What is it?
A parasitic disease caused by the microscopic filarial nematode worm Onchocerca volvulus. Adult worms live up to 14 years in nodules under the skin and release millions of microfilariae.
A parasitic disease caused by the microscopic filarial nematode worm Onchocerca volvulus. Adult worms live up to 14 years in nodules under the skin and release millions of microfilariae.
What are the symptoms?
Adult worms lodge in nodules under the skin, releasing large numbers of microfilariae into surrounding tissues. Immature worms move through the body and after dying, cause a variety of conditions including serious visual impairment and blindness, skin rashes, lesions, intense itching and depigmentation of the skin, lymphadenitis (resulting in hanging groins and elephantiasis of the genitals) and general debilitation.
How is it spread?
Nematodes are transmitted via the bite of infected blackflies (Simulium spp.) that carry immature larval forms of the parasitic worms from human to human
Nematodes are transmitted via the bite of infected blackflies (Simulium spp.) that carry immature larval forms of the parasitic worms from human to human
What is the magnitude of the problem?
17.7 million people are infected in 37 tropical countries of Africa and Latin America, according to WHO estimates. 500,000 individuals are visually impaired and an additional 270,000 are blind, making onchocerciasis the second leading cause of infectious blindness worldwide after trachoma. Morbidity is estimated at 951,000 DALYs.
17.7 million people are infected in 37 tropical countries of Africa and Latin America, according to WHO estimates. 500,000 individuals are visually impaired and an additional 270,000 are blind, making onchocerciasis the second leading cause of infectious blindness worldwide after trachoma. Morbidity is estimated at 951,000 DALYs.
(global distribution of onchocerciasis)What are current treatment options, prevention and control?
Drug treatment: The development of ivermectin in the 1980s provided a safe, effective drug for killing microfilariae in infected people. Ivermectin (1 dose at 150 µg/kg) is used to treat infected individuals, curing skin itching and preventing further damage to the eyes and skin. Annual treatments of entire populations can reduce circulating microfilariae thereby disrupting disease transmission. These treatments do not kill adult worms. There are no vaccines or macrofilaricidal drugs available. Vector control: Insecticide spraying to control blackflies has proved successful in certain areas.
Drug treatment: The development of ivermectin in the 1980s provided a safe, effective drug for killing microfilariae in infected people. Ivermectin (1 dose at 150 µg/kg) is used to treat infected individuals, curing skin itching and preventing further damage to the eyes and skin. Annual treatments of entire populations can reduce circulating microfilariae thereby disrupting disease transmission. These treatments do not kill adult worms. There are no vaccines or macrofilaricidal drugs available. Vector control: Insecticide spraying to control blackflies has proved successful in certain areas.
Current control strategy
Onchocerciasis control is based on two interventions: large-scale ivermectin treatment and vector control. In most of Africa, the principal strategy to control onchocerciasis as a public health problem is annual community-directed treatment (ComDT) with ivermectin in high-risk areas. In the Americas, the strategy involves six-monthly treatment in all endemic areas with the aim to eliminate onchocercal morbidity and, where feasible, to interrupt transmission. In the OCP areas, the main control strategy is vector control, through aerial application of larvicides to vector breeding sites over a period of at least 14 years, to interrupt transmission and eliminate the parasite reservoir. In a few isolated foci in APOC areas, ground larviciding is used with the aim of local vector eradication within a period of 1-2 years. However, following the introduction of ivermectin, OCP combined vector control and ComDT with the objective of interrupting transmission and eliminating the parasite reservoir within 12 years. Where elimination has been achieved, active control is replaced by surveillance and, if and when necessary, by recrudescence control with ivermectin treatment.
Onchocerciasis control is based on two interventions: large-scale ivermectin treatment and vector control. In most of Africa, the principal strategy to control onchocerciasis as a public health problem is annual community-directed treatment (ComDT) with ivermectin in high-risk areas. In the Americas, the strategy involves six-monthly treatment in all endemic areas with the aim to eliminate onchocercal morbidity and, where feasible, to interrupt transmission. In the OCP areas, the main control strategy is vector control, through aerial application of larvicides to vector breeding sites over a period of at least 14 years, to interrupt transmission and eliminate the parasite reservoir. In a few isolated foci in APOC areas, ground larviciding is used with the aim of local vector eradication within a period of 1-2 years. However, following the introduction of ivermectin, OCP combined vector control and ComDT with the objective of interrupting transmission and eliminating the parasite reservoir within 12 years. Where elimination has been achieved, active control is replaced by surveillance and, if and when necessary, by recrudescence control with ivermectin treatment.
Current global strategies for combating the disease
Since 1987, Merck has provided annual doses of ivermectin in Africa and Latin America as part of the Mectizan Donation Program, the largest medicine donation program in history. Other partners include WHO, endemic countries, and the Carter Center. Ongoing annual treatments are required as the drug does not kill the adult worm. From 1974 - 2002, WHO and the World Bank also worked to control onchocerciasis in West Africa by aerial spraying of insecticides to kill blackfly larvae. While this effort succeeded in opening 25 million hectares of arable river valley farmland to settlement and cultivation, closure of the program places the entire burden of disease control on ivermectin treatment. A 2002 conference considered whether the aim of onchocerciasis programs could be changed from control to elimination. The conference concluded that onchocerciasis cannot be eliminated from Africa with current technology, but may be eradicable in the Americas and Yemen.
(http://www.divergence.com/Investors/paper.html)
Since 1987, Merck has provided annual doses of ivermectin in Africa and Latin America as part of the Mectizan Donation Program, the largest medicine donation program in history. Other partners include WHO, endemic countries, and the Carter Center. Ongoing annual treatments are required as the drug does not kill the adult worm. From 1974 - 2002, WHO and the World Bank also worked to control onchocerciasis in West Africa by aerial spraying of insecticides to kill blackfly larvae. While this effort succeeded in opening 25 million hectares of arable river valley farmland to settlement and cultivation, closure of the program places the entire burden of disease control on ivermectin treatment. A 2002 conference considered whether the aim of onchocerciasis programs could be changed from control to elimination. The conference concluded that onchocerciasis cannot be eliminated from Africa with current technology, but may be eradicable in the Americas and Yemen.
(http://www.divergence.com/Investors/paper.html)
Onchocerciasis Control Programme in West Africa (OCP)
A major control initiative launched in 1974 in an area encompassing 7 countries in west Africa. In 1986, the programme was extended to include a further 4 countries, with a total operational area of 1.23 million sq. km, and a combined human population of 30 million. Jointly sponsored by the WHO, World Bank, UNDP and FAO, plus a coalition of 20 donor countries and agencies, the OCP is scheduled to come to an end by 2002.
OCP’s principal method for controlling onchocerciasis involved interrupting transmission by eliminating the blackfly vector. Simulium larvae are killed by applying insecticides via aerial spraying over breeding sites in fast-flowing rivers. Following interruption of transmission, the reservoir of adult worms dies out in humans after 14 years. To complement vector control activities, OCP also distributes ivermectin.
African Programme for Onchocerciasis Control (APOC)
Following the success of the OCP, the same co-sponsors and donors created APOC in 1995. The objective is to create, by 2007, sustainable community-directed distribution systems using ivermectin. These will ultimately cover 59 million people in 17 non-OCP countries, where the disease remains a serious public health problem and some 15 million people are infected. In a few isolated foci, APOC aims to eliminate the blackfly through insecticide spraying.
The Onchocerciasis Elimination Programme in the Americas (OEPA)
Created in 1992 to reach the goal of eliminating pathology and disease in the region.
Documentary film on Onchocerciasis
A small team has begun pre-production and fundraising for a documentary film on the subject of African river blindness, the world’s second leading infectious cause of blindness. Please visit http://www.37millionandcounting.com/ to find out more!!
More pictures on Onchocerciasis
No comments:
Post a Comment