Schistosomiasis (Bilharzia)

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Schistosomiasis (Bilharzia)

• Mohammad Habboub
• Hisham Haj Hamad

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Definition

• Schistosomiasis or bilharzia is a disease
  affecting many people in developing countries. In
  the form of 'acute' schistosomiasis it is
  sometimes referred to as snail fever and
  cutaneous schistosomiasis.

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• Although it has a low mortality rate,
  schistosomiasis can be very debilitating. Bilharzi
  a, or bilharziosis, is named after Theodor
  Bilharz, who first described the cause of urinary
  schistosomiasis in 1851.

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• There are five species of flatworms that cause
  schistosomiasis. Each causes different
  symptoms. Schistosomiasis may travel to different
  parts of the body, and its localization
  determines the person's symptoms.
•  Schistosoma mansoni and Schistosoma
  intercalatum cause intestinal schistosomiasis.
• Schistosoma haematobium causes urinary
  schistosomiasis.
• Schistosoma japonicum and Schistosoma
  mekongi cause Asian intestinal schistosomiasis.

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Geographical distribution and epidemiology

• The disease is found in Africa, the Caribbean
  Eastern South America, East Asia and in the
  Middle East.
•  Schistosoma mansoni is found in parts of South
  America and the Caribbean, Africa, and the Middle
  East.
•  S. haematobium in Africa and the Middle East.
•  S. japonicum in the Far East.
•  S. mekongi and S. intercalatum are found
  focally in Southeast Asia and central West
  Africa, respectively.

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Schistosomiasis map

• Worldwide 207 million people have the disease
  with 120 million being symptomatic. Urbanization,
  pollution, and / or consequent destruction of
  snail habitat has reduced exposure, with a
  subsequent decrease in new infections

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• The most common way of getting schistosomiasis in
  developing countries is by wading or swimming in
  lakes, ponds and other bodies of water which are
  infested with the snails (usually of
  the Biomphalaria Bulinus, or Oncomelaniagenus)
  that are the natural reservoirs of
  the Schistosoma pathogen 

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Schistosomiasis life cycle. 

• Schistosomes have a trematode vertebrate-invertebr
  ate lifecycle (infecting both a vertebrate and
  invertebrate), with humans being the definitive
  host
• The life cycles of all human schistosomes are
  similar parasite eggs are released into the
  environment from infected individuals. The eggs
  hatch on contact with fresh water to release the
  free-swimming miracidium

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Pathology

• schistosomiasis is a chronic disease. Pathology
  of S. mansoni and S. japonicum schistosomiasis
  includes Katayama fever, hepatic perisinusoidal
  egg granulomas, Symmers' pipe stem periportal
  fibrosis, portal hypertension, and occasional
  embolic egg granulomas in the brain or spinal
  cord.

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• Pathology of S. haematobium schistosomiasis
  includes hematuria, scarring, calcification,
  squamous cell carcinoma, and occasional embolic
  egg granulomas in the brain or spinal cord.
•  Bladder Cancer diagnosis and mortality are
  generally elevated in affected areas

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Clinical features

• Many infections are subclinically symptomatic,
  with mild anemia and malnutrition being common in
  endemic areas.Symptoms depend on where the eggs
  are
• Continuing infection may cause granulomatous
  reactions and fibrosis in the affected organs,
  which may result in manifestations that include
• Colonic polyposis with bloody diarrhea (Schistosom
  a mansoni mostly)
• Portal hypertension with hematemesis and
  splenomegaly (S. mansoni, S. japonicum
• Cystitis and ureteritis (S. haematobium) with
  hematuria, which can progress to bladder cancer
• Pulmonary hypertension (S. mansoni, S.
  japonicum, more rarely S. haematobium)
• Glomerulonephritis and central nervous system
  lesions.

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• Occasionally central nervous system lesions
  occur cerebral granulomatous disease may be
  caused by ectopic S. japonicum eggs in the brain,
  and granulomatous lesions around ectopic eggs in
  the spinal cord fromS. mansoni and S. haematobium 
  infections may result in a transverse myelitis
  with flaccid paraplegia.
• Katayama Fever
• Acute schistosomiasis (Katayama's fever) may
  occur weeks after the initial infection,
  especially by S.mansoni and S. japonicum. Manifest
  ations include
• Abdominal pain
• Cough
• Diarrhea
• Eosinophilia-extremely high eosinophil
  granulocyte count.
• Fever
• Fatigue
• Hepatosplenomegaly-the enlargement of both the
  liver and the spleen.

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Laboratory diagnosis

• Microscopic identification of eggs in stool or
  urine is the most practical method for diagnosis
• Tissue biopsy (rectal biopsy for all species
  and biopsy of the bladder for S. haematobium)
• Antibody detection can be useful in both clinical
  management (eg, recent infections) and for
  epidemiologic surveys

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Treatment

• Schistosomiasis is readily treated using a single
  oral dose of the drug Praziquantel

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Prevention through good design

• The main focus of prevention is eliminating the
  water-borne snails which are natural reservoirs
  for the disease
• This is usually done by identifying bodies of
  water, such as lakes, ponds, etc., Which are
  infested, forbidding or warning against swimming
  and adding niclosamide, acrolein, copper sulfate,
  etc., To the water in order to kill the snails.

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• Irrigations schemes can be designed to make it
  hard for the snails to colonize the water, and to
  reduce the contact with the local population.

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Abdel Halim Hafez (1929 1977)
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