(COLORADO) — Colorado Parks & Wildlife (CPW) is alerting anglers of a rare degenerative muscle disease known as, Sandy Flesh disease, confirmed in a single walleye caught in the fall of 2022 at Lake Pueblo State Park.

Although myofibrogranuloma is not believed to be transmittable to humans, CPW warns against the consumption of walleye suspected of infection. Anglers are asked to report infected fish to CPW with good, high-resolution photos for the Aquatic Animal Health Laboratory to analyze.

Anglers who discover fish with Sandy Flesh disease should not discard the entrails back into the lake. They should be disposed of with household waste or buried, according to CPW.

“It’s important that walleye anglers be aware and carefully inspect their catch when they are cleaning them,” stated Carrie Tucker, CPW aquatic biologist in Pueblo.

Fish with the disease look normal on the outside. Sandy Flesh can only be found when a fish is cleaned, stated CPW. Areas of the filet will look semi-translucent or yellowish brown with knotted muscle fibers. It may look granular with mineral deposits or even opaque. The tissue can resemble meat with freezer burn.

Sandy Flesh disease primarily impacts older walleye, but there have been a few cases of infected yellow perch among others, said CPW. The cause of Sandy Flesh and means of transmission are unknown, per CPW. 

CPW says Sandy Flesh disease has been known for decades, but it is the first time it has been found in Colorado.

“It’s not a shock that it has reached Colorado since it occurs in so many neighboring states, but it is unfortunate,” said Tucker. “We don’t expect it to have a big impact because it typically only shows up in a small number of older walleye.

Typically, the disease occurs in the Midwest, particularly in North and South Dakota, Minnesota, Wisconsin and Nebraska. It has spread to the West including in Utah, Idaho, Wyoming and now Colorado, according to CPW.