Animal Diversity Web

Ge­o­graphic Range

Dra­cun­cu­lus in­sig­nis is lim­ited to North Amer­ica. (Roberts and Janovy, Jr., 2000)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

While out­side of a host, Dra­cun­cu­lus in­sig­nis is lim­ited to aquatic en­vi­ron­ments. As such, D. in­sig­nis re­quires a semi-aquatic or fully aquatic host such as a mink, rac­coon, otter, fisher, and oc­ca­sion­ally do­mes­tic dogs. (Crich­ton and Bev­erly-Bur­ton, 1975)

• Habitat Regions
• temperate
• tropical

• Terrestrial Biomes
• desert or dune
• savanna or grassland
• chaparral
• forest
• rainforest
• scrub forest
• mountains

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools

• Wetlands
• marsh
• swamp
• bog

• Other Habitat Features
• urban
• suburban
• agricultural
• riparian

Phys­i­cal De­scrip­tion

Dra­cun­cu­lus in­sig­nis adults are white cylin­dri­cal worms 17.6 to 23.0 cm in length and 3 to 4 mm at max­i­mum width. Dra­cun­cu­lus in­sig­nis is dioe­cious. Fe­males are much larger than males when they are filled with first-stage lar­vae. Lar­vae are ap­prox­i­mately 500 mi­crons long and 50 mi­crons wide. Over the course of de­vel­op­ment, the head changes from a pointed shape to a dome shape by adult­hood.

The worm's cu­ti­cle has three or more main outer lay­ers made of col­la­gen and other com­pounds. The outer lay­ers are non-cel­lu­lar and are se­creted by the epi­der­mis. The cu­ti­cle layer pro­tects the ne­ma­todes so they can in­vade the di­ges­tive tracts of an­i­mals. The worms molt four times, the first two be­fore hatch­ing, and then be­fore their adult stage.

Lon­gi­tu­di­nal mus­cles are along the body wall and are obliquely arranged in bands. Dor­sal, ven­tral and lon­gi­tu­di­nal nerve cords are con­nected to the main body of the mus­cle.

The mouth leads to a thin esoph­a­gus and in­tes­tine. The male in­tes­tine is com­pletely at­ro­phied. As a ne­ma­tode in the group Se­cer­nen­tea, these worms have a spe­cial­ized tubu­lar ex­cre­tory sys­tem with three canals. The canals are arranged to form an “H”.The rec­tum is long and tubu­lar in shape. (Barnes, 1987; Br­usca and Br­usca, 2003; Crich­ton and Bev­erly-Bur­ton, 1975; Gib­son and McK­iel, 1972; Panciera and Stock­ham, 1988; Roberts and Janovy, Jr., 2000)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes shaped differently

• Range length

  17.6 to 23 mm

  0.69 to 0.91 in

De­vel­op­ment

The life cycle of Dra­cun­cu­lus in­sig­nis is fairly sim­ple and in­volves at least two hosts. Fe­males car­ry­ing lar­vae in­ter­nally re­lease a toxin which causes the for­ma­tion of a blis­ter on the hosts skin. This blis­ter bursts open on con­tact with water al­low­ing the fe­male to re­lease her lar­vae upon con­tact with water. Dra­cun­cu­lus in­sig­nis passes through two lar­val stages in an in­ter­me­di­ate cope­pod host, ei­ther Cy­clops ver­nalis or C. bi­cus­p­i­da­tus thomasi. After pen­e­trat­ing the in­ter­me­di­ate host, lar­vae mi­grate to the he­mo­coel within one to two hours. Growth is tem­per­a­ture de­pen­dent. Tem­per­a­tures be­tween 8 and 15°C showed no de­vel­op­ment of lar­vae after sixty days. At 24°C the first molt oc­curs after just eight or nine days. A sec­ond molt fol­lows just seven days later. At the third lar­val stage, D. in­sig­nis exits the host through the skin and must be in water. The lar­vae must be swal­lowed ei­ther by a paratenic host or the de­fin­i­tive host. Frogs often serve as paratenic hosts and Dra­cun­cu­lus in­sig­nis must wait for a de­fin­i­tive host to eat the frog. De­fin­i­tive hosts for D. in­sig­nis are North Amer­i­can car­ni­vores which are usu­ally semi-aquatic. These in­clude, mink, rac­coon, otter, fisher, and oc­ca­sion­ally do­mes­tic dogs. Upon reach­ing the de­fin­i­tive host, D. in­sig­nis un­der­goes two molts be­fore reach­ing adult­hood. The molt to the fourth stage takes place after one to two weeks after being in­gested by the de­fin­i­tive host. Males will have com­pleted the final molt to adult­hood after ap­prox­i­mately sixty days while fe­males ma­ture in sixty-five to sev­enty days. By 120 to 270 days, most fe­males will have been fer­til­ized and have their uterus full of lar­vae. (Crich­ton and Bev­erly-Bur­ton, 1975; Panciera and Stock­ham, 1988; Roberts and Janovy, Jr., 2000)

Re­pro­duc­tion

Fe­males may pro­duce a pher­momone to at­tract males. The male coils around a fe­male with his curved area over the fe­male gen­i­tal pore. The gu­ber­nac­u­lum, made of cu­ti­cle tis­sue, guides spicules which ex­tend through the cloaca and anus. Mat­ing oc­curs when a male in­serts a spicule into the fe­male's vulva and re­leases his sperm. Males use spicules to hold the fe­male dur­ing cop­u­la­tion. Ne­ma­tode sperm are amoe­boid-like and lack fla­gella. The fer­til­ized eggs de­velop into lar­vae within the uterus. By 120 to 270 days, most fe­males will have been fer­til­ized and have their uterus full of lar­vae. Fe­males will cre­ate a le­sion in their host from which they will send their lar­vae into the water by 300 to 365 days post-in­fec­tion. Fe­males re­lease eggs for five to seven days after which they die and are ab­sorbed into the host body. The rare oc­cur­rence of Dra­cun­cu­lus in­sig­nis males is due to their death di­rectly fol­low­ing mat­ing. (Barnes, 1987; Br­usca and Br­usca, 2003; Crich­ton and Bev­erly-Bur­ton, 1975; Panciera and Stock­ham, 1988; Roberts and Janovy, Jr., 2000)

• Key Reproductive Features
• sexual
• fertilization
  • external
• ovoviviparous

• Parental Investment
• pre-fertilization
  • provisioning

Be­hav­ior

Ne­ma­todes such as Dra­caun­cu­lus in­sig­nis can swim in­ter­mit­tently. The worms are usu­ally only able to move ef­fec­tively when the pseudo­coel is filled with fluid and hy­per­tonic to to the sur­round­ing media. (Barnes, 1987; Br­usca and Br­usca, 2003)

• Key Behaviors
• parasite
• motile
• sedentary

Com­mu­ni­ca­tion and Per­cep­tion

Ne­ma­todes within the Se­cer­nen­tea have phas­mids, which are uni­cel­lu­lar glands. Phas­mids likely func­tion as chemore­cep­tors. Fe­males may pro­duce pheromones to at­tract males.

Ne­ma­todes in gen­eral have papil­lae, setae and am­phids as the main sense or­gans. Setae de­tect mo­tion (mechanore­cep­tors), while am­phids de­tect chem­i­cals (chemore­cep­tors).

• Communication Channels
• tactile
• chemical

• Other Communication Modes
• pheromones

• Perception Channels
• tactile
• chemical

Food Habits

Dra­cun­cu­lus in­sig­nis is an en­dopar­a­site with in­di­vid­u­als being found most often in the in­tra­mus­cu­lar con­nec­tive tis­sue of the limbs as well as the sub­cu­ta­neous tis­sue of the ab­domen in the de­fin­i­tive host. The diet of both ju­ve­niles and adult fe­males is com­posed of host tis­sue fluid and a small amount of blood. Pha­ryn­geal glands and in­testi­nal ep­ithe­lium pro­duce di­ges­tive en­zymes. Ex­tra­cel­lu­lar di­ges­tion be­gins within the lumen and is fin­ished in­tra­cel­lu­larly. Adult males, with their at­ro­phied gut, do not feed. (Barnes, 1987; Br­usca and Br­usca, 2003; Roberts and Janovy, Jr., 2000)

• Primary Diet
• carnivore
  • eats body fluids

• Animal Foods
• blood
• body fluids

Pre­da­tion

These par­a­sites are usu­ally not preyed on di­rectly, but are in­gested from host to host. (Barnes, 1987; Br­usca and Br­usca, 2003)

Ecosys­tem Roles

The life cycle of Dra­cun­cu­lus in­sig­nis in­volves at least two hosts: an in­ter­me­di­ate cope­pod host, ei­ther Cy­clops ver­nalis or Cy­clops bi­cus­p­i­da­tus thomasi. De­fin­i­tive hosts for D. in­sig­nis are North Amer­i­can car­ni­vores which are usu­ally semi-aquatic. These in­clude, mink, rac­coon, otter, fisher, and oc­ca­sion­ally do­mes­tic dogs.

• Ecosystem Impact
• parasite

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Dra­cun­cu­lus in­sig­nis does not par­a­sitize hu­mans. How­ever, it does in­fect car­ni­vores, in­clud­ing do­mes­tic dogs. A dog par­a­sitized by D. in­sig­nis will ex­hibit sub­cu­ta­neous swellings be­tween three and five cm in di­am­e­ter. Most often these can be found on the limbs, but they have been re­ported on the head of dogs. De­hy­dra­tion, vom­it­ing, di­ar­rhea, and asthma are also com­mon symp­toms of in­fec­tion. In­fes­ta­tion usu­ally in­volves a trip to the vet­eri­nar­ian for re­moval of the par­a­site. The pro­ce­dure for re­mov­ing D. in­sig­nis in­volves plac­ing the dog in water deep enough to cover the wounds thus caus­ing the adult fe­males to emerge from the swellings. This is fol­lowed by dis­sec­tion to com­pletely re­move the par­a­sites.

A close rel­a­tive of Dra­cun­cu­lus in­sig­nis, D. medi­nen­sis (the Guinea worm) is re­spon­si­ble for a con­di­tion known as dra­cun­cu­lia­sis in hu­mans through­out much of Africa and the Mid­dle East. Chem­i­cals to kill the par­a­site are being tested on D. in­sig­nis in hopes of erad­i­cat­ing the prob­lems caused by D. medi­nen­sis. (Eber­hard, et al., 1990; John­son, 1974; Panciera and Stock­ham, 1988)

• Negative Impacts
• causes or carries domestic animal disease

Con­ser­va­tion Sta­tus

• IUCN Red List

  No special status

Con­trib­u­tors

Renee Sher­man Mul­crone (ed­i­tor).

Daniel Fargo (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Teresa Friedrich (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Barnes, R. 1987. In­ver­te­brate Zo­ol­ogy. Or­lando, Florida: Dry­den Press.

Br­usca, R., G. Br­usca. 2003. In­ver­te­brates. Sun­der­land Mass­a­chu­setts: Sin­auer As­so­ci­ates, Inc..

Carl­son, B., V. Sas­seville. 1984. Dra­cun­cu­lus in­sig­nis in fish­ers in New Hamp­shire. Jour­nal of the Amer­i­can Vet­eri­nary Med­ical As­so­ci­a­tion, 185: 1327.

Crich­ton, V., M. Bev­erly-Bur­ton. 1975. Mi­gra­tion, growth, and mor­pho­gen­e­sis of Dra­cun­cu­lus in­sig­nis (Ne­ma­toda: Dra­cun­cu­loidea). Cana­dian Jour­nal of Zo­ol­ogy, 53: 105-112.

Eber­hard, M., F. Brandt, E. Ruiz-Tiben, A. High­tower. 1990. Chemo­pro­phy­lac­tic drug tri­als for treat­ment of dra­cun­cu­lia­sis using the Dra­cun­cu­lus in­sig­nis-fer­ret model. Jour­nal of Helminthol­ogy, 64: 79-86.

Gib­son, G., D. McK­iel. 1972. Dra­cun­cu­lus in­sig­nis and lar­val Eu­strongylides sp.​in a muskrat from On­tario, Canada. Cana­dian Jour­nal of Zo­ol­ogy, 50: 897-901.

John­son, G. 1974. Dra­cun­cu­lus in­sig­nis in a dog. Jour­nal of the Amer­i­can Vet­eri­nary Med­ical As­so­ci­a­tion, 165: 372.

Michi­gan De­part­ment of Nat­ural Re­sources, 2004. "North Amer­i­can Guinea Worm (Dra­nun­cu­lo­sis)" (On-line). Wildlife Dis­eases. Ac­cessed Sep­tem­ber 23, 2004 at http://​www.​michigan.​gov/​dnr/​0,1607,7-153-10370_12150_12220-27119--,00.​html.

Panciera, D., S. Stock­ham. 1988. Dra­cun­cu­lus in­sig­nis in­fec­tion in a dog. Jour­nal of the Amer­i­can Vet­eri­nary Med­ical As­so­ci­a­tion, 192: 76-78.

Roberts, L., J. Janovy, Jr.. 2000. Ger­ald D. Schmidt and Larry S. Roberts’ foun­da­tions of par­a­sitol­ogy (Sixth Ed.). Boston, MA: Mc­Graw-Hill.

Uni­ver­sity of Penn­syl­va­nia School of Vet­eri­nary Med­i­cine, 2004. "Dra­cun­cu­lus in­sig­nis Home­page" (On-line). Di­ag­no­sis of Vet­eri­nary En­dopar­a­sitic In­fec­tions. Ac­cessed Sep­tem­ber 23, 2004 at http://​cal.​vet.​upenn.​edu/​dxendopar/​parasitepages/​filariidsandspirurids/​d_​insignis.​html.