Ophthalmologic Manifestations of Onchocerciasis Follow-up
- Author: Deborah R Eezzuduemhoi, MD; Chief Editor: Hampton Roy Sr, MD more...
Further Outpatient Care
- Patients should receive follow-up care as needed.
Deterrence/Prevention
- Identification of endemic areas, education of the populace, training of local health care officials, procurement of antifilarial drugs, and vector control create a coordinated effort to eliminate onchocerciasis. Improved socioeconomic status with economic advancement also contributes to disease eradication.
- Onchocerciasis Control Programme
- Onchocerciasis is a chronic disease that affects rural populations. Accepted as inevitable by those who live in impoverished endemic areas, it is a striking example of how a disease can compromise the human potential for economic growth.
- Onchocerciasis has produced economically blind communities. In some villages in Burkina Faso, the prevalence of blindness has reached 35% of the population, reducing the agricultural productivity below their survival level. An estimated average of 22 years of productivity was lost for every blind person. The disease has led to the abandonment of some of the most fertile valleys in tropical Africa.
- Burdened by the adverse health and socioeconomic impact of this disease and encouraged by the prospects of effective control, several West African countries expressed interest in an action against the disease. A joint technical meeting of the Agency for International Development of the United States of America, Organization de Coordination et de Cooperation pour la Lutte Contre les Grandes Endemies, and the World Health Organization (WHO) was held in Tunis, Tunisia, in July 1968 to discuss the feasibility of onchocerciasis control. The implementation of a large-scale intercountry program in West Africa was recommended.
- The United Nations Development Programme (UNDP), Food and Agricultural Organization of the United Nations (FAO), World Bank, and WHO cosponsored a mission to 7 West African countries. The OCP began operations in 1974. The insecticides used were B T (Eriochrome black T), H-14, Abate (Temophos), pyraclofos, phoxim, permethrin, carbosulfan, and vectron. These were used on a rotation basis depending on the sensitivity of the Simulium complex. The rotation of the insecticides also deterred the emergence of resistant strains of the blackfly in the 1980s.
- Today, the number of people infected within the program area is nil because the vector almost has been eradicated. This astonishing result was achieved by a weekly aerial application of insecticides to the breeding sites of blackfly larvae in the rivers over a period of 14 years.
- Fourteen years of intensive public health efforts leading to vector control have led to the elimination of onchocerciasis as a significant public health hazard in 11 participating countries. The OCP established multinational collaboration as a keystone for onchocerciasis eradication. This remarkable public health accomplishment is of particular importance in that onchocerciasis eradication promoted significant socioeconomic development. Vector control continued through the year 2002 in the extension areas, where larviciding started much later. The success of the OCP must be maintained.
- Devolution, already in progress, is a challenge for the involved countries. They have assumed the responsibility of detecting and controlling the disease at the low level achieved by the OCP. Continuous collaboration between the countries is crucial because the blackfly does not recognize borders and can readily convey the infection from country to country.
- The Global 2000 River Blindness Program (GRBP) of the Carter Center played and continues to play a substantial role in controlling this disease.[1] In fact, the Carter Center, in collaboration with the Lions Clubs Sight First program (LCSF), provided 69% of the treatments in 1998 in Nigeria.[1] Approximately 6 million people were treated with ivermectin in the sub-Sahara region in 1998, with Nigeria benefiting the most (3,912,476 persons).
- The GRBP increased the treatment in Sudan 200% from the previous year despite the civil war of more than a decade.
- Of the 1 million Ugandans treated with ivermectin in 1998, 78% were treated under the GRBP. This was considered to be 98% of the annual treatment objectives of the GRBP for that year.
- The GRBP-assisted program in Cameroon achieved a 92% increase relative to the previous year with a total of 407,281 treatments in 1998.
- The World Bank's APOC trust fund has greatly supported the GRBP efforts. The strategy of the APOC is to achieve a complete community based program, called Community Directed Treatment with Ivermectin (CDTI). Under CDTI directions, the GRBP will try to increase community support so that village members will be encouraged and involved in the distribution of ivermectin even after the end of the OCP.
- With the theme "Elimination through sustainability of Mectizan treatment" by President Carter, the Onchocerciasis Elimination Program for the Americas (OEPA) treated 270,622 people in the Americas in 1998. This was 75% of the annual treatment objectives for that year.
- Continuous efforts are being made to identify endemic areas in Venezuela, the most endemic country for river blindness in the Americas, so that ivermectin treatment can be implemented.
- Training of cadres of national experts, who would assume responsibility, is important.
- The prospect for the development of a vaccine against onchocerciasis is hindered by the fact that antigens of O volvulus are complex and show extensive cross-reactivity with other filaria parasites of humans and animals. Challenges to development of the vaccine include development of field-usable immunodiagnostic tests to enable quantification of worm burdens in infected patients and research using immunology and molecular biology to develop a vaccine against O volvulus.
Complications
- See Mortality/Morbidity.
Prognosis
- Vector control has been effectively applied through the OCP in West Africa with remarkable results, interrupting transmission in most parts of the original program area.
- Treatment with ivermectin has been effective in controlling onchocerciasis in all endemic areas. Community-based studies have shown that ivermectin, when administered at 6-month intervals, can maintain low levels of microfilariae in the skin. This treatment clearly has the potential for interrupting transmission in hypoendemic and mesoendemic areas.
- According to the final report of the conference on the eradicability of onchocerciasis, programs in the Americas and other carefully selected sites should aim for complete interruption of transmission.
- Onchocerciasis in Africa cannot currently be eradicated; nevertheless, continuous efforts preserve those areas in West Africa made free of onchocerciasis transmission through the OCP. Indefinitely, the distribution of ivermectin was recommended to keep onchocerciasis controlled in the hyperendemic and mesoendemic foci in Africa to a point where it is no longer a public health problem.
Patient Education
- Training of cadres of national experts, who would assume responsibility for human and vector population surveillance, is important.
The Carter Center. The global 2000 river blindness. River Blindness News. 1999;11:1-8.
Awadzi K, Edwards G, Opoku NO, et al. The safety, tolerability and pharmacokinetics of levamisole alone, levamisole plus ivermectin, and levamisole plus albendazole, and their efficacy against Onchocerca volvulus. Ann Trop Med Parasitol. Sep 2004;98(6):595-614. [Medline].
Ayong LS, Tume CB, Wembe FE, et al. Development and evaluation of an antigen detection dipstick assay for the diagnosis of human onchocerciasis. Trop Med Int Health. Mar 2005;10(3):228-33. [Medline].
Cooper PJ, Guderian RH, Proano R, et al. Absence of cellular responses to a putative autoantigen in onchocercal chorioretinopathy. Cellular autoimmunity in onchocercal chorioretinopathy. Invest Ophthalmol Vis Sci. Feb 1996;37(2):405-12. [Medline].
Dadzie Y, Neira M, Hopkins D, et al. Final report of the Conference on the eradicability of Onchocerciasis. Filaria J. Feb 7 2003;2(1):2. [Medline].
Ndyomugyenyi R, Tukesiga E, Buttner DW, et al. The impact of ivermectin treatment alone and when in parallel with Simulium neavei elimination on onchocerciasis in Uganda. Trop Med Int Health. Aug 2004;9(8):882-6. [Medline].
Nguyen JC, Murphy ME, Nutman TB, et al. Cutaneous onchocerciasis in an American traveler. Int J Dermatol. Feb 2005;44(2):125-8. [Medline].
Pearlman E, Hall LR, Higgins AW, et al. The role of eosinophils and neutrophils in helminth-induced keratitis. Invest Ophthalmol Vis Sci. Jun 1998;39(7):1176-82. [Medline].
Rowe SG, Durand M. Blackflies and whitewater: onchocerciasis and the eye. Int Ophthalmol Clin. Winter 1998;38(1):231-40. [Medline].
World Health Organization. A new drug for river blindness?. Research and Training in Tropical Diseases (TDR) News. Dec 2007;79.
World Health Organization/Onchocerciasis Control Programme. West Africa Without Onchocerciasis. World Health Organization/Onchocerciasis Control Programme; 1997.
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