Helminth infection in populations undergoing epidemiological transition: A friend or foe?

Helminth infections are highly prevalent in developing countries, especially in rural areas. With gradual development, there is a transition from living conditions that are dominated by infection, poor sanitation, manual labor, and traditional diet to a situation where burden of infections is reduced, infrastructure is improved, sedentary lifestyle dominates, and processed food forms a large proportion of the calorie intake. The combinations of some of the changes in lifestyle and environment are expected to result in alteration of the landscape of diseases, which will become dominated by non-communicable disorders. Here we review how the major helminth infections affect a large proportion of the population in the developing world and discuss their impact on the immune system and the consequences of this for other infections which are co-endemic in the same areas. Furthermore, we address the issue of decreasing helminth infections in many parts of the world within the context of increasing inflammatory, metabolic, and cardiovascular diseases.