Sarcocystosis

Today’s path rounds are on 𝐬𝐚𝐫𝐜𝐨𝐜𝐲𝐬𝐭𝐨𝐬𝐢𝐬!

𝐖𝐡𝐚𝐭 𝐢𝐬 𝐢𝐭?
𝐒𝐚𝐫𝐜𝐨𝐜𝐲𝐬𝐭𝐨𝐬𝐢𝐬 is a parasitic infection caused by a protozoal parasite, 𝐒𝐚𝐫𝐜𝐨𝐜𝐲𝐬𝐭𝐢𝐬. The prevalence of this parasite approaches 100% in cattle, sheep and horses, which is nuts!

𝐖𝐡𝐨 𝐠𝐞𝐭𝐬 𝐢𝐭?
Any species can get this!

𝐖𝐡𝐚𝐭 𝐜𝐚𝐮𝐬𝐞𝐬 𝐢𝐭?
Sarcocystis has a two-host lifecycle, meaning it needs two different animal species to move from egg to adult. The first host is usually a prey species, such as a sheep, goat, or cow. Eggs of the parasite are ingested by these animals, which then develop into a juvenile stage that moves into the muscle. These young parasites form a muscle cyst, and remain there until the animal dies. Once the animal dies, the muscle tissue is eaten by a predator species, such as a dog or coyote. This allows the juvenile stage access to its second host, where it develops into an adult stage in the intestine. These adults shed eggs, continuing the lifecycle.

𝐖𝐡𝐲 𝐢𝐬 𝐭𝐡𝐢𝐬 𝐚 𝐩𝐫𝐨𝐛𝐥𝐞𝐦?
Most of the time, the muscular stage of Sarcocystis doesn’t cause any issues at all! They are an 𝐢𝐧𝐜𝐢𝐝𝐞𝐧𝐭𝐚𝐥 𝐟𝐢𝐧𝐝𝐢𝐧𝐠 at necropsy or under the microscope. In growing calves and pigs, Sarcocystis infection can cause anemia and poor weight gain, leading to “poor doing” animals. In predator hosts, Sarcocystis can occasionally cause mild diarrhea.

𝐇𝐨𝐰 𝐢𝐬 𝐢𝐭 𝐝𝐢𝐚𝐠𝐧𝐨𝐬𝐞𝐝?
Diagnosis in predator species, like dogs, is best done through fecal examination. For prey species, the muscle itself is examined either at necropsy or under the microscope.

𝐇𝐨𝐰 𝐢𝐬 𝐢𝐭 𝐭𝐫𝐞𝐚𝐭𝐞𝐝? 𝐇𝐨𝐰 𝐢𝐬 𝐢𝐭 𝐩𝐫𝐞𝐯𝐞𝐧𝐭𝐞𝐝?
Unfortunately there is no real treatment for this parasite. Predator species like dogs should be prevented from eating raw meat whenever possible. Prey species should have their feed stored in secure containers with no predator access, to prevent fecal contamination of their food.