Before we start 912

1
Before we start 9/12

• questions?
• see page 1080 figure 20-1
• see updated white text on slides 25, 33, 35, 37
  39
• lots of stuff review in class? Dont let me
  hurry!
• check out the test review (pobjtest1) posted
  on web page
• Game plan complete helminths life cycle, path,
  ID, etc., then go back to path, ID, etc. on
  intestinal protozoa, blood tissue protozoa ?
  end of course
• helminth life-cycles.....you will see for
  yourself ?
• white text from slide 49 56, and??? is fair
  game for test. You learn as much of the rest as
  you likefor you.

2
Trematode life-cycle facts

• Review trematode characteristics slide 35
• See page 1111
• All fluke pathogens use a snail as an
  intermediate host.
• All fluke pathogens except Schistosoma (blood
  fluke)
• a) are hermaphroditic
  Schistosoma is dioecious - both together in blood
  vessels
• b) use 2 intermediate hosts snail then a
  crustacean or fish Schistosoma has only 1
  intermediate host, a snail
• c) 2nd larval stage is in the form of sporocyst
  then redia
• Schistosoma has sporocyst but no redia stage
• d) the metacercaria phase is infective in
  humans
• cercaria are infective in humans in
  Schistosoma
• e) humans are infected by ingesting metacercaria
• Schistosome cercaria enter directly through
  the skin
• f) have operculated eggs (lid) see images
  next slide Schistosoma eggs are lid-less and
  spined can cause liver and spleen damage
  remember slide 34

?
3
Operculated eggs Schistosoma eggs

Paragonimus egg
Clonarchis egg
Fasciola egg
4
Trematode life-cycle

• 1.Egg Egg passed in feces, urine or sputum of
  definitive host. If the egg reaches fresh water,
  it hatches to release the free-swimming larvae,
  the miracidia. Singular miracidium.
• 2.Miracidia Arise from egg. Micacidia are
  free-swimming, ciliated, larva (1st) which
  penetrate or are eaten by the 1st intermediate
  host, the snail. There they transform into the
  2nd larval stage.
• 3.2nd larval stage Arises from miracidia in the
  snail either a sporocyst in Schistosomes (or
  sporocyst then redia (more motile form) in other
  Trematodes) forms in snail tissues. From this
  2nd larval form numerous cercaria arise through
  mitosis within the 1st intermediate host.
• 4.Cercaria Arise from miracidia via the 2nd
  larval stage. Cercaria are tailed (tail shape
  varies between genera), free-swimming forms which
  encyst in or on aquatic plants or animals (fish
  or crabs), the 2nd intermediate host, and
  metamorphose into encysted metacercariae.
  Schistosome cercaria directly penetrate the
  definitive host and mature to adult worms,
  by-passing the metacercaria stage.
• 5.Metacercaria Definitive hosts (humans) are
  infected when they ingest encysted metacercaria
  on aquatic plants (Fasciola) or in infected
  aquatic animals (Clonorchis, Paragonimus).
  Metacercaria migrate to a particular organ in the
  definitive host where they mature to adults which
  carry out sexual reproduction, eventually forming
  eggs. Again, metacercaria are absent in
  Schistosomes.

5
Generalized trematode life-cycle Fig 20.17,
.19, .20
1.
5.
4.
2.
3.
6
Schistosoma life-cycle Fig 20-18, pg 1119
1.
4.
3.
2.
7
Schistosomes (blood flukes) pg 1111-1116, table
20-6, pg1117?

• 1 Interm host (IH) snail DH human
• Epidemiology 1 global trematode, 2.5 x108
  infections, mostly in W. Central Africa S.E
  Asia, with some cases in S.E. US.
• Pathology/symptoms cercaria penetrate softened
  skin resulting in transient local dermatitis or
  swimmers itch (hypersensitivity). Cercaria
  eventually migrate to the circulatory
  system/portal venous-lower GI tract mature to
  adult flukes 1-3cm long, large enough to plug
  the pipes.
• Other pathology
• 1) fibro-/granulo- tissue damage of portal
  venous system tissue associated with extensive
  egg deposition
• 2) simple portal venous obstruction of liver
  portal, bowel or urinary bladder bowel
  obstruction, hepatosplenomegaly, etc.
• 3) Bowel dysentery, bowel polyps, etc.
• 4) severe cases bladder cancer?, cardiac
  right ventricle damage, CNS disorientation,
  amnesia, coma

8
Schistosome pathology
hepatosplenomegaly bowel obstruction
9
Schistosomes continued see table 20-6, pg 1117

• Diagnosis/ID
• connection to endemic area water assoc.
  activities
• symptoms swimmers itch, etc.
• elevated eosinophil count (all helminths) IgE
  titer
• cercaria has characteristic forked tail
• 1? characteristic eggs with apical spine or
  knob much less obvious in some species - S.
  japonicum has small knob rather than prominent
  spike.

10
Other trematodes of lesser importance

• Fasciola F. hepatica sheep liver fluke fig
  20-17
• IH snail then water plant? DH 1sheep, cattle
  2 humans
• Epidemiology 2x106 cases, found on every
  continent but mainly in Africa, concentrated in
  areas where cattle sheep (1 definitive host)
  are raised, feces introduced into water human
  diet includes consumption of raw aquatic
  vegetables from that water source we are
  considered accidental hosts.
• Pathology/symptoms abdominal pain, hepatomegaly,
  jaundice, anemia
• Diagnosis/ID
• connection to endemic area suspect activities
  see above
• 1 large (150x80 uM), thin walled, opperculated
  eggs in feces
• elevated eosinophil count