Onchocerciasis

Introduction

Onchocerciasis (also known as river blindness) is a vector-borne disease that is transmitted from person to person via the bites of infected blackflies. The disease is caused by the parasitic filarial worm Onchocerca volvulus.

The blackflies introduce immature larval forms of the parasite into the human recipient; these larvae then mature into adult worms, mate and in turn release hundreds of microfilariae a day; these move through the body and cause a number of symptoms, including:

  • blindness
  • skin rashes and lesions
  • intense itching and skin depigmentation

The disease is treated with a drug that kills microfilariae, while its control has often focussed on control of the vector.

TDR related research

Since its foundation, TDR has been at the forefront of a global fight to combat and eradicate onchocerciasis. It effectively became the research arm of the Onchocerciasis Control Programme (OCP) in West Africa, and then the African Progamme for Onchocerciasis Control (APOC).

Research on how to curb disease transmission in broad savanna regions of West Africa led to the breakthrough innovation of incorporating the Bti bacterium to control insect larvae, including that of the blackfly, in 1982.

TDR also contributed to the design of study protocols and dosage for the drug ivermectin, and connected the pharmaceutical owner, Merck, with the OCP networks. In 1986, with the drug about to be registered, CEO of Merck Dr Roy Vagelos made the momentous decision to donate the drug to whoever needed it, as long as it was needed. TDR and partners set up large-scale community trials under field conditions to move the drug from individual treatment in hospitals to mass drug administration, strengthening the value of ivermectin in the onchocerciasis control strategy.

To support this mass drug administration, a new model was proven that empowered communities to put in place their own system for ivermectin distribution and administration, with health services offering support and training.

Today, 98 million people in 31 sub-Saharan African countries receive annual treatments through this system.

Current work

Archival research

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Featured TDR publications

All TDR publications on onchocerciasis