Dracunculus medinensis (guinea worm)

Question 1

What is the classification of D. medinensis

Answer 1

Metazoan: helminths - nematode targets extracellular

Question 2

How is D. medinensis transmitted?

Answer 2

by drinking stagnant water containing copepods of the species cyclops (water fleas) that carry the L3 larvae

Alternative route of transmission - consumption of undercooked or uncooked fisk, frogs or other aquatic animals with infective copepods

Question 3

What is the life cycle of D. medinensis?

Answer 3

1. Humans drink unfiltered water or contaminated seafood containing copepods which are water fleas from species cyclops. These water fleas are infected with 3rd stage larvae from the guinea worm.
2. Guinea worm larvae are released in the stomach
3. Larvae penetrate and enter the abdominal cavity (stomach) and intestinal wall in 15 days. The parasite sexually matures in 3-4 months after which the male and female worm find each other and mate
4. After copulation male worms become encapsulated and die in 6-7 months while female worms can grow up to 80-120 cm in length and 2 mm in thickness
5. Fertilized female worm migrates to the surface of the skin, causes a blister, and discharges larvae. Most often in the lower extremities. This migration process takes 10-14 months and the full emerging of the larvae takes 2-6 weeks. It drops thousands of first-stage larvae in the freshwater source where it can survive for up to 6 days.

People can harbor 2-3 worms

6. Water flaes actively seek out larvae to consume them
7. After 2 weeks of shedding rounds the larvae develop in 3rd stage larvae within the water flae, now infectious to humans

Question 4

What type of life cycle does D. medinensis have? and what are the hosts?

Answer 4

Indirect life cycle

Definitive host: humans

Intermediate host: copepod

Question 5

What are other reservoirs for D. medinensis?

Answer 5

• dogs
• cats
• baboons

Question 6

What are the symptoms of D. medinensis?

Answer 6

Symptoms occur after 1 year - not fetal

• swelling and a blister
• painful throbbing
• bursting sensation and a fever

When the host enters the water for relievement - blister ruptures and L1 larvae discharge
Sickness can take up to 12-18 months due to secondary bacterial infections - 1% mortality rate

Question 7

What is the incubation time of D. medinensis?

Answer 7

10-14 months

Question 8

Where is D. medinensis endemic?

Answer 8

Sub-tropic to tropical regions (temp 25-30 best for larvae developement)
It remains endemic in Chad, Ethiopia, Mali, South Sudan and Angola

Question 9

What is the current treatment for D. medinensis

Answer 9

There is no vaccine/ medicine for it

The best prevention methods are clean sources of drinking water

Once the worm is out the only treatment is wrapping it a few cm a day around a wooden stick

Question 10

How is D. medinensis diagnosed?

Answer 10

Visual examination - white, filamentous adult worm at the cutaneous ulcer
X-ray examination - localization of calcified worms
Microscopy - identifies L1 larvae
Intradermal test - dracunculus antigen
Serology (during active infection) - dracunculus antibodies