In this article we will discuss about the blister formation of Dracunculus medinensis.
Blister is a type of lesion which appears whenever the female worm of Dracunculus medinensis makes an attempt to come to the surface of the body where it can readily discharge its coiled larvae.
Generally the guinea-worms are instinctively attracted to the skin, especially to such parts as are likely to, or frequently do, come in contact with cold water such as the arms of women who wash clothes at river or the legs of water carriers or some part of the lower extremities.
But it may be found in lesser degree in arms, trunk, buttock, scrotum, head, neck and female breast. The female worm pierces the lower layers of the skin with the front end of her body and causes a small bleb or blister to form over the injured spot.
During the formation of blister the head of female worm tries to come to the surface resulting in an itching or burning sensation at the area. An irritant secreted by the worm forms a small red spot which is finally converted into a blister. Now the worm excretes a toxic substance that irritates the tissues and causes a small bleb to form over the injured spot.
Finally the blister ruptures either by itself or by manipulation, revealing a small superficial erosion of V2 to % inch in diameter, with a tiny hole in the center. The fluid in the blister is sterile and milky white in colour. It is found to contain hordes of tiny coiled larvae.
The head of the worm is seen to protrude through this small round hole of the erosion whenever the part comes in contact with water. The central hole leads to a tunnel within the subcutaneous tissue where the female worm resides (Fig. 10.7 and 10.8).
