Description
Sarcosporidiosis (rice breast) is a disease that is primarily present in waterfowl in North America, but it can also be found in some mammals. Rice breast is caused by multiple protozoan parasite species of the genus Sarcocystis. This disease is transmitted in a predator-prey cycle between mammals and waterfowl. Rice breast causes cysts to form in the muscle tissue of infected birds, which typically includes the leg, breast, and heart muscles.
Transmission
Rice breast is spread to waterfowl through a predator-prey transmission cycle. A predator eats the muscle tissue and cysts of the infected bird, and then the parasites that were contained within the cysts are released into the intestine of the predator. The parasite then reproduces by dividing in the intestinal wall of the predator. Sporocysts (small egglike structures) are formed in the predator’s intestine and then passed in its feces. These sporocysts are then eaten by waterfowl to begin the cycle again.
Prominent predator-prey transmission cycles for North American waterfowl occur between Northern pintail ducks and opossums, and Northern shoveler ducks and skunks.
Clinical Signs
There are no reported outward expressions of symptoms of rice breast in waterfowl, but cysts are prominent within muscles of infected birds. Cysts typically look like small grains of rice embedded in the meat. These cysts may feel gritty when cut with a knife. Feces of infected mammals will often contain small egglike structures .
Wildlife Management Implications
Despite being a common infection in waterfowl and some mammals, rice breast does not pose a major threat to the health of individual waterfowl or mammals.
Human Health Significance
There is no documented health risk of rice breast to humans. Cooking infected meat thoroughly typically renders infected meat safe for consumption, but consumption of the infected meat is still not recommended. Raw meat infected with rice breast should not be fed to pets because carnivores are the primary host for this parasite.