What is Onchocerciasis?

Introduction:

Onchocerciasis, also known as river blindness, is a tropical disease caused by the parasitic worm Onchocerca volvulus. It is transmitted to humans through the bites of infected blackflies, which breed in fast-flowing rivers and streams. 

Onchocerciasis

OVERVIEW

What is Onchocerciasis?

Onchocerciasis, also known as river blindness, is a tropical disease caused by the parasitic worm Onchocerca volvulus. It is transmitted to humans through the bites of infected blackflies, which breed in fast-flowing rivers and streams. The worms live in subcutaneous nodules and release larvae that migrate to the skin and eyes, causing itching, skin lesions, and visual impairment. Onchocerciasis is most commonly found in sub-Saharan Africa, but it also occurs in parts of Central and South America and Yemen. It is a leading cause of blindness in the developing world.

CAUSES AND RISK FACTORS

Here are the main causes and risk factors for onchocerciasis:

Causes:

Onchocerciasis is caused by the parasitic worm Onchocerca volvulus, which is transmitted to humans through the bites of infected black flies.

Risk factors:

• Living in or traveling to areas where the disease is endemic (most commonly found in sub-Saharan Africa but also occurs in parts of Central and South America and Yemen)
• Spending time near fast-flowing rivers and streams where blackflies breed
• Having unprotected skin exposed to blackfly bites
• Working or living near rivers and streams (e.g., fishermen, farmers)
• Having a weakened immune system (e.g., due to HIV/AIDS)

SIGNS AND SYMPTOMS

The signs and symptoms of onchocerciasis can vary depending on the stage of infection and the location of the worms in the body. In the early stages of infection, there may be no symptoms at all. As the infection progresses, the worms can cause the following signs and symptoms:

• Itching: The worms release a chemical that can cause intense itching of the skin, especially at night. The itching can be so severe that it interferes with sleep.
• Skin lesions: The worms can cause raised, bumpy lesions on the skin, particularly on the arms, legs, and lower abdomen. These lesions may be red, purple, or black in color.
• Eye problems: The worms can also migrate to the eyes, where they can cause visual impairment and even blindness. Symptoms of eye problems may include eye pain, sensitivity to light, blurry vision, and vision loss
• Lymph node swelling: The worms can also cause swelling of the lymph nodes, particularly in the groin, armpits, and neck.
• Other symptoms: Onchocerciasis can also cause fatigue, weight loss, and muscle and joint pain. In severe cases, the worms can cause severe skin scarring and disfigurement.

DIAGNOSIS

Onchocerciasis is diagnosed through a combination of physical examination, medical history, and laboratory tests. The following tests may be used to diagnose onchocerciasis:

• Skin snip test: A small piece of skin is removed and examined under a microscope for the presence of microfilariae (larvae) of the worms.
• Lymph node biopsy: A small sample of lymph node tissue is removed and examined for the presence of adult worms.
• Blood test: A blood sample is tested for antibodies to the worms, which may indicate an active or past infection.
• Eye examination: An eye examination may be performed to assess the presence and severity of eye problems caused by the worms.

It is important to see a healthcare provider if you have symptoms of onchocerciasis or have been bitten by a blackfly in an area where the disease is prevalent. Early diagnosis and treatment can help prevent or reduce the severity of complications.

MANAGEMENT AND TREATMENT

Onchocerciasis can be managed and treated with medications that kill the worms and prevent further damage to the skin and eyes. The most commonly used medication is ivermectin, which is taken orally. Ivermectin kills the microfilariae (larvae) of the worms but does not kill the adult worms. Therefore, multiple doses of the medication may be necessary to clear the infection.

In addition to medication, management and treatment of onchocerciasis may also include the following:

• Skin care: Keeping the skin clean and moisturized can help reduce itching and prevent skin infections.
• Eye care: If the worms have migrated to the eyes, treatment may include medications to control inflammation and prevent scarring. In some cases, surgery may be necessary to remove scar tissue or repair damaged eye structures.
• Prevention: The use of protective clothing, such as long sleeves and pants, and the use of insect repellents can help prevent blackfly bites and reduce the risk of onchocerciasis.
• Supportive care: People with onchocerciasis may also benefit from supportive care, such as counseling and social support, to help them cope with the physical and emotional effects of the disease.

It is important to note that onchocerciasis is a chronic disease, and treatment may need to be ongoing to control symptoms and prevent further damage to the skin and eyes.

COMPLICATIONS

• Onchocerciasis can cause a number of complications, including:
• Skin scarring: The worms can cause raised, bumpy lesions on the skin, which can lead to scarring. In severe cases, the skin may become thickened and disfigured.
• Eye problems: The worms can migrate to the eyes, where they can cause visual impairment and even blindness. Complications of eye problems may include eye pain, sensitivity to light, blurry vision, and vision loss.
• Other complications: Onchocerciasis can also cause fatigue, weight loss, and muscle and joint pain. In rare cases, the worms can cause serious complications such as meningitis (inflammation of the membranes surrounding the brain and spinal cord) or hydrocephaly (a condition in which fluid builds up in the brain, causing the head to enlarge).

It is important to seek medical treatment for onchocerciasis to prevent complications and manage symptoms. Early treatment can help prevent or reduce the severity of complications.

PREVENTION

There are several measures that can be taken to prevent onchocerciasis, including:

• Avoid areas where the disease is prevalent: Onchocerciasis is most commonly found in sub-Saharan Africa, but it also occurs in parts of Central and South America and Yemen. If you are planning to travel to an area where the disease is prevalent, it is important to take precautions to avoid blackfly bites.
• Wearing protective clothing: Wearing long sleeves and pants can help protect the skin from blackfly bites.
• Using insect repellents: Using insect repellents that contain DEET or picaridin can help repel blackflies and reduce the risk of infection.
• Practicing good hygiene: Keeping the skin clean and moisturized can help reduce the risk of infection and prevent complications.
• Controlling blackfly populations: Efforts to control blackfly populations through the use of insecticides and other methods can help reduce the transmission of onchocerciasis.
• Receiving treatment: If you are living in or have traveled to an area where onchocerciasis is prevalent and you have been bitten by a blackfly, it is important to seek medical treatment as soon as possible to prevent the development of the disease.

PROGNOSIS

The prognosis for onchocerciasis depends on the stage of infection and the severity of symptoms. In the early stages of infection, the prognosis is generally good, as treatment can help kill the worms and prevent further damage to the skin and eyes. However, if the infection is not treated, it can progress and cause serious complications such as skin scarring, eye problems, and even blindness.

The prognosis for people with advanced onchocerciasis may be more guarded, as the damage caused by the worms may be irreversible. However, even in advanced cases, treatment can help manage symptoms and prevent further complications.

Overall, the prognosis for onchocerciasis is generally good with early diagnosis and treatment. It is important to seek medical treatment as soon as possible to prevent the development of serious complications.