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Schistosomiasis

Schistosomiasis

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Schistosomiasis

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  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

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

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

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

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

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

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

  14. Work: Fisherman, agricultural workers, housework

  15. Bathing and Play

  16. Traditions • Ablution

  17. How do eggs get into water supply?

  18. What else do you need?

  19. Snails • Schistosoma mansoni • Biomphilaria glabrata • Schistosoma japonicum • Oncomelania • Schistosoma heamatobium • Bulinus

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

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

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

  23. 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

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

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

  26. # 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

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

  28. #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

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

  30. # 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

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

  32. # 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

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

  34. Trichobilharzia sp.

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

  36. Furcocercous cercariae diagnostic for Schistosomes.

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

  38. Dendritobilharzia spp. • Live in the dorsal aorta of ducks!

  39. Ducks can infect snails that can infect swans!

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