ABSTRACT
This chapter focuses on human parasites, particularly those that are major pathogens. It describes a limited number of parasitic diseases as representative of major groups of parasitic organisms. The course of parasitic infections can be influenced by factors such as the infective dose of the parasite, the virulence of the particular strain or species, the ability of the parasite to circumvent the host's immune system, and the immune status and/or health of the host. Parasites have intrinsic and extrinsic ways of avoiding the host's immune response. In cutaneous leishmaniasis, the parasites remain at the site of infection causing a skin lesion. The helminths are a group of parasitic organisms that includes flatworms and round worms. Parasite epidemiology attempts to explain how diseases are spread from person to person. Most parasitic diseases require an intermediate host before cycling to the human host. Indirect immunofluorescence is a qualitative test for the presence of the parasite in tissue.
