Guinea Worm

Guinea Worm

Causative Agent

Guinea worms (Dracunculus) are nematodes that parasitize areas beneath the skin of the legs of fur-bearing mammals throughout North America.
In North America, two species, Dracunculus insignis and D. lutrae, are recognized under the common name of guinea worm.

Distribution

Geographic:

D. insignis has been reported throughout North America.
D. lutrae has only been reported in the east-central portion of the continent.

Seasonality:

Transmission of Dracunculus worms may occur during only a few weeks of the year or throughout the year depending on the diet of the definitive host species.

Hosts, Transmission and Life Cycle

Female worms are slender and whitish and can be up to 28 cm in length; males appear dark, extremely slender and usually 1.5–4 cm long.
Female worms are located between the skin and muscle on the thorax, abdomen, groin and legs of hosts.
Male worms, which also occur beneath the skin, are rarely found outside of the thorax, abdomen and groin.
Pregnant female worms occur just under the skin in the legs. This causes the development of a blister in the skin of the host that eventually ruptures forming an ulcer.
Larvae leave through the ulcer when the affected area is immersed in water.
Larvae are then ingested by Cyclops sp., a small freshwater crustacean within which they develop until they are infective to the definitive host.
Some fish or frogs may ingest infected Cyclops sp. and serve as reservoir hosts for the parasite.
The definitive host drinks water containing parasitized Cyclops or ingests infected reservoir hosts and Dracunculus larvae are released into the intestinal tract.
Larvae then penetrate the intestine and migrate through the body cavity to connective tissues of abdomen, thorax and groin. After mating male worms remain in this location and fertilized females migrate towards the legs.
After production of larvae, worms may die and be absorbed by the definitive host.

Signs and Symptoms

Infected animals may raise affected legs off of the ground and occasionally scratch at the site of blisters or ulcers. Hair may be lost and skin damage may occur.
Ulcers often heal quickly after the female worm has released the larvae and has died.
Guinea worms are not a significant mortality factor as their infections are limited to the subcutaneous spaces of the legs.
The quality of the pelt is not impaired by the worm's presence for the ulcerations occur only on the legs.

Meat Edible?

Since only the limbs area affected, the remainder of the carcass should be edible.
Dogs and cats are susceptible to Dracunculus infection and as such, dogs or cats should not be allowed to scavenge dead fish or frogs which may contain infected larvae.

Human Health Concerns and Risk Reduction

Humans are not able to contract D. insignis and D. lutrae and therefore, the guinea worms are not of public health significance.

Samples for Diagnosis

Infection with Dracunculus worms can be confirmed by finding and identifying adult worms in the subcutaneous space of the legs.
Finding a Dracunculus worm is more likely if both the pelt and carcass are examined.