Infestations and Parasitoses

Parasitism is a form of symbiosis in which an organism (parasite) lives in or on another organism and benefits at the expense of the host. This host-parasite association may eventuate to the injury of the hosting organism. Parasites may be grouped in endo- and ectoparasites. Infections with endoparasites can cause systemic diseases with possible dermatological signs, whereas infestations with ectoparasites only cause cutaneous lesions. The burden of parasitoses often rests on communities in countries of hot climate zones, but parasitic infections and infestations are also on the rise in clinical practices in developed countries due to the increase of traveling individuals and migrating populations. The debilitating impact which a persistent itch of certain parasitosis may have must be taken into account when assessing these conditions. Ectoparasites can also be vectors of pathogens, as discussed in other chapters; in humans they are comprised of two major animal groups, parasitic arachnids and parasitic insects [1], whereby parasitic arachnids include ticks and mites. As for the ectoparasitic insects, they are exemplified by mosquitoes, tsetse flies, fleas, and lice (Table 16.1).