Dracunculus medinensis

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Dracunculus medinensis

• Katrina Kittleson, Steda Lundak

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Taxonomy

• Class Secernentea
• Subclass Spiruria
• Order Spirurida
• Superfamily Drancunculoidea
• Family Dracunculidae
• Common names- Guinea Worm, Medina Worm,
  Serpent Worm, Dragon
  Worm

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History

• Known as a parasite of humans since about 1530
  B.C.
• Guinea worm is thought to be the "fiery serpent"
  referred to in the Bible.
• The symbol of a Physician is the "Caduceus". The
  serpents are believed to represent the Guinea
  worm.
• Persian physicians removing the D. medinensis
  parasite from patient during the 9th century-?

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Hosts

• Definitive Humans
• Intermediate Copepod

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Distribution

• Except for a few remote villages in the Rajastan
  desert of India and in Yemen, Guinea worm disease
  now occurs only in Africa.
• Infected areas in Africa lie in a band between
  the Sahara and the equator.
• Presently, only 9 countries are endemic Sudan,
  Ghana, Nigeria, Mali, Togo, Burkina Faso,
  Ethiopia, Niger, and Ivory Coast.
• gt50 of all cases of Guinea worm disease are
  reported from southern Sudan.

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Distribution

• Smaller numbers of cases are reported from
  Ethiopia, Chad, Senegal, and Cameroon.
• Most cases occur in poor rural villages that are
  not visited by tourists.

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Morphology

• One of the largest nematodes known.
• Adult females have been recorded up to 800 mm
  long
• Few males known do not exceed 40 mm.
• The mouth is small and triangular and is
  surrounded by a quadrangular, sclerotized plate.
• Lips are absent.
• The esophagus has a large glandular portion
• Spicules of the male are unequal and 490 to 730
  um long. The gubernaculum ranges from 115 to 130
  um long.

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Morphology

• A Adult D. medinensis worms. (A) The adult
  female guinea worm is a long, slender worm
  ranging from 30 to 120 cm in length and from 0.09
  to 0.17 cm in width.
• B Three mature guinea worms.
• Note the tiny size of the mature male (mm)
  compared with the mature female (mf) and
  especially the markedly elongated and
  serpiginous, gravid female worm (gf). The gravid
  female shows an extruded uterus (eu)?

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Characteristics

• Only helminthic parasite transmitted solely
  through water.
• But usually occurs during drought
• Everyone is forced to drink from the same
  stagnant water supplies or pay for well.
• Three conditions to be met before D. medinensis
  can complete its life cycle.
• The skin of an infected individual must come in
  contact with water
• The water must contain the appropriate species of
  microcrustacean
• The water must be used for drinking
• Believed the parasites feed on blood due to the
  gut often being filled with dark brown gut
  material

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Life Cycle
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Life Cycle

• Humans become infected by drinking unfiltered
  water containing copepods (small crustaceans)
  which are infected with larvae of D. medinensis
• Following ingestion, the copepods die and release
  the larvae, which penetrate the host stomach and
  intestinal wall and enter the abdominal cavity
  and retroperitoneal space.
• The worm molts again 20 days and 43 days post
  infection
• Females are fertilized by the third month.
• After maturation into adults and copulation, the
  male worms die and the females (length 70 to 120
  cm) migrate in the subcutaneous tissues towards
  the skin surface
• Approximately one year after infection, the
  female worm induces a blister on the skin,
  generally on the distal lower extremity, which
  ruptures. 
• When this lesion comes into contact with water,
  which the patient seeks to relieve the local
  discomfort, the female worm emerges and releases
  larvae
• The larvae are ingested by a copepod and after
  two weeks (and two molts) have developed into
  infective larvae

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Diagnosis

• Diagnosis is made from the local blister, worm or
  larvae.
• The outline of the worm under the skin.
• Some people claim to be able to feel the worm
  moving towards the surface of the skin.
• Finding Calcified worms.

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Epidemiology

• Dracunculiasis may result in three major disease
  conditions
• Emergent adult worms
• Secondary bacterial infection
• Nonemergent worms
• When worms do not emerge they degenerate and
  release antigens causing fluid filled abscesses
  or allergenic reactions.
• If the worms become calcified they can cause
  inflammation or if they remain in a joint,
  arthritis.
• Can cause paraplegia if it worm gets into the
  central nervous system.

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Pathology

• None until the female worms cause an allergic
  reaction by releasing metabolic wastes into host.
  This occurs at the onset of migration to the
  skin.
• a rash accompanied by severe itching
• nausea
• vomiting
• diarrhea
• dizziness
• edema
• Reddish papule-blister (local itching and intense
  burning).
• Blister ruptures, becomes abscessed-very painful.
• Secondary bacterial infections of opening
  possible.
• Retreating worm can draw bacteria under skin as
  well.
• There may be later symptoms
• fibrosis of the skin, muscles, tendons and joints
  (may interfere with locomotion or use of limbs)

Ruptured Blister
Blister
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Pathology

• Adult in joint ?
• Calcified lesion in soft tissues ?

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Treatment

• Drug TherapyMetronidazole
• To help prevent bacterial infections
• Anti-inflammatory to help reduce swelling
• Treatment includes the extraction of the adult
  guinea worm by rolling it a few centimeters per
  day
• Usually takes weeks or months depending on how
  long the worm is.
• Exposing area to cold water helps remove worm
  faster.
• Preferably by multiple surgical incisions under
  local anesthesia.
• Infection does not make a person immune

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Economic Impact

• Seasonal pattern of worm emergence peaks at
  maximum agricultural labor demand.
• Significant decline in agricultural productivity
  and economic hardship.
• The Dogon people of Mali refer to the infection
  as the disease of the empty granary.

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Control

• Filter, boil, or treat water with chlorine to
  kill intermediate host.
• Finely-meshed cloth or, better still, a filter
  made from a 0.15 mm nylon mesh, is all that is
  needed to filter out the copepods from the
  drinking water.
• Avoid bathing or wading in drinking water.
• Village-based volunteers demonstrating the use of
  cloth filter on a clay pot to filter drinking
  water ? ? ? ? ?

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Control

• Construction of copings around well heads or the
  installation of boreholes with hand pumps.
• Borehole is a deep and narrow well.
• Coping is a cap/cover over a well
• Key is to prevent copepod growth by controlling
  sunlight. Light increases the food source of the
  copepod.

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Eradication Efforts

• Perhaps the only parasite that has potential to
  be eradicated in the near future.
• 98 decline in cases from 1986 to 2000.
• The goal was to have it eradicated by 1995, but
  due to civil unrest in Sudan it has been delayed.
  New goal is 2009.
• A major component of eradication is the use of
  communal filters.
• Education still needed, since many believe that
  the worm comes from the human body, not the water.

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Article Discussion

• Nigeria
• Hand Sewn Filters (HSF)
• Single family use
• Hard to tie, collapsed
• Not very durable, not replaced if holes
• Communal Filtration Units (CFUs)
• 1 worker maintains units
• Whole community served
• Initial cost more than HSF
• Guinea worm decrease 50 with CFUs

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Bibliography

• CDC.org website
• Foundations of Parasitology text
• Dracunculiasis Eradication Delayed, not Denied.
  Am. J. Trop. Med. Hyg. 2000
• Notions and Treatment of Guinea Worm in Northern
  Ghana. Bierlich. 1995
• Dracunculiasis and the Eradication Initiative.
  Cairncross et al. Clinical Microbiology Reviews.
  2002