From the field / Fighting disease /

How our research is finding new ways to fight river blindness

August 2019

Children playing in the water, a man collecting sand to sell it.

For more than 20 years, medication has been distributed in Cameroon to stop the spread of river blindness. Yet large numbers of people are still testing positive for the disease.

It was clear we needed a different approach. So we carried out research to understand why river blindness is persisting, despite our best efforts to tackle it.

We used the findings to design and evaluate a new strategy to help efforts to eliminate river blindness in the region.

River blindness can cause itchy rashes on the skin, and can eventually lead to irreversible blindness.

River blindness is a parasitic infection transmitted by flies that breed near fast-flowing water. If left untreated, the infection can lead to irreversible blindness.

Since 1996, everyone over the age of five in the West Region of Cameroon has been given a yearly dose of medication called ivermectin to treat and prevent river blindness.

The medication is distributed by local community volunteers, who use a dose pole to measure people’s height to determine the amount of medication they need. This technique of delivering preventative medication to large groups of people at once, known as mass drug administration, can eliminate river blindness when carried out over many years.

But in 2015, in one village in the region, 37 per cent of adults still tested positive for the river blindness infection. We needed to find out why.

Volunteers travel from house to house distributing medicine each year, but this hasn’t been enough to stop the disease being spread.
We needed a new strategy.

Two people riding a motorbike in rural Cameroon.

We carried out a comprehensive research study in the West Region of Cameroon, collecting information on potential issues that may be contributing to the disease’s continuing persistence. We also carried out assessments to evaluate infection in flies and humans, and identified a 12km area in Massangam health district where a large number of people have river blindness.

The results showed several reasons why so many people in the area have the disease, including:

Several fast-flowing rivers where flies breed all year round
Nomadic communities missing out on preventative medication and potentially being a source of continued infection
Large numbers of people fishing from the rivers, which exposes them to the flies that carry the disease

Click the arrows on the gallery below to read more.

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Two men herd cattle on a dirt road. — Nomadic communities travelling in and out of the area often don't receive the medication, because they are often missed from the standard distribution campaigns.

A river. — The area is home to several fast-flowing rivers, in particular the Mbam and Nja, where the flies breed. Many residents live close to these rivers, putting themselves at risk of infection.

A women holds a fishing net next to a river. — Fishing is part of daily life for many people in the area. This increases the risk of being bitten by the flies that carry the disease.

Once we’d discovered why the disease has remained a problem in Cameroon, we started working with the local community to discuss new ways of treating it.

The existing approach, carried out via mass drug administration, involves as many people as possible (whether they are infected or not) being given treatment to stop the disease progressing and prevent them passing it to others.

We decided to try a new approach in the affected area: testing people to find out whether they have the disease, then only treating the people who test positive.

Identifying who has river blindness

1. Take a skin sample

In communities that have high rates of river blindness, a small sample of skin from each person is tested to find out if they have the infection.

2. Look for larvae

After 24 hours, the sample is examined to look for microscopic larvae. If larvae are found in the sample, it indicates that the person has river blindness.

3. Prescribe antibiotics

The patient is then given an antibiotic called doxycycline for five weeks. This cures the infection (unlike ivermectin), therefore can speed up elimination.

A lady receive medicine and food from a man.

Efforts are also being made to reach the nomadic communities through a strategy to test and treat them (with doxycycline) in a way that’s culturally appropriate. This is timed to fit in with their migration patterns, to reach the maximum number of people possible.

As well as treating people who have the infection, we also want to stop them becoming infected via fly bites in the first place. To do this, we inspect rivers for black flies, looking for larvae on vegetation or rocks. We then use insecticide to kill the fly larvae and prevent them developing into adult flies.

The process, known as larviciding, uses a safe insecticide that is well tolerated by the environment and other aquatic creatures. During larviciding, the flies are monitored to determine if their numbers are falling. This enables us to change our strategy if it’s not proving effective.

2020 update

Children washing themselves in a stream.

We are presenting the results of this research at the annual meeting of the American Society of Tropical Medicine and Hygiene this year. One finding from the first round of test and treat was that nomadic communities were not reached as consistently as settled communities.

We’ve embarked on a new research project to understand why this is and we’re using a targeted approach involving multiple activities to engage with the nomadic communities. These include using guides and drug distributors from the nomadic community, creating materials in the local language (Fulfulde) with help from language experts, and using satellite imagery to find where nomadic camps are located.

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How our research is finding new ways to fight river blindness

For more than 20 years, medication has been distributed in Cameroon to stop the spread of river blindness. Yet large numbers of people are still testing positive for the disease.

River blindness can cause itchy rashes on the skin, and can eventually lead to irreversible blindness.

Volunteers travel from house to house distributing medicine each year, but this hasn’t been enough to stop the disease being spread.
We needed a new strategy.