Sarco

• Sarcocystis spp


  Infects humans and animals worldwide
• Definitive hosts


  • Humans
  • Carnivores
• Intermediate hosts


  • Herbivores
  • Omnivores
• Sarcocystis species infecting humans


  • Sarcocystis hominis
  • Sarcocystis suihominis
• Life cycle in definitive host

  1. Microgamete fertilizes macrogamete forming unsporulated oocyst

  2. Unsporulated oocyst undergoes sporulation forming mature oocyst with 2 sporocysts, each with 4 sporozoites

  3. Oocyst disintegrates, liberating sporocysts that pass in feces

  
• Life cycle in intermediate host


  1. Sporulated oocyst or sporocyst ingested

  2. Sporozoites liberated, penetrate intestinal mucosa, reach blood vessels

  3. 3 generations of schizogony forming merozoites

  4. 3rd generation merozoites penetrate muscle, transform into bradyzoites in sarcocyst

  
• Life cycle in definitive host (continued)


  1. Sarcocyst containing bradyzoites ingested

  2. Bradyzoites enter intestinal cells, form microgamete and macrogamete

  3. Zygote forms oocyst containing 2 sporocysts

  
• Mature oocyst


  Oval, transparent, containing 2 sporocysts, each with 4 tear-drop shaped sporozoites, 10-18 um
• Sarcocyst stages


  • Containing several metrocytes
  • Containing mature bradyzoites
• Diagnosis


  1. Stool examination showing mature oocyst or sporocysts

  2. Biopsy of infected muscle showing sarcocysts

  3. Confirmatory testing with PAS stain or PCR
• Sarcocystosis


  • Asymptomatic and self-limiting
  • Intestinal form from ingesting sarcocyst with bradyzoites
  • Muscular form from ingesting oocyst or sporocyst with sporozoites
• Characteristics of intestinal vs muscular sarcocystosis

  • Intestinal: Source is raw/undercooked meat, infective stage is sarcocyst with bradyzoites, develops in 3-6 hours, symptoms include GI issues
  • Muscular: Source is contaminated water/food, infective stage is oocyst/sporocyst, develops in weeks-months, symptoms include musculoskeletal, cardiac, respiratory issues

  
• Management


  1. Intestinal: No treatment

  2. Muscular: Albendazole, metronidazole, co-trimoxazole, steroids

  3. Prevention: Thorough cooking/freezing meat, boiling water, no vaccines