Dracunculus medinensisDr. Subhash Chandra Parija MD , PhD, DSc, FRCPathDean (Research) , JIPMER
TaxonomyPhylum NematodaClass SecernenteaOrder SpiruridaFamily DracunculidaeDracunculus medinensisDracunculus medinensisGuinea worm, medina worm, or serpent worm The traditional symbol for a doctor is the serpent wound round a stick. This has always been supposed to be a snake but a more serious suggestion is that the creature is the guinea worm and the sign of a healer is a man who can get rid of the worm.
MorphologyAdult wormsFemaleOne of the largest nematodes knownMilky white, slender wormMeasure 50-120 cm x 07-1.7 mmIn anterior end, a minute triangular mouth is presentThey are viviparousUterus is filled with thousands of eggs, embryos and first stage larvae
MorphologyMaleMeasures 15-40 mm x 0.4 mmDie immediately after fertilizing the females
First-stage larvaUnsheathed and coiled with round anterior end and long slender filariform tail
LarvaHostsDefinitive Host: HumansIntermediate Host: Cyclops (Mesocyclops leuckarti, M. hyalinus)
Life CycleSource: Water containing infected cyclops3rd Stage larva released in stomach and then reaches small intestineAfter fertilisation the female migrates into tissues On contact with water the female releases large number of first stage rhabditiform larvaeThe larvae are ingested by cyclopsIn the cyclops it undergoes 2 moults to develop into third stage larvaeCyclops harbouring the third stage larvae infects the human host and the cycle continues
3 Mandatory ConditionsSkin of infected persons must come into contact with waterWater must have cyclopoid crustaceanWater must be used for drinkingPathology and Clinical SignsThree major disease conditions can occur from Dracunculus infection: 1. Emergent adult females cause hot and painful blisters 2. Secondary bacterial infections 3. Nonemergent worms that die under skin cause allergic reactions that could lead to death
PathologyBacterial infection can cause ulcers and abscesses to develop, which are very painful and can cause disability for extended periods of timeAbout of the cases are complicated by bacterial infection of ulcersApplication of antibacterial agents to ulcers is important in case managementPathologyBacterial infection becomes more serious when the bacteria are drawn under the skin by a receding wormIn parts of Africa, this is the 3rd most common mode of entry for tetanus spores.Other complications that can occur are: synovitis, arthritis, and bubo. PathologySometimes when worms do not emerge, they begin to degenerate and release antigens. Which cause aseptic abscesses, which can also lead to arthritis. Abscesses can be BIG, holding up to Liter of fluidMore commonly the worms become calcified.
PathologyNonemergent worms can cause problems within tissues deeper in the body.Although many die and become absorbed or calcified, without much apparent effect on the host.Chronic arthritis is common if the worm is calcified alongside or in a joint. More serious symptoms, like paraplegia, result from the worm in the CNS.
Host Immune ResponseAllergic reaction occurs due to the release of metabolic wastes from the worm.
This may cause a rash, nausea, diarrhea, dizziness, and localized edema.
Reinfection may occur. No immunity.Clinical manifestationsPre-patent period: 10-14 monthsAsymptomatic until the female worm reaches the skin surfacePapule which develops into a blister is the first signBlisters are usually found on the legs between the metatarsal bones, on the sole and on the anklesIntense burning pain at the site of blisterUrticaria, nausea, dyspnoea, giddinessSecondary bacterial infection
Geographical distributionOnce prevalent in 20 nations of Asia and Africa
But now endemic only inSudan, Mali, Ethiopia (Africa)Saudi Arabia, Iran and Yemen (Middle East)
India was declared free from this disease in 2000 by WHO
In 2010 - < 1800 cases were reported worldwide
94% of the cases are found in South SudanAsia, Africa, IndonesiaDiagnosisParasitic diagnosisFirst stage larvae can be observed in the discharge fluidAdult worm can be detected when it appears at the surfaceSerodiagnosisIHA, IFA, ELISA
Imaging methodsX-ray demonstrates dead and calcified parasitesTreatmentWinding the protruding worm on a stick has been a successful treatment since antiquity.
Because the worm protrudes only a few centimeters per exposure to water, this procedure takes, on average, three weeks to completely remove the worm.
The worm can also be removed surgically, and some drugs are used, but the evidence for their effectiveness is dubious.
Thiobendazole or Mebendazole enables rapid emergence of the worms and quick healing
Control/ PreventionThe most important strategies for the eradication of Dracunculus have been:Supply of safe drinking water.Boiled or filtered water Health education.Early case containment.Vector control. (Temephos, is a chemical that has low toxicity to mammals and fish, but kills copepods for 4-5 weeks at a concentration of 1ppm)Control/Prevention
Onchocerca volvulusFamily OnchocercidaeCauses river blindness Transmitted by female black flies of the Simulium damnosum complexAffects 40 million people mainly in Tropical Africa and South America.Second major cause of blindness in the world.Onchocerca volvulus
Simulium damnosumThe black flyDefinitive host-ManIntermediate host- Female black flies of genus SimuliumThey are pool feeders and suck in blood and tissue fluidsLife-cycleLife cycle
Life cycleMicrofilariae migrate to thoracic muscles of fly Develop into filariform (infective stage)Infective stage migrate to the mouth parts.Extrinsic incubation period is -6 days.Life span of adult worm in human host is about 15 years.Life span of microfilariae- 1 year.
DiagnosisSkin snips for microfilaria with oculoscleral biopsy forcepsUN Development Program, World Bank, and WHO funded the OnchocerciasisControl Programin 11 West African countries, 1974-2002 (extended to 2007)African Program for OnchocerciasisControl in 19 central African countries, 2000-2010Goal: Disease elimination through drug therapyControl of Onchocerciasis
Stop black fly transmission of parasite to humansOver time, the human reservoirof parasites decreases9-11 year parasite life cycle, 14-20 years of insecticide applications needed>35,000 miles of river sprayed weekly
Strategy of Vector Control:Ivermectin is the drug of choice.
DEC causes the Mazzotti reaction- pruritus, rash, lymphadenopathy, fever, hypotension, and eye damage.TreatmentLoa loaLoa loaAlso called 'eye wormCauses Calabar swellingsCurrently endemic in west and central Africa.Adult worm- 30-70x 0.3-0.5mmSheathed microfilariae.Vector- Chrysops
Affecting the conjunctivaDiagnosisAdult worm- removal from the skin or the conjunctivaMicrofilaria- peripheral blood collected during the day.Treatment Surgical removal of the adult worms.