Angiostrongylus cantonensis (Neuroangiostrongyliasis) – PCR, Microscopy, and Antibody

Consistent with O. Reg. 671/92 of the French Language Services Act, laboratory testing information on this page is only available in English because it is scientific or technical in nature and is for use only by qualified health care providers and not by members of the public.

Background
This page provides PCR, microscopy, and antibody (serology) testing information for neuroangiostrongyliasis (also known as rat lungworm disease) at Public Health Ontario (PHO). The causative agent of neuroangiostrongyliasis is the parasitic larval nematode Angiostrongylus cantonensis. Infections mainly occur in subtropical and tropical regions following ingestion of undercooked gastropods, crustaceans, or unwashed produce in the preceding days (up to 3 months).

Neuroangiostrongyliasis manifestations primarily comprise neural larva migrans (NLM), including acute transient meningitis with elevated cerebrospinal fluid (CSF) opening pressure, eosinophilic pleocytosis, and high protein levels. Ocular larva migrans (OLM), including diffuse unilateral subacute neuroretinitis or DUSN, uveitis, or endophthalmitis, and visceral larva migrans (VLM), including, transient pulmonary or hepatic inflammation, are also rarely reported.

Note: Testing for Angiostrongylus costaricensis, the causative agent abdominal angiostrongyliasis (eosinophilic nodulo-ulcerative intestinal wall infiltration) in Latin America and the Caribbean, is not currently available at PHO.

*Uncontrolled print copy. Valid only on day of print: 19 Oct 2026.

Testing Indications

Empiric management is recommended for neuroangiostrongyliasis based on compatible exposure history and clinical presentation.

Although prolonged turnaround times limit its utility, A. cantonensis PCR may be considered on CSF specimens to aid in the diagnosis of individuals suspected of NLM. CSF microscopy is generally negative and of limited utility. PCR is not currently available for the less common presentations of OLM or VLM. Antibody testing is primarily available for investigational use and retrospective diagnosis, since there are no clinically validated serological assays.^1-2

Acute meningitis, including NLM, is a Disease of Public Health Significance (DOPHS) under the Health Protection and Promotion Act (HPPA). Additional testing and management recommendations are stated in the Ontario Ministry of Health Infectious Disease Protocol Appendix 1 for Disease: Meningitis.

Acceptance/Rejection Criteria

All Angiostrongylus testing requests require pre-approval by a PHO microbiologist or designate prior to submission.

Testing will only be performed when all the following criteria are documented on the requisition form:

International travel or migration
Exposure to undercooked gastropods, crustaceans, or unwashed produce
Clinical signs or symptoms consistent with angiostrongyliasis
Eosinophilia, eosinophilic pleocytosis, or ocular lesion(s)

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
Angiostrongylus cantonensis – PCR	General Test Requisition	Cerebrospinal fluid (CSF)	1.0 ml	Sterile container
Angiostrongylus cantonensis – Microscopy	General Test Requisition	Cerebrospinal fluid (CSF)	1.0 ml	Sterile container
Angiostrongylus cantonensis – Antibody	General Test Requisition	Serum Cerebrospinal fluid (CSF)	1.0 ml 1.0 ml	Red top (clotted) tube or serum separator tube (SST) Sterile container

Submission and Collection Notes

Complete all fields of the requisition form.

Important: Specify all the following testing indications on the requisition. Failure to provide this information may result in rejection:

International travel or migration
Exposure to undercooked gastropods, crustaceans, or unwashed produce
Clinical signs or symptoms consistent with angiostrongyliasis
Eosinophilia or eosinophilic pleocytosis

Label the specimen container(s), including the slide mailer itself and each individual slide, with the patient’s first and last name, date of collection, and one other unique identifier such as the patient’s date of birth or Health Card Number. For additional information see: Criteria for Acceptance of Patient Specimens. Failure to provide this information may result in rejection or testing delay.

Timing of Specimen Collection

For serology testing: Both acute (collected within 2 weeks of symptom onset) and convalescent (collected 1-3 weeks later) serum samples are required, as serology testing may be negative during the acute phase of illness.

Limitations

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

Storage and Transport

Centrifuge tube if using serum separator tube (SST).

Place specimen container in a biohazard bag and properly seal the bag. Specimens should be stored at 2-8°C and shipped to PHO on ice packs within 48 hours of collection.

All clinical specimens must be shipped in accordance to the Transportation of Dangerous Good Act.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Angiostrongylus cantonensis PCR testing is referred out to the US Centers for Disease Control and Prevention (US CDC) upon request. Turnaround time for PCR is up to 30 calendar days from receipt at PHO.

Angiostrongylus cantonensis antibody testing is referred out to Mahidol University in Thailand upon request. Turnaround time for antibody testing is up to 60 calendar days from receipt at PHO.

Angiostrongylus cantonensis microscopy is performed daily from Monday to Saturday at PHO. Turnaround time for microscopy is up to 3 calendar days from receipt at PHO.

Test Methods

Angiostrongylus cantonensis PCR is performed at the US CDC using an A. cantonensis specific ITS1 rRNA gene target from Qvarnstrom Y et al. (2016).³

Angiostrongylus cantonensis microscopy is performed at PHO using direct wet mount.

Angiostrongylus cantonensis antibody testing is performed in Thailand using an immunoblot test targeting the 31-kDa protein in adult worm preparations.⁴

Performance and Limitations:
The clinical sensitivity of A. cantonensis PCR in CSF is reported to range between 60-85%. Intermittent positivity may be seen over different days in some patients, therefore repeat collection after a negative result may be considered if the clinical suspicion remains high. There is no expected cross-reactivity with A. cantonensis, but cross-reactivity has been documented with A. mackerrasae, a species not yet known to cause human infection.^1-4

The clinical sensitivity of A. cantonensis antibody testing is dependent on the specimen type and stage of infection. In serum, antibody testing sensitivity is reported to vary from under 50% during the acute phase (within 2 weeks) to 70-95% during the convalescent phase. Therefore, collection of both acute and convalescent sera is required. The clinical sensitivity of antibody testing in CSF specimens is usually under 70%. Specificity ranges from 80-95%, with potential for cross-reactivity with other helminths (e.g., other Angiostrongylus species, Gnathostoma, Toxocara, Strongyloides). The assay may remain positive after therapy and may not be able to distinguish between active, resolved, or recurrent infection. ^1-10

The clinical sensitivity of A. cantonensis microscopy in CSF is usually under 15%. One study suggests that placing a patient in a sitting position for 1 hour before the lumbar puncture may increase the yield of larvae seen in the CSF.^1-10

Algorithm

If microscopy is positive, the sample will be reflexed to PCR for species identification.

Interpretation

For A. cantonensis PCR results:

A. cantonensis PCR	Interpretation
Detected	Angiostrongylus cantonensis DNA present.
Indeterminate	Inconclusive result. An indeterminate PCR result may be due to a low level of target genetic material in the specimen, inadequate specimen content, or a non-specific signal. Please resubmit another specimen for testing if clinically indicated.
Not Detected	Angiostrongylus cantonensis DNA not present.
Invalid	No result available. Test results are invalid due to the failed amplification of the extraction control. Amplification failure may be due to inadequate specimen content, extraction failure, or PCR inhibition. Please resubmit another specimen for testing if clinically indicated.

For A. cantonensis antibody test results:

A. cantonensis Antibody – Referred Out	Interpretation
Reactive	Angiostrongylus cantonensis antibodies detected. May not distinguish between active, resolved, or recurrent infection.
Non-reactive	Angiostrongylus cantonensis antibodies NOT detected. A single negative antibody result during the acute phase of illness does not rule out infection; refer to convalescent serum sample result if seroconversion has occurred.

For A. cantonensis microscopy:

Parasite Microscopy	Interpretation
Parasite(s) found: Angiostrongylus species	Refer to PCR for species confirmation.
Parasite(s) NOT found	Does not rule out infection. Refer to PCR for confirmatory results.

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.

Specimens that are positive for Angiostrongylus cantonensis from sterile sites (e.g. CSF) are reported to the Medical Officer of Health as per Health Protection and Promotion Act.

References

Wilkins PP, Qvarnstrom Y, Whelen AC, Saucier C, da Silva AJ, Eamsobhana P. The current status of laboratory diagnosis of Angiostrongylus cantonensis infections in humans using serologic and molecular methods. Hawaii J Med Public Health. 2013 Jun;72(6 Suppl 2):55-7. PMID: 23901386; PMCID: PMC3689480.
Martins YC, Tanowitz HB, Kazacos KR. Central nervous system manifestations of Angiostrongylus cantonensis infection. Acta Trop. 2015 Jan;141(Pt A):46-53. doi: 10.1016/j.actatropica.2014.10.002. Epub 2014 Oct 13. PMID: 25312338; PMCID: PMC4312175.
Qvarnstrom Y, Xayavong M, da Silva AC, Park SY, Whelen AC, Calimlim PS, Sciulli RH, Honda SA, Higa K, Kitsutani P, Chea N, Heng S, Johnson S, Graeff-Teixeira C, Fox LM, da Silva AJ. Real-Time Polymerase Chain Reaction Detection of Angiostrongylus cantonensis DNA in Cerebrospinal Fluid from Patients with Eosinophilic Meningitis. Am J Trop Med Hyg. 2016 Jan;94(1):176-81. doi: 10.4269/ajtmh.15-0146. Epub 2015 Nov 2. PMID: 26526920; PMCID: PMC4710426.
Sears WJ, Qvarnstrom Y, Dahlstrom E, Snook K, Kaluna L, Baláž V, Feckova B, Šlapeta J, Modry D, Jarvi S, Nutman TB. AcanR3990 qPCR: A Novel, Highly Sensitive, Bioinformatically-Informed Assay to Detect Angiostrongylus cantonensis Infections. Clin Infect Dis. 2021 Oct 5;73(7):e1594-e1600. doi: 10.1093/cid/ciaa1791. PMID: 33252651; PMCID: PMC8492198.
Jarvi SI, Nakayama K, Eamsobhana P, Kaluna L, Shepherd L, Tagami Y. Immunodiagnostic Detection of Angiostrongylus cantonensis Exposure on Hawaii Island Using Isogeographic 31-kDa Antigen. Am J Trop Med Hyg. 2023 Jun 12;109(2):335-342. doi: 10.4269/ajtmh.22-0643. PMID: 37308099; PMCID: PMC10397453.
Nuamtanong S. The evaluation of the 29 and 31 kDa antigens in female Angiostrongylus cantonensis for serodiagnosis of human angiostrongyliasis. Southeast Asian J Trop Med Public Health. 1996 Jun;27(2):291-6. PMID: 9279992.
Brummaier T, Bertschy S, Arn K, Treumann T, Ruf MT, Nickel B, Paris DH, Neumayr A, Blum J. A blind passenger: a rare case of documented seroconversion in an Angiostrongylus cantonensis induced eosinophilic meningitis in a traveler visiting friends and relatives. Trop Dis Travel Med Vaccines. 2019 Apr 15;5:6. doi: 10.1186/s40794-019-0084-x. PMID: 31016026; PMCID: PMC6466724.
Roure S, Fernández-Rivas G, Ruf MT, Grau-López L, Guarro L, Matas L, Nickel B, Valerio L. A cluster of travelers with headache and a hidden travel companion, Angiostrongylus cantonensis: A diagnostic challenge. Travel Med Infect Dis. 2021 Nov-Dec;44:102187. doi: 10.1016/j.tmaid.2021.102187. Epub 2021 Oct 21. PMID: 34688893.
Dard C, Tessier E, Nguyen D, Epelboin L, Harrois D, Swale C, Cabié A, de Meuron K, Miossec C, Desbois-Nogard N. First cases of Angiostrongylus cantonensis infection reported in Martinique, 2002-2017. Parasite. 2020;27:31. doi: 10.1051/parasite/2020032. Epub 2020 May 12. PMID: 32394891; PMCID: PMC7216674.
Tsai HC, Liu YC, Kunin CM, Lee SS, Chen YS, Lin HH, Tsai TH, Lin WR, Huang CK, Yen MY, Yen CM. Eosinophilic meningitis caused by Angiostrongylus cantonensis: report of 17 cases. Am J Med. 2001 Aug;111(2):109-14. doi: 10.1016/s0002-9343(01)00766-5. PMID: 11498063.
Kuberski T, Wallace GD. Clinical manifestations of eosinophilic memingitis due to Angiostrongylus cantonensis. Neurology. 1979 Dec;29(12):1566-70. doi: 10.1212/wnl.29.12.1566. PMID: 574219.