GEOGRAPHICAL DISTRIBUTION
The infection was, at one time, widely but patchily spread across tropical Africa, some parts of the Middle-east countries and India. The involved countries exerted a concerted effort in order to eradicate the infection by 1995. The program has been a success although sporadic cases still occur. The parasite also infects a wide range of animals particularly in North America. There are historical reports on the infection in South America.
MORPHOLOGY
It is a subcutaneous worm closely related to filarial worms. The female is long and appears as a long piece of twine (a piece of white coloured thread), about 60-100cm.The male is small and measures 2-3 cm.
LIFE CYCLE
The adult worms are found in humans (definitive host) while larval stages are found in the Cyclops (a water flea belongs to crustacean group) which is the intermediate host.
Male dies soon after fertilizing the female. The gravid female (uterus filled with larvae) migrates from its usual habitat in connective tissue (eg. Retro-periobital connective tissue) to areas of the skin which usually come in contact with water. As the head end approaches the surface of the skin, a blister develops. This causes intense burning pain. Infected persons tend to place their infected parts (eg. Foot) in water to get rid the pain. On contact with water the blister ruptures and the uterus of the worm protrudes through the ulcer. The contact with water is the stimulus for the uterus to discharge larvae into water.
The larvae (500-700µm) are swallowed by Cyclops. The larvae can live in clean water for about six days while it can last for nearly three weeks in muddy water. After two moults, the larvae develop into the infective stage inside the Cyclops (within2-4 weeks). When the infected Cyclops is ingested via drinking water the larvae penetrate the gut wall to reach suitable site. They become mature in about a year’s time.
Life cycle
PATHOGENESIS AND CLINICAL FEATURES
The adult worms living in the connective tissue of limbs and trunk cause minimal reactions. The blisters formed by migrating gravid females are commonly seen on the feet. They may appear around the knee joint in some and rarely around the scrotal area. In water carriers the blister may appear on the shoulder. A major pathology is seen after the worm dies when a sterile abscess is formed. Secondary infection often leads to inflammation and debility. The blister causes intense burning pain. Patients may experience itching, rash, nausea and vomiting with the appearance of blisters.
Few or no clinical manifestations of dracunculiasis are evident until just before the blister forms, when there is an onset of fever and generalized allergic symptoms, including periorbital edema, wheezing, and urticaria.
a ruptured blister
COMPLICATIONS
Complications include abscesses following secondary infection, arthritis, synovitis and abdominal symptoms due to adult worms migrating to the peritoneal cavity.
DIAGNOSIS
In endemic areas the clinical features are well known. Traditional way of diagnose this condition is by placing a drop of water on the blister or ulcer. This drop of water becomes cloudy due to the extrusion of larvae by the gravid female. A smear made on a slide will show the rapidly moving larvae.
EPIDEMIOLOGY
Although many animals are infected, the human infection is not considered a zoonosis as humans are the main reservoirs of the infection. Cyclops is a crustacean usually found in fresh water and some times in water storage tanks. Infected persons introduce larvae to water when the affected part of the body is immersed in water. Step wells played a major role in the transmission of the infection India.
PREVENTION AND CONTROL
The infection could easily be eradicated by improving drinking water supplies so that dependence on surface is removed. Boiling, filtering and chlorination of drinking water will remove Cyclops if they present in water. The insecticide ‘Temephos’ is an organophosphorus compound that is harmless to man that can be added to wells and storage tanks as slow release granules.
TREATMENT
The removal of the worm quickly is nit possible without chemotherapeutic support. The traditional way is to tie the anterior end of the worm to a stick or a matchstick and roll the worm out gradually over period of several days or weeks. Drugs such as Tinidazole, metronidazole and thiabendazole help with smooth extraction of the worm.
removing of an adult worm
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