WS/T 321-2010 in English

Angiostrongylus cantonensis is a parasitic disease caused by the invasion of the central nervous system by the larvae of Angiostrongylus cantonensis, with the characteristic manifestation of eosinophilic meningoencephalitis. This standard clearly stipulates a three-level diagnostic system from suspected cases to confirmed cases.

1. Determination of suspected cases

The following conditions must be met simultaneously: epidemiological history + typical clinical manifestations (headache/radicular pain/hyperalgesia). Data from 2010 to 2018 show that the confirmed rate of suspected cases in my country is about 35%.

2. Supplementary criteria for clinical diagnosis of cases

• Routine blood test: absolute eosinophil value > 0.5×10⁹/L
• Cerebrospinal fluid: pressure > 180mmH₂O and increased protein
• Immunology: ELISA antibody test positive (P/N≥2.0)

3. Gold standard for confirmed cases

The larvae of Angiostrongylus cantonensis are found in the cerebrospinal fluid or eyes. The pathogen detection rate is about 10%. Multiple lumbar punctures are recommended to improve the detection rate.

Precautions for cerebrospinal fluid collection

Use No. 7-9 puncture needle and immediately send for inspection after puncture. Inspection process:

1. Pressure measurement (normal value 80-180mmH₂O)
2. Routine examination (cell count + biochemical analysis)
3. Wright-Giemsa staining microscopy

Comparison of immunological detection methods

Method	Antigen source	Sensitivity	Specificity
Double antibody sandwich ELISA	Adult crude antigen	89.7%	93.2%
Indirect fluorescent antibody	Third-stage larvae	82.4%	88.6%

It is important to differentiate from the following diseases:

• Cerebral cysticercosis: There is a history of tapeworm disease, and CT shows characteristic cystic lesions
• Tuberculous meningitis: Decreased cerebrospinal fluid sugar/chloride, positive acid-fast staining
• Cerebral paragonimiasis: Coughing up rusty sputum, abnormal chest X-ray

Core indicators for identification: elevated eosinophilia + etiological evidence.

Implementation paths for medical institutions

1. Outpatient and emergency departments: inquire in detail about the raw food history and record the characteristics of headaches
2. Laboratory departments: conduct eosinophil counts in a standardized manner
3. Radiology departments: cooperate to exclude other intracranial lesions

Key points for prevention and control by disease control agencies

• Surveillance in epidemic sources: focus on investigating the infection rate of Pomacea canaliculata (up to 66.9% in some areas)
• Health education: prohibit the consumption of raw snail products
• Outbreak management: establish a rapid testing channel