Onchocerciasis: (On-kough-sir-KY-A-sis)

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Onchocerciasis
(On-kough-sir-KY-A-sis)
River blindness
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Key Learning Goals

• Onchocerciasis will be defined.
• You will be able to identify the mode of
  transmission and host of the disease
• The burden of the disease will be defined showing
  the incidence and prevalence rates
• Control measures through prevention and treatment
  will be characterized

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Onchocerciasis

• World's second leading infectious cause of
  blindness
• About 18 million people are currently infected
  with this parasite
• Approximately 300,000 have been permanently
  blinded

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Onchocerciasis

• Blackflies that transmit the disease abound in
  riverside areas, where they breed in fast-flowing
  water.
• Onchocerciasis causes intense itching,
  disfiguring dermatitis, and eye lesions that can
  result in blindness.
• Without able workers, production is greatly
  diminished, increasing poverty and famine.

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The Life Cycle
http//timpanogos.files.wordpress.com/2007/09/rive
r_blindness_cycle-carter-center-alberto-cuadra.jpg
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The Blackfly

• 4 stages of development egg, larva, pupa, and
  adult. The eggs, larvae, and pupae are confined
  to rivers and streams.
• Eggs hatch, larvae drift and attach themselves to
  rocks and vegetation in flowing water.
• Larvae feed by filtering nutrients from the water
  and grow to about 6-10 mm. They pupate within two
  or three weeks.
• After a few days in the pupal stage the adults
  escape from the pupa and float to the surface in
  an air bubble.
• Both adult male and female black flies feed on
  nectar and plant juices to meet their energy
  requirements.
• Mating occurs soon after emergence.
• Females of biting species then seek blood, which
  they require to produce eggs.

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Mode of Transmission

• Parasites are transmitted from the bite of black
  flies
• Simulium species
• Worms spread throughout the body
• Strong immune system response that can destroy
  nearby tissue, such as the eye.

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Worldwide Distribution
gt99 in Africa Yemen S. America Mexico Guatemala
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Onchocerciasis affects the body

• In the human body, the larvae form nodules in the
  subcutaneous tissue, where they mature to adult
  worms.
• After mating, the female adult worm can release
  up to 1000 microfilariae a day.
• These move through the body, and when they die
  they cause a variety of conditions, including
  blindness, skin rashes, lesions, intense itching
  and skin depigmentation.

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Causes of morbidity

• Microfilariae elicit the onchocerciasis syndrome
  that includes blindness, lymphadenitis, and
  dermatitis.
• O volvulus infection reduces immunity and
  resistance to other diseases, resulting
  in a reduction of the life expectancy
  of infected individuals by approximately 13
  years.

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The Good NewsPrevention andControl Measures

• Spraying of blackfly breeding sites with
  insecticide
• Mectizan
• Surgical removal of worms

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More Good News
http//www.mectizan.org/treatment.asp
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Thank you