Infection that affects ducks resembles rice

Talk about rice in Arkansas, and the relationship to ducks and duck hunting follows.

A rice look-alike that hunters may discover often fuels calls to the Arkansas Game and Fish Commission’s biologists and wildlife health line.

“Rice breast” is the common name for a parasitic infection called Sarcocystosis, which occasionally turns up when a hunter begins cleaning ducks at the end of a hunt. The malady is evident as small, white lesions within the fibers of a duck’s muscle tissue, predominantly in the strong flight muscles and thighs of dabbling ducks.

There are no external signs of rice breast, and animals infected with it generally behave normally. The only way a hunter usually discovers his bird is infected is when he peels away the feathers and skin to expose the muscle tissue underneath.

There is no evidence that Sarcocystis seen in ducks is harmful to humans, said Dr. Jenn Ballard, state wildlife veterinarian with Game and Fish.

Proper cooking kills the parasite, but it can be visually unappealing. Many waterfowl hunters discard infected meat, especially in ducks that have large amounts of cysts.

The pathogen responsible for the little “rice grains” visible in the meat of an infected duck is a single-celled parasite called Sarcocystis, a type of protozoan, Ballard said.

The life-cycle of the organism involves two hosts: a prey species to act as the intermediate host (ducks and geese), and a predator species (primarily skunks and foxes), which is the primary host. The grain-like nodule found in the duck is a cyst that is ingested by a predator when the duck dies. Inside the predator’s intestines, the parasite will then mature and lay eggs, which are deposited in the animal’s feces.

These deposits are then accidentally ingested by new ducks feeding at the water’s edge. The eggs hatch and the new parasites find their way to skeletal muscles to form the trademark “rice” cysts, and the cycle starts anew.

“The parasite rarely causes a problem for either host, but severe infections could weaken muscles of a duck, making it more susceptible to predation,” Ballard said. “There’s no need to treat for the parasite because it does not pose a substantial risk to wildlife populations. Most animals just carry it without it being noticed.

“Since it can complete its life cycle in other carnivores, it’s good to err on the side of caution and not feed uncooked infected meat to your pets. Any meat that is discarded also should be disposed of in a way that it cannot be scavenged by small mammals and predators where it could continue its life cycle,” Ballard said.