River Blindness – What is?, Symptoms, Treatment, Causes

River blindness, also called Onchocerciasis, is a disease brought about by a small worm known as Onchocerca volvulus commonly transmitted by an infected black fly that usually attacks the eyes.

Deemed as the second greatest cause of infectious blindness, this disease is called river blindness because the black fly which transmits the disease usually breeds in free-lowing water such as rivers or streams. Other than the eyes, the condition can also cause skin disorders.

The disease proliferates when the fly feeds on humans infected with the disease, and consequently, the fly gets infected. The worm that is now carried by the fly matures over a span of two weeks, and the disease becomes most contagious and communicable to humans. When the infected fly feeds on other humans, infective larvae are passed through its bite, therefore, transmitting the disease.

A Man Showing River Blindness

Signs and Symptoms of River Blindness

People who contract the disease are either symptomatic or asymptomatic. Those who are symptomatic experience common symptoms such as the following:

1. Prickling sensation all over the body
2. Eruptions of the skin
3. Skin blemishes or blotches
4. Abrasions in the eye
5. Protuberances (subcutaneous part of the skin is raised)
6. Glaucoma
7. Blindness

The skin assumes forms of discoloration when the eruptions are treated. The grimmest demonstration of the disease is the abrasion seen in the eye which progresses until the person becomes blind. The worm can even be visualized floating in the front chamber of the eye during the eye examination with the aid of an instrument. Upon reaching the end of their cycle, these worms die, causing inflammatory reactions which result in the inflammation of the uvueal tract, the vitreous chamber, and retina and finally, blindness. Associated glaucoma can also arise due to corneal damage, causing intense inflammation of the keratin of the eye, severe trauma, and sightlessness. The symptoms usually become visible one to three years after acquisition of the disease.

Causes

The only noted cause of river blindness is the parasite Onchocerca volvulus which lives inside the black fly. The transferred parasite develops inside the fly, evolving from infective larvae to full-grown worms, completing the disease cycle. These worms can live inside the human body for 14 to 15 years. The disease is endemic in Africa and in some isolated places in Latin America and Yemen.

Diagnosis

River blindness is diagnosed with a wide array of examination studies which include laboratory work-up, imaging results, and even immunologic tests.

Laboratory Work-up

1. Immunologic diagnosis: This study is done to differentiate current infections from earlier ones.
2. Antigen studies: This test utilizes the urine or tears of an infected person to detect specific infections caused by the parasite.
3. Complete blood count: This is usually done to detect levels of white blood cells which are normally high due to infection.
4. Imaging studies: Although this is not useful in the diagnosis of the disease, it is still used to detect bumps on the skin which are not palpable.

Other Tests

The following are tests that have been used earlier to diagnose the disease:

1. Diethylcarbamazine patch test. This test, which is done by applying DEC cream on the skin, shows reactions on the site of application which is a common reaction of dying parasites.
2. Skin snip procedure: This is done by cutting skin samples from different sites of the body and placing in solution with salt for observation. Results would show that worms arise from the skin samples dipped in the salt solution.
3. Removal of nodules: This is the most obtrusive procedure since it involves the removal of skin nodules. Removal of these nodules also helps to remove the parasite since it is found inside the nodules.

Treatment

The treatment of the disease is aimed at removing the larvae stage of the parasite inside the body of an infected person.

Medical Management

Antiparasitic agents: These drugs help arrest evolution and propagation of the parasites inside the body.

1. Ivermectin (Mectizan): This is the first-class drug for river blindness. Its mechanism of action is known to cause damage on the parasite’s nervous and muscle systems, eradicating the parasite by paralyzing it until it dies. This drug is only effective on the larvae stage of the parasite and has no effect on adult worms but will hinder the larvae production. Hence, this antiparasitic drug helps to prevent people from acquiring the disease and its transfer to other people.
2. Diethylcarbamazine (Hetrazan): Although this drug is rarely used for treating the disease, it is known to elicit deterioration of the parasite’s organs, resulting in the death of their cells.

Antibacterial agents: These drugs are used mainly to stop the growth of other microorganisms that may affect the disease progression.

1. Doxycycline: This antibiotic is utilized to help reduce the number of bacteria living inside the body of an adult worm and break the egg production chain. Despite the effectiveness of this drug, there is difficulty in administering the drug since treatment needs daily dosage for four to six weeks to achieve desired effects.

Surgical Management

Excision or removal of skin nodules is an effective cure of the disease if all of the adult worms are removed. This treatment is not highly recommended since there are patients whose nodules are not distinct whereas others show diverse nodules.

Complications

Untreated and uncontrolled river blindness poses an increased risk of complications which include the following:

1. Eye complications: Complications related to the eye involve blindness which is consequential to inflammation of the conjunctiva, formation of excessive fibrous tissue in the cornea, keratitis, accumulation of vascularised granulation tissue in the cornea, inflamed retina and chorion, glaucoma, and deterioration of the optic nerve.
2. Skin complications: These complications include rashes all over the body, increased skin pigmentation and discoloration, and skin blemishes and blotches. Decreased pigmentation of the skin, loosening of skin elasticity, and severe inflammation of the skin which may be limited to one limb may also occur.
3. Blood and immune system complications: These complications involve a severe and anomalous increase in the size of lymph nodes.

Prevention

There is no specific medicine that will stop people from contracting river blindness and no other ways of prevention other than awareness and health education. It is very important that those living in places where the disease is endemic and those who visiting such places are educated about the disease and ways to avoid being in contact with the black flies. The use of defensive clothing and application of offensive topical agents such as mosquito repellent lotion can be used to avoid being bitten by flies. Another preventive strategy is total black fly elimination and regular prophylactic treatment of antiparasitic drugs in endemic areas.

River Blindness Pictures

Onchocerca Volvulus Parasite that Causes River Blindness

A Black Fly Biting a Person

Skin Blotches with Raised Edges Characteristic of River Blindness