Taenia Infection Workup

Updated: Jul 24, 2018
  • Author: Supatida Tengsupakul, MD; Chief Editor: Russell W Steele, MD  more...
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Workup

Laboratory Studies

Intestinal taeniasis

CBC count detects mild eosinophilia.

Examine 3 stool samples (direct and concentrated stool preparations) collected on 3 different days from patients and contacts.

  • Determination of species on the basis of ova examination is difficult because the eggs of T. solium and T. saginata are identical.

  • Examining the gravid proglottids helps identify the species; count the main uterine branches (7-16 branches for T. solium, 14-32 branches for T. saginata and 11-32 branches for T. asiatica). [24]

  • Examining the scolex helps differentiate the species because a T. solium scolex has 4 suckers and an armed rostellum and hooks but T. saginata scolex does not have rostellum and hook. T. asiatica has rostellum without a hook. [24]

Serology

Copro-Ag ELISA can be used to detect T. solium tapeworm carrier with sensitivity of 84.5% and specificity of 92%. [25]

Molecular analysis

  • Copro-PCR has been used to detect T. solium carrier with sensitivity of 82.7% and specificity of 99%. [25]
  • Multiplex loop-mediated isothermal amplification (multiplex LAMP) targeting mitochondrial cytochrome c oxidase subunit 1 ( cox 1) gene couple with dot enzyme-linked immunosorbent assay (dot-ELISA) help identify human Taenia species ( T. solium, T. saginata and T. asiatica). This technique is easy to perform and interpret and does not require expensive equipment which make it feasible to perform in resource-limited settings. [26]  Unfortunately, these molecular methods are not commercially available.

Endoscopy/capsule endoscopy can help diagnose taenia infection. [27, 17]

Neurocysticercosis (NCC)

Examine stool samples as described above.

Perform a lumbar puncture. [28]

  • CSF findings are abnormal in 50-90% of patients with NCC (but may be normal in children with single-lesion disease).

  • Protein levels are usually elevated (but may be normal in children with single-lesion disease).

  • Glucose levels are usually mildly to moderately depressed (but may be normal in children with single-lesion disease).

  • A predominantly mononuclear pleocytosis is common.

  • Cell counts rarely exceed 300/μL.

Eosinophils in the CSF are a common but nonspecific finding. Giemsa or Wright stains should be performed to detect their presence.

An enzyme-linked immunotransfer blot (EITB) assay is the test of choice to confirm the diagnosis of NCC indicated by clinical and radiologic findings. Test specificity is 100% and sensitivity is 90% with more than 2 lesions; sensitivity declines to 50-70% with a solitary lesion. Therefore, EITB assay may have limited value for children because most present with a single lesion. A serum immunoblot assay is more sensitive than the assay using CSF, thus obtaining CSF solely for that purpose is unnecessary.

Although an enzyme-linked immunosorbent assay (ELISA) can be performed on both CSF and serum, CSF provides better reliability. ELISA may provide either false-positive or false-negative results. ELISA provides a reported sensitivity of 75%. ELISA can aid in diagnosis in patients with few CNS lesions and relatively mild disease. Newer serologic methods may allow improved diagnostic testing. [29]

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Imaging Studies

Radiography

Plain films of the chest, neck, arms, and thighs can depict calcified cysticerci, although calcification takes approximately 3 years, and sometimes longer, to occur.

A central calcified scolex surrounded by a calcified cyst wall is pathognomonic.

CT

Perform CT scanning in all children presenting with new-onset focal seizures.

Although CT scanning is superior to MRI to detect intracerebral calcification, calcification occurs less frequently in children than in adults.

CT scanning reveals both cysts and granulomata. Cysts, which may be single or multiple, are approximately 5-20 mm in diameter. Most children (ie, 75%) have a single cyst, usually located in the cortex or at the junction of gray and white matter.

CT scanning can also detect edema associated with dead worms. The dead worms appear as spherical hypodensities, often with the parasite's protoscolex appearing as an eccentric dot of calcium (ie, mural nodule).

CT scanning with contrast shows a ring-enhancing image. Later obliteration of the cyst may produce a solid-enhanced image.

MRI

MRI is superior to CT scanning in detecting intraventricular and subarachnoid cysts.

MRI may reveal a mural nodule within the cyst, which is pathognomonic for NCC.

MRI with parallel imaging may facilitate detection of cysts. [30]

See the Neurocysticercosis Case from the Gorgas Course in Clinical Tropical Medicine and the image below for typical lesions revealed using CT scanning and MRI.

Brain MRI that reveals a cystic lesion containing Brain MRI that reveals a cystic lesion containing a dead parasite with surrounding vasogenic edema on fluid-attenuated inversion recovery (FLAIR) imaging. MRI is of a 16-year-old Guatemalan adolescent with first-time afebrile seizure and normal EEG, cerebrospinal fluid (CSF), and examination findings.
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Other Tests

Ocular cysticercosis

Funduscopic examination may show freely floating cysticerci in the anterior chamber and vitreous chamber and may provide visual identification of the movements and morphology of larval forms. Larvae may be found adhering to subretinal tissues.

Subretinal cysts are associated with vasculitis and edema.

Cysts in vitreous are associated with chorioretinitis and retinal detachment.

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Procedures

Excise or perform biopsy of subcutaneous nodules.

For skeletal cysticercosis, perform a biopsy or excision of the nodule and histologic examination of the cysticerci.

For neurocysticercosis, perform a lumbar puncture (see Lab Studies).

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Histologic Findings

Mature cysticerci are ellipsoidal, translucent, fluid-filled cysts, 1-2 cm in diameter. Younger cysticerci are smaller. A single dense white body can be seen through the membrane. The spiral canal of the cyst wall, which has a wavy appearance in most tissue preparations, is most frequently observed in biopsy specimens. The wall, which is 100-200 micrometers wide, is characterized by an internal parenchymal layer of longitudinal and circular muscle, a middle layer of pseudoepithelial cells, and an outer cuticular layer composed of a dentate membrane with a microvillus projection that interfaces with host tissues. The scolex region is thickened and more organized. Cross sections of the scolex appear as several layers of folded smooth muscles, which may contain parts of the suckers or hooklets.

The parasite is surrounded by an adventitia of host tissue reaction. A scant local cellular reaction that consists of some eosinophils and macrophages surrounds live cysticerci; dead cysticerci are surrounded by a dense inflammatory infiltrate that consists of the entire spectrum of inflammatory cells, including multinucleated giant macrophages.

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