Each fall, I receive a call or e-mail regarding “white looking maggots” in the breast meat of ducks being cleaned. This year is no different. I thought I would take a moment to discuss this occurrence.

Photo by James Runningen; The USGS-National Wildlife Health Center Field Manual of Wildlife Diseases: General Field Procedures and Diseases of Birds

Sarcocystis or rice breast

The condition described above is called Sarcocystis or "rice breast." Sarcocystis is a nonfatal, usually asymptomatic, infection that is caused by a parasitic protozoan. Various species of this parasite affect mammals, reptiles and birds. The most commonly reported species in North America is Sarcocystis rileyi, the species found most often in waterfowl. Current knowledge of the disease does not indicate a need to initiate control because there is little evidence that bird health is compromised by this parasitic infection.

Sarcocystis sp. presents no known health hazard to humans. The primary importance to humans of Sarcocystis in waterfowl is the loss of infected birds for food. The unaesthetic appearance of parasitized muscle may prompt hunters to discard the carcass. Many hunters who pluck birds never observe the parasite as cooking generally makes the parasite less noticeable than seen in raw muscle tissue.

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If you would like to learn more about this and other diseases, see the USGS-National Wildlife Health Center Field Manual of Wildlife Diseases: General Field Procedures and Diseases of Birds