What is a tapeworm

Tapeworms are flat, ribbon-like worms that can live in your gut if you swallow their eggs or small, newly hatched worms.

Taeniasis in humans is a parasitic infection caused by the tapeworm species Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), and Taenia asiatica (Asian tapeworm). Humans can become infected with these tapeworms by eating raw or undercooked beef (Taenia saginata) or pork (Taenia solium and Taenia asiatica). People with taeniasis may not know they have a tapeworm infection because symptoms are usually mild or nonexistent.

Tapeworm infections are rare in the US, but are fairly common in other parts of the world.

Many tapeworms don’t cause obvious symptoms and can be easily treated. But very occasionally, the tapeworms can spread to other parts of the body and cause serious problems.

Tapeworm infection is caused by eating the raw or undercooked meat of infected animals. Cattle usually carry Taenia saginata (T saginata). Pigs carry Taenia solium (T solium).

• T. saginata (beef) tapeworms are usually 4-12 m in length, but can grow to be 25 m; the adult tapeworms produce 1,000 to 2,000 proglottids/ worm and may produce up to 100,000 eggs per worm.
• T. solium (pork) tapeworms are smaller, 2-8 m in length, produce an average of 1,000 proglottids/worm, and may produce 50,000 eggs per worm.
• T. asiatica (Asian) tapeworms range in size from 4-8 m, produce 700 proglottids/worm and may produce 80,000 eggs per proglottid.

In the human intestine, the young form of the tapeworm from the infected meat (larva) develops into the adult tapeworm. A tapeworm can grow to longer than 12 feet (3.5 meters) and can live for years.

An adult tapeworm consists of a head, neck and chain of segments called proglottids. Tapeworms have many segments (proglottids) and each segment is able to produce eggs. The eggs are spread alone or in groups, and can pass out with the stool or through the anus.

When you have an intestinal tapeworm infection, the tapeworm head adheres to the intestinal wall, and the proglottids grow and produce eggs. Adult tapeworms can live for up to 30 years in a host.

Intestinal tapeworm infections are usually mild, with only one or two adult tapeworms. But invasive larval infections can cause serious complications.

How do you know if you have a tapeworm

Tapeworms usually cause few or no symptoms. You may only find out you have one if you spot a bit of worm in your feces.

Tapeworms in your feces

Bits of tapeworm found in poo are often:

• flat and rectangular
• white or pale yellow
• the size of a grain of rice – but sometimes they’re joined together in a long chain

The pieces of tapeworm may move about.

If you see tiny white worms that look like pieces of thread, they’re probably pinworms (threadworms). These are common in the US, particularly in children.

Other symptoms

Tapeworms can also sometimes cause other symptoms, such as:

• tummy pain
• diarrhea
• feeling sick or vomiting
• loss of appetite or increased appetite
• weight loss

More serious symptoms can appear if tapeworms get into other parts of the body, such as the brain or liver.

Pork tapeworm

Tapeworm infection is caused by eating the raw or undercooked meat of infected animals. Pigs carry Taenia solium (T. solium).

In the human intestine, the young form of the pork tapeworm from the infected meat (larva) develops into the adult tapeworm. A tapeworm can grow to longer than 12 feet (3.5 meters) and can live for years.

Tapeworms have many segments. Each segment is able to produce eggs. The eggs are spread alone or in groups, and can pass out with the stool or through the anus.

Adults and children with pork tapeworm can infect themselves if they have poor hygiene. They can ingest tapeworm eggs they pick up on their hands while wiping or scratching their anus or the skin around it.

Those who are infected can expose other people to pork tapeworm (Taenia solium) eggs, usually through food handling.

Pork tapeworm (Taenia solium) infections can lead to neurocysticercosis, the infection of the human brain by the larvae of pork tapeworm (Taenia solium). Neurocysticercosis is a major cause of acquired epilepsy or seizures in most low-income countries, so it is important seek treatment.

Life cycle of Pork tapeworm (Taenia solium) cysticercosis

The lifecycle of pork tapeworm (Taenia solium) involves two hosts. Humans harbor the sexually reproducing mature tapeworm in the small intestine (taeniasis). Eggs released with the feces are infectious if eaten by pigs in which the larval parasite (cysticercus) encysts in the muscle tissues and brain, causing porcine cysticercosis. Ingestion of poorly cooked, infected pig meat by humans leads to growth of the tapeworm, completing the lifecycle. Eggs in the feces of a patient infected with the adult tapeworm are also infectious if they are ingested by humans, in which case the cysticerci may lodge in muscle and other tissues, including the central nervous system causing neurocysticercosis.

Cysticercosis is an infection of both humans and pigs with the larval stages of the parasitic tapeworm, Taenia solium. This infection is caused by ingestion of eggs shed in the feces of a human tapeworm carrier (1). Pigs and humans become infected by ingesting eggs or gravid proglottids (2), (7). Humans are infected either by ingestion of food contaminated with feces, or by autoinfection. In the latter case, a human infected with adult T. solium can ingest eggs produced by that tapeworm, either through fecal contamination or, possibly, from proglottids carried into the stomach by reverse peristalsis. Once eggs are ingested, oncospheres hatch in the intestine (3), (8) invade the intestinal wall, and migrate to striated muscles, as well as the brain, liver, and other tissues, where they develop into cysticerci (9). In humans, cysts can cause serious sequellae if they localize in the brain, resulting in neurocysticercosis. The parasite life cycle is completed, resulting in human tapeworm infection, when humans ingest undercooked pork containing cysticerci (4). Cysts evaginate and attach to the small intestine by their scolex (5). Adult tapeworms develop, (up to 2 to 7 m in length and produce less than 1000 proglottids, each with approximately 50,000 eggs) and reside in the small intestine for years (6).

Cysticercosis is a parasitic tissue infection caused by larval cysts of the tapeworm Taenia solium. These larval cysts infect brain, muscle, or other tissue, and are a major cause of adult onset seizures in most low-income countries. A person gets cysticercosis by swallowing eggs found in the feces of a person who has an intestinal tapeworm. People living in the same household with someone who has a tapeworm have a much higher risk of getting cysticercosis than people who don’t.

People do not get cysticercosis by eating undercooked pork. Eating undercooked pork can result in intestinal tapeworm if the pork contains larval cysts. Pigs become infected by eating tapeworm eggs in the feces of a human infected with a tapeworm.

Both the tapeworm infection, also known as taeniasis, and cysticercosis occur globally. The highest rates of infection are found in areas of Latin America, Asia, and Africa that have poor sanitation and free-ranging pigs that have access to human feces. Although uncommon, cysticercosis can occur in people who have never traveled outside of the United States. For example, a person infected with a tapeworm who does not wash his or her hands might accidentally contaminate food with tapeworm eggs while preparing it for others.

Figure 1. Pork tapeworm (Taenia solium) Lifecycle

Figure 2. Tapeworm anatomy

Neurocysticercosis is endemic in many low- and middle-income countries ²⁾ and is the most frequent cause of acquired epilepsy in those countries and probably the world ³⁾. In endemic areas, 29% of neurological seizures are attributable to neurocysticercosis ⁴⁾.

Symptoms of neurocysticercosis vary depending, among other things, on the number, size and location of the cysts. They include headache, blindness, convulsions, epilepsy and death. The disease usually affects very poor communities, where pigs live in close contact with humans, and hygiene, sanitation and education are limited. The disease has a very strong social impact; epilepsy sufferers are often stigmatized, especially if sufferers are women and girls, as it is linked with witchcraft.

Diagnosis of neurocysticercosis is complicated, and neuroimaging is frequently required for a definite diagnosis ⁵⁾. Currently available methods for the diagnosis of T. solium taeniasis lack either sensitivity, specificity, or both ⁶⁾. Current methods include fecal microscopy to identify parasite eggs, detection of coproantigens or copro-DNA, and detection of specific antibodies in serum.

Current tests for the diagnosis of neurocysticercosis include antibody detection (enzyme-linked immunoelectrotransfer blot, ELISA) and antigen detection (ELISA) tests. A challenge with the currently available tests is that a proportion of people living in endemic areas might test transiently positive on either antibody or antigen detection tests, apparently in the absence of mature or clinically-relevant cysticercosis ⁷⁾. Antibody tests do not differentiate between patients having viable cysts from those with non-viable cysts.

Currently there are no standard treatment guidelines for neurocysticercosis, and treatment is tailored to the individual cases ⁸⁾, depending on factors such as location and viability of the cysts. Therapeutic approaches might include symptomatic therapy, anthelmintic treatment, or surgery, and often more than one of these options is needed ⁹⁾. The administration of anthelmintic drugs may elicit or increase pre-existing cerebral oedema and therefore is contraindicated in cases with cysticercotic encephalitis, increased intracranial pressure and subarachnoid neurocysticercosis in close proximity to blood vessels ¹⁰⁾, thus it is very important to have the neuroimaging diagnostic before starting the treatment of living cysts. Suitable imaging diagnostic facilities are not readily available in the poor rural communities where the disease is endemic, and there is a need for better diagnosis tools to identify patients in rural and remote communities with viable cysts that need to be referred to neuroimaging before treatment.

Dog tapeworms (hydatid disease)

In some parts of the world (and rarely in the US), a type of tapeworm found in dogs can spread to people. This is called hydatid disease.

Hydatid disease (also known as Echinococcosis or cystic hydatid disease) results from infection with the larvae (a developing phase) of the tapeworm Echinococcus granulosus. The tapeworm is found most commonly in dogs that consume organs or meat of infected sheep.

Infections with these tapeworms can be serious and difficult to treat, but simple precautions like getting your dog dewormed regularly and not feeding them raw meat can help you avoid it.

The eggs of this tapeworm are excreted in the feces of infected dogs and are directly infectious to other animals. Sheep (in particular) and cattle can become infected by grazing on pasture contaminated with dog feces containing these tiny eggs. These eggs are highly resistant and can survive on the ground for up to a year.

After the eggs have been ingested from contaminated grass, they hatch inside the intestine of the sheep and the next (larval) stage of the tapeworm penetrate the gut wall and are carried by the bloodstream to various parts of the body, such as the liver and lungs, where they slowly develop into cysts (called hydatids). These cysts can grow quite large and contain many young tapeworms floating in clear fluid (hydatid sand).

If a dog is then fed on, or allowed to scavenge an infected animal carcass, the cysts are ingested and the cyst wall is digested in the gut, releasing protoscolices which develop over about two months into adult tapeworms inside the dog’s intestine, producing eggs. These are then excreted in the feces of the dog, causing further spread of infection.

Humans can also become infected by the eggs shed in dog feces (for example by the dog licking the face after it has been cleaning itself), followed by oral transfer. The eggs may also contaminate other objects such as leads The egg then hatches in the intestine, penetrates the gut wall and travels throughout the body where they lodge in the tissues.

Who gets dog tapeworm and how serious is it?

Anyone can pick up the infection from swallowing the infectious eggs. Humans are usually exposed to these eggs in one of two ways:

• By directly ingesting food items or drinking water that is contaminated with feces from an infected dog.
• By petting or having other contact with dogs that are infected. These pets may shed the eggs in their feces, contaminating their fur. They may also contaminate other objects, such as leads, which can also result in the spread of infection through subsequent hand to mouth transfer.

Because the cysts are usually slow-growing, infection may not produce symptoms for years. Symptoms usually reflect the size and location of the cysts.

Dog tapeworm prevention

There are currently no effective drug treatments or vaccines to protect humans against the disease.

Measures to prevent ingestion of the infective eggs and the infestation of dogs with the worm are key in stopping the spread of hydatid disease.

Other measures include:

• Feeding dogs with cooked dog foods
• Worming dogs every six weeks with a wormer containing Praziquantel
• Not allowing dogs to roam or come into contact with sheep carcasses
• Not allowing dogs to lick the face
• Washing hands thoroughly after handling dogs
• Washing all fruit and vegetables thoroughly before eating or cooking

Below a certain density of infection in either host (dog or sheep) and sufficient opportunities for animals to become infected, the life-cycle of the parasite becomes unsustainable. It is currently thought that the elimination of the tapeworm from dogs will free sheep and cattle of infection, though tapeworm eggs can persist in the environment for years.

Dog tapeworm diagnosis

Hydatid disease is diagnosed by a combination of techniques, including a blood test that detects the presence of antibodies to the parasite.

Dog tapeworm treatment

The only effective treatment in humans in the surgical removal of cysts with supplementary chemotherapy.

How do you get a tapeworm

You can get a tapeworm infection if their eggs or small newly hatched worms (larvae) get in your mouth.

There are several ways this can happen, including:

• eating raw or undercooked beef, pork, or freshwater fish (like salmon or trout) – these can contain live tapeworm larvae if they’re not cooked thoroughly
• drinking water or eating food that contains or has been in contact with bits of feces of an infected person or animal
• close contact with someone who has a tapeworm – they may pass out eggs in their feces, which can get on clothing, surfaces, and food

Tapeworms are found throughout the world, including in the US, but you’re more likely to get them in places with poor sanitation and less strict food hygiene standards.

A tapeworm infection starts after ingestion of tapeworm eggs or larvae.

• Ingestion of eggs. If you eat food or drink water contaminated with feces from a person or animal with tapeworm, you ingest microscopic tapeworm eggs. For example, a pig infected with tapeworm will pass tapeworm eggs in its feces, which gets into the soil. If this same soil comes in contact with a food or water source, it becomes contaminated. You can then be infected when you eat or drink something from the contaminated source. Once inside your intestines, the eggs develop into larvae. At this stage, the larvae become mobile. If they migrate out of your intestines, they form cysts in other tissues, such as your lungs, central nervous system or liver.
• Ingestion of larvae cysts in meat or muscle tissue. When an animal has a tapeworm infection, it has tapeworm larvae in its muscle tissue. If you eat raw or undercooked meat from an infected animal, you ingest the larvae, which then develop into adult tapeworms in your intestines. Adult tapeworms can measure more than 80 feet (25 meters) long and can survive as long as 30 years in a host. Some tapeworms attach themselves to the walls of the intestines, where they cause irritation or mild inflammation, while others may pass through to your stool and exit your body.

Risk factors for catching tapeworm

Factors that may put you at greater risk of tapeworm infection include:

• Poor hygiene. Infrequent washing and bathing increases the risk of accidental transfer of contaminated matter to your mouth.
• Exposure to livestock. This is especially problematic in areas where human and animal feces are not disposed of properly.
• Traveling to developing countries. Infection occurs more frequently in areas with poor sanitation practices.
• Eating raw or undercooked meats. Improper cooking may fail to kill tapeworm eggs and larvae contained in contaminated pork or beef.
• Living in endemic areas. In certain parts of the world, exposure to tapeworm eggs is more likely. For instance, your risk of coming into contact with eggs of the pork tapeworm (Taenia solium) is greater in areas of Latin America, China, sub-Saharan Africa or Southeast Asia where free-range pigs may be more common.

Preventing tapeworm infections

To help reduce your chances of getting a tapeworm:

• Don’t eat raw or undercooked pork, beef, or (freshwater) fish
• Cook meat and fish thoroughly and all the way through at temperatures of at least 145 °F (63 °C) for whole cut meat and 160°F (71°C) for ground meat to kill tapeworm eggs or larvae– don’t allow raw meat or fish to touch cooked meat or fish. Use a food thermometer to measure the thickest part of the meat.
• Freeze meat for as long as seven to 10 days and fish for at least 24 hours in a freezer with a temperature of -31 °F (-35 °C) to kill tapeworm eggs and larvae.
• Wash vegetables and fruit before you eat them
• Wash your hands with soap and water before handling food, before eating, after using the toilet, and after close contact with animals
• When traveling abroad, only drink water you know is clean – read more advice about food and water safety abroad
• Eliminate livestock exposure to tapeworm eggs by properly disposing of animal and human feces.
• Promptly treat dogs infected with tapeworm.

Take extra care if you work or live closely with animals or are staying in a part of the world where tapeworm infections are common.

Tapeworm infections complications

In rare cases, worms can cause a blockage in the intestine. If tapeworms grow large enough, they can block your appendix, leading to infection (appendicitis); your bile ducts, which carry bile from your liver and gallbladder to your intestine; or your pancreatic duct, which carries digestive fluids from your pancreas to your intestine.

In rare cases, tapeworms can cause serious problems if newly hatched worms get from the gut into other organs, such as the brain or liver.

The worms can form sacs called cysts, which can stop the affected organ working properly.

This can only occur if you swallow the eggs of a type of tapeworm found in pigs, which can happen if tiny bits of feces of someone with this tapeworm get into your mouth. It can’t happen from eating pork.

Depending on where they form, the cysts can cause problems such as:

• headaches and fits (seizures)
• yellowing of the skin and eyes (jaundice)
• a cough, shortness of breath, or coughing up blood
• vision problems
• a serious allergic reaction (anaphylaxis) – this can happen if a cyst bursts open

Cysts can be difficult to treat. Treatment may involve a long course of anti-worm medicine and possibly surgery to remove the cysts.

Brain and central nervous system impairment. Called neurocysticercosis, this especially dangerous complication of invasive pork tapeworm infection can result in headaches and visual impairment, as well as seizures, meningitis, hydrocephalus or dementia. Death can occur in severe cases of infection.

Organ function disruption. When larvae migrate to the liver, lungs or other organs, they become cysts. Over time, these cysts grow, sometimes large enough to crowd the functioning parts of the organ or reduce its blood supply. Tapeworm cysts sometimes rupture, releasing more larvae, which can move to other organs and form additional cysts.

A ruptured or leaking cyst can cause an allergy-like reaction, with itching, hives, swelling and difficulty breathing. Surgery or organ transplantation may be needed in severe cases.

Tapeworm signs and symptoms

Many people with intestinal tapeworm infection don’t have symptoms. If you do have problems from the infection, your symptoms will depend on the type of tapeworm you have and its location. Invasive tapeworm infection symptoms vary depending on where the larvae have migrated.

Intestinal infection

Signs and symptoms of intestinal infection include:

• Nausea
• Weakness
• Loss of appetite
• Abdominal pain
• Diarrhea
• Dizziness
• Salt craving
• Weight loss and inadequate absorption of nutrients from food

Invasive infection

If tapeworm larvae have migrated out of your intestines and formed cysts in other tissues, they can eventually cause organ and tissue damage, resulting in:

• Headaches
• Cystic masses or lumps
• Allergic reactions to the larvae
• Neurological signs and symptoms, including seizures

Tapeworm diagnosis

To diagnose a tapeworm infection, your doctor may rely on one of the following:

• Stool sample analysis. For an intestinal tapeworm infection, your doctor may check your stool or send samples to a laboratory for testing. A laboratory uses microscopic identification techniques to check for eggs or tapeworm segments in your feces. Because the eggs and segments are passed irregularly, the lab may need to collect two to three samples over a period of time to detect the parasite. Eggs are sometimes present at the anus, so your doctor may use a piece of transparent adhesive tape pressed to the anus to collect eggs for microscopic identification.
• Blood test. For tissue-invasive infections, your doctor may also test your blood for antibodies your body may have produced to fight tapeworm infection. The presence of these antibodies indicates tapeworm infestation.
• Imaging exam. Certain types of imaging, such as CT or MRI scans, X-rays, or ultrasounds of cysts, may suggest invasive tapeworm infection.

Microscopic identification of eggs and proglottids in feces is diagnostic for taeniasis; however, eggs and proglottids are not released into the feces until approximately 2 to 3 months after the adult tapeworm is established in the upper jejunum. Repeated examination and concentration techniques will increase the likelihood of detecting light infections. Examination of 3 stool samples collected on different days is recommended to increase the sensitivity of microscopic methods. Eggs of Taenia spp. cannot be differentiated; a species determination may be possible if mature, gravid proglottids (or, more rarely, examination of the scolex) are present.

Recently developed coproantigen and molecular assays are more sensitive than stool examination, but these assays are not yet available outside of the research laboratory. Serologic methods, which are available only in research settings, may be used to identify T. solium tapeworm carriers.

Household contacts of neurocysticercosis cases should be evaluated for taeniasis to reduce the risk of cysticercosis.

Tapeworm treatment

Some people with tapeworm infections never need treatment, for the tapeworm exits the body on its own. Others don’t realize they have it because they have no symptoms. However, if you’re diagnosed with intestinal tapeworm infection, medication will likely be prescribed to get rid of it.

Tapeworm treatment for humans

The most common treatment for tapeworm infection involves oral medications that are toxic to the adult tapeworm, including:

• Praziquantel (Biltricide)
• Niclosamide
• Albendazole (Albenza)
• Nitazoxanide (Alinia)

Which medication your doctor prescribes depends on the species of tapeworm involved and the site of the infection. These drugs kill the adult tapeworm, not the eggs, so it’s important to avoid reinfecting yourself. Always wash your hands after using the toilet and before eating.

• Praziquantel is the medication most often used to treat active taeniasis, given at 5-10 mg/kg orally once for adults and 5-10 mg/kg orally once for children. If the patient has cysticercosis in addition to taeniasis, praziquantel should be used with caution. Praziquantel is cysticidal and can cause inflammation around dying cysts in those with cysticercosis, which may lead to seizures or other symptoms. Oral praziquantel is available for human use in the United States.
• Niclosamide is an alternative, given at 2 g orally once for adults and 50 mg/kg orally once for children. After treatment, stools should be collected for 3 days to search for tapeworm proglottids for species identification. Stools should be re-examined for Taenia eggs 1 and 3 months after treatment to be sure the infection is cleared. Niclosamide is NOT available for human use in the United States.

To be certain that your tapeworm infection has cleared, your doctor will probably have your stool samples checked after a few months after you’ve finished taking your medication to see if the treatment has worked. Successful treatment — meaning that your stool is free of tapeworm eggs, larvae or proglottids — is most likely if you receive appropriate treatment for the type of tapeworm causing your infection.

In the weeks after taking the tablet, make sure you wash your hands regularly – particularly before eating and after using the toilet. This will stop any eggs getting into your mouth and infecting you again.

Even if you’ve passed a large piece of worm, this doesn’t always mean it’s gone completely. It could regrow if some of it’s left in your gut.

Treatments for invasive infections

Treating an invasive infection depends on the location and effects of the infection.

• Anthelmintic drugs. Albendazole (Albenza) can shrink some tapeworm cysts. Your doctor may monitor the cysts periodically using imaging studies such as ultrasound or X-ray to be sure the drug is effective.
• Anti-inflammatory therapy. Dying tapeworm cysts can cause swelling or inflammation in tissues or organs, so your doctor may recommend prescription corticosteroid medication, such as prednisone or dexamethasone, to reduce inflammation.
• Anti-epileptic therapy. If the disease is causing seizures, anti-epileptic medications can stop them.
• Shunt placement. One type of invasive infection can cause too much fluid on the brain, called hydrocephalus. Your doctor may recommend placing a permanent tube (shunt) in your head to drain the fluid.
• Surgery. Whether cysts can be removed surgically depends on their location and symptoms. Cysts that develop in the liver, lungs and eyes are typically removed, since they can eventually threaten organ function. Your doctor might recommend a drainage tube as an alternative to surgery. The tube allows aggressive rinsing (irrigation) of the area with anti-parasitic solutions.