1. Blood Flukes (Schistosomes)
Infect mammals, and birds.
Live in the mesenteric veins (most species); some in urinary plexus veins, nasal veins, and dorsal aorta.

2. Blood Flukes Veins Mesenteric veins Anterior (superior)
Small intestine
Posterior (inferior)
Large intestine
Urinary bladder

3. Schistosoma Small elongate 1-2 cm Dioecious Gynecophoric canal
Male helps female eat

4. Schistosomiasis
Major Parasitic disease, with million people infected.
many are school age children

5. Schistosomiasis Schistosoma Bilharzia Egyptian papyri Egyptian mummies
1850 Theodor Bilharz
Egyptian papyri
Egyptian mummies
Joshua’s curse on Jericho
1800 Napoleon’s army

6. Species that infect humans
Schistosoma japonicum
Anterior mesenteric veins
Schistosoma mansoni
Posterior mesenteric veins
Schistosoma haematobium
Veins draining the urinary bladder
Schistosoma intercalatum
Intestinal schistosomiasis in Africa
Schistosoma mekongi
Small intestine like S. japonicum (Vietnam)

7. } Species Schistosoma japonicum Schistosoma mansoni Big three!
Anterior mesenteric veins
Schistosoma mansoni
Posterior mesenteric veins
Schistosoma haematobium
Veins draining the urinary bladder
Schistosoma intercalatum
Intestinal schistosomiasis in Africa
Schistosoma mekongi
Small intestine like S. japonicum (Vietnam)
Big three!

8. Schistosomiasis Estimates
1947: ,000,000
1968: ,000,000
1972: ,000,000
1979: ,000,000
Current: More than 200,000,000

9. Why the Increase?
Due to irrigation farming and building of dams to facilitate irrigation.
Snail habitat has expanded and increases exposure to people.

10. Life Cycle
Schistosomes live in blood vessels that drain tissues such as the bladder, S. intestine and L. intestine.
They produce eggs within blood vessels!

11. Eggs have spines, no operculum, also have prominent secretory glands!
S. mansoni S. japonicum S. haematobium

12. Eggs
Eggs are shed to outside through excrement (feces or urine).

13. Chemical Signaling with arginine
Life Cycle
Chemical Signaling with arginine
Adults can live years
3 weeks
Release Eggs in 5-8 Weeks

14. Distribution

15. Distribution

16. How do the eggs get out of the body?

18. How do the eggs get out of the body?
Female worm leaves the male and migrates down to lay eggs.

19. How do the eggs get out of the body?
Female worm leaves the male and migrates down to lay eggs.
Egg spines help the eggs work their way into the tissue, but the miracidia also produces enzymes.

20. Granuloma can move with the eggs by peristaltic action.
Immune response
Granuloma
(Eosinophils, macrophages, neutrophils)
Granuloma can move with the eggs by peristaltic action.

21. Schistosomiasis
Big picture the key to schisto pathology is the eggs not the adult worms!

22. # 3 Control How do you prevent people from contacting cercariae?
Education
Protective gear (waders, boots)
Provide non-contaminated water
Vaccines
Why don’t these methods work?
People need water
Fishermen, Agricultural workers can’t avoid
60% world calories from rice
Protective gear hot and cumbersome
Ablution
Cost of clean water
Vaccines unsuccessful

23. Control Infected People Uninfected People Occupation Behavior Habitat
Sewage
Occupation
Behavior
Bathing
Season
Habitat
Infected
People
contact
Uninfected
People
contact

24. # 4 Control How can you eliminate the parasite? Drug treatment
Genetically modified snails
Do these work?
Cost
Dose of praziquantel = $0.20
No genetically modified snails yet

25. Cercarial Dermatitis/ Swimmer’s Itch
10 species (U.S.)

26. Trichobilharzia sp.

27. Matt’s leg with cercarial dermatitis or “swimmers’s itch” caused by cercariae of avian blood flukes.

28. Furcocercous cercariae diagnostic for Schistosomes.

29. Cercarial Dermatitis/ Swimmer’s Itch
Inflammatory response
Pus-filled pimples
Itching and pain
4 days

30. Dendritobilharzia spp.
Live in the dorsal aorta of ducks!

32. Ducks can infect snails that can infect swans!

33. Eggs can enter CNS via arterial circulation causing CNS disease!