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 diseaseThe burden of the disease will be defined showing the incidence and prevalence ratesControl measures through prevention and treatment will be characterized

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

OnchocerciasisBlackflies 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

http://timpanogos.files.wordpress.com/2007/09/river_blindness_cycle-carter-center-alberto-cuadra.jpg

The Blackfly4 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

Parasites are transmitted from the bite of black fliesSimulium speciesWorms spread throughout the body Strong immune system response that can destroy nearby tissue, such as the eye.

>99% in AfricaYemen

S. AmericaMexico

Guatemala

Worldwide Distribution

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

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 andControl Measures

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

http://www.mectizan.org/treatment.asp

More Good News

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