Sarcocystis

• Protozoan infection that can cause gastrointestinal or muscle disease

Background

Microbiology

• Species that cause human intestinal sarcocystosis include Sarcocystis hominis and Sarcocystis suihominis
• Other species may be involved in causing human muscular sarcocystosis (as incidental hosts)

Epidemiology

• Zoonosis of primarily of cattle (S. hominis) and pork (S. suihominis), with a two-host cycle
• Worldwide, but most cases are in tropics or subtropics of Southeast Asia (especially Malaysia)

Life Cycle

• Tissue sarcocyst is eaten by the definitive host
• Sarcocyst releases motile bradyzoites which penetrate into the lamina propria
• Bradyzoites mature into male and female forms, followed by sexual reproduction creating oocysts
• Mature oocysts (containing two sporocysts) are shed
• Sporocysts are eaten by the other host
• Sporocysts release sporozoites, which penetrate the intestinal all and enter the vascular endothelium
• Asexual reproduction creates merozoites, which spread hematogenously to muscle
• In muscle, the merozoites develops into a sarcocyst, which contains two bradyzoites
  • It takes about two months to become infections

Clinical Manifestations

Human intestinal sarcocystosis

• Mostly asymptomatic
• If symptomatic, may cause nausea, abdominal discomfort, diarrhea, and fever
• Incubation period, if diarrhea is a symptom, of two days
• Self-limited illness

Human muscular sarcocystosis

• Mostly asymptomatic, but can develop a fulminant eosinophilic myositis
• May develop fever, myalgias, eosinophilia, and elevated CK

Diagnosis

• Stool microscopy for intestinal disease
• Muscle biopsy for muscle disease

Management

• Supportive
• No known effective antiparasitic, although albendazole has been tried at least once