Khalid Md. Bahauddin
Public health officials often use the term “tropical diseases” to refer collectively to a list of infectious diseases that are found primarily in developing countries. These include malaria, schistosomiasis, dengue, trypanosomiasis, leprosy, cholera, and leishmaniasis, among others. Many of these diseases are spread by insect vectors, and all of them disproportionately affect the world’s poor.
Global attention on infectious disease is primarily focused on HIV/AIDS, tuberculosis and malaria. The ‘big three’, as they are called, were responsible for over five million deaths in 2007 and are responsible for 39 per cent of all deaths attributed to infectious disease. Unfortunately, this attention has not extended to other lesser known diseases, sometimes referred to as the neglected tropical diseases (NTDs). These diseases are largely overlooked, due to their low mortality rate and the poverty of their sufferers, where over 70 per cent of the affected areas have low to lower-middle income economies. They thrive under poor sanitary conditions, where clean water and food are unavailable and where insect vectors are abundant.
WHO estimates that neglected tropical diseases affect over one billion people and cause about 570,000 deaths each year. For example, some 200 million people are currently infected with schistosomiasis, a parasite that is transmitted through poor sanitation. Perhaps 50 million cases of dengue occur each year, of which 500,000 lead to devastating hemorrhagic fever, with 22,000 resulting in deaths.
These are just some of so-called neglected tropical diseases, which are diseases of poverty. Despite the numbers they affect, and their health and social consequences, these diseases attract less than one per cent of the total health funding for the developing world. Furthermore, the potential impact of climate change on the transmission of the neglected tropical diseases has received insufficient attention from scientific communities and different organisations.
Bangladesh is highly vulnerable to climate change. Natural disasters present a major challenge for the country faces, resulting in economic and human losses. During and after floods, water-borne diseases increase due to heavy contamination of the surface water. Thus, climate change induced floods and break-down of sanitation systems lead to more water and food-borne diseases like soil-transmitted helminthiasis, cholera, and other diarrhoeal diseases.
The incidence of vector-borne diseases like malaria, filaria, leishmania and dengue are likely to increase as a result of climate change in this region. It is reported that 34 districts of Bangladesh are known to be endemic for filariasis and 45 for visceral leishmaniasis. Dengue has been detected in six divisions of Bangladesh whereas soil-transmitted helminthiasis affects population throughout the country. Filariasis is a parasitic disease which is believed to have infected about 20 million people; 10 million are with various forms of disability, leaving another 70 million at risk of infection. The incidence of visceral leishmaniasis on the other hand is estimated to be about 12,000 per year with about 65 million people at risk of contracting the disease. Some reports claimed a death rate of more than 10 per cent in patients suffering from visceral leishmaniasis.
In addition, Bangladesh may be one of the countries in the world worst hit by the predicted rise in sea level. The increase in salinity in underground water will affect the availability of fresh safe water. As a result, people will be more inclined to use unsafe, contaminated surface water and will be more at risk of contracting various water-borne infectious diseases.
The impact of climate changes on neglected tropical diseases is itself neglected. There is an urgent need to investigate further the potential impact of climate changes on the transmission of these diseases. The findings of such research are required so that populations might be able to adapt or, if necessary, migrate to overcome increased risks for transmission of neglected tropical diseases caused by climate change.
(Khalid Md. Bahauddin is Head of Research and Learning at Hope for Humanity, Bangladesh and Visiting Scholar at the University of Leuven, Belgium.)
Khalid Md. Bahauddin