Leishmaniases' Burden of Disease: Ways Forward for Getting from Speculation to Reality

In this month’s issue of PLoS Neglected Tropical Diseases, Bern et al. [1] review the disease burden of the leishmaniases. In their article, the authors review the clinical pathology and eco-epidemiology of the disease as well as provide us with current data on the morbidity, mortality, and socioeconomic impact of the leishmaniases throughout their endemic range. They conclude that ‘‘current methods of assessing disease burden fail to take into account the clinical and epidemiological diversity’’ of the leishmaniases and the ‘‘intense medical, social and economic impact’’ that they might have in highly affected foci. Bern et al. [1] rightly argue that estimates of the burden of the leishmaniases, both in terms of morbidity and mortality, or in terms of disability adjusted life years (DALYs), are outdated, and/or it is unclear how currently used numbers are derived. Up-to-date figures would assist in garnering funding and political support for the prevention and control of this neglected tropical disease. Clearly, such revised figures could be obtained in a number of ways, including by (i) discussing whether used estimates are actually accurate and/ or up-to-date (referring to the commonly used, below-mentioned figures, whether right or wrong); (ii) reviewing whether the methodology to estimate past or current numbers is adequate; or (iii) describing a way forward to collect data allowing for more robust disease burden estimates. In their review, Bern et al. [1] primarily focus on the former, reviewing reports from several countries showing an increase in leishmaniases case numbers. Based on these reports, the authors conclude that the disease burden of the leishmaniases is inaccurate and out-of-date, and the reader is left thinking that it must be higher than currently acknowledged. Additionally, it is highlighted that the approach and formula to estimate the burden of leishmaniases, in terms of DALYs, is flawed: namely, that the values of the used visceral and cutaneous leishmaniasis disability weight and other input parameters are erroneous. Unfortunately, it is unclear from Bern et al.’s arguments [1] what the value of DALY input parameters should be, and as such, their criticism is similar to the criticisms levelled with regards to the burden of disease of every infectious disease of public health importance [2,3]. Thus, how does one go about in quantifying the burden of the leishmaniases more accurately? The aim of this viewpoint is to elaborate on points (ii) and (iii) above, which with the data reviewed by Bern et al. [1] will provide a platform from where a more accurate estimate of the leishmaniases’ burden of disease can be obtained.