Dracunculiasis also called guinea worm disease (GWD), is a parasitic

Parasitism

Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...

 infection

Infection

An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

 caused by Dracunculus medinensis

Dracunculus medinensis

Dracunculus medinensis is a nematode that causes dracunculiasis.Dracunculiasis, also known as Guinea worm disease, is caused by the large female nematode, Dracunculus medinensis, which is among the longest nematodes infecting humans. The adult female is primarily larger than the adult male. The...

, a long and very thin nematode

Nematode

The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

 (roundworm). The infection begins when a person drinks stagnant water

Water stagnation

Water stagnation occurs when water stops flowing. Stagnant water can be a major environmental hazard.-Dangers:Malaria and dengue are among the main dangers of stagnant water, which can become a breeding ground for the mosquitoes that transmit these diseases.Stagnant or Stailment water can be...

 contaminated with copepod

Copepod

Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...

s infested by the larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e of the guinea worm. Approximately one year later, the disease presents with a painful, burning sensation as the worm forms a blister, usually on the lower limb. Once prevalent in 20 nations in Asia

Asia

Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

 and Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, the disease remains endemic

Endemic (epidemiology)

In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...

 in only four countries in Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

.

The guinea worm is one of the best historically documented human parasites, with tales of its behaviour reaching as far back as the 2nd century BC in accounts penned by Greek chroniclers.