Sarcocystis

Question 1

why phylum does sarcosytis belong to?

Answer 1

Apicomplexa
just like Toxoplasma gondii which infects virtually all warm-blooded vertebrates; Cytoisospora infects humans and animals

Question 2

two hosts required to maintain sarcocystis life cycle

Answer 2

• an intermediate or prey host, whose muscles become infected with cysts (sarcocysts) containing infectious zoites
• a definitive, or predator host that ingests the cysts, becomes infected with intestinal stage parasites, and excretes oocysts or sporocysts into the environment

Question 3

definitive hosts for S. hominis (bovihominis) and S. suihominis

Answer 3

humans and non-human primates
- intestinal infection from cattle and pigs

Question 4

this species has been identified in humans and non-human primates servings as intermediate hosts for sarcocystis

Answer 4

S. nesbitti
- humans have muscle cysts rather than intestinal infection
- snakes = definitive host?

Question 5

two phases of life cycle of sarcocystis (morphology)

Answer 5

• asexual: trophoxoites in muscle tissue cysts; seen in intermediate (animal, rarely humans)
  > large, oval elongated
  > compartments (trabeculae)
  > surrounded by complex wall ( w layer of villi)
  > each compartment has merozoites (small trophozoites; multiplying by endodyogeny/internal budding)
• sexual: sporocysts with sporozoites = differentiate into merozoites -> gametic cells -> oocytes -> intestinal lumen of definitive host -> environment

Question 6

detailed life cycle of S. bovihominis and suihominis

Answer 6

• cysts in muscles (ingested undercooked)
• digested away = intestinal cells = sporocysts and thin-walled oocytes in feces (micro- and macrogametes); immature oocytes start dividing = discharged as feces
• sporocysts and oocysts ingested by cows and pigs (intermediate)
• ruptured sporocysts ruptures releasing sporozoites that enter endothelial cells of blood vessels and undergo schizogony
• schizonts rupture = merozoites = penetrate muscle cells and develop into cysts (can lasts for months to years until ingested by human or primate)

Question 7

pathogenesis of sarcocystis disease

Answer 7

gut proliferative stages = little or no rxn unless very large infective dose (humans shed cysts for 10 days to 6 mos; infects environment for that long)

muscle cyst = no inflammation when intact; tissue damage when cysts disintegrate = muscle inflammation, necrosis, vasculitis

Question 8

Sarcocystis symptoms

Answer 8

muscle invasion (weeks to months after exposure) (difficult to diagnose, rare)
= painful swelling w fever; sometimes rash and difficulty breathing

intestinal invasion (3-6 hrs after exposure)
= beef: mild nausea, diarrhea, stomach discomfort
= pork: acute diarrhea and vomiting, stomach ache, cramps

MAJORITY of muscle invasion = asymptomatic

Question 9

epidemiology of intestinal form of Sarcocystis

Answer 9

cattle = Germany 60->90%, Asia 40-80%

pigs = worldwide; 3-30%

humans = 1-10%
Europe (most common, Asia

Question 10

epidemiology of muscle form of Sarcocystis

Answer 10

rare! <100 cases
humans considered aberrant intermediate hosts as they accidentally substitute for natural hosts
- Europe
- Central and SA, Southeast Asia, West Indies, few cases in Africa
recent two outbreaks in Malaysia!

Question 11

diagnosis for sarcocystis

Answer 11

cysts in feces
muscle biopsy

Question 12

prevention of sarcocystis disease

Answer 12

freeze meat at -20C for 1 day
cook till colour changes (>65C for 15-20 mins)