Onchocerciasis on kough sir ky a sis river blindness
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Onchocerciasis : (On- kough -sir- KY-A -sis) “ River blindness”. Key Learning Goals. Onchocerciasis will be defined. You will be able to identify the mode of transmission and host of the disease

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Onchocerciasis on kough sir ky a sis river blindness

Onchocerciasis: (On-kough-sir-KY-A-sis)“River blindness”

Key learning goals
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


  • 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


  • 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.

The life cycle
The Life Cycle


The blackfly
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.

Mode of transmission
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.

Worldwide Distribution

>99% in Africa


S. America



Onchocerciasis affects the body
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.

Causes of morbidity
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.

The good news prevention and control measures
The Good News…Prevention andControl Measures

  • Spraying of blackfly breeding sites with insecticide

  • Mectizan

  • Surgical removal of worms

More Good News