Intestinal parasitic infections are among the most prevalent infectious diseases worldwide. According to the World Health Organization (WHO), more than 1.5 billion people—approximately 24% of the global population—are infected by some type of helminth or intestinal parasite.

Although the popular imagination tends to associate “worms” with childhood, clinical reality shows that adults are equally vulnerable, especially in regions with deficiencies in basic sanitation, limited access to drinking water or eating habits that facilitate transmission.

The lack of information about symptoms in adults causes late diagnoses that lead to avoidable complications.

Worms do not distinguish ages

When talking about worms or intestinal parasites, most people automatically think of young children. However, specialists in internal medicine and gastroenterology warn that adults are just as susceptible to contracting parasitic infections, and that the problem is far from being marginal.

The main responsible agents include Ascaris lumbricoides (roundworms), Enterobius vermicularis (pinworms), Taenia spp. (tapeworm), hookworms and Giardia lamblia, among others. Each of them produces particular clinical manifestations, although they share a set of common symptoms that should be known.

How adults get infected

The most frequent route of transmission is fecal-oral: ingestion of water or food contaminated with eggs or cysts of the parasite. Infection can also occur through contact with infested soil, consumption of undercooked meat (especially in the case of tapeworm) or even through contact with infected people in the home.

Travel to tropical areas, work in agriculture without adequate protection, and overcrowded conditions are recognized risk factors in adults.

The most frequent symptoms

Worm infection in adults can be completely asymptomatic for weeks or even months, complicating early diagnosis. When manifestations appear, they vary depending on the type of parasite and the parasite load, but the most common are:

Persistent digestive discomfort. Abdominal pain or discomfort, generally diffuse or located in the periumbilical area, is one of the first signs. It may be accompanied by nausea, a feeling of bloating, and excessive flatulence. Some patients also describe episodes of diarrhea alternating with constipation.

Weight loss without apparent cause. The parasite competes with the host for ingested nutrients. This phenomenon can translate into a progressive weight reduction without the person having modified their diet or physical activity.

Fatigue and general weakness. Malabsorption of iron, vitamin B12 and other essential micronutrients generates a state of exhaustion that patients usually attribute to stress or lack of sleep, delaying medical consultation.

Anemia. Certain parasites such as hookworms feed on blood attached to the intestinal mucosa, which can trigger iron deficiency anemia with symptoms such as paleness, dizziness and tachycardia.

Anal itching, especially at night. It is the characteristic symptom of pinworms. Females migrate to the outside of the anus during the night to deposit eggs, producing intense itching that disturbs sleep.

Changes in appetite. Both unusual increases in hunger and loss of appetite can be signs of active parasitosis.

Skin manifestations. In some cases, larval migration can cause skin rashes, hives, or even serpiginous lesions characteristic of cutaneous larva migrans.

Neurological or psychological symptoms. Although less common, severe infection by certain parasites can be associated with irritability, difficulty concentrating and even mood disturbances, especially if there is associated malnutrition.

Diagnosis, warning signs and prevention

The diagnosis is confirmed mainly by coproparasitological examination, which analyzes a stool sample for eggs, cysts or fragments of the parasite. In some cases it is complemented with blood tests (high eosinophilia is a guiding marker), serology or imaging techniques.

Treatment depends on the parasite identified. The most used antiparasitics in adults include albendazole, mebendazole and metronidazole, always under medical prescription and supervision. Self-medication, although common, can be ineffective if the causative agent is not known.

Some symptoms should prompt an urgent medical consultation: the visible presence of parasites or segments of them in the stool, acute and intense abdominal pain, high fever or the appearance of a palpable mass in the abdomen. In cases of massive Ascaris infestation, there is a risk of intestinal obstruction, a surgical emergency.

Experts insist that most intestinal parasites are preventable with simple measures: washing hands with soap and water before handling food and after going to the bathroom, consuming drinking or boiled water, cooking meat well, washing fruits and vegetables well and avoiding walking barefoot on soils with possible fecal contamination.

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