Dracunculus medinensis Iman Diriye and Mikayla Hardy
Introduction • 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
History • 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”
Geographic distribution • 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.
Taxonomy • Kingdom: Animalia • Phyla: Nematoda • Class: Secernentea • Order: Spiruroidae • Family: Filaroidae • Genus: Dracunculus • Species: medinensis
Morphology • 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
Life Cycle Continuation… • 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.
Pathogenesis • 3 Major Disease Conditions: • Emergent Adult Worms-allergic reaction, blisters, and burning pain • Secondary Bacterial Infection-bacteria drawn under skin by retreating worms, lack of proper care, third most common mode of entry for tetanus spores • 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
Transmission • Drinking water containing Cyclops Copepod that are infected with mature L3 larvae • No immunity after infection
Symptoms • 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
Complications • 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
Diagnosis • There is no dependable method of diagnosisother 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
Treatments • 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
Control • 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
Video • http://www.youtube.com/watch?v=Qwk-THcjmlI
Review! • 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?
References • 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