Schistosomiasis

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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
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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!

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Pathology and Symptoms

• Migratory Phase
• Penetration to Egg production
• Symptomless
• Dermal rash

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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

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Pathology and Symptoms

• 3. Chronic Phase
• Asymptomatic
• S. haematobium
• Blood in the urine
• Pain with urination
• Loss of bladder function
• Bladder cancer?
• Eggs dont metastasize?

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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

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Ascites
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Schistosoma japonicum

• Anterior mesenteric veins
• Small intestine
• Interfere with absorption
• Stunting
• Eggs can go to brain
• Smaller
• Brain lesions

25 year old
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Pathology

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

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Diagnosis

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

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Treatment

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

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Epidemiology

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

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Epidemiology

• What causes people to come into contact with
  water?

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Work Fisherman, agricultural workers, housework
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Bathing and Play
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Traditions

• Ablution

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How do eggs get into water supply?
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What else do you need?
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Snails

• Schistosoma mansoni
• Biomphilaria glabrata
• Schistosoma japonicum
• Oncomelania
• Schistosoma heamatobium
• Bulinus

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Snail Habitat

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

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Seasonal Transmission

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

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Human Manipulations

• Agricultural projects
• Improve agriculture
• Unintended consequences
• Increase snail habitat
• Zimbabwe 10 million irrigation project
  abandoned
• Aswan High Dam in Egypt

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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

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Reservoir Hosts

• Schistosoma haematobium
• None known
• Schistosoma mansoni
• Many mammals monkeys and rodents
• Schistosoma japonicum
• Least host specific
• Many mammals

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Control
Infected People
Uninfected People
contact
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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

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Control
Infected People
Uninfected People
contact
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2 Control

• How do you prevent eggs from contaminating water
  supplies?
• Sewage treatment
• Eliminate night soil
• Education
• Why doesnt this work?
• Expensive
• Reservoir hosts

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Control
Infected People
Uninfected People
contact
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3 Control

• How do you prevent people from contacting
  cercariae?
• Education
• Protective gear (waders, boots)
• Provide non-contaminated water
• Vaccines
• Why dont these methods work?
• People need water
• Fishermen, Agricultural workers cant avoid
• 60 world calories from rice
• Protective gear hot and cumbersome
• Ablution
• Cost of clean water
• Vaccines unsuccessful

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Control
Infected People
Uninfected People
contact
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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

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Cercarial Dermatitis/ Swimmers Itch

• 10 species (U.S.)

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Trichobilharzia sp.
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Matts leg with cercarial dermatitis or
swimmerss itch caused by cercariae of avian
blood flukes.
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Furcocercous cercariae diagnostic for
Schistosomes.
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Cercarial Dermatitis/ Swimmers Itch

• Inflammatory response
• Pus-filled pimples
• Itching and pain
• 4 days

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Dendritobilharzia spp.

• Live in the dorsal aorta of ducks!

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Ducks can infect snails that can infect swans!
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Eggs can enter CNS via arterial circulation
causing CNS disease!