PhD defence Natalie Vinkeles Melchers-Martinez

Onchocerciasis and lymphatic filariasis (LF) are two important parasitic infectious diseases of the tropics. They are caused by a specific species of filarial worms and can cause a wide spectrum of clinical morbidity in the affected population, including blindness (onchocerciasis) and elephantiasis or “elephant legs” (LF). The PhD research focussed on how the disease burden of onchocerciasis and LF, in terms of total number of cases and disability-adjusted life years (DALYs), has changed since the introduction of large-scale mass treatment programmes in Africa and what burden will remain by 2030. DALYs are a measure that accounts for both loss in quality of life as well as premature mortality. In order to calculate this, she first quantified the pre-control association between community-based infection and morbidity levels. Mathematical modelling was then used to estimate the impact of interventions on the pre-control infection levels of onchocerciasis and LF throughout Africa. She predicted the past, current and future disease prevalence, number of cases, and DALYs lost due to onchocerciasis and LF. One major conclusion of this work was that interventions have a remarkable impact on levels of onchocerciasis and LF, although still millions of people will be suffering from morbidity by 2030 by either or both infections in Africa.