What is the approach to testing for lungworms (parasitic infection) in a primary care setting?

Testing for Lungworms in Primary Care

The evidence provided does not address human lungworm testing in primary care settings, as all available guidelines focus on fungal infections rather than parasitic lungworm infections. However, based on the limited research evidence on human lungworm disease (specifically Angiostrongylus cantonensis), I can provide guidance extrapolated from veterinary protocols and case reports.

Clinical Context and When to Suspect Lungworm

• Consider lungworm infection (Angiostrongylus cantonensis, rat lungworm) in patients presenting with eosinophilic meningitis, severe headache, or neurological symptoms with a history of travel to or residence in endemic areas (Hawaii, Southeast Asia, Pacific Islands, Caribbean, or increasingly the southeastern United States) 1
• Key exposure history includes deliberate or inadvertent ingestion of raw or undercooked snails, slugs, freshwater prawns, or contaminated produce 1
• Symptoms are diverse and nonspecific, making diagnosis challenging without appropriate clinical suspicion 1

Diagnostic Approach in Primary Care

Initial Testing Strategy

• Peripheral blood eosinophilia: Order complete blood count with differential as the first screening test, looking for elevated eosinophil count, which is commonly present in parasitic infections 1
• Cerebrospinal fluid (CSF) analysis: If neurological symptoms are present, lumbar puncture showing eosinophilic pleocytosis (>10 eosinophils/μL or >10% eosinophils) is highly suggestive 1

Limitations of Direct Parasite Detection

• Important caveat: Unlike veterinary lungworm diagnosis where larvae can be detected in feces using the Baermann migration technique 2, 3, human Angiostrongylus cantonensis larvae typically cannot be recovered from stool because the parasite does not complete its life cycle in humans 1
• Larvae die in the central nervous system and are not shed, making copromicroscopic examination unhelpful in human cases 1

Referral for Specialized Testing

• Serology: Refer to reference laboratories or infectious disease specialists for Angiostrongylus antibody testing, though availability is limited and sensitivity/specificity data are not well-established 1
• Molecular diagnostics: PCR testing of CSF may be available through specialized laboratories or public health departments, but is not routinely accessible in primary care 1

Management Considerations

• Treatment remains controversial, with corticosteroids as the primary intervention to reduce inflammation rather than anthelmintics, which may worsen symptoms by causing parasite death and increased inflammatory response 1
• Urgent referral to infectious disease or neurology is warranted for suspected cases given the potential for fatal outcomes 1

Common Pitfalls to Avoid

• Do not assume absence of eosinophilia excludes the diagnosis, as timing of testing relative to infection may affect results 1
• Do not order stool ova and parasite examination expecting to find lungworm larvae, as this is not useful for human Angiostrongylus infection 1
• Do not delay referral while awaiting specialized testing if clinical suspicion is high, as early corticosteroid therapy may improve outcomes 1