Parasitic diseases may be presented by a wide variety of clinical manifestations according to the tissue invaded, resistance or susceptibility of the host, parasite density, virulence and host status. Control and prevention of parasitic diseases depend on the interactions among many factors such as the environment, the human behaviour and socio-cultural factors that determine transmission and persistence of parasites. Today we are talking about Modern Parasitology discussing on host defence mechanisms consisting of innate immunity, adaptive immunity, drug action, drug effect and drug delivery, ultrastructural (SEM and TEM) investigations, biochemistry and physiology of parasites, parasite ecology, vector biology, pest management, molecular biology, DNA sequencing of parasites and vaccine formulations. Molecular-based diagnostic approaches are becoming popular due to their great sensitivity and specificity. Nanotechnology is upcoming as one of the most recent diagnostic procedure utilizing nanodevices. Thus these findings must be penned down to assist fellow researchers to acquaint them with the current areas of research and help them in designing their future experiments.