Neglected Tropical Diseases

Through studying a NTD this year there are soo many 'simple' questions that I should fully understand, however I don't. If asked I can only give a singular sentence that makes little sense with a whole lot of waffle for luck. So lets answer two of them.

What is a tropical disease? What makes a tropical disease one that can be categorised as negleted?

According to WHO a tropical diseases is one that 'encompass all diseases that occur solely, or principally, in the tropics. In practice, the term is often taken to refer to infectious diseases that thrive in hot, humid conditions, such as malaria, leishmaniasis, schistosomiasis, onchocerciasis, lymphatic filariasis, Chagas disease, African trypanosomiasis, and dengue.' That description makes sense to me but what makes a tropical disease a neglected tropical disease (NTD)? 

There are a few things that makes a tropical disease 'neglected'; reinforcing poverty and not receiving significant levels of importance such as in funding for research. These diseases mostly affect people who themselves could be categorised as neglected as they are the poorest of the world's population, living in areas that are remote and/or lack sanitation such as in developing countries and conflict zones causing geographical clustering of these diseases aiding spread within those regions. Here these diseases persist under conditions of poverty, hence most of them being zoonosis and/or infectious. The spread within this region causes it to not be a problem for developed countries and so not regarded as a research priority. What further categorised them as neglected is the fact that as poorer individuals in low income economies, they will have a voice not regarded as important leading to the diseases that persist in their communities being overlooked. However, this negligence has led to NTD's affecting over a billion people of which many could have been prevented, eliminated or eradicated. Although not many lead to death, they can cause significant problems for life such as disfigurement and blindness which diminishes quality of life and morbidity which is more difficult to calculate and convey than death, encouraging the cycle of poverty to continue. All this makes neglected tropical diseases a particularly important area to study.