Water is one of the most common incubators when it comes to little beasties that cause tropical diseases. Onchoceriasis, also known as river blindness, is one of those diseases which originate from the water. It is a parasitic disease caused by a worm which lives in the water and is the one of the top causes of blindness from infection.
The worm which causes river blindness is the Onchocerca volvulus and is quite thin and cannot really be seen by the naked eye. The disease is transmitted from person to person from the bite of a blackfly. The larvae passed onto an unsuspecting victim turns into adult worms which can live for up to 15 years in the body!
How River Blindness Happens
The blackfly lays its eggs in river waters, particular those which have swift flowing waters. These eggs mature in about 12 days and become adults.
The female adult blackfly typically seeks to mate and after doing so is quite hungry for a little blood. When she bites someone infected with Onchocerciasis, she ingests the larvae from the parasitic worm which causes the disease. Then, the next person the female blackfly bites will get the larvae transmitted to them.
This worm larva then takes up residence in the human body and grows up into adult worms. These adult worms nestle into sinewy, threadlike nodules close to the skin’s surface as well as near joint areas causing great pain to the human host.
The Worm’s Effect on the Human Body
The adult female parasitic worm can be almost 20 inches long and literally produce millions of microscopic babies. It is these baby worms which travel through the skin. And when these worms die, the result is extreme itching as well as loss of pigmentation in the skin where the worm death occurs.
In addition, some people experience serious swelling in the lymph tissue, particularly in the groin areas as well as the eyes resulting in dropping genital parts as well as blindness or severe visual impairment. Symptoms of this parasitic worm infestation in the human body can take several years, finally manifesting itself anywhere from 1-4 years after becoming infected!
A Global View of the Disease
Many of the countries of Africa has occurrences of this river blindness in addition to the Arabian Peninsula, southern Mexico and countries in Central and South America like Ecuador, Guatemala, Venezuela, Colombia and Brazil. Almost 20 million people worldwide are affected by Onchocerciasis aka river blindness. At the very least, many of these people suffer complicated dermatitis and itching while up to half of them become blind.
Prevention and Intervention
The World Health Organization (WHO) is concentrating on intervention techniques to reign in the occurrences of river blindness. They are targeting the areas where these blackflies breed and therefore multiply. Using larvicides in special sprays, these are sprayed around the breeding sites of the rivers which harbor the flies.
In addition, a drug called Ivermectin is often administered to those people who are infected with the parasitic worm transmitted from the blackfly which causes river blindness. This drug kills the young worms inside the body before they can truly become detrimental to a person’s health. Both actions have helped lower the statistics of those affected by this tropical disease.
Photo: Onchocerca volvulus in its larval form. Image credit: CDC/Ladene Newto