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July 21 2020

8 Common Parasitic Worms That May Lurk in Humans

​Did you know that parasitic worms could feed off humans? People can lightly joke about having worms in the human body, but it is possible to have them. Parasite transmission occurs and often happens during childhood due to higher exposure and improper hygiene. Other organisms can also be transmitted through water, soil, food, or person-to-person contact.
What are parasitic worms?
Parasites are organisms that live in or feed off a living host like humans to survive. They invade a person’s body as part of their lifecycle and move out to find a new host. This may progress to an infectious disease if it gets worse. Statistics show that roughly 70% of parasites are not visible to the human eye.
The risk of being infected with parasites is higher in rural areas or developing countries, especially in places where sanitation is poor, and food and drinking water are susceptible to contamination.
Some parasitic worms cling to humans for a short stay, while others stick around for years. This can result in the host's malnutrition or cause them to get sick for a long time. As the worm holds on tighter, the harder it is to expel them out of the body. Different types of parasitic worms bring different effects.
Most Common Parasitic Worms
Below are the most common types of parasitic worms that infect humans and are not usually visible to the naked eye.

1. Pinworms (Enterobius vermicularis)
These are small, thin, white roundworms that are about the length of a staple, which sometimes stays at the colon and rectum. Humans infected by this parasite usually feel itchy at the anus where the pinworms lay their eggs. When itched, the larvae’s oral-fecal route transmission via hand contact happens, though it can also happen indirectly through contaminated materials.
Pinworm eggs can survive in clothing, bedding, and other objects. The parasite affects humans of all ages or socioeconomic levels, but an infection can be treated with either prescription or over-the-counter medications. Since it can easily spread, reinfection can occur. Practicing strict proper hygiene should be observed to avoid it.

2. Tapeworms (Taenia solium)
Taenia solium, also known as the pork tapeworm, uses the hooks on its “head” to attach itself to the host’s intestine or they can feed off its human host for up to 25 years. It is common in developing countries.
Their eggs are discharged in the feces and can survive on vegetation. Cattle or pigs may eat the contaminated vegetation, ultimately passing the parasite to humans. These worms can also be transmitted by consuming undercooked beef (taenia saginata) or pork.
Symptoms of tapeworm infection include diarrhea, nausea, vomiting, inflamed intestine, dizziness, weight loss, and malnutrition. It can be removed through prescription medication.

3. Roundworms (Ascaris lumbricoides)
The most common species of roundworms, Ascaris lumbricoides, get into the body through the consumption of contaminated food or drink, which is common in areas without proper sanitation. Its eggs can quickly sneak into the intestinal wall, where the larvae can travel through the bloodstream.
These worms grow 15 to 35 centimeters long and may appear in feces. Generally, the infection does not cause symptoms, but it manifests once the infection grows, causing fever, tiredness, an allergic rash, vomiting, diarrhea, nerve problems, wheezing, coughing, and weight loss, among others.

4. Roundworms (Wuchereria bancrofti)
Mosquitoes spread the infection of Wuchereria bancrofti. The parasite is transmitted into the bloodstream of the host as they feed off of them. Human hosts experience swelling in the infected lymph nodes, usually in the legs and genital area, where the eggs evolve into an adult worm over a year.
This type of roundworms affects people of any age and gender. It is more common in tropical and subtropical regions and places with high exposure to mosquitoes and unsanitary conditions. Its symptoms include skin infections, painful lymph nodes, thickened skin, swelling, fever, and chills.
W. bancrofti is one of the three types of parasitic worms that causes elephantiasis, a rare condition characterized by the enlargement and hardening of an area of the body.

5. Roundworms (Trichinella )
The trichinella roundworm is commonly found in animals that eat meat. Transmission to humans occurs when they consume raw or undercooked meat of an animal that carries Trichinella larvae. Once ingested, the capsule surrounding the larvae dissolves, and the parasites move to the intestine or muscle tissue, where they develop into adult worms.
The disease caused by Trichinella is called trichinosis. The infection can cause fever, muscle aches, diarrhea, nausea, fatigue, unexplained rashes, and facial swelling, among others. It can be treated with steroids or antiparasitic and pain medication. They work by alleviating the symptoms and preventing further complications.

6. Flatworms (Fasciola hepatica)
Fasciola hepatica parasites are flatworms, also known as "the common liver flukes." The primary sources of liver flukes in humans are raw watercress and other freshwater plants and contaminated drinking water.
People can get infected with fasciola by accidental ingestion. However, it cannot be transmitted directly from one person to another. These parasitic worms find their way into the body’s intestines, blood, or tissues. Fascioliasis, the infectious disease caused by Fasciola parasites, can be treated with prescription medication.

7. Whipworm (Trichuris trichiura)
Trichuris trichiura, also called the human whipworm, live in the large intestine. Their eggs are passed in feces, and transmission occurs after ingestion of eggs through the soil-contaminated hands or food, such as unwashed vegetables or fruit.
This is common around the world. Mild infections usually do not present symptoms, but severe ones can cause the infected to experience the painful passage of stool, as well as anemia. Whipworm infections can be treated with anthelmintic medications (drugs that get rid of parasitic worms).

8. Hookworms Necator americanus and Ancylostoma duodenale)
The parasite Necator americanus develops outside the body and is acquired through the ingestion of contaminated water, fruits, and vegetables. When inside the human intestines, they would attach themselves to the walls with their two pairs of teeth and consume the host’s blood. Ancylostoma duodenale can also be transmitted through ingestion and latch itself using its cutting plates in the buccal capsule.
Transmission of both hookworm types happens when an infected person defecates outside. If human feces is used as fertilizer on soil, then another person walks barefoot on that soil, the parasites may also penetrate the human skin through the feet. Hookworm infection severe symptoms include abdominal pain, nausea, anemia, diarrhea, and weakness.

Observe proper hygiene and watch what you eat
The best way to avoid contracting parasites is to be extra vigilant with what you are exposing yourself to and be careful of what you are ingesting. Take precautions like using an insect repellant, washing hands, or drinking only from a sealed water bottle when going out and traveling, and wearing different footwear for indoor and outdoor use.
If the person experiences unusual symptoms or discomfort in their body, especially after traveling from another country, it is best to consult with a doctor. Patients may go under imaging tests like an MRI scan, fecal test, colonoscopy, tape test, or blood test to determine the cause of the symptoms and evaluate parasitic infections.

Feel free to reach out to Makati Medical Center’s Gastroenterology Department for any questions concerning intestinal parasitic infections.