Oct 26 2006
The World Health Organization (WHO) and a group of more than 25 partner organizations unveiled a new strategy to fight some of the most neglected tropical diseases that destroy the lives and health of poor people.
The approach contained in a newly published manual, Preventive Chemotherapy in Human Helminthiasis, focuses on how and when a set of low-cost or free drugs should be used in developing countries to control a set of diseases caused by worm infections. Preventive chemotherapy in this context means using drugs that are effective against a broad range of worm infections to simultaneously treat the four most common diseases caused by worms: river blindness (onchocerciasis), elephantiasis (lymphatic filariasis), schistosomiasis, and soil-transmitted helminthiasis. Significant opportunities also exist to integrate these efforts with the prevention and control of diseases such as trachoma.
"Preventive chemotherapy does not necessarily stop infection taking place but it can help to reduce transmission. The benefit of preventive chemotherapy is that it immediately improves health and prevents irreversible disease in adults," says Dr Lorenzo Savioli, Director of the WHO Department for the Control of Neglected Tropical Diseases in Geneva. “In the same way as we protect people against a number of vaccine-preventable diseases throughout their lives, the regular and coordinated use of a few drugs can protect people against worm-induced disease, improving children's performance at school and the economic productivity of adults."
The new approach provides a critical first step in combining treatment regimens for diseases which, although different in themselves, require common resources and delivery strategies for control or elimination.
The second key component of the strategy brings together for the first time dozens of agencies, NGOs, pharmaceutical companies and others into a coordinated assault on neglected diseases. These organizations are integrating their expertise and resources to deliver the manual’s protocols for wide-scale drug use. A wealth of experience and success already exists in the public health community in dealing with these diseases.
More than one billion people are afflicted by these diseases. Their impact can be measured in the impaired growth and development of children, complications during pregnancies, underweight babies, significant and sometimes disabling disfigurements, blindness, social stigma, and reduced economic productivity and household incomes. These effects can now be dramatically reduced by scaling up interventions using highly effective drugs of proven quality and excellent safety record -- the majority donated free by companies or costing less than US$ 0.40 per person per year, including the cost of the drugs and their delivery.
"We need to urgently work together to improve access to rapid-impact interventions and quality care," says Dr David Heymann, WHO Acting Assistant Director-General for Communicable Diseases. "The need to do so is incontestable from all perspectives: moral, human rights, economic and global public good. The task is feasible and must be done."
Work must now begin in earnest to implement the practical guidelines in the manual and sustain the progress that preventive chemotherapy offers. The governments of the Member States of the United Nations have committed themselves to attaining the Millennium Development Goals. The application of preventive treatment for worm infections will make a significant contribution to overcoming the challenges set out for us in the Millennium Development Goals.
Lymphatic filariasis: It is estimated that 1.2 billion people in 83 countries live in areas endemic for lymphatic filariasis and about 120 million people are affected by the disease. Filarial infection may be clinically asymptomatic; the disease may also present as one or more acute manifestations (fever, local swelling, tropical pulmonary eosinophilia syndrome, lymphangitis). Chronic complications include lymphoedema or elephantiasis of the limbs, damage to the genital organs (including hydrocele in men), and damage to the kidney (including chyluria) and lymphatic system. The causal agents of lymphatic filariasis are the filariae Wuchereria bancrofti, Brugia malayi and Brugia timori.
Schistosomiasis: It affects about 200 million people worldwide, and more than 650 million people live in endemic areas. Urinary schistosomiasis is caused by Schistosoma haematobium and intestinal schistosomiasis by any of the organisms S. intercalatum, S. mansoni, S. japonicum, and S. mekongi. Disease is caused primarily by schistosome eggs, which are deposited by adult worms in the blood vessels surrounding the bladder or intestines. The classical sign of urinary schistosomiasis is haematuria (blood in urine). Bladder and ureteral fibrosis and hydronephrosis are common findings in advanced cases, and bladder cancer is a possible late-stage complication. Intestinal schistosomiasis has a nonspecific clinical picture of abdominal pain, diarrhoea, and blood in the stool. Liver enlargement is common in advanced cases and frequently associated with ascites and other signs of increased portal pressure. In such cases there may also be splenomegaly.
Onchocerciasis: Onchocerciasis is endemic in 30 countries in Africa, 6 countries in the Americas, and in Yemen in the Arabian peninsula. It is estimated that 100 million are at risk of infection while 37 million are estimated to be infected. The causal agent of onchocerciasis is Onchocerca volvulus, a nematode filaria. Symptoms begin 1–3 years after infection, usually at the time when adult females begin to produce microfilariae. These include: rashes, papular skin lesions, subcutaneous nodules, intense itching and depigmentation of the skin, lymphadenitis, which results in “hanging groin” and elephantiasis of the genitalia, and general debilitation. Eye lesions lead to serious visual impairment including blindness.
Soil-transmitted helminthiasis (ascariasis, trichuriasis, hookworm infections): Soil-transmitted helminthiasis affects more than 2 billion people worldwide. Recent estimates suggest that Ascaris lumbricoides infects 1.221 billion people, Trichuris trichiura 795 million, and hookworms (Ancylostoma duodenale and Necator americanus) 740 million. The causal agent of soil-transmitted helminthiasis is any of the following worms: Ascaris lumbricoides, Trichuris trichiura and the hookworms. Infection is caused by ingestion of eggs in contaminated soil or food (Ascaris lumbricoides and Trichuris trichiura) or by active penetration of the skin by larvae in the soil (hookworms). Soil-transmitted helminths produce a wide range of symptoms that include intestinal manifestations (diarrhoea, abdominal pain), general malaise and weakness that may affect working and learning capacities, and impaired physical growth. Hookworms cause chronic intestinal blood loss that results in anaemia.
Trachoma: Trachoma affects about 84 million people of whom about 8 million are visually impaired. It is caused by Chlamydia trachomatis – a microorganism which spreads through contact with eye discharge from the infected person (on towels, handkerchiefs, fingers, etc.) and through transmission by eye-seeking flies. After years of repeated infection, the inside of the eyelid may be scarred so severely that the eyelid turns inward and the lashes rub on the eyeball, scarring the cornea (the front of the eye). If untreated, this condition leads to the formation of irreversible corneal opacities and blindness.
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