Approach
The diagnostic approach depends on the clinical presentation. Patients with intestinal infection may be asymptomatic or present with vague symptoms, while patients with neurocysticercosis generally present with headaches, seizures, and increased intracranial pressure. Stool examination and serology are the investigations of choice; however, imaging is required for extra-intestinal manifestations. Neuroimaging is the mainstay of diagnosis for neurocysticercosis.
History
Travel, diet, and exposure history, along with compatible clinical syndromes, can help in diagnosing tapeworm infections.
Patients with intestinal infection (e.g., with Hymenolepis nana, Diphyllobothrium latum, Taenia saginata) can be asymptomatic.[13] However, they may present with vague intestinal symptoms including abdominal pain, hunger pain, sore tongue, sore gums, loss of appetite, increased appetite, weight loss, bloating, constipation, diarrhoea, a feeling of 'something moving inside', and/or nausea.[2]
Patients who are definitive hosts for T solium may also be asymptomatic or may present with vague intestinal symptoms as above, or with anxiety, headaches, dizziness, urticaria, and a variety of other pleomorphic symptoms.
Patients with H nana may present with an itchy rash.[27] There are also very rare cases of malignant transformation.[28][29]
The majority of patients with cystic echinococcosis (hydatiditis) are asymptomatic, and hydatid cysts are often observed as incidental findings at autopsy or detected by abdominal ultrasound performed for other reasons. The severity and nature of the signs and symptoms that may be produced by these tapeworms are extremely varied and never pathognomonic. Due to the distensible nature of the liver, cysts may grow for years before becoming symptomatic. Symptoms include right upper quadrant (RUQ) or epigastric pain, nausea, or vomiting. Communication and rupture of hepatic cysts into the biliary tree is well described and can result in cholangitis and cholestasis. In these instances, patients present with epigastric pain and RUQ pain, which can be intermittent and mimic gallstone disease. If left untreated, cholangitis can occur with resultant bacterial superinfection of the cyst cavity and abscess formation. Thoracic complications of hepatic hydatid cysts may be seen in up to 15% of cases.[30] Less commonly, portal hypertension can occur, either by extrinsic compression of the liver or by obstruction of the inferior vena cava and hepatic outflow tract. Cysts may rupture into the peritoneal cavity, usually secondary to trauma, with resultant anaphylaxis or secondary cystic echinococcosis. Mild to severe anaphylactoid reactions (and occasionally death) may follow the sudden massive release of cyst fluid. Intact hydatid cysts in the lungs may cause no symptoms, while chest pain, cough, or haemoptysis can occur when there is leakage or rupture of the cyst. Rupture or leakage of echinococcal cysts into the peritoneum usually results in acute or intermittent allergic manifestations (anaphylaxis or urticaria).
When patients are harbouring the adult tapeworm, they may present after noticing large tapeworm segments (proglottids) in the toilet bowl or after feeling the spontaneous movement of proglottids through the anus. Some patients with D latum only become aware of the infection when spontaneously passing proglottids. In T saginata infection, proglottids usually spontaneously emerge out of the anus and in T solium infection, proglottids are usually passed with stools.
Seizures and headaches are the most common presenting symptoms in patients with neurocysticercosis. The disease is pleomorphic and may present with a variety of symptoms depending on the location, the number of cysticerci, and the associated host response.[31] Increased intracranial pressure can occur in the setting of intraventricular and subarachnoid disease, and less commonly in intraparenchymal disease, and can be life threatening. Sudden death can occur. Subarachnoid disease can result in stroke or hydrocephalus due to the exuberant host inflammation in response to this form of disease.
Physical examination
Physical examination is generally unremarkable in hosts harbouring adult intestinal tapeworm. However, patients with H nana may have macular-papular skin eruptions, and patients with Echinococcus species infection may demonstrate signs of echinococcal liver cysts, including hepatomegaly and evidence of sepsis if biliary tree communication, with subsequent superinfection, occurs.[27] Visible or palpable subcutaneous nodules can occur in some patients with cysticercosis.[10][32]
Examination of patients with neurocysticercosis may reveal neurological defects corresponding to central nervous system cysts. Neurocysticercosis may present with increased intracranial pressure and hydrocephalus and tends to be more severe in its presentation.[31] Funduscopic examination is generally recommended to exclude intra-ocular cysticerci.[33]
Stool examination
Stool examination of definitive hosts can help confirm the diagnosis in patients who harbour the adult tapeworm. The eggs of T saginata and T solium cannot be distinguished; therefore, it is necessary to obtain proglottids, which can differentiate the two tapeworms.[34]
Infection with D latum is often first recognised in asymptomatic patients when stool examination is performed for other reasons.
Baseline stool examination for ova and parasites is important prior to starting any treatment.
Commercially available polymerase chain reaction-based stool diagnostic tests are able to detect some parasites (e.g., Cryptosporidium, Cyclospora, Entamoeba, Giardia) but currently do not detect tapeworms.
Serology
Serologic testing with enzyme-linked immunotransfer blot (EITB), an assay that uses semi-purified membrane antigens, is recommended as a confirmatory test in patients with neurocysticercosis. Enzyme-linked immunosorbent assays using crude antigen should be avoided due to their poor sensitivity and specificity.[33] With EITB, binding to any one of seven bands is considered positive. Studies have confirmed nearly 100% specificity, but rare false positives have been noted with a single gp50 band.[35] The sensitivity is limited in subjects with either a single lesion or only calcified lesions. The predictive value of the EITB assay for neurocysticercosis is better with serum than with cerebrospinal fluid.
Western blot is the confirmatory test for Echinococcus species. Serology is 80% to 100% sensitive and 88% to 96% specific for liver cyst infections. It is less sensitive for lung involvement (50% to 56%) and for other organ involvement (25% to 26%).[1]
Serodiagnosis is helpful in many parasitic diseases, but can be problematic in the diagnosis of cysticercosis due to cross-reactions to other parasites and non-specific binding.
Other laboratory investigations
A full blood count should be routinely ordered in all patients. Helminthic parasitic infections cause eosinophilia during migration through host tissue; however, eosinophilia is not always encountered in tapeworm infections. Tapeworms causing intestinal infections can remain wholly in the lumen of the gut, while extra-intestinal infections can be walled off. When cystic structures are disrupted, eosinophilia is more likely.[36]
D latum infections may present with megaloblastic pernicious anaemia due to absorption of vitamin B12 by the tapeworm. About 40% of people harbouring the worm have reduced serum vitamin B12, but fewer than 2% develop anaemia.[37]
Screening for latent tuberculosis and strongyloidiasis is recommended in patients who are likely to require long-term corticosteroid therapy (i.e., 1 month or more) for neurocysticercosis, due to the risk of immunosuppression and opportunistic infections with this type of treatment.[33]
Imaging
Abdominal ultrasound may detect hydatid cysts (e.g., echinococcosis of the liver). The World Health Organization classifies the stages of Echinococcus granulosus into active versus inactive, and classification guides therapy. CE1 is a unilocular anechoic cystic lesion with a double sign. CE2 is a multiseptated, 'rosette-like honeycomb' cyst (this is a mother cyst filled with daughter cysts). Both CE1 and CE2 are considered active, usually fertile cysts containing viable protoscolices. CE3a is a cyst with detached membranes (water-lily sign), while CE3b has daughter cysts in a solid matrix. These are considered cysts in the transitional stage where the integrity of the cyst has been compromised either by the host or by chemotherapy. A cyst with heterogeneous hypoechoic/hyperechoic contents and no daughter cysts is the CE4 stage, while calcified cysts are considered CE5. CE types 4 and 5, which are inactive, have normally lost their fertility and are degenerative.[38]
Neuroimaging, with magnetic resonance imaging (MRI) and a non-contrast computed tomography (CT) scan of the brain, is the mainstay of diagnosis for neurocysticercosis. MRI is superior to CT in identifying extraparenchymal cysts and posterior fossa lesions, but CT is better in visualising calcified cysts.[39] MRI may also reveal the scolex, which is usually not visible on CT scans. Ideally, both tests should be considered.
Management depends on careful staging, and patients can be classified as having parenchymal (i.e., viable, non-viable, or single small enhancing lesion) or extraparenchymal (i.e., intraventricular, subarachnoid, spinal, or ocular) disease. Patients can have cysts in more than one location. Specific findings on neuroimaging depend on the location of the cysts. All patients with subarachnoid disease should also have an MRI of the spine.[33][40] MRI is more effective for imaging extraparenchymal cysticerci.
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