Elimination and eradication of neglected tropical diseases with mass drug administrations: a survey of experts

Abstract

Background: Lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminths, and trachoma are the five most prevalent neglected tropical diseases in the world, and each is frequently treated with mass drug administrations. We performed a survey of neglected tropical diseases experts to elicit their opinions on the role of mass drug administrations for the elimination of these infections.

Methodology/principal findings: We sent an online survey to corresponding authors who had published an article about a neglected tropical disease from 2007 to 2011. Of 825 unique authors who were invited to complete the survey, 365 (44.2%) responded, including 234 (28.4%) who answered questions regarding one of the five most prevalent neglected tropical diseases. Respondents had varying opinions about the goals of programmatic activities for their chosen neglected tropical disease, with elimination or eradication identified as the most important goal by 87% of lymphatic filariasis respondents, 66% of onchocerciasis respondents, 55% of trachoma respondents, 24% of schistosomiasis respondents, and 21% of soil-transmitted helminth respondents. Mass drug administrations, other non-medication health measures, and education were generally thought to be more important for elimination than vector control, development of a new tool, or the presence of a secular trend. Drug resistance was thought to be a major limitation of mass drug administrations for all five neglected tropical diseases. Over half of respondents for lymphatic filariasis and trachoma thought that repeated mass drug administrations could eliminate infection within ten years of the initiation of mass treatments.

Conclusions/significance: Respondents for lymphatic filariasis, onchocerciasis, and trachoma were more enthusiastic about the prospects of elimination and eradication than were respondents for schistosomiasis or soil-transmitted helminths. Mass drug administrations were generally believed to be among the most important factors for the success of elimination efforts for each of the five neglected tropical diseases, highlighting the opportunity for integrating drug distributions.

Figure 1. Opinions about the goal of treatment programs for five neglected tropical diseases.

Eradication was defined as the permanent reduction of infection to zero worldwide, not requiring any further intervention. Elimination was defined as reduction of infection to zero in a defined geographical area, requiring continued measures to prevent re-establishment of transmission. Control was defined as reduction of infection to an acceptable level, which requires continued intervention. LF = lymphatic filariasis, Oncho = onchocerciasis, Trach = trachoma, Schisto = schistosomiasis, STHs = soil-transmitted helminths.

Figure 2. Circumstances under which local elimination of infection could occur for each of five neglected tropical diseases.

Respondents were asked under what conditions elimination could occur: mass drug administrations (MDAs) using currently available drugs, MDAs plus other health measures, other health measures alone, or only if a new diagnostic test or interventional tool were developed. Alternatively, respondents could answer that elimination was not possible under any circumstances. LF = lymphatic filariasis, Oncho = onchocerciasis, Trach = trachoma, Schisto = schistosomiasis, STHs = soil-transmitted helminths.

Figure 3. Ranking of most important factors for local elimination for five neglected tropical diseases.

Each column lists the factors ranked for a specific disease, with the most important factor listed on top. In each cell, the mean rank for each factor is shown in parentheses, and the distribution of the ranks are shown in a box plot with the median rank shown as a thick grey line, and the range of rankings shown with whiskers. The boxes are color coded by that factor's mean rank across all five diseases, from most important (darkest green) to least important (darkest red).

Figure 4. Timeline for elimination and eradication for five neglected tropical diseases.

Beliefs regarding the earliest time at which (A) local elimination and (B) global eradication could be achieved in a district if repeated mass drug administrations began in 2011. LF = lymphatic filariasis, Oncho = onchocerciasis, Trach = trachoma, Schisto = schistosomiasis, STHs = soil-transmitted helminths.