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The Biology of Schistosomiasis

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intermediate fresh water snail host. cercariae. Life Cycle in the Human. cercariae. human host ... Snail Control. Diagnosis and Treatment. Diagnosis. blood tests ... – PowerPoint PPT presentation

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Title: The Biology of Schistosomiasis


1
The Biology of Schistosomiasis
  • By Tricia Stone, Marielle Remillard Tracy
    Wright

2
Schistosomes
  • macroscopic parasite from the genus Schistosoma
  • characterized by significant sexual dimorphism
  • Schistosomasplit body

3
Types of Schistosomes
  • Three species affect humans
  • 1.) S. mansoni large intestine
  • 2.) S. japonicum small intestine
  • 3.) S. haematobium urinary bladder

4
Life Cycle
intermediate fresh water snail host
miracidia
feces and urine
5
Intermediate Snail Hosts
  • S. mansoni Biomphalaria (Africa)
  • S. haematobium Bulinus (Africa)
  • S. japonicum Oncomelania (Asia)

Biomphalaria
Bulinus
Oncomelania
6
Life Cycle
intermediate fresh water snail host
cercariae
7
Life Cycle in the Human
cercariae
human host
human host
8
Life Cycle in the Human
schistosomulum
human host
9
Life Cycle in the Human
schistosomulum
human host
adult schistosome
10
Life Cycle in the Human
eggs
excreted in the feces and urine
adult schistosome
11
Life Cycle
12
Stage 1 Migratory Phase
  • moves through the body to target tissue
  • begins with penetration through egg production
  • often symptomless
  • possible rash and itchy skin
  • some upper respiratory complications (i.e. cough)

13
Stage 2 Acute Phase
  • 4-10 weeks after infection
  • begins with egg production
  • Symptoms
  • - fever
  • - headache
  • - diarrhea
  • - fatigue
  • - nonspecific abdominal pain

14
Stage 3 Chronic Phase
  • prolonged infection (up to 10 years)
  • symptoms
  • - cirrhosis of the liver
  • - kidney damage
  • - bleeding of upper bowel
  • - urinary bladder damage
  • - enlargement of liver and spleen

15
Slippery Little Suckers Arent They Julia
Roberts (Pretty Woman)
  • Innate Immunity
  • penetration of skin
  • Specific Immunity
  • adults take on host antigens

16
Incidence
17
Risk Factors
  • 200 million infected globally
  • 20 million with chronic schistosomiasis
  • 600 million at risk
  • -extreme poverty
  • -lack of public health facilities
  • -unsanitary conditions
  • -unawareness among the people

18
Prevention
  • avoid swimming in fresh water in countries where
    schistosomiasis is prevalent.
  • drink clean water
  • scrape body down after accidental exposure
  • water-resistant creams
  • Snail Control

19
Diagnosis and Treatment
  • Diagnosis
  • blood tests
  • examination of stool and urine samples to detect
    eggs
  • Treatment
  • Drugs
  • Praziquantel - effective in the treatment of all
    forms of schistosomiasis, with virtually no side
    effects
  • Oxamniquine - used exclusively to treat
    intestinal schistosomiasis in Africa and South
    America
  • Metrifonate - effective for the treatment of
    urinary schistosomiasis
  • Vaccination
  • Research efforts are directed at finding a
    vaccine, but no success

obtained from W.H.O.
20
Interested in More???
  • http//www.wellcome.ac.uk/en/labnotes5/animation_p
    opups/schisto.html
  • http//www.cdc.gov/ncidod/dpd/parasites/schistosom
    iasis/default.htm
  • http//en.wikipedia.org/wiki/Schistosomiasis
  • http//www-micro.msb.le.ac.uk/224/Schisto.html
  • http//www.path.cam.ac.uk/schisto/

21
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