Dracunculus medinensis

Iman Diriye and Mikayla Hardy

One of the largest Nematodes Common name is Guinea worm or the “fiery

serpent” Disease Caused: Dracunculiasis Definitive host: humans, dogs, horse, cattle,

monkeys Intermediate hosts: Cyclops copepods Obligate Parasite Ovoviviparous

Introduction

Dead female worms have been discovered in remains of mummified 3,000 years old Egyptian

The first physical evidence of this was a calcified male Guinea worm in an Egyptian mummy

Mentioned in the Bible as the “fiery serpent”

History

Mainly found in Sub-Saharan African Countries◦ Mauritania, Mali, Ghana, Togo, etc.

93% of cases are in Nigeria, Ghana, and Sudan

Remote Villages of India and Yemen Freshwater habitats preferably stagnant.

Geographic distribution

Map of Geographic Distribution

Kingdom: Animalia Phyla: Nematoda Class: Secernentea Order: Spiruroidae Family: Filaroidae Genus: Dracunculus Species: medinensis

Taxonomy

Adult females- 600-800mm in length and 2mm in diameter

Adult Males- are smaller and do not exceed 40mm in length

Mouth is small and triangular with quadrangular scletorized plate

Lips are absent in both male and female Larvae: 500-700 micrometers

Morphology

Lifecycle

Humans become infected by drinking unfiltered water containing copepods which are infected with L3 larvae.

Following ingestion, the copepods die and release larvae which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space.

The larvae mature into adult worms and reproduce After maturation and copulation, the male worms die and the females migrate

into the subcutaneous tissues towards the skin surface. Approximately one year after infection, the adult female worm induces a blister

on the skin which ruptures The adult female emerges from the skin at the site of the ruptured blister Person with protruding worms enters water and female releases larvae The larvae must enter water directly to survive and can live for 4-7 days, but

only are able to infect intermediate host for a 3 day period. The larvae(L1) are ingested by a copepod and after two weeks and two molts

they develop into an infective larvae(L3). Infected copepods are ingested by definitive host and lifecycle is able to

repeat.

Life Cycle Continuation…

3 Major Disease Conditions:1) Emergent Adult Worms-allergic reaction, blisters,

and burning pain2) Secondary Bacterial Infection-bacteria drawn

under skin by retreating worms, lack of proper care, third most common mode of entry for tetanus spores

3) Non-emergent Worms-fail to reach skin causing complications in deep tissue, absorbed and calcified, can cause arthritis, paraplegia if worm in central nervous system, can be found in heart

Pathogenesis

Drinking water containing Cyclops Copepod that are infected with mature L3 larvae

No immunity after infection

Transmission

Symptoms typically do not develop until around 1 year after initial infection.

Slight fever, itchy rash, vomiting, diarrhea, nausea, dizziness

Blister develops, usually in the lower region of the body (90% of cases) but can occur anywhere on the body

Blister grows within several days and is accompanied by a burning pain

Emergence of blistered area into cool water often relieves burning but causes blister to bursts releasing larvae

Symptoms

Swelling of skin Redness of skin Generalized infections Abscesses Lock Jaw (tetanus) Infections of the joints causing joint to deform

and lock If worm breaks during removal, intense

inflammatory response caused by degrading dead worm

Can lead to disability

Complications

There is no dependable method of diagnosis other than visibility of adult worm from the site of the blister

The appearance of an itchy red papule that rapidly transforms into a blister is the first strong indicator of infection

Patients that had previous infections are often more aware of presence of the parasite

Diagnosis

No drug treatment or vaccine available Removal of worm and care is only treatment

◦ Affected body part is immersed in water to coax more of the worm out

◦ Wound area is cleaned◦ Gently worm is pulled farther out until reach a resistance◦ After resistance is met, pulling is stopped so worm does not break◦ Portion of the worm that is emerged is wrapped around a stick or

piece of gauze to maintain some tension so worm cannot retract back into the body

◦ Topical antibiotics applied to prevent secondary bacterial infection ◦ Affected area wrapped in sterile gauze to protect site◦ Ibuprofen or aspirin are often given to reduce pain and inflammation◦ Steps are repeated until the entire worm is removed◦ Can take several days to weeks, depending of length of the worm

Treatments

Main control is through education Safe drinking water- underground wells free

of contaminants, filter drinking water to remove copepods, avoid entering water used for drinking if have a blister or ulcer

Early case containment- bandaging lesions to prevent contact with water sources

Vector control: larvicide to kill copepods

Control

http://www.youtube.com/watch?v=Qwk-THcjmlI

Video

What disease does Dracunculus Medinensis cause?

Where is Dracunculus found geographically? What are 2 symptoms that are observed? What is the definitive host of Dracunculus? Is there a vaccine or drug treatment

available?

Review!

http://www.stanford.edu/class/humbio103/ParaSites2004/Dracunuliasis/Guinea%20Worm.html 

http://www.cdc.gov/parasites/guineaworm/disease.html

http://www.infectionlandscapes.org/2012/03/guinea-worm.html

http://xyala.cap.ed.ac.uk/research/nematodes/fgn/pnb/dracmed.html

Roberts,L.Janovy, J.Foundations of Parasitology, 8th ed. New York: McGraw-Hill,2009

References