Ed i t o r i a l ivermectin distribution to populations in of the major achievements within the References need in endemic areas. Thus, the present Global Initiative for Elimination of Avoid- 1 World Health Organization. Onchocerciasis and estimated annual treatments are in the able Blindness, launched in 1999 by WHO its Control. Report of a WHO Expert Committee order of 15 million cases in the OCP and in collaboration with a dedicated group of on Onchocerciasis. TRS No. 852, WHO, Geneva, APOC areas. non-governmental development organiza- Switzerland. 1995. It can be safely stated today that the tions, under the theme of ‘Vision 2020: 2 Abiose A. Onchocercal eye disease and the impact of Mectizan treatment. Ann Trop Med elimination of onchocerciasis as a public The Right to Sight’. The Initiative, which Parasitol 1998; 92: S11-S22. health problem is now within reach. The focuses on five major causes of avoidable 3 Amazigo U, Noma M, Boatin BA, Etya’ale DE, ongoing and planned operations in the blindness, is an outstanding effort for glob- Seketeli A, Dadzie KY. Delivery systems and cost recovery in Mectizan treatment for three control programmes (OCP, OEPA al action and partnership in the prevention onchocerciasis. Ann Trop Med Parasitol 1998; and APOC) will cover all disease foci, of blindness. The possibility of eliminating 92: S23 – S31. where intervention is necessary. Thus, by onchocerciasis as a public health and 4 World Health Organization. 25 OCP years the year 2010, it will be possible to con- socio-economic obstacle to development, (1974–1999). Onchocerciasis Control Programme in West Africa. Ouagadougou, Burkina Faso, clude that visual loss due to this dreadful is perhaps the first victory in sight for the 1999. disease will disappear. This would be one ‘Vision 2020’ Global Initiative. ❏ Review Article Vision 2020: Update on Onchocerciasis Daniel Etya’ale MD Recent studies in Ethiopia, Nigeria and After entering the skin of the human Prevention of Blindness Unit Sudan have also shown that onchocerciasis host through the bite of an infected black- World Health Organization is responsible for poor school performance fly, the infective larvae (usually two to six) 1211 Geneva 27 and a higher drop out rate among infected migrate through the subcutaneous tissues. Switzerland children (due to itching, lack of sleep, etc.), Here, over the next 12 months, each larva while low productivity, low income and will mature into an adult male or female nchocerciasis, also known as ‘river higher health-related costs are found worm. Before a heavy load of adult worms Oblindness’, is an insect-borne disease, among infected adults. and pathogenic microfilariae builds up in caused by a nematode worm, Onchorcerca the human host, this sequence has to be volvulus. It is the world’s second leading Disease Transmission repeated many times over, and many years of exposure are usually required. infectious cause of blindness. In most of The parasite. Onchocerca volvulus, the these countries it constitutes a public causal agent of onchocerciasis is one of a Clinical Manifestations health problem and a serious obstacle to large group of nematodes. The adult socio-economic development. worms live encysted in fibrous nodules. The people most at risk from onchocercia- Each nodule contains between 2-3 female sis are those who for reasons of occupation Disease Prevalence and Burden worms lying in a twisted, tangled mass, (e.g., fishermen, farmers, sand diggers) • About 125 million people world-wide hence the term volvulus. Adult female have spent long hours or live nearer to the are estimated at risk of onchocerciasis, worms have a life span of 8 to 10 years but breeding sites. Early manifestations of the and, of these, 96% are in Africa. may live up to 15 years, during which time disease in infected persons usually appear • Of the 37 countries where the disease is each releases millions of first-stage larvae, one to three years after the injection of endemic, 30 are in sub-Saharan Africa, also known as microfilariae. In hyperen- infective larvae. Nearly all the lesions of six are in the Americas and one is in the demic areas, the total microfilaria load in onchocerciasis including those in the eye, Arabian Peninsula. the body of affected individuals may be as are directly or indirectly related to local • A total of 18 million people are infected high as 150 million. death of microfilariae. Generally, live with the disease, of whom 99% live in The vector. Onchocerciasis is transmitted microfilariae stimulate very little inflam- Africa and at least one million are either from one individual to another by a black matory response and the mechanisms that blind or severely visually disabled. To fly of the genus Simulium. The blackfly protect them from the host’s immune these are added each year an estimated larvae require well-oxygenated water to response are still largely unknown. 40, 000 new blind. mature, and eggs are laid in rapids in fast flowing rivers and streams. Female black Box 1: Non-Ocular Manifestations As the name ‘river blindness’ suggests, flies require a blood meal to produce/lay • Pruritus: often severe and unrelenting onchocerciasis is essentially a focal dis- eggs, and it is during this meal that they • Nodules: subcutaneous, painless, typically ease. However, where it exists, its impact may transmit or receive the onchocercal found around bony prominences (iliac crest, on affected communities may be quite infection. greater trochanters, ribs, knees, coccyx and extensive and devastating. Thus, in many Cycle of infection. Microfilariae enter a skull) hyperendemic areas with blinding oncho- female blackfly when she bites an infected • Severe, disfiguring skin disease: cerciasis, almost every person will be person. A small percentage of these reach may lead to thedistress ofsocial stigma, infected, and half of the population will be the insect’s thoracic muscles where after psychological and sleep disorders blinded by the disease before they die. several moults, they become third-stage • Ly m p h a t i c : lymphadenopathy, hanging groin Once blind, affected individuals have a life infective larvae. They then migrate to the • Unproven but suspected associations: expectancy of only one third that of the insect’s salivary glands and are ready to be hyposexual dwarfism, higher prevalence of sighted and most die within 10 years. transferred during the next blood meal. epilepsy Community Eye Health Vol 14 No. 38 2001 19 Onchocerciasis

For reasons of cost and operational feasi- Passive or clinic-based treatment. This is bility, vector control could not be applied the form of treatment available to all those or extended to other endemic countries out- seeking medical treatment and in whom a side the OCP area of operation. clinical diagnosis of onchocerciasis has Chemotherapy. Ivermectin is the only been made in a hospital or health centre. It chemotherapeutic agent recommended for is directed primarily to infected individuals use against onchocerciasis. Its mass distri- and is the main method of treatment in bution constitutes the main strategy for the hypoendemic areas where the risk of blind- other two regional programmes, APOC ness or severe skin disease is virtually non- and OEPA. It is a semisynthetic, macro- existent. cyclic, lactone antibiotic widely used in the Community mass treatment. Also known Sclerosing keratitis in onchocerciasis field of veterinary medicine against a wide as community-wide treatment, this is the Photos: Ian Murdoch & Allen Foster range of animal parasites. It was developed method of choice in meso- and hyperen- The clinical features of onchocerciasis during the 1980s. In 1987, the manufac- demic areas of onchocerciasis, i.e., where may be divided into two main groups: turers, Merck & Co., made the generous onchocerciasis is considered a public ocular and non-ocular, as summarised in decision to donate ivermectin free for the health problem. In these areas ivermectin is Boxes 1 and 2. treatment of human onchocerciasis, ‘to as given once a year for at least 14 years, as recommended in Table 1, to all members Control of Onchocerciasis Box 2: Ocular Manifestations of the community except for the exclusions Anterior segment defined in Box 3. The past ten years have seen a rapid and Over the years mass treatment has remarkable expansion of onchocerciasis • Live microfilariae in anterior chamber (AC) control activities worldwide, thanks to • Punctate keratitis, leading on to sclerosing keratitis Box 3: Exclusion Criteria for joint efforts and support from WHO and • Early uveitis, leading on to chronic uveitis Ivermectin Treatement other UN agencies, the World Bank and a growing coalition of Non-Governmental Posterior segment • Children under 5 years (age), or Less than 15 kg (weight), or and Development Organizations (NGDOs). • Choroido-retinitis, leading on to choroido- Less than 90 cm (height) These efforts are coordinated by three retinal atrophy or optic nerve atrophy • Pregnant women major regional programmes, one in Central • Acute optic neuritis, leading on to optic atrophy • Lactating mothers of infants and Latin America, the Onchocerciasis Others less than one week old Control Programme of the Americas • Severely ill persons (OEPA); and two in Africa, the Oncho- • Night blindness • Use with extreme caution in areas cerciasis Control Programme (OCP), and • Visual field loss and constriction co-endemic with Loa loa • Irreversible blindness the African Programme for Oncho- evolved from mobile strategies used in the cerciasis Control (APOC). Together these many as needed and for as long as early days following ivermectin donation three regional programmes cover more required’. Its main characteristics can be to various forms of community-based than 99% of all endemic populations and summarised as follows: treatment. In nearly all cases, these all but one (Yemen) endemic countries. changes have been dictated by the need to (Please see the Editorial by Dr Bjorn • It is a microfilaricide, with a very wide reduce operation costs, increase treatment Thylefors). therapeutic range (150–800 micrograms/ coverage and maximise programme impact kg) on affected communities. The latest and Strategy Options for the Control of • It is highly attractive and popular in most widely used of these community- Onchocerciasis endemic communities for its many other based strategies is known as Community beneficial effects on intestinal worms, Directed Treatment with Ivermectin The control of onchocerciasis today is scabies, head lice, and for its supposed based essentially on two strategies: enhancing effect on libido (CDTI). With this method considerable Similium vector control and large-scale • Given at the recommended single dose efforts are made to involve affected com- chemotherapy with ivermectin. Each may of 150m/kg, it is effective for up to a munities themselves in the planning, be used alone or in combination. year. implementation and monitoring of treat- Vector control. This is the chief strategy • When given to the largest sections of ment activities. CDTI is the preferred and used in West Africa by the Onchocerciasis affected communities, it may significantly official method used throughout Africa by Control Programme (OCP) since 1974. reduce disease transmission both OCP and APOC. The main goal in vector control is to inter- • However, because ivermectin has no Table 2 is a summary of current uses of rupt transmission of O. volvulus by regular demonstrable direct effect on the adult ivermectin in onchocerciasis control, based aerial spraying of all Simulium larval worm, it must be given repeatedly for up on endemicity levels. breeding sites, and to maintain this for at to 12–15 years, i.e., the time it takes for Ivermectin treatment greatly reduces least 14 years until the infection has died most adult worms to die. transmission of the parasite, but does not out in human populations. This strategy, halt it. As and the adult worm may live for used alone at the beginning and now in Current Uses of Ivermectin in as long as 14-15 years, annual large-scale combination with ivermectin, has been Onchocerciasis Control treatment will therefore have to continue highly effective: onchocerciasis has been for a very long time. Recent predictions virtually eliminated in the original seven There are two main uses of ivermectin in with a simulation model have indicated OCP countries, and progress elsewhere in the treatment of onchocerciasis: passive or that at coverage levels of around 65%, the programme area is so advanced as to clinic based, and active, as in large scale or annual treatment may have to continue for justify the closing down of OCP in 2002. mass treatment of entire communities. up to two decades. The main challenge 20 Community Eye Health Vol 14 No. 38 2001 Onchocerciasis

Table 1: Recommended Doses of Table 2: Treatment Approaches Based on Endemicity Levels Ivermectin in Mass Treatment Hyper-endemic Mass treatment (CDTI) (40+% nodule carriers) Weight Height No. of Tablets Meso-endemic (kg) (cm) (3 mg) (20-39% nodule carriers) 15–25 90–119 1 Hypo-endemic Clinic-based treatment (<20% nodule carriers) 26–44 120–140 2 Non endemic No treatment 45–64 141–158 3 65 or more 159 or more 4 Macrofilaricide: Moxidectin References facing ivermectin-based control, therefore, The development of a macrofilaricide drug 1 Report of WHO Expert Committee, Technical Report Series No. 852. Geneva, World Health is to develop and implement simple meth- is currently being undertaken through the Organization, 1995. ods of ivermectin delivery which can be MACROFIL project, a WHO based project 2 Epidemiology of Onchocerciasis. Report of sustained by the communities themselves. which aims to develop a macrofilaricide, WHO Expert Committee, Technical Report i.e., one which kills the adult worms. Series No. 752. Geneva, World Health Hence the attractiveness of CDTI. Organization, 1987. The risk of resistance to ivermectin is Of the many candidate drug compounds 3 Duke BOL. Onchocerciasis. In Johnson GJ, remote within the time frame of the pro- that been tested and identified so far, Minassian DC, Weale R (eds.). The Epidemi- posed Programme. However, the history of moxidectin, has shown to be the most ology of Eye Disease, London, pp 227–247, 1998. parasite disease control based on promising. 4 Buck AA. Onchocerciasis: Symptomatology, chemotherapy suggests that a cautious Final results of moxidectin trials in ani- Pathology, Diagnosis. Geneva, World Health approach should be adopted. Recent model mal models were reviewed by WHO in Organization, 1974. simulations and molecular biological stud- March 2000. These pre-clinical studies 5 Benton B. Economic impact of onchocerciasis control thrpugh the African Programme for ies indicate that resistance could become a have shown it to fulfil many of the criteria Onchocerciasis Control: An overview. Ann Trop problem over a twenty- to thirty-year time for a potential macrofilaricide: easy to use, Med Parasitol 1998; 92(1): S33–S39. period, despite the long generation time of safe and effective. 6 Etya’ale DE. Mectizan as a stimulus for the development of novel partnerships: the interna- O. volvulus. It is important, therefore, to At present moxidectin is only available tional organization’s perspective. Ann Trop Med continue the development of alternative in veterinary formulations, but plans are Parasitol 1998; 92(1): S73-S77. drugs for the treatment of onchocerciasis. under way to start clinical trials in humans. ❏

ROYAL COLLEGE OF OPHTHALMOLOGISTS 17 Cornwall Terrace, Regent’s Park, London NW1 4QW, UK

Diploma Examination in Ophthalmology DRCOphth ANNOUNCING A CHANGE TO THE STRUCTURE From November 2001, there will be no Practical UK and Overseas Examination Calender 2001 Refraction section in the Diploma Examination Exam Dates of examination Location Closing date The New Diploma Examination (DRCOphth) is a test of ophthalmic knowledge including relevant basic Part 1 23–24 April UK, India 12 March sciences and clinical skills for candidates who have MRCOphth 8–9 October UK, India, 27 August worked in ophthalmology for one year (full-time or Egypt equivalent). This work experience need not have been gained in the UK. Part 2 18–22 June UK 7 May MRCOphth 10–11 October India 27 August 5–9 November UK 24 September Information, Exams syllabi, Applications from: The Head of the Examinations Department at Part 3 12–15 March UK 29 January the above address MRCOphth 17–21 September UK 6 August Or tel: 00 44 (0) 20 7935 0702 11–12 October India 27 August Or fax: 00 44 (0) 20 7487 4674 Or e-mail: [email protected] DRCOphth 25–28 June UK 14 May Or visit the College website www.rcophth.ac.uk 19–20 November UK 8 October Overseas Locations: • Aravind Eye Hospital, Madurai, Tamil Nadu, India • The British Council, Cairo, Egypt

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