Sarcocystosis

Sarcocystosis is a zoonotic protozoal disease caused by Sarcocystis. Human infection is mostly asymptomatic or causes mild transient symptoms. Sarcocystis can infect humans as definitive or intermediate hosts; two species use humans as definitive hosts: S. suihominis (pig-human) and S. bovihominis (cattle-human, also called S. hominis), collectively called human intestinal sarcocystis. Species using humans as intermediate hosts and parasitizing muscle are collectively called human muscular sarcocystis. When humans ingest Sarcocystis cysts and become definitive hosts, bradyzoites escape and invade small intestinal mucosal goblet cells, undergo gamogony then migrate to the lamina propria for sporogony, finally developing into mature oocysts excreted in feces. When humans ingest mature oocysts from definitive host feces, they become intermediate hosts, with sarcocysts in muscle tissue.

Common Symptoms

Diarrhea; abdominal distension; abdominal pain; fatigue; dizziness; nausea

Causes and Pathogenesis

(1) Etiology: Sarcocystis can infect humans as definitive or intermediate hosts. Two species use humans as definitive hosts: S. suihominis and S. bovihominis, collectively human intestinal sarcocystis. Species using humans as intermediate hosts in muscle are human muscular sarcocystis. (2) Pathogenesis: Sarcocystis is usually highly pathogenic for intermediate hosts but weakly or non-pathogenic for definitive hosts. Human intestinal sarcocystosis results from eating undercooked pork or beef containing sarcocysts (human as definitive host); human muscular sarcocystosis results from food contaminated with oocysts or sporocysts (human as intermediate host). Sarcocysts in the intestinal lamina propria rarely cause lesions or only mild inflammation. Intramuscular sarcocysts with intact walls cause only mild mechanical irritation and nutrient absorption; when metrocytes and bradyzoites degenerate, the fluid contains highly toxic sarcocystin causing local inflammation, especially severe when cysts rupture, with allergic reactions. Animal experiments show the toxin resembles bacterial endotoxin, causing endotoxic shock-like symptoms, fever, bleeding, edema, and even death in livestock; it also directly inhibits bone growth and growth hormone-releasing factor, indirectly affecting growth. Intestinal pathology is mild; mesenteric lymph nodes may be edematous or necrotic. Muscle changes include dermatomyositis and myositis, with petechial bleeding, nodular granulomas, or gray-white myocardial foci. Microscopically, muscle degeneration, interstitial fibrosis, striated muscle bleeding, lymphocyte, plasma cell, and scant eosinophil infiltration, myocardial dystrophy, and muscle fiber degeneration are seen.

Treatment

Drug therapy, supportive therapy

Preventive Measures

Health education: 1. Personal dietary hygiene: Do not eat raw or undercooked pork or beef. Do not drink water that fails hygiene standards. 2. Livestock management: Strengthen husbandry of pigs, cattle, and sheep; handle animal feces properly to prevent drinking water and food contamination by dog and cat feces.

Department to Visit

It is recommended to visit the Infectious Diseases department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.