Nematodes: Is the Threat of Roundworms and Barefoot Exposure Still Relevant?

What are Nematodes?

Did your mother insist on you wearing shoes outdoors during your childhood? Her concern likely stemmed from protecting you from nematodes, commonly referred to as roundworms. These tiny worms, which rank as the most abundant multicellular organisms on Earth, frequently act as parasites in humans, animals, plants, and even insects. Scientists have identified around 20,000 species, though many experts argue this figure vastly underestimates their true diversity.

Nematodes in Soil

Think you’ll never encounter nematodes? Thousands can inhabit just a small scoop of soil. It’s wise to avoid walking barefoot in dirt. "Certain nematodes are labeled as 'soil-transmitted parasites,' posing a risk as they can breach the skin, particularly on the feet," says Dr. Chad Cross, a research scientist at the University of Nevada, Las Vegas School of Community Health Sciences, via email. "The term 'roundworm' is a common name for 'nematoda,' encompassing both harmless species and notorious parasites like hookworms, filarial worms, ascarid worms, whipworms, pinworms, and more."

Parasitic Nematodes

Certain individuals face a higher risk of encountering these microscopic worms. "In regions where hookworms are prevalent—such as rural farming areas, children playing in soil, or waste-contaminated beaches—nematode larvae can easily penetrate the skin. Wearing shoes in such environments is crucial," Cross emphasizes.

In such scenarios, the worms have already hatched, enabling them to infiltrate the skin. However, this is not the sole method of ending up with intestinal nematodes. People often ingest eggs by touching contaminated soil and then eating without washing their hands. Consuming unwashed fruits and vegetables is another common route. Once inside the body, the eggs hatch, larvae develop, and the cycle perpetuates.

Not all nematodes significantly impact humans. "Certain nematodes, especially those that typically infect animals, may struggle to penetrate deep into human tissues," Cross notes. "In such instances, the larvae might migrate beneath the skin, creating visible, intensely itchy trails—a condition known as 'cutaneous larva migrans.'"

However, some nematodes that enter through the skin can penetrate deeper tissues, migrating extensively within the body. Since most nematodes favor the intestines as their habitat, they embark on a lengthy journey through the body, reaching the lungs before settling in the intestines. "This is where they absorb nutrients and produce eggs that are later expelled through feces," Cross explains.

How can one detect if nematodes are causing harm? The itchy trails Cross mentioned are a possible indicator, though not always present. Symptoms can range from mild to severe, sometimes going unnoticed but potentially escalating. "When nematodes reach the lungs, unexplained coughing may occur. Once they migrate to the intestines, symptoms like loss of appetite, abdominal pain, and signs of malnutrition—such as weight loss, vitamin deficiencies, and anemia—may arise," Cross states. He adds, "In severe cases, a high parasite load can even lead to bowel obstruction." Extreme infections can trigger sudden malnutrition, leading to further complications.

Nematode Treatment

Treatment varies based on the infection's severity but is generally highly effective. Antihelminthic drugs, such as albendazole and mebendazole, specifically designed to eliminate parasites, are ideal for acute cases. In high-risk areas, some individuals undergo regular treatments (e.g., every six months) to reduce parasite levels. "This not only alleviates the individual's burden but also minimizes environmental contamination by eggs and larvae, thereby lowering infection rates in the community," Dr. Cross explains.

So, perhaps take that extra second to slip on shoes before heading outdoors. While you're at it, scrub your hands thoroughly before meals and give fresh produce a good rinse. Your parasite-free stomach will be grateful.