Onchocerciasis, also known as river blindness, is a parasitic infection caused by Onchocerca volvulus, a nematode.
It is gotten when infected blackflies (Simulium species) bites a person, during a blood meal.
These species breed near fast-flowing rivers and streams. As a result, people who live in riverine areas like Rivers, Cross river, Akwaibom states in Nigeria, are more at risk of getting this disease.
Also people living in sub-Saharan Africa, and in some parts of Latin America and Yemen.
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How Does One Get Onchocerciasis?
The blackfly is the primary vector for onchocerciasis. And Just like with mosquitoes in malaria, when an infected blackfly bites a person, it deposits larvae (microfilariae) under the skin. The microfilariae then mature into adult worms, forming nodules in the skin.
The adult worms release thousands of microfilariae, which migrate through the skin, eyes, and other tissues.
A bite from another blackfly spreads the infection further, by carrying the microfilariae from the infected person to another person and on it goes, perpetuating the cycle.
How then can one tell they have it.
Symptoms
The symptoms of onchocerciasis can vary depending on the intensity of the infection and the affected tissues:
Skin Symptoms: Intense itching, rashes, and depigmentation (“leopard skin”).
Eye Symptoms: Visual impairment (blurry vision, permanent blindness). Caused by microfilariae invading the cornea and other parts of the eye.
Nodules: Painless lumps (onchocercomas) under the skin, housing adult worms.
Diagnosis
Diagnosing onchocerciasis involves a combination of clinical evaluation and laboratory tests. This is discussed extensively here.
Clinical manifestation: The presence of the teltale signs of onchocerciasis listed above, prompts treatment.
Skin Snip Test: A small piece of skin is taken and incubated in saline or culture medium to observe the emergence of microfilariae under a microscope.
Polymerase chain reaction (PCR) for detecting Onchocerca DNA.
Serological Tests: Detect antibodies specific to O. volvulus. Tests like OV-16, OvH2 and OvH3 are highly sensitive to Onchocerca antigen.
Slit-Lamp Examination: Used to identify microfilariae in the eye.
Complications
Untreated onchocerciasis leads to severe consequences and some of them are irreversible damages.
Blindness: A major outcome, that’s why the nickname of onchocerciasis is “River blindness.”
Chronic Skin Disease: Disfiguring and hyperpigmentation. Debilitating conditions, including elephant-like skin thickening.
Mental and Social Impact: There is often stigma, isolation, and reduced quality of life associated with the physical manifestation of onchocerciasis.
Treatment
The antiparasitic drugs used albendazole and Mectizan (Ivermectin), with ivermectin as the primary treatment.
This antiparasitic drug kills microfilariae but not the adult worms.
It is usually administered every 6–12 months until the adult worms naturally die, which can take 10–15 years.
Other treatments include:
Doxycycline: Targets the Wolbachia bacteria, essential for the survival of adult worms.
Surgical Removal: In some cases like hydrocele, where nodules are accessible and causing significant discomfort.
Conclusion
Onchocerciasis continues to pose a public health threat in endemic regions, especially in Nigeria, where it distorts livelihoods and impacts communities negatively.
Early diagnosis and treatment, combined with vector control measures, are very important in reducing its burden.
Public awareness and health education also play key roles in breaking the cycle.
