Causes and risk factors
Onchocerciasis is caused by a parasite called as Onchocerca volvulus [filarial group]. It is spread through the repeated bites of female black flies that breed in swiftly flowing streams [hence, the term river blindness]. It is common in remote villages in the fertile lands where people depend on agriculture. The cycle of infection begins when a black fly bites an infected person and is infected with pre-larval forms of the worm called microfilariae. When the fly bites another person, larvae are passed into that person’s skin. The larvae move under the skin and form lumps [nodules], where they develop into adult worms in 12 to 18 months. Adult female worms may live up to 15 years in these nodules. After mating, mature female worms produce eggs, which develop into microfilariae that leave the worm. A worm may produce 1000 microfilariae each day. Thousands of microfilariae move through the tissues of the skin and eyes and are responsible for the disease. Usually, many bites are necessary before the infection causes symptoms. Thus, the infection is much less likely to develop in visitors to affected areas.
Clinical presentation
Predominantly it affects skin and eyes. Symptoms may take several months to years to appear. Microfilariae produce inflammatory response in subcutaneous tissues. Rash on skin, and itching can occurs. Nodules are seen on skin. Skin atrophy may be seen. There can be swollen lymph nodes. Disturbed vision, glaucoma occurs. Visual impairment , loss of vision, blindness can occur.
Investigations
Medical history by the patient and clinical examination by the doctor helps in diagnosis. Skin biopsy is done. Blood tests are advised. Diagnosis of the infection is made by identifying a pre-larval form of the worm in a skin sample.
Treatment
Treatment involves administration of anti- parasitic medicines along with antiboitics as per WHO recommendation and protocol in endemic areas. OCP, i.e., onchocerciasis control program has been implemented in regions affected with the disease which controls and prevents the spread of disease.
Complications
Complications such as permanent loss of vision can occur.
When to Contact a Doctor
One must consult a doctor if there is a visible skin rash with intense itching.
Prevention
Personal protective measures such as wearing insect repellents while working in farm, wearing long sleevesd shirt and long pants prevents the disease.
Facts and figures
25 million people are infected with onchocerciasis out of which 300,000 are blindbecome blind. ; 123 million people are at risk of becoming infected.
Systems involved
Circulatory system, integumentary system, CNS
Organs involved
Skin, eyes, lymph nodes
WHO statistics
OCP relieved 40 million people from infection, saved 600,000 people from blindness, and prevented 18 million children to be born free from the disease.
Recent updates
Columbia was declared as the first country to become onchocerciasis free in 2013. Ecuador is the second country free from the disease, declared in 2014.
