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Dracunculus insignis Infection 275.e1

Dracunculus insignis Infection
VetBooks.ir Diseases and Disorders

• The gravid female worm moves in the
BASIC INFORMATION
nodules or abscesses, but adult heartworms
subcutaneous connective tissues of the dog’s adult heartworms may produce subcutaneous
Definition extremities, producing a large cutaneous usually do not protrude from the lesions.
Rare parasitic infection of dogs, characterized swelling that eventually develops into a • Foreign bodies in the skin may produce
by a non-healing ulcerative cutaneous lesion, non-healing ulcer. From this ulcer, the female non-healing ulcerous lesions; however, the
typically on a dog’s distal limb worm extrudes her anterior end. foreign bodies are not visible in the lesion
• When the female worm makes contact or, if they are, do not resemble a protruding
Synonyms with water, her uterus prolapses through female worm.
Canine Guinea worm disease, canine dracun- her anterior end, releasing a mass of first-
culiasis, “serpent-on-a-stick” stage larvae into the water. These larvae Initial Database
are 500-750 microns long with unique, • CBC and serum chemistry profile:
Epidemiology characteristically long tails. unremarkable
SPECIES, AGE, SEX • The larvae are ingested by the intermediate • Impression smears of the lesion may reveal
Infects dogs or any wild carnivore member of host, a copepod aquatic crustacean (water inflammatory cells and first-stage larvae.
the Canidae family; raccoons and mink are flea) usually belonging to the genus Cyclops;
reservoir hosts eventually, larvae develop into infective third- Advanced or Confirmatory Testing
stage larvae within the intermediate host. • With the worm still embedded in tissues
GENETICS, BREED PREDISPOSITION • Dogs become infected by drinking the water and protruding from the non-healing ulcer,
Sporting breeds of dogs are predisposed. containing the Cyclops harboring the infective the protruding (anterior) end of the worm
larvae or by eating frogs that have consumed should be dipped into a test tube contain-
RISK FACTORS Cyclops. ing cool water to elicit release of a mass of
Hunting/foraging and drinking water from • In approximately 1 year, the ingested larvae first-stage larvae into the water; a cloudy
freshwater environments inhabited by aquatic mature to adult parasites. Male and female discharge (containing microscopic larvae)
crustaceans (water fleas), intermediate hosts worms copulate. The female eventually may be observed.
belonging to genus Cyclops migrates to the extremities, where she • The test tube should be centrifuged and the
produces the nodule that eventually will water supernatant collected. The larvae may
CONTAGION AND ZOONOSIS develop into a cutaneous ulcer in the dog. be found in the sediment at the bottom of
Although they have their own species of this the test tube.
parasite (Dracunculus medinensis), humans are DIAGNOSIS • Microscopic examination of the sediment
not susceptible to infection with the canine reveals the first-stage larvae (500-750 microns
parasite. Diagnostic Overview long) with their characteristic long tails.
Suspicion of dracunculiasis is first raised with
GEOGRAPHY AND SEASONALITY the appearance of a cutaneous ulcer and is TREATMENT
Found in definitive hosts throughout North greatly heightened if a fine, threadlike structure
America; no seasonality is seen protruding from the lesion. Confirma- Treatment Overview
tion is simple, using a test tube filled with cool The female parasite must be manually extracted
Clinical Presentation water, a centrifuge, and a microscope. from the ulcerous lesion using careful surgical
HISTORY, CHIEF COMPLAINT intervention with blunt dissection.
• One or more blister-like cutaneous swellings/ Differential Diagnosis
non-healing ulcers. Lesions often occur on • This nematode may be confused with a single Acute General Treatment
the extremities or ventral abdomen. aberrant (erratic) adult Dirofilaria immitis, • Do not attempt to pull on the female worm;
• Owners may notice the characteristic which can be found in a variety of ectopic she is entwined within the subcutis, very
protruding end of the female worm in the sites throughout a dog’s body. These “lost” friable, and prone to breakage. Surgical
ulcerated skin lesion.

PHYSICAL EXAM FINDINGS
• Ulcerative nodules or abscesses can be found
on the skin of the limbs (typical), head, and
abdomen.
• The female worm typically protrudes
from the ulcerated lesion, making it easily
visible.
○ Do not attempt to pull the worm out
because it is liable to break.
• Lesions may be painful or pruritic.
• The dog may or may not be febrile.
Etiology and Pathophysiology
• The adult female worm may be up to 100 cm
(3 feet) long.
• This is an unusual parasite in that the
female possesses no vulva to allow exit of DRACUNCULUS INSIGNIS INFECTION Third-stage larvae of Dracunculus insignis (500-750 microns long).
her offspring. Note the characteristic long tail of each larva.

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