ABSTRACT

Parasitism is one of the major types of symbiotic relationships between organisms representing different species. This relationship is stable, and one of the species-the parasite, lives at the expense of the other organism-the host. Moreover, the parasite lives inside or on the surface of the host. Parasitism is a ubiquitous phenomenon, probably as old as the appearance of heterotrophic organisms. The earliest known records of parasitic diseases date back to 2700 BC (Bush et al. 2001, Niewiadomska

15.1 The Nature of Parasitism ..............................................................................245 15.2 Ways of Infection ..........................................................................................246 15.3 Tapeworm Infections (Cestoda) ....................................................................246