Tapeworm

What is Tapeworm?

Cestodes, also known as tapeworms, are flat, parasitic worms that can live in animals, including humans. They are hermaphroditic, which means that each worm has both male and female reproductive organs. Their life cycles are complicated and involve several stages. Although many types of tapeworms can infect humans, this explanation focuses on three types: Taenia solium (pork tapeworm), Taenia saginata (beef tapeworm), and Diphyllobothrium (fish tapeworm).

People can get two kinds of infections from tapeworms, depending on how they come in contact with the parasite. If someone swallows the eggs of a tapeworm – which comes from the poop of an infected animal or person – they can get a disease called cysticercosis. In this disease, the eggs hatch into larvae called cysticerci inside the person’s body. If these cysticerci end up in the brain or spinal cord, the condition is known as neurocysticercosis.

The second way a person can get a tapeworm is by eating infected meat that has not been adequately cooked. In this case, they swallow the cysticerci, which then grow into adult tapeworms inside the person’s digestive system. This condition is called taeniasis if the tapeworm came from the Taenia family or diphyllobothriasis if it came from the Diphyllobothrium family.

Tapeworm infections pose a significant problem, not only for human health but also for animal health and the economy. One serious health issue related to tapeworms is neurocysticercosis, a leading cause of seizures. In fact, it’s responsible for about 30% of epilepsy cases in most developing countries.

What Causes Tapeworm?

Tapeworms need one or more hosts to complete their lifecycle. Whether a host becomes infected or not depends on the stage of life the tapeworm is in when the host is exposed.

In the case of a disease called diphyllobothriasis, people can become infected by eating fish that is raw or undercooked and carrying the larval stage (an early stage in the tapeworm’s life) of the tapeworm. This worm then attaches itself to the intestine, matures, and releases eggs through human feces. If these feces pollute water due to bad sanitary conditions, the eggs hatch and are eaten by a type of small crustacean called copepods, which is then eaten by fish. Humans become infected again when they eat these fish. Some of the species of fish that most commonly carry these infected copepods include perch, pike, burbot, whitefish, salmon, and trout. After someone eats raw or under-cooked fish, the larva attaches to the small intestine and grows into a mature tapeworm within 5 to 6 weeks. The most common species of tapeworm that infects humans is D. latum, but other species are also being recognized as harmful with improved testing methods. Diphyllobothrium, a type of tapeworm, can live and continue to produce eggs in the human host for decades.

A similar lifecycle is seen in Taeniasis, another type of tapeworm. Eggs from human or animal feces can contaminate the water and vegetation that cattle or pigs eat. The eggs or worm segments are ingested and penetrate the intestine walls to infest various muscles or other tissues, developing into cysticerci (another life stage of the worm). If humans then eat undercooked pork or beef containing these cysticerci, the worm will attach to a part of the intestines called the jejunum and mature into an adult worm, which can live for up to 25 years, or the lifespan of the host.

It is important to note that ingesting cysticerci only leads to taeniosis, which is an adult tapeworm infestation in the intestines. However, cysticercosis, a disease caused by cysts formed by the tapeworm infesting the muscle and other tissues, comes from directly eating T. solium eggs found in feces. An infected person could accidentally ingest these eggs leading to what is called an autoinfection, where embryos hatch and then spread to different parts of the body including the central nervous system or muscle.

This person-to-person spreading seems more common than previously thought, as opposed to contamination through environmental sources.

Risk Factors and Frequency for Tapeworm

Taeniidae, a type of parasite, can be found worldwide, although Taenia asiatica usually only appears in Asian countries. Taenia solium and Taenia saginata are found everywhere, but are more prevalent in areas with poor sanitation and those where raw or undercooked meat is commonly eaten. In Europe, North America, and Australia, T. solium has been largely controlled, but it is far more common in Africa, Asia, Latin America, Eastern Europe, China, Pakistan, and India. It’s also important to be aware that neurocysticercosis, a condition caused by T. solium, is likely underreported due to diagnostic challenges. T. saginata is most prevalent in Southern and Eastern Africa.

Diphyllobothriasis is an infection that’s globally distributed, with cases decreasing in North America, Asia, and much of Europe, but also reappearing in some areas like Russia, South Korea, Japan, and South America. It’s typically associated with the cold waters of the Palaearctic region, with a few cases in South America, and hasn’t been recorded in Africa and Australia. D. latum, a species of this parasite, is thought to be the most common cause of Diphyllobothriosis. It’s mainly reported in northern Europe, Russia, and North America, but recent findings also indicate its presence in South America, specifically Chile.

Signs and Symptoms of Tapeworm

Tapeworm infection often doesn’t cause any symptoms or only causes mild issues. Some people might not know they have a tapeworm until they spot worm segments in their feces or feel an itch around their anus (caused by the worm segments). Even then, the symptoms are usually very mild and might include a mild stomach ache, a change in appetite, feeling weary, losing weight, and less commonly headaches, constipation, dizziness, and diarrhea. In rare cases, the person might vomit a worm segment. Even though kids often experience stronger symptoms than adults, severe complications such as blockages of the intestines, gallbladder, or pancreas are rare.

Diphyllobothrium is a type of tapeworm that can grow very long, but often doesn’t cause any noticeable symptoms. One in five people infected may experience symptoms like diarrhea, stomach ache, tiredness, constipation, anemia due to vitamin B12 deficiency, and less commonly headache and allergic reactions. Other symptoms might include bloating, a sore tongue or gums, or a change in appetite. Similar to other tapeworm infections, in rare cases the worms can cause a blockage in the intestines or inflammation of the gallbladder. In cases of serious infection, the tapeworm may consume a significant amount of vitamin B12 from the gut, leading to anemia. However, even if 40% of people with this tapeworm infection have lower levels of vitamin B12, only 2% develop anemia.

Cysticercosis is a complicated tapeworm infection that can affect various tissues in the body. In most cases, cysts in tissues remain symptomless and go unnoticed. They are often destroyed by the body’s immune response, although some can survive in areas such as the central nervous system and the eye, where immune responses are weaker. Symptoms can vary widely, from undetectable brain lesions to mimicking various neurological disorders. Signs can include seizures, localized neurological problems, increased pressure inside the skull, cognitive decline, and vague symptoms like headaches. Cysticercosis in the brain (neurocysticercosis) is often associated with seizures and epilepsy, but the risk of developing epilepsy is variable, ranging from 10% to 50%.

Testing for Tapeworm

Diagnosing a patient with an adult tapeworm infection mostly revolves around the scrutiny of stool samples under a microscope to search for tapeworm eggs. While this method can help identify the type (or genus) of parasite, it is often inadequate to distinguish between different species of the parasite. To gauge the precise species of the tapeworm, additional tests on stool and blood samples as well as imaging may be needed. A common symptom of tapeworm infection is the presence of elevated levels of certain white blood cells, known as eosinophils, but this increase is often limited and does not exceed 50%.

The eggs of two kinds of tapeworms, T. saginata and T. solium, can be spotted under the microscope, but the species can’t be differentiated this way. However, they may be distinguished by their proglottids, a special segment of the tapeworm that is passed out in stool. It’s important to note that stool examinations might not always be effective for spotting T. saginata tapeworms, as the proglottids often pass out of the body on their own. Therefore, doctors might recommend anal swabs to collect eggs. Despite its limitations, the main method of diagnosing tapeworms is still through direct microscopy of feces. Other techniques, such as copro-Ag ELISA detection from stool samples, might increase the likelihood of detecting an infection but still cannot distinguish between species.

Another tapeworm infection, called Diphyllobothriasis, also relies on stool examinations for diagnosis, which can identify the genus, but not the species. More reliable for identifying the species are techniques such as PCR testing on stool samples. Note that it’s not clinically important to know the exact species of the tapeworm, as the treatment will be the same; but it does help in tracing the spread and incidence of the infection.

Normally, tapeworm cysts are symptomless and often go unnoticed, except when the cysts grow in the nervous system, causing Neurocysticercosis (NCC), which leads to noticeable symptoms. These cysts can cause an inflammation reaction from the host’s immune system. Imaging techniques such as MRI and CT can help identify these cysts in the brain. Diagnosis of NCC depends on matching up the results of the imaging with blood tests.

For NCC, there are tests that can detect antibodies and antigens in blood and cerebrospinal fluid (CSF) samples. Enzyme-linked immunoelectrotransfer blot assay (EITB) is a type of test used to detect antibodies against T. solium, and ELISA testing can identify the presence of live parasites. Understanding the results of these tests, though, can be complex. For example, even after successful treatment, some patients’ tests may still show positive antibodies for years. In general, positive antibody and antigen tests suggest a viable infection, while negative tests may suggest less severe infection or that the infection was missed.

Treatment Options for Tapeworm

If an adult has a tapeworm from the species Taenia, it’s usually pretty easy to treat with common anti-parasitic medications. Some such drugs are niclosamide, praziquantel, tribendimidine, and albendazole. Out of these, praziquantel and niclosamide are often the top choices. Praziquantel is most commonly chosen because it’s cost-effective. However, it’s worth noting that praziquantel and albendazole can pass a barrier in your body known as the blood-brain barrier while niclosamide can’t. This is important because if a parasitic infection has spread to your brain unnoticed, activating it might lead to neurological symptoms.

There’s a way to get rid of tapeworms through an endoscopic procedure, which involves inserting a tube with a tiny camera through your mouth and into your digestive tract to find and remove the tapeworm. However, this isn’t typically done for T. solium tapeworms. It can, though, be done alongside treatment with praziquantel and has shown good outcomes.

Overally, praziquantel is generally safe with minor side effects like feeling unwell, headache, dizziness, stomach discomfort and nausea. Infrequently, a raised body temperature or skin rash can happen.

Neurocysticercosis (NCC), a condition where tapeworm infections have spread to the brain, may require different treatment approaches depending on the location of the infection and the number of cysts. This could include medications to relieve symptoms like seizures, antiparasitic therapy, or surgery. Sometimes, a combination of these is needed.

It’s also important to know that antiparasitic drugs can at times cause temporary inflammation and worsen symptoms, so it’s vital to take them under supervision. A few lesions in the body’s tissues can possibly be treated with short-term use of albendazol and corticosteroids (drugs reducing inflammation). But if there are multiple lesions, a combination of albendazol and praziquantel might be needed, along with steroids. Cysts blocking the fluid-filled structures in your brain called ventricles usually need to be surgically removed. Cysts in the fluid-filled space surrounding the brain might need longer-term treatments with antiparasitic and anti-inflammatory medications.

What else can Tapeworm be?

Tapeworm infections in adults can often go unnoticed or present with very mild symptoms, making them hard to identify. Diagnosis usually depends on a patient’s travel history or exposure to areas where tapeworms are common. If someone from such an area shows signs of stomach pain, diarrhoea, or constipation, doctors may examine stool samples under a microscope. However, this method is not highly sensitive, so a negative result doesn’t completely rule out tapeworms. In situations where pain persists, other causes both infectious (like bacterial diarrhoea, or viral illnesses) and chronic inflammatory disorders should also be considered. Sometimes, doctors may have to repeatedly test or go ahead and treat for tapeworm infection even without a confirmed diagnosis.

Bear in mind, tapeworms in stool can be mistaken for other parasites due to their similar sizes and appearances. Moreover, new, advanced stool testing methods also might give false results due to cross-reactivity with other parasites. It’s crucial for medical professionals to pinpoint the exact species of the tapeworm, particularly because some, like T. solium, can lead to a serious condition known as neurocysticercosis, while others, like T. saginata, do not.

To diagnose neurocysticercosis, doctors use imaging techniques and analysis of the patient’s blood (serology). The cause of multiple circular patches (ring-enhancing lesions) in the brain, shown by these images, is not only limited to neurocysticercosis. Other possible causes could be:

• Bacterial (like abscess, tuberculosis, syphilis)
• Fungal (like coccidioidomycosis, cryptococcosis, aspergillosis)
• Parasitic (like toxoplasmosis, echinococcosis)
• Cancer related (like metastasis, CNS lymphoma)
• Inflammatory (like multiple sclerosis, sarcoidosis)

What to expect with Tapeworm

Adult tapeworms can be effectively treated with anti-worm medication, and most patients fully recover and no longer have symptoms. The biggest worry is getting re-infected or having undiagnosed parasites leading to health complications or inadequate nutrition.

Neurocysticercosis (NCC), a condition where tapeworm larvae enter the brain, generally has a good prognosis with most symptoms improving after treatment. However, the specific outcomes can vary depending on where the worms are located and the severity of the infection. Cysts in the fluid-filled spaces (subarachnoid and intraventricular regions) of the brain could lead to serious illness or even death. On the other hand, a single cyst in the brain tissue (parenchymal lesions) has a high chance of recovery without recurrent seizures. Multiple cysts can potentially be fatal or cause recurring seizures.

Possible Complications When Diagnosed with Tapeworm

In rare cases, an adult tapeworm infection could result in complications due to the worm moving within the digestive tract. Problems can include inflammation of the pancreas (pancreatitis), gallbladder infection (cholecystitis) if the worm gets stuck in the gallbladder or common bile duct, Meckel’s diverticulitis (inflammation of a small pouch in the digestive tract) and bowel obstruction (blockage in the intestine) which might call for surgical treatment. Moreover, the Diphyllobrothrium worm can absorb vitamin B12 from the gut, putting patients at risk for a type of anemia called pernicious anemia. Neurocysticercosis (NCC), a brain infection caused by tapeworm larvae, may lead to other complications like epilepsy, headache, problems with brain function, strokes and accumulation of fluid in the brain (hydrocephalus).

Potential Complications:

• Pancreatitis
• Cholecystitis
• Meckel’s diverticulitis
• Bowel obstruction
• Surgical intervention
• Pernicious anemia
• Epilepsy
• Headache
• Neurologic deficits
• Strokes
• Hydrocephalus

Preventing Tapeworm

To prevent getting infected by three types of tapeworms, it’s crucial to pay attention to cleanliness, specifically during meat inspection and preparation. Tapeworms can produce thousands of eggs per day, and without proper hygiene, it’s easy for places to become contaminated. Notably, tapeworms can live and grow in non-human hosts, so treating humans affected by the disease does not necessarily stop the tapeworm from spreading in high-risk areas.

A good way to avoid Diphyllobothrium, one type of tapeworm, is by not eating raw, smoked, or pickled fish. It’s safer to eat fish that has been well-cooked or frozen for 24 to 48 hours at -18 C. The Food and Drug Administration (FDA) suggests that if you’re planning to eat fish raw, it should first be frozen to -35 C for 15 hours or to -20 C for 7 days. In the U.S., smoked salmon is cured in brine before it is smoked, so it’s generally not a source of infection.

The current method to prevent T. solium, another type of tapeworm, in pigs includes visually inspecting the meat for signs of infection. However, some studies have shown that this alone may not be enough to control bovine cysticercosis, another parasitic infection. Science is making use of molecular methods to test animals, but some tests only show previous infection, not current ones. Protection from infection by Taenia, a genus of tapeworm, is ensured by thoroughly cooking or freezing beef or pork; for instance, T. solium is killed when pork is cooked to an internal temperature of 65C (150F) or frozen at -20 C (-38 F) for at least 12 hours. Pickling or salt-curing pork does not guarantee that it’s safe from infection. For T. saginata, another tapeworm species, cook beef to an internal temperature of 56C (131F) or freeze it at -10 C for 5 days. Beef pickled in 25% brine for 5 to 6 days is believed to be safe.