Onchocerciasis

A public health problem close to solution

A child guides their blind parent. Photo credit Sightsavers

In many parts of tropical Africa, it is the children who have to guide their parents.
Some years ago, we often came across "cursed villages" close to rivers where practically every adult had gone blind. Children had to leave school, where there were schools, to look after their parents. All the while, waiting to go blind themselves. There was no curse on these villages. They are merely located near to water courses that provide drinking water and irrigation. However these water courses also harbour tiny flies that carry the Onchocerca volvulus worm. It is for this reason that the resulting disease is known as river blindness.

Black fly breeding site (Photo credit WHO)


Cause

The filarial worm Onchocerca volvulus is transmitted through repeated bites of a blackfly (Simulium spp.), whose breeding sites are fast-flowing water courses that often serve as essential resources for communities relying on fertile riverside lands for agriculture.

The adult worms encyst beneath the skin of the host where they form nodules, regularly releasing thousands of embryonic larvae (microfilariae) over a period of 12-15 years. These microfilariae then move around the body in the subcutaneous tissue, to organs including the skin and eyes.

These microfilariae cause an inflammatory response (particularly when they die) and in many cases develop into nodules under the skin.

Some patients also develop eye lesions, and it is these that can lead to visual impairment and permanent blindness.

The accumulation of dead microfilariae in the eye causes severe eye damage (by the cornea, retina, optic nerve) and can lead to irreversible blindness after several years of exposure.

This is called "economic blindness" resulting from social and economic disadvantages, well before the blindness becomes final and complete.

A man blinded by onchocerciasis

History

Between 1974 and its close in 2002, the WHO’s OCP (Onchocerciasis Control Programme) had relieved 40 million people from the disease, prevented blindness in 600,000 people and ensured that 18 million children were born free of the threat of the disease. Furthermore, 25 million hectares of abandoned fertile farmland was reclaimed and repopulated.

The economic rate of return (ERR) from this programme is estimated at 20% by the World Bank over the period 1974 - 2012, from an estimated total expenditure of US$571 million. Given this impressive ERR, the OCP is often cited as one of the most cost-efficient public health programmes in the world.

In 1995 the WHO launched APOC (African Programme for Onchocerciasis control), with the objective of controlling onchocerciasis in the remaining endemic countries in Africa, targeting an estimated 125 million people exposed to the disease. Amongst the targeted population, 18 million people already harboured the parasite in their body, 900,000 suffered from low vision and 400,000 were already completely blind.

According to the results of an assessment carried out by the Erasmus University of Rotterdam, it is believed that each year APOC prevents 40,000 cases of blindness and regains more than 700,000 disability-adjusted life years (DALYs). APOC uses community-directed treatment with ivermectin (CDTI) to administer mass drug treatment to communities, an approach that is widely respected for its effectiveness (after 7-9 rounds of treatment the proportion of the population reached is 70%). Not only does treatment with ivermectin tackle onchocerciasis, but other public health issues such as lymphatic filariasis, malaria and geoheminths. Since the beginning of its involvement in onchocerciasis control in 1992, and today working within the framework of APOC, the OPC has implemented the same approach to treatment.

Solidarity at all levels

Provided that anyone threatened by onchocerciasis is treated each year for at least 15 years, ivermectin will allow us to completely eradicate the disease.

Since 1992, the OPC has been committed to following through with this challenge. We are the only French-speaking organisation involved in APOC, which is active in 31 African countries, with programmes treating an estimated total population of 88 million.

In order that are actions are delivered with the greatest efficiency, even in the most remote communities, we have developed an impressive chain of solidarity, made up of 13,800 volunteer villagers and around 500 health workers from every level (from doctors to health assistants), trained by the OPC. Many of them also contribute to the primary eye care network through early diagnosis of visual deficiencies in their villages. Preparations ahead of ivermectin distribution

Thanks to this magnificent system, the OPC covers, for the remarkably low cost of just 18 Euro cents per patient, all the homes affected by the disease. Thanks to this magnificent system, the OPC covers, for the remarkably low cost of just 18 Euro cents per patient, all the homes affected by the disease.

A young girl takes an ivermectin tablet

In the Republic of the Congo - Results on track for elimination after 30 years

Results from 2013 :

710,456 people in 760 eligible villages treated with ivermectin, in line with the required 80% coverage rate given that there were 886,606 people eligible.

The operations are supervised by the national team and 209 national health agents — doctors and nurses — either trained or retrained according to their needs, supported by 1,922 village community distributors. Their roles include : awareness-raising, census taking, training, distribution, monitoring and supervision, collation and analysis of results, and retro information.

2013’s results were maintained in line with those of previous years, allowing us to predict the medium-term elimination of the infection and stopping its transmission amongst two-thirds of Congolese households.

2013 was the first of five years of the OPC’s partnership with Sightsavers in Congo. The project has as its aim to cement the transition from a control-based approach to one of elimination, with the extension of treatment to previously ineligible hypo-endemic areas, intensification of treatment quality control in problematic areas, installation of networks of national epidemiological and entomological surveillance teams as well as the integration of lymphatic filiarosis elimination into the onchocerciasis elimination programme.

In the former OCP (Onchocerciasis Control Programme) countries of Mali, Guinea and Senegal

Since the early 1990s the OPC has had a pioneering role in the fight against onchocerciasis and ocular defects, with the rollout of Community-Directed Treatment with Ivermectin and the training of community distributors in early diagnosis of visual deficiencies at village level.

Since then, control activities continue with a constant efficiency across households through the framework of the African Programme for Onchocerciasis Control (APOC) under the auspices of national programmes, the action of 12,000 distributors agents community, framed by national health professionals (doctors and nurses Chief Medical Post) extending the initial training provided by the OPC allows more than 3 million people to always be protected in over 6,300 villages.

The infection is now considered virtually extinct in Senegal and should see the same status in almost all of the Guinea and Mali, where interruptions experimental treatments have been undertaken in several homes. Thus, populations recolonize the most fertile lands and the richest abandoned due to onchocerciasis.

However, the OPC continues its efforts in Congo, where the disease has not yet been eliminated.

Perspectives

The OPC is a founding member of the Onchocerciasis Elimination ONG Group and is represented on APOC’s Technical Committee, for which role our experts are frequently engaged in mission work as consultants.

2016 : PENDA (Programme for the Elimination of Neglected Diseases in Africa)

In these various capacities, the OPC has actively contributed to the development of PENDA, which will replace APOC for ten years from 2016. It will push for the implementation of a systematic approach to the diseases’ evaluation in the former Onchocerciasis Control Programme’s countries, in the run up to the definitive elimination of onchocerciasis in West Africa.

Thanks to onchocerciasis control, life returns to normal (Photo credit : extract from "Mara, le regard du lion", a film directed by Bernard Surugue (c) Orstom/ird-OMS)

With a donation of just 15 €, you protect 150 people from river blindness. To make a donation, click HERE

Sources :
- http://elibrary.worldbank.org/doi/b...
- http://www.who.int/apoc/publication...
- http://www.who.int/apoc/about/en/