River Blindness
- mrsaepts
- Nov 16, 2022
- 5 min read
BY Pitchapa Srisamut
Edited by Napasjutha Kongsonthana
What is river blindness ?
Onchocerciasis (ON-koh-sur-KY-uh-sis), commonly recognized as “river blindness”, is a parasitic infection which after an individual has been infected, the infection may result in visual impairment, permanent blindness and skin conditions—for example, intense itching and rashes. River blindness is regarded by the World Health Organization as one of the Neglected Tropical Diseases (NTD).
Neglected Tropical Diseases are a diverse group of twenty medical conditions that are mainly prevalent in tropical areas where they mostly affect more than a billion people who live in mostly impoverished areas (Neglected Tropical Disease, World Health Organization, 2021). Neglected Tropical Diseases also include other conditions such as leprosy, lymphatic filariasis, mycetoma, rabies, etc.
Based on an article by the World Health Organization, it is estimated that in the year 2017, at least 220 million individuals around the globe needed preventive chemotherapy against onchocerciasis, 14.6 million infected patients already suffered skin disease and 1.15 million people had lost their vision (Onchocerciasis, World Health Organization, 2021).
What countries get river blindness?
Onchocerciasis or “River Blindness” is endemic in Africa, and in six countries of the Americas including Brazil, Colombia, Mexico, Guatemala, Ecuador, and Venezuela, where the disease was introduced through slave trade.
(Onchocerciasis, World Health Organization, 2021)
Cause/ Type (Waterborne diseases/ Water-Washed diseases/ Water-Based diseases/ Water-Related insect vector diseases)
Onchocerca volvulus, a parasitic worm spread to humans via a vector, which is a genus of blackflies called Simulium. A typical blackfly of this kind measures about 1 to 5 millimeters in length and its thorax is in various colors from black to different shades of gray or even yellow. Simulium blackflies are generally found around rivers and they feed on blood; therefore, these blackflies bite humans along with some other animals. Since the blackflies carrying the disease can be found near rivers, hence its common name ‘river blindness’.
When a Simulium blackfly carrying Onchocerca larvae bites a person—although the blackfly has to bite the individual multiple times to be able to cause onchocerciasis—the larvae then enters the host’s body and multiplies itself inside the bumps on the skin, avoiding the body’s immune system. In the succeeding 12 to 18 months, these larvae inside the body will mature into adults, then spread to, live and reproduce in other parts of the body while feeding on a lot of different bodily fluids for over the course of 10 years.
Onchocerciasis symptoms started to occur when the onchocerca larvae spread to the eyes, the body’s inflammatory response (a kind of response from the body when tissues are injured by toxins, heat, trauma, etc. The damaged cells then release chemicals leading blood vessels to leak fluid into the damaged tissues to prevent the foreign substances from further contact with the tissues, this also causes swelling) kills the larvae. When the larvae get killed, the accumulated dead larvae lead to scars in tissues of the eye. Together with the inflammatory response damages, these will sooner or later result in vision loss and skin conditions over time.
Symptoms & Diagnosis
In early stages, the symptoms may seem to be out of sight. It takes at least a year after the infection for the visible symptoms to appear. The symptoms of onchocerciasis can be separated into 2 categories, skin symptoms and eye symptoms. These symptoms are listed as follows:
Skin symptoms:
-Extremely itchy skin
-Rashes
-Raised bumps on the skin
-Skin pigment loss
-Dry, flaky skin
-Loss of skin elasticity
Eye symptoms:
-Light sensitivity
-Redness and irritation
-Cataracts (progressively opaque lens of the eyes)
-Visual impairment
-Complete Blindness
In rare or extreme cases, the infected patients may also suffer swollen lymph nodes, glaucoma and other parts of their eyes such as the cornea and the retina may be damaged as well.
Diagnosis
There are several ways to diagnose river blindness. The first option is called a skin snip in which a doctor will have to perform a skin snip, a biopsy to remove an infinitesimal portion of the skin, then put the skin sample into a saline solution to cause the larvae to emerge from the skin. The sample will then be examined closely under a microscope.
Secondly, a Mazzotti test can be performed to diagnose the disease. The test is a skin patch test performed with the help of a drug called diethylcarbamazine (DEC), which will lead to the rapid death of microfilariae. There are two ways for a doctor to perform a Mazzotti test, they may either prescribe the drug to be taken orally and observe the infected patient’s body for extreme itching within two hours or apply the drug on a skin patch. However, when the other side of the coin has been taken into account, the use of diethylcarbamazine may cause further severe symptoms. That is why this method is seldom used.
Other methods include nodulectomy, which is rarely used nowadays, and newer technology such as the polymerase chain reaction test (PCR) and rapid format antibody cards tests.
Treatment
In cases of onchocerciasis, research and studies have shown that the recommended treatment for onchocerciasis is ivermectin, which should be taken at least once a year for the life span of the adult worms (10-15 years) or for as long as the skin or eye conditions are present. However, we need to make sure the patient does not have another parasite called Loa loa, a parasite often found in the same areas as Onchocerca volvulus, which can cause serious side effects to the medications used to treat onchocerciasis.
Another method to treat onchocerciasis is to use a drug named doxycycline to kill the bacteria called Wolbachia, a kind of bacteria that the adult worms depended on to survive. In some cases, the doctor may prescribe the patient both of the mentioned medicine.
Prevention
At the moment, there are no vaccines or medications available to prevent onchocerciasis. The best preventions an individual is able to receive at this point are the following:
-Avoiding high infection areas
-Exposing as little skin as possible e.g. wearing long sleeves and long pants
-Using insect repellent e.g. N,N-Diethyl-meta-toluamide (DEET)
-Wearing clothes treated with effective insect repellent
Interesting facts
Let us leave the serious medical matters there. Now, for one to expand one’s knowledge database further and deeper, they must understand beyond the study of medicine. Let us begin with the intriguing and lighthearted facts. Perhaps, these may even “come in handy” one day.
In the year 2015, the Nobel Prize in Physiology or Medicine was awarded to three individuals, namely, William C. Campbell, Satoshi Ōmura and Tu Youyou. For Youyou, she was awarded the prize for her discoveries of a novel therapy against malaria. While for Campbell and Ōmura , the prize was awarded to them for their discoveries of a novel therapy against roundworm parasites, which include numerous infectious diseases with river blindness as one of them. In 1978, 37 years before the prize was awarded, they successfully cultured a strain from Campbell’s purified substance called avermectin, which can be later chemically modified to ivermectin, it was then proved effective against infectious disease such as river blindness and elephantiasis.
Our last fact for today is rather obscure or unexpected by most people. The fact begins with a tone that could easily occupy one’s mind. Then it is followed by the sound of a string instrument, and a voice goes…
“Human Kindness - River Blindness.
Black flies rise as the water flows.
Human Kindness - River Blindness.
Angels cry as the fever grows.”
That is correct, there is a song called ‘River Blindness’ released by The J. Geils Band back in 1981 when the disease was the leading cause of blindness across Africa and it still remains the second infectious cause of blindness today around the world.
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