Dracunculus medinensis-The Guinea Worm  BIO 203

D. medinensis larvae

Form and Function


   Courtesy of cmr.asm.org
     Dracunculus medinensis is one of multiple other parasitic nematodes such as Dirofliaria immitis and Anisakis simplex. Dracunculus medinensis is interestingly one of the longest nematodes. A mature female Dracunculus medinensis can measure up to a meter long (Dawes 1971). Dracunculus medinensis is different from filarial worms as it does not have two uteri, but it has one large uterus. It has a plugged vulva in which the uterus extends most of the body. It allows the Dracunculus medinensis to have large amounts of larvae. It can have upwards of 1 to 3 million larvae in its uterus at once (Cairncross 2002). This adaption allows for more larvae the possibility to survive when trying to find a copepod because the larvae only have an estimated 3 days to find a copepod (Liu 2012).
    Dracunculus medinensis uses a copepod to infect a human. It usually is transferred by the drinking of water that is not filtered, and the human/animal ingests the copepodXyala with the larvae of Dracunculus medinensis. The key is the copepod dies in the digestive system, and allows the larvae to go into the wall of the infected host (CDC 2012). The Dracunculus medinensis chooses the copepod because it is not harmed much by the parasite. Dracunculus medinensis strategically chooses the host it takes so it is not likely to be digested or be responsible for the host dying because of it infecting the host (Liu 2012).
    To enter the copepod the Dracunculus medinensis worm must be ingested by the copepod. The ingested Dracunculus medinensis worm then burrows its way into the digestive wall of the copepod. It does this by contracting its muscles and pushing its way into the intestinal wall with its penetrated head first (Dawes 1971).
    When the human host is infected, males and females will reproduce. The male dies off fast so the female is the only one that will rise out of the skin. The female has multiple layers of epicuticle and one very thick cuticle on the outside shell for protection (LiuWikipedia 2012). The Dracunculus medinensis moves around the body after moving through the intestinal tissue. It moves by the lymphatic system and travels around through lymph (Dawes 1971).
    In order to release larvae the Dracunculus medinensis has adapted by protruding the uterus through the skin of the host. It causes irritation inside of the host and that creates a blister which bursts and creates a burning sensation. When cooled, the worm detects the temperature change, and then expels its larvae through the uterus (Liu 2012).

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