The wound remains intensely painful as the worm slowly emerges over several weeks to months.In an attempt to alleviate the excruciating burning pain, the host will nearly always attempt to submerge the affected body part in water. When this occurs and the worm is exposed to water, it spews a white substance into the water containing thousands of larvae. As the worm emerges, the open blister often becomes infected with bacteria, resulting in redness and swelling, the formation of abscesses, or in severe cases gangrene, sepsis or lockjaw. When the secondary infection is near a joint (typically the ankle), the damage to the joint can result in stiffness, arthritis, or contractures.Infected people commonly harbor multiple worms – with an average 1.8 worms per person; up to 40 at a time – which will emerge from separate blisters at the same time. 90% of worms emerge from the legs or feet. However, worms can emerge from anywhere on the body. Cause
Dracunculiasis is caused by infection with the roundworm Dracunculus medinensis. D. medinensis larvae reside within small aquatic crustaceans called copepods or water fleas. When humans drink the water, they can unintentionally ingest infected copepods. During digestion the copepods die, releasing the D. medinensis larvae. The larvae exit the digestive tract by penetrating the stomach and intestine, taking refuge in the abdomen or retroperitoneal space. Over the next two to three months the larvae develop into adult male and female worms.
When the test is performed in an eye with an afferent pupillary defect, light directed in the affected eye will cause only mild constriction of both pupils (due to decreased response to light from the afferent defect), while light in the unaffected eye will cause a normal constriction of both pupils (due to an intact efferent path, and an intact consensual pupillary reflex). Thus, light shone in the affected eye will produce less pupillary constriction than light shone in the unaffected eye.Anisocoria is absent. A Marcus Gunn pupil is seen, among other conditions, in optic neuritis. It is also common in retrobulbar optic neuritis due to multiple sclerosis but only for 3–4 weeks, until the visual acuity begins to improve in 1–2 weeks and may return to normal.A total CN II lesion, in which the affected eye perceives no light, is very similar to a Marcus Gunn pupil; to distinguish them, in a CNII total lesion shining the light in the affected eye produces zero dilation nor constriction. See also
References


== External links ==