Guinea Worm, Dracunculus medinensis

The Guinea worm (Dracunculus medinensis) is a species of roundworm with the Nematoda phylum. This species is once ranged throughout Asia and Africa, including the west coasts of Africa in Guinea. Although it is not present in this range anymore, the species retains its common name. It was identified in this area by Carl Linnaeus, who discovered the parasite in many merchants along the coast. Its scientific name was also given due to a large population in one area, called Medina. Dracunculus medinensis is derived from the Latin phrase “little dragon from Medina,” but this area is now also free of the Guinea worm. This worm typically varies in size depending upon the sex, with the longest female measuring 31 inches and the longest male measuring 1.6 inches.

The Guinea worm lifecycle begins in water, when females release their larvae into the water. These larvae are in their first stage, but reach their third larval stage after being ingested by a copepod within the water. This process takes about two weeks and consists of two molts. At this stage, the larvae can infect humans that drink from waters that contain the infected copepods. The copepods die after entering a human and release the third stage larvae, which move into the stomach and intestinal walls of the host. Both males and females stop traveling when they reach the retroperitoneal space and the abdominal cavity. Sexual maturity is reached in these parts of the body, after which time the males will die and the females will move into the subcutaneous tissues near the surface of the skin. The females remain here for about one year, after which time skin lesions begin to appear, typically near or on the foot. After these lesions break open, many hosts will place their feet in the water, which allows the female to emerge from the lesion and release her first stage larvae into the water.

An infection caused by the Guinea worm is known as dracunculiasis and is unique to humans. Hosts display many symptoms including severe pain where lesions are present, nausea, rashes, dizziness, diarrhea, and localized edema. These symptoms, which occur from an allergic reaction, will subside once the worm is taken out of the body, but if any worms die within the joints of the host, paralysis of the spinal cord and arthritis can occur. Because the worms emerge from the skin, diagnosis is simple. Traditionally, this worm has been removed from hosts by wrapping it around a stick and extracting it from the skin, but surgery is now becoming a common option if the worm has not emerged yet. Drugs, such as metronidazole, can be used to relieve the symptoms of a Guinea worm infection, but these do not kill the worm. It is possible to prevent contracting this worm by boiling the water or by filtering it with a nylon cloth. Efforts to control the spread of this worm include killing copepods by using insecticides and larvicides.

In order to eradicate this species, it is important to stop its lifecycle before it enters its human hosts. In 1984, the World Health Organization (WHO) gave the Centers for Disease Control and Prevention (CDC) leadership in eradication efforts. The Carter Center joined in these efforts, which have been very successful. By 2008, five thousand cases of dracunculiasis had been reported, a drastic reduction from 3.5 million cases in 1985.

This species was once common in Pakistan, but was eradicated by 1993, and was completely eliminated from Asia in 2004. President Jimmy Carter proposed the efforts in Pakistan in the 1980’s, and after President Zia al-Haq accepted the proposal, the eradication was successful. Many other areas adopted these efforts, including Asia, and successfully eradicated the worms as well. These efforts were not as successful in Sudan. The Guinea worm once populated the Banswara, Dungarpur, and Udaipur regions of south Rajasthan in high numbers. Because of the rapidity of dracunculiasis infections here, the government instituted the SWACH program in 1986. This program created enhanced sanitary conditions and provided for clean water in the areas where the worm was native, and by 1996, the government announced that the species was eradicated. However, two cases were reported between 2002 and 2003 in the Banswara and Dungarpur areas.

The Guinea worm is still present in Ghana, although there were no recorded cases in 2009. National Guinea Worm Eradication Program, funded by the Japanese International Cooperation Agency, the WHO, and UNICEF, initiated many control and eradication efforts in the early 2000’s. These efforts included water treatments in public areas and in homes and the monitoring of bodies of water, like dams, in order to prevent infected hosts from polluting the water. All of these efforts are leading Ghana to Guinea worm free status.

Image Caption: Dracunculus medinensis larvae. Parasite. Credit: CDC/Dr. Mae Melvin/Wikipedia