are not at risk for flukes from U.S. freshwater game fish.

Symptoms in Humans

None. People are not at risk.

Protect Myself and Others

Fillet may be unappetizing; trim away affected tissue. Consume fish fillets like any other, by properly cleaning, preparing, and cooking the fish to 145°F.

Safe for Pets?

Yes. There is no known health risk when fish are properly cooked.

What Causes It?

The larvae of various species of trematode flatworms (flukes). Common species include Uvulifer ambloplitis, Neascus spp., Clinostomum spp., and Diplostomulum spp.

Fluke larvae burrow into the flesh of the fish and form a cyst. The larvae only emerge when the fish is consumed by a fish-eating bird, typically a heron or a kingfisher.