Intermediate Host

A secondary host or intermediate host is a host that harbors the parasite only for a short transition period, during which (usually) some developmental stage is completed. For trypanosomes, the cause of sleeping sickness, humans are the secondary host, while the tsetse fly is the primary host, given that it has been shown that reproduction occurs in the insect. Cestodes (tapeworms) and other parasitic flatworms have complex life-cycles, in which specific developmental stages are completed in a sequence of several different hosts.

As the life cycles of many parasites are not well understood, sometimes the "more important" organism is arbitrarily defined as definitive, and this designation may continue even after it is determined to be incorrect. For example, sludge worms are sometimes considered "intermediate hosts" for whirling disease, even though it is known that the parasite causing the disease reproduces sexually inside them .

In Trichinella spiralis, the roundworm that causes trichinosis, a host has both reproductive adults in its digestive tract and immature juveniles in its muscles, and is therefore considered both an intermediate host and a definitive host.

Other articles related to "intermediate host, host":

Cestoid - Reproduction and Life Cycle of The Tapeworms
... phases as in other flatworms, but complicated in that at least one intermediate host is required as well as the definitive host ... Many tapeworms have a two-phase life cycle with two types of host ... This is known as the intermediate host ...
Tarebia Granifera - Ecology - Parasites
... Tarebia granifera serves as the first intermediate host for a variety of trematodes in its native south east Asia ... Tarebia granifera also serves as intermediate host for the philopthalmid eyefluke Philopthalmus gralli Mathis Ledger, 1910 which has recently (2005) been reported affecting ostriches Struthio ... The snail host implicated in this outbreak was Melanoides tuberculata but the rapid spread and high population densities achieved by Tarebia granifera ...
Schistosoma Indicum
... The most important the first intermediate host is a freshwater snail Indoplanorbis exustus that is the sole natural intermediate host for Schistosoma indicum (and other two Schistosoma species) on the Indian sub-contine ... The main reasons were the use of a different intermediate host (Ferrissia tenuis) and final host (man) with difference in location (urinary system ) which is not possible for any ... demonstrated cross-immunity against Schistosoma incognitum by immunising the host against Schistosoma indicum ...
Planorbarius Corneus - Parasites
... This species of snail functions as a host for several parasite species First intermediate host for Prosthogonimus ovatus First intermediate host for Apatemon gracilis First and as second intermediate host ...

Famous quotes containing the words host and/or intermediate:

    When you are invited by someone to a wedding banquet, do not sit down at the place of honor, in case someone more distinguished than you has been invited by your host...But when you are invited, go and sit down at the lowest place, so that when your host comes, he may say to you, Friend, move up higher’; then you will be honored in the presence of all who sit at the table with you.
    Bible: New Testament, Luke 14:8,10.

    Complete courage and absolute cowardice are extremes that very few men fall into. The vast middle space contains all the intermediate kinds and degrees of courage; and these differ as much from one another as men’s faces or their humors do.
    François, Duc De La Rochefoucauld (1613–1680)