Neglected tropical diseases (NTDs) are having a serious impact on some of the world's poorest populations by depressing economic development. In this blog, we examine the economic impact of onchocerciasis, commonly known as river blindness, which is such a disease. Spread by blackflies, the sufferer's body is eventually infested with worms, causing a range of debilitating symptoms, including blindness. The socioeconomic impact of the disease is complex, affecting individuals, village communities and the national workforce, with an estimated 1 million disability-adjusted life-years (DALYs) lost worldwide. Leaders of past successful control programmes declared victory over river blindness, but in reality, millions of people still remain at risk of the disease. However, it is clear that unlike other diseases such as HIV/AIDS, successful elimination of onchocerciasis could be achieved more easily than we think.
The parasitic nematode causing the disease is rife in 27 sub-Saharan African countries, with around 37 million people infected, and 90 million more at risk. The parasite was also imported through the slave trade to six Latin American countries.
To begin to understand the economic burden of NTDs, we searched key repositories of health-related publications including PubMed, the World Health Organisation (WHO) and Cochrane websites combining a variety of disease-related search terms with a selection of economic-related terms. Disease-related search terms included all of the 17 NTDs as defined by the WHO, and economic-related search terms included words such as burden, cost and employment. Diseases with inexpensive treatments that affect the largest populations were prioritised, such as onchocerciasis. The economic burdens of NTDs in developing countries were reported in a total of 282 articles, which we then subdivided by disease area giving 22 articles for onchocerciasis. Of these, we were able to access 16 articles for our review.
The socioeconomic burden of the disease can be felt on several levels. The early symptoms are often disabling, with itchy skin, muscle pain, reduced immune response, and visual impairment that can lead to blindness. We see the most drastic effects in small communities where most people are infected: up to 6.5% of the villages surveyed in Guinea were blinded. After losing his sight, a previously healthy young man whose body was his only means to an income, is unable to work properly, can hardly walk beyond the village and spends the little he earns on health costs. His self-esteem and concentration suffer, and he is unlikely to ever get married or have a family. Even without visual impairment, he would earn significantly lower wages. For a child, the impact on their education damages their future prospects and leads to an estimated 17% drop in future income. Whole villages are abandoned for fear of the disease, leaving acres of fertile land deserted, which has a knock-on effect on the wider economy.
This extensive impact of onchocerciasis is responsible for 1 million DALYs worldwide, which is a measure of healthy life-years lost due to disability and mortality. This impact is three times that of the effect of asthma in the UK. To counter this, several control strategies have tried to bring an end to the debilitating effects of the disease. Historically, both anti-vectorial and anti-parasitic measures have been used with some success. In 1974, the WHO started the Onchocerciasis Control Programme (OCP), poisoning blackfly breeding grounds in West Africa to try to interrupt parasite transmission. In some areas, children born after the initiation of the programme were no longer at risk. A similar international programme, the African Programme for Onchocerciasis Control (APOC) was also established in 1989, with the help of pharmaceutical giant Merck, to begin mass distribution of the anti-parasite agent invermectin. By the end of 2005, over 40 million people living in 90,000 African villages affected by onchocerciasis had been treated. The cost of this programme was estimated to be only $0.74 per person, making this a highly cost-effective approach.
The success of these programmes has consigned onchocerciasis to the bottom of the public health agenda at a time when consolidating these achievements and ensuring long-term success would be critical. It is clear from our research that control of onchocerciasis needs to be extended to wider areas, and that elimination is feasible. For example, one study estimates that three NTDs, including onchocerciasis, could be eliminated from Latin America and the Caribbean by 2020 for $128 million. In Nigeria, which has the highest rate of infection in the world, onchocerciasis could be eliminated in just a few years for an annual cost of less than $1 per person. Having said that, new programmes need to be designed to be sustainable and supported by communities in order to make onchocerciasis a disease of the past.
By Julia Heckenast, working pro bono on behalf of Costello Medical Consulting, with a wider team at Costello Medical Consulting
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