Clinical Overview of Guinea Worm

Cause

People become infected with Guinea worms by consuming unfiltered drinking water from ponds and other stagnant water (e.g., ponds, pools in drying riverbeds, and shallow hand-dug wells without surrounding protective walls) containing copepods (near-microscopic freshwater crustaceans) that are too small to be clearly seen without a magnifying glass. The copepods swallow Guinea worm larvae (immature forms of the worm), and then people who drink water containing the infected copepods can develop Guinea worm disease (GWD). GWD is not normally caught from drinking flowing water (e.g., rivers and streams).^{1 2 3}

People and animals might also become infected by eating certain aquatic animals (e.g., fish or frogs) that might swallow infected copepods and carry Guinea worm larvae, though they do not themselves suffer the effects of infection. If people or animals eat raw or undercooked aquatic animals either whole or in part (e.g., small whole fish that have not been gutted, fish guts, and frogs), the Guinea worm larvae are then released into the human or animal digestive tract. ⁴

After people or animals consume them, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and move to the connective tissues of the abdomen where they mate. After mating, the pregnant female worm grows to 60 – 100 centimeters (2 – 3 feet) in length and as wide as a cooked spaghetti noodle during the next 10 – 14 months (on average, one year).

When the adult female worm is ready to release her larvae, approximately one year after infection, she moves to a spot just beneath the skin. A blister forms on the skin where the worm will eventually emerge. This blister may form anywhere on the body, but usually forms on the legs and feet. This blister causes a very painful burning feeling, and it bursts within 24 – 72 hours.

Who is at risk

People's risk for GWD varies. These differences reflect how and where people get their drinking water in different areas and countries.

• GWD occurs in all age groups but is most common among young adults 15 – 45 years old, possibly due to the type of work people of these ages do.
• Farmers, herders, and those fetching drinking water for the household may be more likely to become infected because they might consume unfiltered water while away from home.
• In certain areas, GWD affects some ethnic groups more than others.^{1 2 3}

Risk factors

GWD can occur at any time of the year, but is most common during peak transmission season, which varies by country.

• In dry regions, people generally get infected during the rainy season, when stagnant surface water is available.
• In wet regions, people generally get infected during the dry season, when surface water is drying and becoming stagnant. ^{2 3}

Reinfection

People do not become immune to Guinea worm infection if they have had it before. In fact, an important risk factor for new GW infection is having had GWD the year before. In the past, when GWD cases were higher, some people in affected villages suffered from GWD year after year, most likely due to the same water sources being repeatedly contaminated. Biological characteristics may also influence a person's susceptibility.

Not everyone drinking from the same contaminated water supply will become infected. Some people seem to keep getting infected while others drinking the same water do not. ^{1 3 5}

How it spreads

Whether to relieve pain or as part of their daily lives (e.g., to collect water, bathe, wash clothes, cool off, etc.), people and animals infected with Guinea worm usually enter bodies of water. Water contact triggers the Guinea worm to release a milky white liquid that contains hundreds of thousands of immature larvae into the water. Copepods that live in ponds and other stagnant water sources swallow these larvae, and the cycle begins again when people or animals consume the water containing infected copepods.

Spread in animals

Guinea worm infection in animals has been a challenge since 2012.

This has led to consideration of the possibility of GWD transmission though a previously unrecognized route — consumption of fish, frogs, or other aquatic animals that carry Guinea worm larvae, but do not themselves suffer the effects of transmission.⁶ The situation has been carefully investigated⁷ and control measures have been implemented (e.g., tethering of dogs, educating residents to fully cook aquatic animals before eating them and not feed fish guts to dogs.

In 2023, there were a total of 714 animal infections worldwide, with a slight increase in reports from 2022 following expanded surveillance activities. This included 495 animals in Chad, 47 in Mali, 97 in Cameroon, 73 in Angola, one in Ethiopia, and one in South Sudan.

Patient management

There is no drug nor vaccine to prevent or treat Guinea worm infection. People can learn how to manage GWD and prevent further spread.

When the Guinea worm is ready to come out of the body, it creates a painful burning blister on the skin, which eventually ruptures, exposing the worm.

If infected, people can take the following steps:

1. Ensure the infected person does not enter drinking water sources.
2. Clean the wound by soaking the affected body part in water (far away from any water source to avoid contamination). Soaking the wound will encourage the worm to contract and release larvae, which makes it easier to remove the worm.
3. Wrap the worm around a piece of rolled piece of gauze. This will maintain tension on the worm and help more of the worm come out, while also preventing the worm from slipping back inside.
4. Use gentle traction on the worm to slowly pull it out. Stop pulling when you feel resistance to avoid breaking the worm. Because the worm can be as long as three feet (one meter), extraction can take several days to weeks.
5. After extracting the worm, apply topical antibiotics to the wound to prevent secondary bacterial infection.
6. Bandage the wound with fresh gauze to protect the site. Medicines (e.g., aspirin or ibuprofen) can be taken to ease the pain and reduce inflammation.
7. Repeat these steps daily until the whole worm is successfully pulled out.

Complications

Once part of the worm begins to come out of the wound, the rest of the worm can only be pulled out a few centimeters each day by winding it around a piece of gauze. Sometimes the whole worm can be pulled out within a few days, but the process usually takes weeks. Care must be taken not to break the worm during removal. If the worm breaks and part of the worm is not removed, there is a risk for significant inflammation and secondary bacterial infection, with resulting complications. This makes the pain worse and can increase the time an infected person is unable to function from weeks to months. Sometimes, permanent damage can occur if a joint is infected and becomes locked. Anti-inflammatory medicine can help reduce pain and swelling. Antibiotic ointment can help prevent infections.

References

1. Cairncross, S., R. Muller, and N. Zagaria, Dracunculiasis (Guinea worm disease) and the eradication initiative. Clin Microbiol Rev, 2002. 15(2): p. 223–46. https://journals.asm.org/doi/10.1128/CMR.15.2.223-246.2002
2. Greenaway, C., Dracunculiasis (Guinea worm disease). CMAJ, 2004. 170(4): p. 495–500. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC332717/
3. Ruiz-Tiben, E. and D.R. Hopkins, Dracunculiasis (Guinea worm disease) eradication. Adv Parasitol, 2006. 61: p. 275–309. https://www.sciencedirect.com/science/article/pii/S0065308X0561007X?via%3Dihub
4. Hopkins DR, et al., Progress Toward Global Eradication of Dracunculiasis, January 2016–June 2017. MMWR, 2017 Dec 8. 66(48): p. 1327–31. https://www.cdc.gov/mmwr/volumes/66/wr/mm6648a3.htm?s_cid=mm6648a3_w
5. Tayeh, A., S. Cairncross, and G.H. Maude, Water sources and other determinants of dracunculiasis in the northern region of Ghana. J Helminthol, 1993. 67(3): p. 213–-25.
6. Eberhard ML, Ruiz-Tiben E, Hopkins DR, Farrell C, Toe F, Weiss A, Withers PC Jr, Jenks MH, Thiele EA, Cotton JA, Hance Z, Holroyd N, Cama VA, Tahir MA, Mounda T. The Peculiar Epidemiology of Dracunculiasis in Chad. Am J Trop Med Hyg, 2014 Jan. 90(1): p. 60–71. https://www.ajtmh.org/view/journals/tpmd/90/1/article-p61.xml
7. Hopkins DR, Weiss AJ, Yerian S, Sapp SGH, Cama VA. Progress Toward Global Eradication of Dracunculiasis—Worldwide, January 2021–June 2022. MMWR, 2022. 71(47): p. 1496–1502. https://www.cdc.gov/mmwr/volumes/71/wr/mm7147a2.htm?s_cid=mm7147a2_w.