Taenia solium (Cysticercosis) – Antibody and PCR

Testing Indications

Cysticercosis is primarily diagnosed based on clinical, imaging, and epidemiological evidence (e.g., central nervous system, muscular, and/or ectopic cystic manifestations). Serology provides supportive laboratory evidence in individuals with findings compatible with cysticercosis. When diagnostic uncertainty persists after these investigations, PCR -with or without microscopy- on sterile body fluids or tissue specimens may be considered.

Patients with larval cysticercosis may also be co-infected with the adult intestinal stage of Taenia solium. If co-infection is suspected, microscopy of enteric specimens can be considered to diagnose intestinal taeniasis, as outlined on the PHO webpage: Enteric Helminths (Nematodes, Trematodes, Cestodes, Acanthocephalans) and Balantioides – Microscopy.

Note: Antigen tests for Taenia solium are not currently available at PHO

Acceptance/Rejection Criteria

• Testing will only be accepted when the following information is documented on the requisition:
• Signs or symptoms compatible with cysticercosis (e.g. CNS, muscular, or ectopic cystic lesion)
• Serology and PCR requests for patients with suspected isolated intestinal taeniasis (without cysticercosis) will be cancelled.
• Specimens from non-sterile sites (e.g. enteric specimens) submitted for PCR will be cancelled.
• Specimens are only accepted if originating from human sources. Specimens submitted from animal sources (e.g. pets) or environmental sources (e.g. food) will be rejected.

Limitations

For serology: Grossly haemolysed, lipemic, contaminated specimens, and specimens containing anti-coagulant are unsuitable for testing.

Storage and Transport

Place specimen container in a biohazard bag and properly seal the bag. Centrifuge tube if using SST for serum specimens.

Unpreserved and serum specimens should be stored at 2-8°C and shipped to PHO within 48 hours of collection; if delayed beyond 48 hours of collection, store unpreserved specimens frozen at -20°C. All specimens must be shipped in accordance to the Transportation of Dangerous Good Act.

Test Frequency and Turnaround Time (TAT)

Serology and PCR are forwarded to the National Reference Centre for Parasitology (NRCP) in Montreal. Turnaround time is up to 42 calendar days from receipt at PHO.

Microscopy is performed daily from Monday to Friday at PHO’s Toronto site. Turnaround time is up to 7 calendar days from receipt at PHO.

Serology is performed at the NRCP using a laboratory-developed immunoblot assay (also known as enzyme-linked immunosorbent assay or EITB) based on antibody capture using purified lentil lectin purified glycoprotein (LLGP) antigens from T. solium pork cysts.

PCR is performed at the NRCP using a laboratory developed assay. Microscopy is performed at PHO using standard sedimentation.

Performance:
For serology, the NRCP states a sensitivity of 98% and specificity of 100% for neurocysticercosis infections with 2 or more active intraparenchymal cysts, while CSF antibody sensitivity is usually 90% or lower. Serology sensitivity for single and/or calcified intraparenchymal cysts may vary from 25-80%. For extraparenchymal cysts (e.g. ventricular or subarachnoid, sometimes referred as “racemose”), serum sensitivity may be blow 80% while CSF sensitivity may be higher. Serology sensitivity for non-neurologic cysts (e.g. muscular) is below 50%. Cross-reactivity with other Taenia species causing similar infections (e.g. cysticercosis from T. crassiceps or coenurosis from T. multiceps, T. serialis, or T. brauni) is not known. Serology may persist for months to years following resolution of infection and may be positive in the absence of identifiable cystic lesion(s), therefore results should be interpreted with caution.^1-4

For PCR, performance at the NRCP has not yet been established. Other assays have reported a sensitivity of 70-95% for extraparenchymal neurocysticercosis infections and 40-90% for parenchymal neurocysticercosis infections. Performance for non-neurologic cysts is not known. Specificity has been reported to range from 90-100%.^5-10

Interpretation

Serology:

PCR:

Reporting

Results are reported to the physician, authorized health care provider (General O. Reg 45/22, s.18) or submitter as indicated on the requisition.

References

1. White AC Jr, Coyle CM, Rajshekhar V, Singh G, Hauser WA, Mohanty A, Garcia HH, Nash TE. Diagnosis and Treatment of Neurocysticercosis: 2017 Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA) and the American Society of Tropical Medicine and Hygiene (ASTMH). Clin Infect Dis. 2018 Apr 3;66(8):e49-e75. doi: 10.1093/cid/cix1084. PMID: 29481580; PMCID: PMC6248812.
2. Garcia HH, Gonzalez AE, Gilman RH. Taenia solium Cysticercosis and Its Impact in Neurological Disease. Clin Microbiol Rev. 2020 May 27;33(3):e00085-19. doi: 10.1128/CMR.00085-19. PMID: 32461308; PMCID: PMC7254859.
3. Garcia HH, Nash TE, Del Brutto OH. Clinical symptoms, diagnosis, and treatment of neurocysticercosis. Lancet Neurol. 2014 Dec;13(12):1202-15. doi: 10.1016/S1474-4422(14)70094-8. Epub 2014 Nov 10. PMID: 25453460; PMCID: PMC6108081.
4. Proaño-Narvaez JV, Meza-Lucas A, Mata-Ruiz O, García-Jerónimo RC, Correa D. Laboratory diagnosis of human neurocysticercosis: double-blind comparison of enzyme-linked immunosorbent assay and electroimmunotransfer blot assay. J Clin Microbiol. 2002 Jun;40(6):2115-8. doi: 10.1128/JCM.40.6.2115-2118.2002. PMID: 12037074; PMCID: PMC130799.
5. Michelet L, Fleury A, Sciutto E, Kendjo E, Fragoso G, Paris L, Bouteille B. Human neurocysticercosis: comparison of different diagnostic tests using cerebrospinal fluid. J Clin Microbiol. 2011 Jan;49(1):195-200. doi: 10.1128/JCM.01554-10. Epub 2010 Nov 10. Erratum in: J Clin Microbiol. 2012 Jan;50(1):212. PMID: 21068283; PMCID: PMC3020422.
6. Romo ML, Carpio A, Parkhouse RME, Cortéz MM, Rodríguez-Hidalgo R. Comparison of complementary diagnostic tests in cerebrospinal fluid and serum for neurocysticercosis. Heliyon. 2018 Dec 1;4(12):e00991. doi: 10.1016/j.heliyon.2018.e00991.
7. Carpio A, Campoverde A, Romo ML, García L, Piedra LM, Pacurucu M, López N, Aguilar J, López S, Vintimilla LC, Toral AM, Peña-Tapia P. Validity of a PCR assay in CSF for the diagnosis of neurocysticercosis. Neurol Neuroimmunol Neuroinflamm. 2017 Jan 16;4(2):e324. doi: 10.1212/NXI.0000000000000324.
8. Yera H, Dupont D, Houze S, Ben M'rad M, Pilleux F, Sulahian A, Gatey C, Gay Andrieu F, Dupouy-Camet J. Confirmation and follow-up of neurocysticercosis by real-time PCR in cerebrospinal fluid samples of patients living in France. J Clin Microbiol. 2011 Dec;49(12):4338-40. doi: 10.1128/JCM.05839-11.
9. Hernández M, Gonzalez LM, Fleury A, Saenz B, Parkhouse RM, Harrison LJ, Garate T, Sciutto E. Neurocysticercosis: detection of Taenia solium DNA in human cerebrospinal fluid using a semi-nested PCR based on HDP2. Ann Trop Med Parasitol. 2008 Jun;102(4):317-23. doi: 10.1179/136485908X278856.
10. O'Connell EM, Harrison S, Dahlstrom E, Nash T, Nutman TB. A Novel, Highly Sensitive Quantitative Polymerase Chain Reaction Assay for the Diagnosis of Subarachnoid and Ventricular Neurocysticercosis and for Assessing Responses to Treatment. Clin Infect Dis. 2020 Apr 15;70(9):1875-1881. doi: 10.1093/cid/ciz541.