Parasitology deals with the study of parasites infecting humans. The diseases
caused by them and the clinical manifestations produced in infected humans. It
is also concerned with various methods of their diagnosis, treatment and their
prevention and control. There are different types of parasites and hosts.
Parasiteslivesonitshostforitsnourishment and survival. The relationship between
host and the parasite can be symbiotic, commensalic or parasitic. Parasites of
medical importance comes under the kingdom called Protista and Animalia.
Protista includes the microscopic single - celled eukaryotes known as protozoa.
In contrast, helminths are macroscopic, multicellular worms possessing well
differentiated tissues and complex organs belonging to the kingdom Animalia. Protozoa
includes Entamoeba and Giardia which cause intestinal
infections (dysentery and diarrhoea)
Leishmania donovani, the unicellular tissue flagellatis causes Leishmaniasis.
Plasmodium spp., the protozoan parasite which causes malaria are transmitted by
female Anopheles mosquito carring sporozoites forms of the parasite. The four
species infective to humans are P.
falciparum, P. malariae, P. vivax and P. ovale. Multicellular organisms and intestinal worms. The helminths such as Ascaris lumbricoides
causes Ascariasis, an infection of the small intestine. Ascariasis is the most
common roundworm infection.