Onchocerciasis – now on target for eradication thanks to Mectizan

Adrian Hopkins - Mectizan Donation Program

Onchocerciasis (or River Blindness) is caused by a parasite worm and is a major cause of blindness in communities living near infected rivers.

GBM roundelOnchocerciasis is transmitted by small black flies which breed in the river. Mectizan (Ivermectin) donated by Merck & Co. Inc. (known as MSD outside of USA and Canada) can be used to control the disease.

Mectizan kills the larvae of the parasite which are found in the skin and has almost no side effects. It does not provoke inflammation within the eye or increased risk of blindness, like other medication, so it can be used for mass drug administration, giving it to everyone in the community apart from children under five years old and pregnant women . It does not kill the adult worm, although it sterilises the females temporarily, and so needs to be given regularly once or twice a year until the adults die. If the skin is kept clear by regular treatment, no larvae are transmitted and no new adults develop.

Total Mectizan treatments approved and distributed for Onchocerciasis to date

Twice yearly treatment to small communities in Central America has been so successful that transmission of the disease has been eliminated everywhere apart from small communities of Yanomami Indians living on the Brazil/Venezuela border in the Amazon jungle .

Controlling and eliminating in Africa

In Africa, the problem is much larger, with around 140 million people at risk . The programme started by way of control, targeting the worst-affected communities where blindness and skin disease had serious consequences. In some of the worst areas, half of all adults would be blind or severely visually impaired. In these worst-affected areas effective treatment has been ongoing for 15 to 20 years and new cases of severe disease are now virtually unknown.

The programme became so successful that in 2009 a decision was made to move from control to elimination of transmission of the disease where possible and, hopefully, in most countries in Africa by 2025. The transition to elimination requires a fundamental change in attitude :

  • Areas not yet under treatment due to low endemicity or other reasons must be mapped out
  • Every focus of the disease must be reviewed to determine if transmission is still ongoing and to do this staff need to be trained and laboratories equipped
  • Where there is still transmission of the disease, different strategies will be needed, probably twice-a-year treatment, improving coverage, possibly vector control, other treatment for systematic non-compliers with mass treatment, test and treat and the possible use of individual treatment with macrofilaricides
Distribution of Onchocerciasis
in Africa and Middle East

Distribution of Onchocerciasis in Africa and Middle East

Good progress, with
treatment expected to
stop in 2016 - 2017
On target to be able to
stop treatment between
2018 and 2020
Likely to require
treatment beyond 2020

in the Americas


Verified as free of
Small pockets of active Onchocerciasis
transmission remains

Looking to the future

These modified strategies, however, will cost more than annual Mass Drug Administration. The end game will cost proportionally more and after stopping treatment ongoing surveillance will still be required with the necessary funding. However, the prize is more than worthy of this investment – River Blindness could be the first blinding disease to be eradicated globally . Already, studies are underway, and it is hoped by 2018 eight or nine countries could stop treatment, 20 by 2020 and all but certain problem countries by 2025.

The programme has been so successful that in 2009 a decision was made to move from control to elimination