Schistosomiasis

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Schistosomiasis
Original presentation Dr C.Stanley

• Modified for the webpage
• Dr M. Levin
• Contact e-mail for webmasters
  webadmin_at_ich.uct.ac.za
• Target audience Undergraduates
• Category Infectious diseases

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Schistosomiasis
The silent scourge of the developing world

• The following talk was presented at a continuing
  education forum at the UCTs department of
  Paediatrics in May 2000 by Dr Clare Stanley.
• Apart from this one, all slides with this
  background were used in the original
  presentation. Slides with a white background
  contain a selection of explanatory notes for the
  following slide.

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Global Impact

• Increasing global incidence.
• Second most prevalent tropical disease.
• Refugee and migrant labour contribute to spread
  in South Africa.
• Agricultural development facilitates this spread.
• Easily treatable condition.
• Successfully eradicated from other areas.
• Wilderness tourism exposes travellers.

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Historical Perspective

• Recognised since the times of Egyptian pharoahs
  hieroglyphics refer to the symptoms.
• Egypt was known as the land of the menstruating
  males.
• Mentioned in Ancient Assyrian records
• Referred to in Japanese folklore with dread of
  death. Katayama fever also featured here.
• African folklore?

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continued

• Theodur Bilharz (1825-1862), a German
  pathologist discovered the parasite.
• Identified the eggs and the adult worm.
• Patrick Manson recognised that the eggs from
  different species differed slightly.
• Katayama fever was first recognised and connected
  to the parasite by a physician working in the
  rice paddies of Japan.

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Case History

• 6 year old girl - ex Transkei
• - painful terminal haematuria
• - recent worm infestation
• Well grown, not pale .
• Normotensive .
• Kidneys not palpable.
• S. Haematobium on midday urine micro
• Hb 10.5
• Chemistry normal.
• Stat dose Praziquantel discharged.

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Epidemiology

• The organism produces large numbers of offspring.
• Peak age of infection in 1st two decades of
  life.
• Indiscriminate habits of rural children with poor
  sanitation facilities.
• Agricultural development and the building of dams
  facilitates the spread of areas in which the
  parasite can live - hence the epidemic being the
  scourge of the developing world.

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Man Snail Water Schistosomiasis

• Trematode or blood fluke.
• Eggs are passed in the urine at midday.
• Fresh water snails are the intermediate hosts.
• Cercaria penetrating skin give rise to early
  manifestations of infection.
• Clinical disease related to parasitaemia, eggs
  various organs, and to adult worms in ectopic
  sites.

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Continued

• Adult worms pair off in the venules, laying eggs
  after 1 month.
• Katayama fever occurs at time of laying eggs.
• Eggs penetrate surface mucosa of bowel and
  bladder, using cytotoxic enzymes.
• Colitis, ileitis and acute cystitis ensue.
• Chronic infection with fibrosis and granuloma
  formation leads to morbidity.
• Complicated by secondary bacterial infections.
• Ectopic sites of infection esp CNS, presenting
  with focal neurological signs.

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Major Features

• S. haematobium
• - perivesical and rectal veins
• - terminal spine
• - chronic cystitis, hydronephrosis, ca.
  bladder,
• - rectal lesions
• - pulmonary HT
• - RVF

• S.mansoni S.japonicum
• - mesenteric and
• portal veins
• - lateral or rudimentary spine
• - hepatic fibrosis portal HT, splenomegaly
• - intestinal lesions and polyps
• - pulmonary HT
• - RVF

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Diagnosis

• Travel history (in non-endemic areas).
• A history of dermatitis or Katayama fever.
• Urine dipstix for blood /or protein (terminal
  haematuria)
• Blood eosinophilia
• Urine microscopy (for the ova)
• Stool microscopy
• Rectal biopsy
• Serological markers

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Chemoprophylaxis refers to the practice of
treating everyone in endemic areas 6 monthly with
Praziquantel whether or not they show signs of
the disease. In some cases this will be a
treatment and it also serves to decrease the
spread of the organism to uninfected
people. Praziquantel is given as a single dose in
infection with S. Haematobium and S. Mansoni and
as a thrice daily dose for S. Japonicum. Metrifona
te and oxamniquine are expensive drugs that are
not often used.
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Treatment

• Molluscicidal plants.
• Safe and effective chemoprophylaxis.
• Praziquantel single dose vs tds dose.
  s/e include abdominal distension, fever and
  headache.
• Metrifonate and oxamniquine.
• Corticosteroids dampen the immune response, esp
  in CNS disease.

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TNF - alpha has been implicated in the following
aspects of the response to the parasite. In
Zimbabwe, there is a subgroup of people in which
the prognosis is poorer and the response to the
treatment is worse. It has been postulated that
there may be a genetic contribution to causing
these differences in these people.
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Whats New?

• Role of TNF-alpha - hepatosplenomegaly
  - granuloma formation - signal to lay
  eggs
• Genetic predisposition to severe fibrosis and
  hence severe morbidity
• Drug resistance is high in some areas, is this
  genetic?
• S. haematobium vaccine is currently being tested
  in France with further testing planned for
  Africa.
• S. japonicum vaccine has been tested on animals.

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Prevention

• Chemotherapy with regular treatment of high risk
  groups.
• Snail control.
• Health education if community and school groups
• Safe water and sanitation
• Environmental management
• Economic development