Dracunculiasis
By Kenan Zamore
Parasites and Pestilence

 

Dracunculiasis is the scientific name for a disease most of the world knows as Guinea Worm Disease. Except for a few remote villages in the Rajastan desert of India and in Yemen, dracunculiasis now occurs only in Africa. Most cases occur in poor rural villages that are not visited by tourists. Mainly endemic in 13 countries (All in Sub-Saharan Africa), it is caused by the Nematode Dracunculiasis Medinensis. The nematode infects small copepod crustaceans known as Cyclops in water supplies, and human infection consequently occurs with ingestion of water containing the contaminated Cyclops .
Although it is not a cause of mortality, Dracunculiasisis aformidable public health problem, a real burden in terms of morbidity, incapacity and suffering for those affected.
 
Prophylactic measures against this disease are relatively simple, amd eradication is thought to be imminent thanks to aggressive measures and joint cooperation between multiple agencies like the Carter Center, United Nations Children's Fund [UNICEF], WHO, U.S. Peace Corps, Ghana Red Cross Society.

 

Agent

The pathogen causing Guinea Worm disease is the nematode Dracunculiasis Medinensis, and the vector is the Cyclops or water flea.

Cyclops

http://www.dpd.cdc.gov/dpdx/HTML/Dracunculiasis.htm

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

 

History:

Has been known since antiquity, with various examples of its documentation. The fiery serpent of the exodus is believed to be Dracunculiasis. The first physical evidence was a calcified male Guinea worm found in Egyptian mummy from New Kingdom period. (Would like to find some of these actual excerpts to include with completed project).
-Carlus Linnaeus: first to suggest that they were worms
- Alesej Pavlovich Fedchenko: discovered Cyclops as the intermediary host (1870)
- Robert Leiper (1905) and Dyneshvar Turkhud (1913): Determined the life cycle for Guinea Worm.

 

 

Clinical Presentation

Multiple worms can be present in the host’s body simultaneously. Adult worms usually break through the skin, where a papule develops. Before the papule erupts, the patient may show symptoms such as nausea, vomiting, diarrhea, or asthma attacks. After the eruption of the worm, the papule becomes ulcerated.. Symptoms usually disappear when the ulcer erupts and fluid drains. A painful, localized reaction continues around the ulcer.
The worm is normally removed by winding it around a stick and merely pulling it out bit by bit. If the worm is not removed, it may withdraw back into the body and be reabsorbed, or be expelled. If the worm is broken during extraction, severe inflammation and pain will ensue. This may result in formation of abscesses, cellulitis, or necrotic tissue. If the worm does not reach the skin at all, it disintegrates, or becomes calcified. These calcifications can be seen on x-rays. Symptoms also include pain in joints, nausea, fever, pruritus, blisters, ulcers, eosinophilia, and secondary infections. Just under 50 percent of all patients experience severe disability, with 1 percent suffering permanent damage from synovial ankylosis.

 

Below: An erupting papule where the worm's emergence is imminent.

http://www.dpd.cdc.gov/dpdx/HTML/Dracunculiasis.htm

Beow: A ruptured papule with the gravid female worm visible

http://www.dpd.cdc.gov/dpdx/HTML/Dracunculiasis.htm

Transmission


1. Person drinks well or pond water containing Cyclops, small crustaceans known also as "water fleas," that are infected with mature (third stage) worm larvae.
2. Gastric juices in the human stomach digest the Cyclops and worm larvae are released and within two weeks, move into the abdominal tissue where they mature and mate.
3. Fertilized female worms migrate to various body regions, usually the lower limbs, and male worms die soon after mating.
4. Approximately one year after infection, the female worm emerges at the site of a painful blister (found 90% of the time on the foot).
5. The infected person will most often rush to a water source, and place the limbs with the blister in water to relieve some of the pain. As soon as the emerging worm comes into contact with water, the worm release 1-3 million larvae into the water source, often a pond or shallow well.
6. Cyclops then swallows the larvae (a free living larvae only survives for 3 days without a host).
7. The parasite punctures the digestive tract of the Cyclops and makes its way to the abdomen, where it develops into an infectious (3rd stage) larvae, which can infect humans. 1-3 weeks after the larvae reaches the infectious stage, the Cyclops, which can no longer swim, sinks to the bottom of the water supply and dies.

 

 

travel.atlas.or.kr/disease/ Dracunculiasis.html

There are no known zoonotic reservoirs for Guinea Worm disease (making eradication possible).

Incubation

 

In Cyclops, 2 weeks after it swallows the parasite, the larvae puncture the digestive tract and lodge in the abdominal area, where they become infectious. 1- 3 weeks after the larvae are infective, they overwhelm the Cyclops host and it dies.
In humans, symptoms appear about a year after ingesting infected water. ( It takes a year for the worm to reach maturation).

 

Morphology

Female adult worms up to a metre long and 2mm across, with males much smaller at about 3mm.

Diagnostic Tests

There are no known diagnostic tests other than the location of the adult worm. The disease is discovered after the worm's eruption and papule formation on the host.

 

Management and Therapy

The onus is normally on helping the patient cope with the pain and disability experienced with infection. Surgical removal of worms is common and has been practiced for centuries. When removing the worm it is imperative to remove it whole, for breaking the worm triggers n inevitable secondary infection.

Metronidazole is the drug most often prescribed, with adults taking 250mg 3 times daily for 10 days. Thiabendazole is another, less prescribed drug (More pronounced side effects) which also gives good results. Adults would take 50mg/kg body weight for 2 days.

 

Epidemiology and Public Health Measures

 

Guinea Worm disease is the next disease slated for eradication. Experts predict the disease will be banished to a sporadic zoonosis within the next 7 to 10 years. Some factors augmenting the facility of eradication are:

*Diagnosis is easy and unambiguous (emerging worm).
* Cyclops is not a mobile vector like a mosquito.
* Incubation period in both cyclops and human is of limited duration.
* Interventions are effective, cheap and simple.
* The disease has a limited geographic distribution and seasonal
* Political commitment is available.
* Success has been demonstrated in several countries in Asia and the Middle East.
* No known animal reservoir.

Since Dracunculus transmission depends almost entirely on water for its transmission and perpetuation, the onus is on providing clean water and preventing the infected from immersing their papules in water (this is how the larva are distributed).

Guinea Worm transmission still occurs in Benin, Burkina Faso, Central African Republic, Côte d'Ivoire, Ethiopia, Ghana, Mali, Mauritania, Niger, Nigeria, Sudan, Togo, and Uganda.An estimated 354 million people live in these countries and are thus at risk.The disease continues to affect the poorest populations deprived of access to basic health care provision, safe water supply and health education, and it remains a barrier to development as it affects the workforce of the society and prevents children from attending school.

http://www.who.int/ctd/dracun/geo.htm

About 78 percent of the world's cases occur in Sudan. As part of the eradication efforts free pipe filters are being distributed throughout Sudan.In Sudan, the 19-year-old civil war is the main reason for the high rate of disease. If the intensified political negotiations now under way between the two sides in Sudan succeed in ending hostilities, full access to the final areas of endemic dracunculiasis in southern Sudan might be possible soon. After the war ends and health-care workers gain access to this area, at least 4--5 years will be required to eliminate dracunculiasis, given the extent to which the disease is endemic and Sudan's enormous size, geographic barriers, and poor infrastructure and communications networks. With the devotion of sufficient resources and the resolution of civil conflict, Sudan and the other countries in which dracunculiasis is endemic can eradicate this disease. Education is key, and efforts are being made to educate those at risk about the disease's transmission and prophylactic measures, especially water purification. Also, Abate is now regularly used to kill Cyclops and sterilize water supplies. Extreme care is being taken to not overuse this chemical so as to incur resistance from the vector.

 

References/ Works Consulted

World Health Assembly. Elimination of dracunculiasis: resolution of the 39th World Health Assembly. Geneva, Switzerland: World Health Organization, 1986 (resolution no. WHA 39.21).


WHO Weekly Epidemiological Record, Vol 77, No 18, 2002

Dracunculiasis elimination efforts 2002 Volume 28

Markell, John, & Krotoski, (1999). Markell and Voge’s: Medical Parasitology, Eighth Edition. Philadelphia: Saunders Company.

Useful Sites

http://www.stanford.edu/class/humbio103/ParaSites2003/Dracunculiasis/Index.html

Carter Center

WHO