In many developing countries, people earn their income thanks to agriculture and fishing, which makes leaving near water essential. But for some, living near water can also mean confronting neglected tropical diseases (NTDs) like onchocerciasis, a disease more commonly called river blindness.
River blindness is an eye and skin disease that has irritating inflammatory effects on the body. As its name suggests, it commonly affects people who live or work near fast-flowing rivers and streams, where blackflies breed.
There are 18 million people infected with the disease. An estimated 120 million people at risk around the world, but almost all of them (96%) live in Africa, according to the World Health Organization.
Female blackflies infected with a parasite known as the filarial worm (Onchocerca volvulus) bite their hosts, allowing larvae to enter the body. As the larvae mature into adult worms, they group together to live in bumps under the skin called “nodules.”
From there, the adult worms release up to 1,000 embryonic larvae — known as microfilariae — per day. These microfilariae travel throughout the body and migrate to the skin, where they cause skin rashes, lesions, and intense itching. They can also make their way to various parts of eye, from the cornea to the retina, and cause damage to its delicate structures, leading to blindness. Infection and irritation occur when the microfilariae die, which causes intense inflammatory responses within the human body.
While river blindness is not technically contagious as it cannot be passed from one person to another, the cycle continues when a fly bites an infected person, ingests the microfilariae, and then carries the parasite to another victim.
Often this means people working on fertile land, who rely on agriculture for their livelihood, are forced to move. Leaving endemic areas like this can be extremely disruptive.
Emmanuel, a 60-year-old man from Ghana, contracted river blindness after years of making his living by fishing in the local river.
“I noticed a long time ago I had a problem with my eyes but it started gradually, it didn’t come all of a sudden — but week by week,” he told Sightsavers in 2016.
Luckily, he was able to receive treatment (ivermectin), which helped with his symptoms — but he noted that treatment was not just important for his own well-being.
“I already have blindness, but we are now protecting the others, the little ones,” he said.
River blindness can affect entire families. When children are forced to take care of their parents or if children themselves are infected, they may have to stay home from school, which puts a stop to their education and furthers the cycle of poverty.
Insecticides and treated clothing that can protect against blackfly bites are the best means of prevention for this diease, as there is no preventative vaccine or medication.
In the mid '70s, the Onchocerciasis Control Programme (OCP) started spraying insecticide against blackfly larvae, and supplemented that with large-scale mass distribution of ivermectin treatment in 1989. They were able to relieve 40 million people from infection, prevent blindness in 600,000 people, and ensure that 18 million children were born free from the threat of the disease.
The program restored and reclaimed 25 million hectares of abandoned arable land to live on and for agricultural production, which could feed 17 million people annually.
Every year, more countries are able to declare themselves free of river blindness after decades of mass drug administration and elimination work. Today, the disease persists mainly in tropical areas in sub-Saharan Africa, Yemen, Brazil and Venezuela — but the end of this NTD is in sight.