Dermatologic Manifestations of Onchocerciasis (River Blindness) Treatment & Management

Updated: Jun 22, 2018
  • Author: Jason F Okulicz, MD, FACP, FIDSA; Chief Editor: William D James, MD  more...
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Treatment

Medical Care

The treatment of onchocerciasis was revolutionized with the introduction of ivermectin in 1987. Ivermectin therapy does not have the adverse reactions of DEC, and it eliminates the need for 6 weekly injections of suramin. The treatment is suitable for both clinical use and mass distribution in endemic areas. [13, 14, 15]

Ivermectin is a compound derived from the bacterium Streptomyces avermitilis. [16] The drug causes nematode paralysis by impairing neuromuscular function. Ivermectin not only prevents ocular disease but also improves and eliminates the skin disease. A single dose of 150 mcg/kg clears the microfilariae from the skin for several months. Ivermectin temporarily decreases the release of microfilariae, but it does not kill adult worms.

Adverse reactions are similar to the responses of the body to dying microfilariae, but the intensity and rate of development are increased. Adverse effects include fever, edema, pruritus, lymphadenitis, and body pains.

The frequency and duration of ivermectin therapy still is being debated. As many as 33% of patients in nonendemic areas are cured with only 1 dose of ivermectin, but most patients require additional therapy. [17]

Resistance to ivermectin may be emerging. A study from Ghana showed that female worms isolated from skin snips in some communities were not responsive or resistant to the antifecundity effects of ivermectin. [18]

Moxidectin is an antiparasitic drug approved by the US Food and Drug Administration (FDA) in June 2018to treat onchocerciasis in patients aged 12 years or older. The World Health Organization initiated clinical trials for use in onchocerciasis in 2009. Moxidectin is closely related to ivermectin, but it has a more sustained reduction in microfilarial levels. FDA approval was based on a double-blind, parallel group, superiority trial (n=1472) that compared moxidectin (8 mg PO once) with ivermectin (150 mcg/kg PO once). [19] The trial took place in Ghana, Liberia, and the Democratic Republic of the Congo. Results showed skin microfilarial loads (ie, parasite transmission reservoir) were lower from month 1 to month 18 after moxidectin treatment than after ivermectin treatment, with an 86% difference at month 12. Moxidectin would therefore be expected to reduce parasite transmission between treatment rounds more than ivermectin could, thus accelerating progress towards elimination.>

Small studies have shown that administration of doxycycline for 6 weeks in addition to ivermectin therapy led to Wolbachia depletion followed by interruption of embryogenesis and reduction in microfilarial loads lasting 18 months. [20]

Strategies targeting eradication of Wolbachia have been undertaken to identify alternative agents for treatment. A study of 5 weeks of doxycycline use without ivermectin showed a reduction in live worms in nodulectomy specimens. [21, 22] Additional studies using azithromycin [23] or rifampicin [24, 25] for Wolbachia eradication have been less efficacious than studies using doxycycline; however, further research may support the use of these agents as alternatives for those intolerant of doxycycline.

Suramin is used less often than ivermectin and given intravenously.

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Surgical Care

Nodulectomy has been a traditional form of therapy in Mexico and Guatemala. Moving from village to village, healthcare workers remove nodules from patients, especially nodules in the head.

This surgical approach may reduce the number of microfilariae that enter the eye, but no strong evidence supports its effectiveness in preventing blindness. The removal of nodules may be a valuable adjunct in patients treated with ivermectin.

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Prevention

The Onchocerciasis Control Programme (OCP) began in 7 West African countries in 1974. The major strategy for interrupting transmission of onchocerciasis was vector control. Hand spraying of black fly breeding sites along rivers, combined with the aerial distribution of larvicide, has been successful in this region. To prevent reinvasion by black flies, parts of 4 other countries were also included in 1986. This program closed in 2002, with all subsequent control efforts transferred to the participating countries.

The introduction of ivermectin in 1987 allowed assistance to be extended to other areas. Merck & Co decided to provide the drug, at no cost, in whatever quantities were needed, for as long as it was needed. Community-based distribution programs were established in endemic areas to administer the drug 1-2 times per year, even to remote villages.

Encouraged by successes with the OCP and ivermectin, the World Bank launched the African Programme for Onchocerciasis (APOC) in the remaining areas of Africa in 1995. The goal of the program is to eliminate the disease as a public health issue in these areas by 2007. Unlike the OCP, the APOC uses the community-based distribution of ivermectin as its primary control strategy. The Onchocerciasis Elimination Program for the Americas (OEPA), a similar program, also aims to eliminate onchocerciasis by 2007 in the Americas.

These programs face many challenges in the future. Whether or not successful control of the disease can be accomplished without the use of vector control has yet to be determined. The organization and effectiveness of community control programs, as well as their funding, may need to be addressed.

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Long-Term Monitoring

Considerable debate exists regarding the proper dosing frequency of ivermectin in endemic areas. The drug is given from every 3 months to every year, depending on the degree of symptoms, cost constraints, and patient compliance.

In nonendemic areas, a reasonable approach is the administration of a single dose of ivermectin. Depending on the patient's skin symptoms, the dose can be repeated every 3-6 months as needed. Strict follow-up care to determine the need for therapy is important after several doses are administered. The continuation of treatment throughout the entire 12- to 15-year life cycle of the worm has not been proven effective.

Nodulectomy remains an important adjunctive treatment.

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