Prospects for the Control of Neglected Tropical Diseases by Mass Drug Administration

Henk L. Smits


Expert Rev Anti Infect Ther. 2009;7(1):37-56. 

In This Article

Improved Efficacy Through Integration

Mass drug administration programs may take a considerable toll on the capacity of the health system. Therefore, careful attention needs to be paid to the training and strengthening of the field staff involved in the program, and integration with existing healthcare delivery systems should be attempted as much as possible.[8] Furthermore, as MDA for different NTDs can be achieved through similar strategies and means, an integrated approach will yield significant cost savings in areas where several diseases coexist.[21,22,23] The efficacy of MDA combinations for STH and LF and for STH and schistosomiasis have been reported Table 2 . The efficacy of the concurrent administration of two drugs was equal or better than that of each of drug alone.[24,25,26] Crucial for coadministration of drugs in MDA programs is that the drug combinations do not show pharmacokinetic interactions and show no increased adverse effects. Studies have demonstrated the safety of combinations of ALB and IVM, and ALB and DEC for treatment of coinfections of LF and STH, of ALB and PZQ for schistosomiasis and STH, and of ALB, IVM and PZQ triple therapy but not for combinations with AZM.[27,28,29,30] Important in this respect is that a recent study in Thailand revealed no clinically relevant drug interactions between PZQ, IVM and ALB when administered concurrently as single oral doses in healthy volunteers.[27] In general, adverse effects are mild, limited to infected individuals and generally considered acceptable provided that individuals receiving the drug are informed well. Furthermore, the frequency of events falls after the first or second round of treatment. Since many of the countries where these NTDs are important public-health problems also cope with malaria, TB and/or HIV/AIDS, integration with control programs for these major health problems may provide additional benefits. An initiative to look into the possibility of combined malaria and trachoma control was started in the Amhara region in Ethiopia.[31] MDA programs also have the potential for combining with immunization for the main vaccine preventable diseases.

The implementation of an integrated approach for NTD control and prevention in resource-poor communities is not an easy task and the problems that may be faced should not be underestimated. The communities that are plagued most by these NTDs are marginalized and neglected, dwell in unsanitary and crowded settings, live in remote areas or places that are difficult to access and are often devoid of most, if not all, basic prerequisites and conditions for improvement, including work, education, healthcare and nutrition. To be successful, an integrated effort for NTD control should be supported by a community-based initiative that places broad-based emphasis on health protection and promotion with a clear planning and targets that are supported and agreed upon by the entire community, including local authorities, such as community and religious leaders and to all of whom it is clear that these targets once met will upgrade the living conditions.[32] Community participation and mobilization provides a means to give people greater control over their own health and make problems more easily identified and solved. However, as integration means a certain degree of complexity additional guidance, training and program control are essential.

This article, has reviewed the literature for evidence for reduced MDA efficacy for NTDs and drug resistance and put these findings in a context of essential disease knowledge and facts of disease control programs. Investigation of drug resistance is hampered by lack of test systems and knowledge of the mechanisms of action of the major drugs used in MDA. Development of reduced drug sensitivity and, possibly, the emergence of resistant strains is of concern for STH, LF and onchocerciasis, which rely on the use of ALB and or IVM; signs of drug resistance or reduced efficacy are much less evident for PZQ used in control programs of onchocerciasis and has not been reported for AZM used in the control of trachoma. Low coverage of MDA and suboptimal efficacy of drugs used appear to be a major thread to the success of the programs and are a major risk for drug-resistance development. Appropriate health education delivered during the early stages of the MDA programs and stimulation of community participation appear to be essential prerequisites for optimal coverage and, hence, success of MDA programs. Unless coverage is improved and further commitments are made to fully enroll these programs; elimination of these NTDs as a public-health problem in much of the endemic areas in resource-poor countries may not be realized and diseases may persist or re-emerge. Implementation of complementary measures, such as vector control, improved hygiene and environmental sanitation, is crucial to the success of MDA programs and should be fully implemented once MDA programs have been rolled out and morbidity is reduced. Combining programs and integration with ongoing efforts to control the major tropical infectious disease may help to reduce costs and reduce pressure on the health system. Integration will increase complexity of measures and should be pursued gradually once effectiveness of the MDA program is established. A strong public-health system is a prerequisite for the success of MDA programs and efforts should be undertaken to strengthen the health system in endemic countries with a weak government to allow introduction of the MDA programs and make them available to communities that are still plagued with these diseases.