Dracunculus medinensis - Introduction, Classification, History, Habitat, Morphology

Introduction to Dracunculus medinensis

Dracunculus medinensis is also known as serpent worm, guinea worm, or medina worm. It is the etiological agent of dracunculiasis or dracontiasis and is characterized by a chronic cutaneous ulcer on the part of the body that frequently comes in contact with water.

Classification of Dracunculus medinensis

The classification of Dracunculus medinensis is as follows:

Kingdom: Animalia

Phylum: Nematoda

Class: Secernentea

Order: Camallanida

Family: Dracunculidae

Genus: Dracunculus

Species: D. medinensis

History of Dracunculus medinensis

In 1853, Baston first described the morphological feature of the spirurid nematode. Russian biologist Fedtschenko discovered cyclops as vectors causing transmission of the disease.

Habitat of Dracunculus medinensis

Adult Dracunculus medinensis females inhabit the subcutaneous tissues of humans’ feet or lower limbs. The parasite may also inhabit other parts of the body such as the head and neck.

Morphology of Dracunculus medinensis

The morphological features of Dracunculus medinensis include adult worm, first-stage larva, and infective form.

Adult form

The adult form of Dracunculus medinensis includes separate male and female parasites.

Male

• adult male of Dracunculus medinensis die immediately after fertilizing female

• are difficult to demonstrate in the specimen

• measures 15 to 40 mm in length and 0.44 mm in diameter

• are obtained from experimental animal infections

• life-span is around three to six weeks

Female

• female Dracunculus medinensis is one of the longest nematodes infecting humans

• measures 50 to 120 cm in length and 0.7 to 1.7 mm in diameter

• milky white, slender, resembles a thick twine of thread

• rounded anterior end, tapering pointed posterior end forms a hook-like structure

• the anterior end has a minute triangular mouth

• mouth surrounded by an inner layer of 4 to 6 papillae and an outer layer of 4 pairs of papillae

• the female genital tract consists of a pair of uteri, tubules, oviducts, and a single unpaired vagina

• viviparous

• uterus completely filled with thousands of eggs, embryos, and first-stage larvae

• over a period of 3 weeks, larvae laid in successive batches through the vaginal opening

• lives for about a year – longer life-span than males

First-stage larva

• first stage larva of Dracunculus medinensis is unsheathed, coiled with a round anterior end long slender filariform tail

• large in size

• measures 650 to 750 mm in length and 17 to 20 mm in diameter

• conspicuous striated cuticula

• locomotion takes place with a stiff motion, briskly coiling and uncoiling body – shows tadpole-like movement

• the short life span of 6 days – dies if not taken up by cyclops

• if taken up by cyclops, further development of Dracunculus medinensis takes place in cyclops

Infective form

The infective form of Dracunculus medinensis is the third-stage larva. It is found in the body cavity of cyclops.