1. Schistosomiasis
Miracidia produces enzymes and secretions while in the egg.
Ag/Ab reaction to miracidial secretions through egg, resulting in egg granuloma the Hoeppli phenomenon!
Ag/Ab

2. How many eggs make it to the lumen?
2/3 of those that enter tissue do not leave.
Many eggs do not enter tissue
Swept away in blood stream
Liver and spleen are first organs
Then Lungs
Other organs
Eggs look like
Psuedotubercles
100, 000 eggs/gram!

3. Pathology and Symptoms
Migratory Phase
Penetration to Egg production
Symptomless
Dermal rash

4. Pathology and Symptoms
2. Acute Phase
Egg Production
Chills, fever, fatigue, headache, malaise
Much exposure to antigens
Granulomas surround eggs
Eosinophils, neutrophils, macrophages
1-2 weeks fibroblasts enter granuloma
Psuedotubercles-fibrous granulomas

5. Pathology and Symptoms
3. Chronic Phase
Asymptomatic
S. haematobium
Blood in the urine
Pain with urination
Loss of bladder function
Bladder cancer?
Eggs don’t metastasize?

6. Pathology and Symptoms
3. Chronic Phase
S. japonicum, S. mansoni
Mild, chronic dysentery
Abdominal pain
8% infections develop liver fibrosis that impedes blood flow
Cirrhosis of liver
Long term problems
Hepatosplenomeagly
Long term: loss of tissue function

7. Ascites

9. Schistosoma japonicum
Anterior mesenteric veins
Small intestine
Interfere with absorption
Stunting
Eggs can go to brain
Smaller
Brain lesions
25 year old

10. Pathology Adults cause no pathology Pathology due to eggs
“hide” from immune system
Absorb host antigens
Pathology due to eggs

11. Diagnosis Schistosoma mansoni and S. japonicum?
Schistosoma haematobium?
Small number of eggs
Serodiagnosis

12. Treatment Praziquantel Prognosis Effective
Much of fibrosis can be reversed
Severe damage irreversible

13. Epidemiology
How do you get infected with a species of Schistosoma?

14. Epidemiology
What causes people to come into contact with water?

15. Work: Fisherman, agricultural workers, housework

16. Bathing and Play

17. Traditions
Ablution

18. How do eggs get into water supply?

19. What else do you need?

20. Snails Schistosoma mansoni Schistosoma japonicum
Biomphalaria glabrata
Schistosoma japonicum
Oncomelania
Schistosoma heamatobium
Bulinus

21. Snail Habitat Any freshwater Eutrophic bodies of water
Shallow areas near shore
Associated with
Aquatic plants
Decaying organic debris

22. Seasonal Transmission
Transmission can occur only during certain seasons
Snail abundance
Dry season
Some species burrow into mud

23. Human Manipulations Agricultural projects Unintended consequences
Improve agriculture
Unintended consequences
Increase snail habitat
Zimbabwe: $10 million irrigation project abandoned
Aswan High Dam in Egypt

24. Aswan High Dam Increased snail habitat Increased Schistosomiasis
Below dam
Varied by significant increases
From 5%-35%
Above dam
From 5% in 1968 to 77% in 1993

25. Reservoir Hosts Schistosoma haematobium Schistosoma mansoni
None known
Schistosoma mansoni
Many mammals: monkeys and rodents
Schistosoma japonicum
Least host specific
Many mammals

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

30. # 1 Control How do you get rid of snails? Remove by hand Molluscicide
Biological control
Eliminate habitat
Do these work?
Too many snails
Molluscicides ineffective
Oncomelania
Biological control sometimes effective
People need water, too

31. #2 Control How do you prevent eggs from contaminating water supplies?
Sewage treatment
Eliminate night soil
Education
Why doesn’t this work?
Expensive
Reservoir hosts

32. # 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

33. # 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

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

35. Trichobilharzia sp.

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

37. Furcocercous cercariae diagnostic for Schistosomes.

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

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

41. Ducks can infect snails that can infect swans!

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