NTD Burden of Disease may be More than Double that of TB and Half that of Malaria Almost 90% of Disease Burden Results from Helminth Infections
A new analysis published today in the open-access journal PLoS Neglected Tropical Diseases, sheds new light on the devastating toll neglected tropical diseases (NTDs) take on Sub-Saharan Africa (SSA), with an estimated 500 million suffering from these debilitating and sometimes deadly diseases. Helminth infections account for approximately 85 percent of the NTD burden. Overall, the NTD burden could be equivalent to more than double that caused by tuberculosis and up to one-half of SSA’s malaria disease burden. The report’s findings will be critical to the work of the Global Network of Tropical Diseases and its partners, the WHO and other global health organizations developing prioritization strategies for effective NTD control.
“It is appalling that helminth infections and other NTDs are having such a devastating impact on the poor in Sub-Saharan Africa given that we have effective treatments to alleviate their sufferings. For $200 to $400 million a year over five years we could significantly reduce the burden of helminth infections and other NTDs from much of Sub-Saharan Africa. That’s a minimal investment with maximum returns,” said Peter Hotez, author of the analysis, President of the Sabin Vaccine Institute and Distinguished Research Professor at George Washington University.
While the prevalence of helminth infections has diminished elsewhere in the world, it has remained relatively constant in SSA. Between one-quarter and one-third of SSA’s population is affected by one or more helminth infections, with children, especially school-aged children, disproportionately affected. Helminth infections, like other NTDs, produce profound physical and mental deficits in children. In addition a high percentage of pregnant women are also affected.
Moreover, the authors note that NTDs in SSA may produce a level of disease equivalent to as much as one-half and one-third of the of the region’s malaria and HIV/AIDs disease burden, respectively. Given that treating NTDs could be achieved at affordable costs, the authors conclude that “helminth control should continue to be prioritized by public health experts, health ministries, and global policy makers”. In addition, based on revised estimates for schistosomiasis that fully consider the morbidities of chronic infection including effects on anemia, malnutrition, growth stunting, and diminished child development, the possibility remains that maternal and child helminthiases may increase even further in their disease control priority infections.
The authors additionally note that high priority must be placed on examining the impact that reducing helminth infections might have on malaria and HIV/AIDS. In many parts of sub-Saharan Africa, helminths are co-endemic with malaria where they worsen the course of malaria, while in others, schistosomiasis, one of the most important helminth infections, causes genital lesions and may increase a woman’s susceptibility to HIV/AIDS
“A full analysis of all Africa’s NTDs is an essential step towards prioritizing these conditions relative to ongoing HIV/AIDs and malaria control efforts supported by private foundations and the group of eight nations,” the authors concluded.
The following is a list of the major NTDs currently devastating SSA:
• Hookworm infection – is the most common helminth and most common NTD in SSA, infecting approximately 200 million people and accounting for up to one-third of the total burden from NTDs in SSA.
• Ascariasis and trichuriasis – 173 million and 162 million are infected with ascariasis and trichuriasis, respectively. The largest numbers occur in Nigeria, where co-infections with hookworm are common.
• Schistosomiasis – Of the world’s 207 million cases of schistosomiasis, approximately 93% occur in SSA. Genital schistosomiasis promotes the transmission of HIV/AIDS and is also linked to the malaria.
• Filaria Infections (LF, Onchocerciasis, Loiasis, and Dracunculiasis) – Approximately 40% of the world’s 120 million cases of LF over in SSA. LF is associated with huge economic losses impairing economic activity up to 88%. More than 99% of the estimated 37 million cases of onchocerciasis occur in SSA.
- Loiasis – The African eyeworm has a high prevalence in rainforest areas of low socioeconomic status and in some savanna regions
- Dracunculiasis – All of the world’s cases of dracunculiasis occur in SSA
• HAT – Through stepped up public health control efforts over the last decade, the major endemic countries in SSA have made great strides in reducing the number of cases of HAT from 300,00 to 500,00 cases to approximately 50,000 to 70,000 cases, along with 17,000 new cases annually.
• Leishmaniasis – Because many cases occur in areas of conflict and forced human migrations the exact number occurring in East Africa is not well known. High incidence of the disease is being seen in refugee camps.
• Trachoma – is the leading cause of infectious and preventable blindness worldwide and the most important bacterial infection in SSA. Of the 63 million cases of active trachoma globally, 48% occur in SSA (30 million).
• Mycobacterial Infections
- Buruli ulcer – of the estimated 7,000 cases reported annually, more than 4,000 cases occur in SSA
- Leprosy – at the beginning of 2008, approximately 30,055 cases of leprosy were registered in Africa, with 31, 037 new cases in 2007
- Bovine tuberculosis – TB is a major opportunistic infection among HIV-infected populations in SSA and it is estimated that 70% (6 million) of the people co-infected with TB and HIV live in SSA
The paper, “Neglected Tropical Diseases in Sub-Saharan Africa: Review of their Prevalence, Distribution, and Disease Burden,” was written by Peter Hotez MD PhD, Distinguished Research Professor and Walter G. Ross Professor and Chair of the Department of Microbiology, Immunology, and Tropical Medicine at George Washington University and President of the Sabin Vaccine Institute, and Aruna Kamath MPH, a medical student at George Washington University.