What is the screening test and treatment for Giardia (Giardiasis)?

Screening and Treatment for Giardia

The primary screening test for Giardia is stool examination, and the first-line treatment is tinidazole as a single oral dose due to its high efficacy rate of 80-100%. 1, 2

Diagnostic Testing

• Multiple stool examinations may be necessary to detect Giardia lamblia, as the organism may be shed intermittently 3
• Special stool preparations are required for proper diagnosis, including:
  • Microscopic examination of wet mounts 4
  • Permanent or fluorescent antibody stains 4
  • Enzyme immunoassay (EIA) tests for Giardia antigens 3
• Molecular methods (PCR) have become increasingly popular for diagnosis, particularly for environmental samples 4

Treatment Recommendations

First-Line Treatment

• Tinidazole is recommended as the primary treatment for giardiasis 1, 2
  • Adult dosage: 2g as a single oral dose 2
  • Pediatric dosage: 50 mg/kg as a single oral dose (FDA approved for children ≥3 years) 1, 2
  • Advantages: Single-dose regimen, high efficacy (80-100% cure rate) 2, 5

Second-Line Treatment

• Metronidazole is an effective alternative when tinidazole is not available 1, 2
  • Adult dosage: 250 mg three times daily for 5 days 2
  • Pediatric dosage: 15 mg/kg/day divided into three doses for 5 days 1, 2
  • Efficacy comparable to tinidazole but requires longer treatment course 5
  • Cure rates with metronidazole range from 76-88% depending on dosing regimen 6, 7

Other Treatment Options

• Nitazoxanide is approved for giardiasis treatment 1, 5
  • Pediatric dosage: 200 mg twice daily for children 4-11 years old 1
  • Does not have the bitter taste of nitroimidazoles 5
• Albendazole may be considered as an alternative 5, 8
  • Comparable effectiveness to metronidazole when given as 400 mg/day for 5 days 8
  • Potentially fewer side effects than metronidazole 8
• Paromomycin is recommended during pregnancy 5

Special Considerations

• For children under 3 years, consult with a pediatric specialist as tinidazole is only approved for children ≥3 years 2
• Treatment failures may require:
  • Alternative medication regimen 1
  • Consultation with infectious disease specialist 1
• Supportive care should include:
  • Adequate oral hydration, especially with diarrhea 1
  • Continuation of age-appropriate diet 1
  • Emphasis on hand washing after using bathroom and before preparing/eating food 1

Treatment Pitfalls to Avoid

• Antimotility agents (like loperamide) should not be administered to children under 18 years with acute diarrhea 1
• Do not accept treatment failure without considering reinfection, especially in endemic areas or with continued exposure 3
• Less effective drugs (quinacrine, furazolidone) should be reserved for cases refractory to first-line agents 5