The Most Common Worms in Humans
Worms in Humans
Worms in humans have been a cause of misery for millenia. These parasites contribute to disease, disability, disfigurement and death in a large portion of the world's population.
We'll look at the most common worms in humans as well as some less common parasites
Inflammation of skin and lymph nodes
Tissue thickening - elephantitis
Fluid accumulation in groin, breasts, or extremities.
Lymphatic system damage
Lymphatic Filariodidea, Phylum Roundworm
Wuchereria bancrofti, Brugia malayi, and Brugia timori: This family of filiarial worms causes the disease lymphatic filariasis which is commonly known as elephantitis. The worms are indigenous to the tropical areas of Asia, Africa, and Central and South America.
According to the World Health Organization over 120 million people world-wide are currently infected with filiarial worms. The majority of people infected have mild infestations and exhibit no symptoms, although 40 million of those people who are infected are badly disabled and disfigured.
These worms are spread from human to human by mosquitoes. While feeding on a human's blood the mosquito will transmit the worm larvae into the skin. The larvae then reside and reproduce in the human circulatory and lymph system.
The larvae mature in the lymph nodes, and severe infestations block the lymph ducts. This causes the extreme lymphedema of the extremities and genitals. The worms can live in the human body for seven years,
Infection usually occurs in childhood, with the severe disfiguration occurring later in life.
- Diagnosis: The disease can be detected by microscopic examination of the patient's blood.
- Treatment: The prevention of this disease by controlling mosquito populations is the goal of WHO. Diethylcarbamazine (DEC) is the most prescribed treatment for filiarial worms. A combination of albendazole and ivermectin are also used.
Blood in the stool
Vaginal itching or irritation
Loss of appetite
Coughing up blood
Tiny worms around anus
Pinworms, also known as threadworms, are the most common parasitic worm infection in the United States. They affect everybody equally without regard to race, gender, or economics status.
Pinworms do not affect dogs or cats, but different types of pinworms do infect horses and rabbits.
Pinworm eggs are easily spread by physical contact with an infected person, bedding, a pet's fur, and even through dust in the air. The eggs may be inhaled, or ingested orally by thumbsucking or nail biting. Eggs around the anus of an infected person may hatch, and the larvae can reenter the body through the rectum, repeating the cycle of infection.
Once inside the body, the eggs hatch in the duodenum, the first part of the small intestine. The worms then travel into the large intestine where the males and females copulate. The males die and are expelled along with the feces. The female worm attaches herself to the mucousa of the large intestine and ileum, where she feeds as her eggs mature.
After 5 weeks, the female exits the body through the rectum and lays her eggs around the anus. The eggs are then ready to be be spread and to begin the cycle again. The adult pinworm is about the length of a staple.
- Diagnosis: A stool sample is generally not an effective means of detecting pinworms. The best method to detect the worms is to apply tape to a person's perianal region after they have been asleep for a few hours. The worms will be most active at this time. The tape will then be removed and looked at under a microscope. Scrapings can also be taken from under a person's fingernails,
- Treatment: Mebendazole, pyrantel pamoate, and albendazole are all used to treat pinworms. A single dose will be given, followed by a single second dose two weeks later. All people living in the same household should be treated.
Most infected people do not exhibit symptoms
Itchy skin eruptions
Loss of appetite
Hookworms are also a common parasitic infection in humans. Cats and dogs also can carry hookworms, but only one species of canine hookworms has infected humans. This was an isolated incidence which happened to 150 people in Australia.
Hookworms are spread through contact with infected feces. A person may ingest the larvae orally, or more commonly, become infected by walking barefoot through feces contaminated dirt. Once the worms have penetrated the skin, they enter the bloodstream. Most worms travel to the lungs, then the trachea where they are swallowed. The hookworm then migrates to the intestines where it reproduces and lays eggs.
The eggs are expelled in the feces, then hatch, and the lifecycle is repeated. Some hookworms become dormant in muscle fibers, and later become active during a woman's pregnancy. The larvae will pass into the mother's milk, subsequently infecting her newborn with worms.
Hookworms in the Skin: cutaneous larva migrans
In the Americas, subcutaneous larva migrans, also known as creeping eruptions, is caused by the animal hookworm larvae of the species Ancylostoma braziliense. It is also known as sandworms in some areas of the southern United States.
People will become infected with hookworms by coming into direct contact with contaminated feces deposited in the soil or sand. The larvae of these hookworms will burrow under the skin and will cause intense itching, skin rashes, and visible raised tracks on the skin.
Cutaneous larva migrans is the most common skin disease occurring in people who have traveled to tropical or subtropical regions of the world. Complications like skin infections and allergic reactions, together with the extreme itchy rashes and the detrimental, long-lasting effects of the disease make treatment a must.
- Diagnosis: Hookworms will be diagnosed by analyzing a stool sample. In the case of creeping eruptions, skin analysis and tissue biopsies are used to diagnose the condition.
- Treatment: Both intestinal and cutaneous infections will be treated with albendazole and mebendazole. The medication will be taken for up to 3 days, and has few side effects.
Light infestations will usually be asymptomatic
Vitamin A deficiency
Whipworms: Trichuris Trichiura
Named for their resemblance to a whip, whipworms are an intestinal parasite. They are found in warmer climates in countries around the globe.
An estimated 2 million people in the southeastern states of the US are believed to be infected by whipworms, with many of the sufferers showing no symptoms. An estimated 795 million people are infected with whipworms worldwide.
Whipworms enter the human body ingesting unwashed fruits, vegetables, or dry goods or by hand-to-mouth contact.
Whipworms reproduce in the small intestine, with the resulting larvae hatching and maturing in the cecum. Some eggs are expelled through the feces, and the whipworm eggs contaminate anything the feces touches.
- Diagnosis: Whipworm infections are diagnosed by examining a stool sample using a microscope.
- Treatment: Albendazole and mebendazole pills are given for three consecutive days to kill the whipworms.
Vitamin and mineral deficiencies
Loss of appetite
Segments of worm in stool
Tapeworms are a type of flatworm that live in the intestines of animals. All vertebrates have at least one type of flatworm that can infect it.
There are more than 1,000 different varieties of flatworms recognized by scientists, but only six species are known to live in humans.
Tapeworms can be transmitted to humans by eating undercooked beef, pork, or fish which are infected with the tapeworm larvae. People can also be infected by being bitten by insects and by coming into contact with fecal matter contaminated with tapeworm eggs.
Some species of tapeworm can grow over 100 feet in length, although the tapeworms that infect humans will typically be less than 30 feet long.
Tapeworms can live for up to 30 years in the digestive tract. The adult worms have "hooks" in their mouths which they use to attach themselves to the abdominal wall.
Tapeworms can invade other tissues in the body also. When the worms find their way into the brain, it will cause a disease known as neurocysticercosis.
- Diagnosis: Tapeworms can be diagnosed by examining a stool sample, or checking the blood for an antibody produced by a tapeworm infection.
- Treatment: The most commonly used medicines used to kill tapeworms are biltricide oral and albendazole. The medication will kill the tapeworms, which will then dissolve and pass out with feces. The medications are 95% effective.
Watery, itchy eyes
Loa loa is a filiarial worm found in areas of West Africa, and the worm can actually live inside a human's eye! Loa loa is spread by the bite of flies; the fly transmits the loa loa larvae into the person's skin while the fly is feeding. The larvae then burrow down into the subcutaneous tissue. The loa loa lives inside the host, travelling throughout the person's body.
The disease caused by the worm is known as "African eye worm, Loaiasis, Loa loa filariasis, Filaria lacrimalis, Filaria subconjunctivalis, and Fugitive swellings", among others.
The disease causes a rash and eye problems in the infected person. It can cause eye pain or vision changes when the worm moves across a person's eye.
- Diagnosis: The loa loa worm can be detected by seeing the worm in the eye, or upon removal of the worm from the skin. The worm can also be detected by examining blood from an infected person. A blood test can also be used to detect antibodies, but this may give a false positive if the person has had a past infection.
- Treatment: According to the CDC there are two medications used to treat the loa loa infection: "Diethylcarbamazine (DEC), which kills both the larvae and the adult worms and is the treatment of choice, and albendazole, which is thought to kill the adult worms. There is a risk of fatal brain inflammation from treatment with DEC."
Shortness of breath
Presence of worms in vomit or stool
Blood in the stool
Ascariasis, Phylum Roundworm
According to the CDC, ascariasis is present in almost 45% of the world's population, accounting for much of the world's diseases. Ascariasis is uncommon in the United States.
Ascariasis is spread through ingesting the ascariasis eggs, usually by eating contaminated food or by hand-to-mouth contact.
After the ascariasis eggs are ingested, they travel to the intestines where they hatch. The larvae then burrow through the intestinal wall and travel into the lungs where they burrow into the alveoli.
The ascariasis larvae then travel up the trachea to the esophagus where they are swallowed by their host. The larvae mature in the intestines, lay more eggs, and the cycle begins anew. Eggs from the mature worms are expelled through the feces of an infected person.
- Diagnosis: Ascariasis can be detected by looking at a stool sample with a microscope.
- Treatment: Albendazole and mebendazole are used to treat Ascaris infections. the patient is generally treated for 1-3 days.
Guinea Worms: Dracunculus medinensis
The almost total world-wide eradication of the Guinea worm is near. No human cases were reported in January 2013, a huge drop considering there were millions of cases reported in the 1980s.
The Guinea worm is transmitted by drinking water containing water fleas infected by the Guinea worm nematode. The flea is dissolved in the stomach, but the nematode survives, eventually drilling out of the intestines and migrating into muscle and connective tissue by way of the blood vessels. The female worm, sometimes reaching 1 meter in length, eventually burrows to the skin's surface. Every time the host contacts water, the female expels eggs, contaminating the water supply and continuing the cycle. The female is removed by slowly pulling it from the skin over the course of weeks or months.
- Symptoms: The first symptom of an emerging Guinea worm is a blister that may feel as though it is on fire. Once the head of the worm emerges, the wound may become red and inflamed due to a secondary infection.
Technically fly larvae, the human botfly, Dermatobia hominis, is a member of the Oestridae family. It is the only botfly known to inhabit humans flesh.
Mosquitoes, muscoid flies, and ticks are the vectors of the botflies eggs. The female fly attaches her eggs to the host, and as the host feeds it releases the botfly eggs. The eggs enter the skin where they incubate for 8 weeks and hatch. After this time the botfly larvae crawl out of the skin, drop to the ground, and metamorphosize into new botflies to begin a new cycle.
Petroleum jelly is sometimes used to smother the larva under the skin. The larva can then be safely removed with a pair of sterilized tweezers.
Botfly named Gertrude emerging from a man's leg
Ringworm is NOT a worm. It is a fungus. It is spread through contact with contaminated animals or surfaces. Ringworm can be treated with a topical antifungicide.
Can Pets Transmit Worms to People?
Yes, many worms can be transmitted from pets to people. For more information, read Pet to People Worms.
Need more worms? Check these links out.
- Hidden Epidemic: Tapeworms Living Inside People's Brains | DiscoverMagazine.com
Parasitic worms leave millions of victims paralyzed, epileptic, or worse. So why isn’t anyone mobilizing to eradicate them?
More by this Author
CT contrast, also known as contrast dye, is used to better visualize blood vessels and some internal organs. But how does it work, and what are the side effects and risks?
Three infectious diseases are poised to spread in the United States thanks to the climate change and a little pest.
This article explains what the abdominal/pelvic CT procedure is, why it may be done, and what the doctor may be looking for. Three videos are included to demonstrate what the images may look like.