Symptoms of Giardia lamblia Infection
Giardia lamblia infection characteristically presents with diarrhea (watery, nonbloody), abdominal cramps, bloating, flatulence, and weight loss or malabsorption, though many infected individuals remain completely asymptomatic. 1
Primary Clinical Manifestations
The hallmark symptoms include:
- Diarrhea without blood - the most common presenting symptom, typically watery in nature, distinguishing it from bacterial dysentery 2, 3, 4
- Abdominal cramps and pain - often described as cramping discomfort in the abdomen 1, 2, 4
- Bloating and excessive flatulence - prominent gastrointestinal distress 1, 2, 4
- Weight loss or malabsorption - particularly with chronic infection, can lead to failure to thrive in children 1, 2, 3
Additional Symptoms
Less frequent but important manifestations include:
- Nausea and anorexia 5
- General malaise - may be a presenting feature, especially in adults 5
- Foul-smelling diarrhea - characteristic of the infection 6
Disease Course
The infection typically lasts 2-6 weeks but can become chronic and may recur even after treatment. 2 The clinical presentation resembles functional diarrhea or diarrhea-predominant irritable bowel syndrome. 2
Asymptomatic Infection
A critical caveat is that many infected persons remain completely asymptomatic despite harboring the parasite. 1, 3 This makes epidemiologic control challenging, as asymptomatic carriers can transmit infection.
Special Populations
- Immunocompromised patients (especially those with HIV) may experience more severe and prolonged symptoms 2
- Children may present with failure to thrive and chronic malabsorption 3
- Travelers with symptoms persisting beyond 14 days should raise specific suspicion for giardiasis 2
Diagnostic Considerations
Symptoms alone cannot reliably distinguish giardiasis from other causes of diarrhea, necessitating laboratory confirmation. 2 The absence of bloody diarrhea helps differentiate it from invasive bacterial pathogens, as Giardia does not invade the bowel wall. 4, 7