What are the clinical signs and diagnostic approaches to suspect worm infestation in a patient with a relevant demographic and medical history, including travel history, living conditions, and previous gastrointestinal issues?

Clinical Suspicion of Worm Infestation

Suspect worm infestation in any patient presenting with eosinophilia, particularly those with travel history to tropical/subtropical regions, poor sanitation exposure, or gastrointestinal symptoms, and immediately obtain detailed travel history, stool microscopy, and consider empirical treatment based on clinical presentation. 1

Key Clinical Presentations by Syndrome

Eosinophilia as Primary Indicator

• Eosinophilia occurs in 21-33% of returning travelers and migrants asymptomatically, making it the single most important laboratory clue for helminth infection 1
• Moderate to high-grade eosinophilia (>1.5 × 10⁹/L) suggests tissue-migrating helminths and warrants immediate investigation even without symptoms 1
• Migrants typically have higher parasite burden with multiple species, while travelers show more pronounced eosinophilia due to acute immune response 1
• Eosinophilia may be transient during tissue migration phase and can resolve when parasites reach the gut lumen, potentially causing false-negative stool tests during peak eosinophilia 1

Respiratory Manifestations (Loeffler's Syndrome)

• Fever, urticaria, wheeze, dry cough, and rarely hemoptysis occurring 1-2 weeks post-exposure suggests larval migration through lungs from Ascaris, hookworm, or Strongyloides 1, 2
• Migratory pulmonary infiltrates on chest radiograph with peripheral eosinophilia is pathognomonic 1
• Larvae may be visualized in sputum or bronchoalveolar lavage, though this is rare 1

Acute Systemic Syndromes

• Katayama syndrome presents with fever, urticaria, hepatosplenomegaly, and marked eosinophilia in acute schistosomiasis, typically in travelers rather than migrants 1, 2
• This occurs during the pre-patent period when stool microscopy is still negative, requiring serological diagnosis 1

Dermatological Signs

• Larva currens presents as rapidly moving serpiginous urticarial rash (advancing several centimeters per hour), pathognomonic for Strongyloides migration 1, 2
• "Ground itch" with maculopapular rash suggests hookworm penetration through skin, followed weeks later by gastrointestinal symptoms 1

Gastrointestinal Presentations

• Nocturnal perianal pruritus, especially in children with restless sleep, is the hallmark of pinworm (Enterobius vermicularis) 1, 3, 4
• Visible worms in stool require immediate species identification: earthworm-sized white worms (15-35 cm) suggest Ascaris; flat ribbon-like segments indicate tapeworm 1, 5, 6
• Abdominal pain, diarrhea, nausea, and vomiting are non-specific but common with heavy infections 1
• Dysentery or bloody diarrhea warrants investigation for Trichuris (whipworm) in heavy infections or schistosomiasis 1

Chronic Manifestations

• Hepatosplenomegaly with portal hypertension suggests chronic schistosomiasis, more common in migrants than travelers 1
• Anemia, particularly in children, indicates chronic hookworm infection with significant blood loss 1
• Rectal prolapse in children can occur with heavy Trichuris infection 1

Critical History Elements

Travel and Exposure History

• Exact timing and location of freshwater swimming in Africa (schistosomiasis risk) 1
• Walking barefoot on soil or sand in tropical/subtropical regions (hookworm, Strongyloides) 1
• Consumption of raw or undercooked meat: beef (T. saginata), pork (T. solium), fish (various flukes) 1
• Consumption of unwashed vegetables or contaminated water (geohelminths: Ascaris, Trichuris, hookworm) 1
• Living conditions with poor sanitation or use of human waste as fertilizer 3, 7, 8

Timing Considerations

• Incubation periods vary widely: 1-2 weeks for Loeffler's syndrome, 4-12 weeks for most intestinal helminths to become patent 1
• Serological tests require 4-12 weeks post-infection to become positive, so early testing may be falsely negative 1
• Symptoms may precede positive stool microscopy by weeks during tissue migration phases 1

High-Risk Populations

• Children aged 5-14 years have highest prevalence of pinworm and geohelminths 4, 7
• Immunocompromised patients (HIV, steroids, chemotherapy, HTLV-1) are at extreme risk for Strongyloides hyperinfection syndrome 1
• Migrants from endemic areas may harbor chronic infections for years asymptomatically 1

Physical Examination Findings

Dermatological Examination

• Inspect for serpiginous urticarial tracks (larva currens) on buttocks, thighs, or trunk 1, 2
• Examine for ground itch lesions on feet in patients with barefoot exposure 1
• Look for urticaria in acute presentations like Katayama syndrome 1, 2

Abdominal Examination

• Palpate for hepatosplenomegaly suggesting chronic schistosomiasis or heavy helminth burden 1
• Assess for abdominal distension in children with heavy Ascaris or Trichuris loads 1

Perianal Examination

• Inspect perianal area in morning before bathing for visible pinworms (small white threads, 2-13 mm) 1, 4
• Look for excoriation from scratching in suspected pinworm cases 3, 4

Respiratory Examination

• Auscultate for wheezing in suspected Loeffler's syndrome 1

Diagnostic Approach Algorithm

Initial Laboratory Testing

1. Complete blood count with differential to assess eosinophil count - absolute eosinophilia >0.5 × 10⁹/L warrants investigation 1
2. Concentrated stool microscopy for ova and parasites on three consecutive days - single sample sensitivity only 50% for many helminths 1, 4
3. Stool culture for bacterial pathogens and C. difficile in patients with diarrhea to exclude superinfection 1

Specialized Testing Based on Clinical Presentation

• Cellophane tape test applied to perianal area on three consecutive mornings for suspected pinworm (90% sensitivity with three tests) 1, 9, 4
• Serology for schistosomiasis, strongyloidiasis, and filariasis in patients with appropriate exposure and eosinophilia 1
• Stool PCR offers higher sensitivity than microscopy for many helminths 1
• Chest radiograph if respiratory symptoms present to identify migratory infiltrates 1
• Abdominal ultrasound for suspected hepatosplenic schistosomiasis 1

Timing of Investigations

• Repeat stool microscopy 4-6 weeks after initial presentation if early samples negative but suspicion remains high (allows time for pre-patent period to pass) 1
• Repeat serology 4-12 weeks post-exposure if initial serology negative but clinical suspicion high 1

Critical Pitfalls to Avoid

Diagnostic Errors

• Never assume single negative stool test excludes helminth infection - three samples required for adequate sensitivity 1, 4
• Do not rely on stool examination for pinworm diagnosis - eggs are deposited perianally, not in stool 9, 4
• Recognize that eosinophilia may resolve when parasites reach gut lumen, creating false reassurance despite active infection 1
• Be aware of serological cross-reactivity: filarial serology may be positive in strongyloidiasis; Strongyloides serology may cross-react with filariasis 1

Treatment Errors

• Never treat suspected T. solium with praziquantel without first excluding neurocysticercosis - can precipitate fatal cerebral inflammation 1, 5
• Never use corticosteroids empirically for eosinophilia without excluding Strongyloides - risk of fatal hyperinfection syndrome 1
• Always screen for Strongyloides before initiating immunosuppression in patients from endemic areas 1

Population-Specific Considerations

• In migrants with long-standing eosinophilia >1.5 × 10⁹/L, assess for end-organ damage from eosinophilia itself 1
• In immunocompromised patients with Strongyloides, send both stool AND sputum for microscopy as serology may be negative in hyperinfection 1
• Consider empirical treatment with ivermectin 200 μg/kg plus albendazole 400 mg if Loeffler's syndrome present but organism unidentified 1

When to Suspect Specific Helminths

Strongyloides (Most Dangerous)

• Any patient from endemic area requiring immunosuppression must be screened regardless of symptoms 1
• Larva currens rash is pathognomonic 1, 2
• Chronic diarrhea, abdominal bloating, or unexplained eosinophilia in endemic area travelers 1

Schistosomiasis

• Any freshwater exposure in Africa (especially Lake Malawi, Lake Victoria, Nile River) 1
• Acute febrile illness with eosinophilia 4-8 weeks post-exposure (Katayama syndrome) 1, 2
• Hematuria suggests S. haematobium (genitourinary schistosomiasis) 1

Ascaris

• Visible large worms in stool or vomitus 1, 5, 6
• Loeffler's syndrome in endemic area travelers 1
• Biliary obstruction in children 1

Hookworm

• Iron-deficiency anemia disproportionate to dietary intake in endemic area residents 1
• Ground itch history with barefoot walking 1

Tapeworms

• Visible proglottids (flat segments) in stool or actively expelled per rectum 1, 5
• History of raw/undercooked beef or pork consumption 1
• For T. solium, always obtain cysticercosis serology even if asymptomatic 1