Three scenarios in insect-borne diseases

This chapter deals with the core of the book, considering that insect-borne diseases are not only a human matter; there are important effects regarding plants and animals with enormous economic consequences and connected with our first interest: the production of food and its quality. In fact, it is useful to concentrate on the consequences of these diseases for our health, when this is part of the problem. Parasites are interested in any kind of appropriate host and we are generally a secondary target. Therefore, this chapter will be divided into three parts: diseases affecting mankind, animals, and plants. However, first let’s consider the general frame of this argument, whose roots are in the distant past. Plague caused the decline of villages, towns, and empires, changing the direction of history. Plague is no longer a menace to humanity, and this is clearly evidenced by the improvements of medicine and hygiene in the last centuries—but it can return. It depends, as in the past, on us. Several factors are changing the impact and the occurrence of insect-borne diseases, although most of general aspects are maintained and have been present for a long time. Thanks to recent analytic techniques, it is possible to explain new aspects of the presence and diffusion of these diseases, as well as their past, present, and future impacts. Information about the main current insect-borne diseases is reported and divided into four steps. First, the story of the plague is presented as the most important one in the past. Later, diseases affecting mankind, animals, and plants are reported. In particular, the influences of environmental change, introduction of alien species, and new alerts are considered. The outbreaks concerning malaria, Bluetongue, and Xylella are reported in detail as model cases of current interest. The scientific study of insect-borne diseases started about 100 years ago, but we have now accumulated a large quantity of data and research, whose quantity and quality are continuously increasing. However, information about the incidence in human activities is largely available.