Giardiasis Clinical Presentation

Updated: Jan 30, 2023
  • Author: Hisham Nazer, MBBCh, FRCP, DTM&H; Chief Editor: Burt Cagir, MD, FACS  more...
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Clinical signs and symptoms of giardiasis include the following [8, 9, 18] :

  • Diarrhea

  • Malaise, weakness

  • Abdominal distention

  • Flatulence

  • Abdominal cramps

  • Nausea

  • Malodorous, greasy stools

  • Anorexia

  • Weight loss

  • Vomiting

  • Low-grade fever (infrequent)

  • Various neurologic symptoms (eg, irritability, sleep disorder, mental depression, neurasthenia)

  • Urticaria

The nature of the overall clinical manifestations in affected patients is influenced by numerous factors, including the parasite load, virulence of the isolate, and the host immune response.

Diarrhea is the most common symptom of acute Giardia infection, occurring in 90% of symptomatic subjects. Abdominal cramping, bloating, and flatulence occur in 70-75% of symptomatic patients.

Symptoms of chronic infection include chronic diarrhea, malaise, nausea, and anorexia. Weight loss, as extensive as 10-15 pounds in an adult, occurs in approximately 66% of symptomatic patients. Chronic sporadic diarrhea may continue for months. Postinfection lactase deficiency also is a common finding, occurring in 2-40% of cases.

Extraintestinal manifestations are rare and include allergic manifestations such as urticaria, erythema multiforme, bronchospasm, reactive arthritis, and biliary tract disease. The etiology of such extraintestinal symptoms is likely a result of host immune system activation and cross-reactivity/molecular mimicry.

Gastrointestinal manifestations

A small number of persons develop abrupt onset of explosive, watery diarrhea, abdominal cramps, foul flatus, vomiting, fever, and malaise; these symptoms last 3-4 days before transition into the more common subacute syndrome. Most patients experience a more insidious onset of symptoms, which are recurrent or resistant.

Stools become malodorous, mushy, and greasy. Watery diarrhea may alternate with soft stools or even constipation. Upper GI symptoms, often exacerbated by eating, accompany stool changes or may be present in the absence of soft stools. These include upper and midabdominal cramping, nausea, early satiety, bloating, substernal burning, and acid indigestion.

Constitutional symptoms

Anorexia, fatigue, malaise, and weight loss are common. Weight loss occurs in more than 50% of patients and averages 10 pounds.

Chronic illness may occur. Adults may present with long-standing malabsorption syndrome and children, with failure to thrive.


Physical Examination

Physical examination does not contribute to the diagnosis of giardiasis. Weight loss may be evident, but no known unique physical findings are attributable to giardiasis.

On abdominal examination, patients may have nonspecific tenderness without evidence of peritoneal irritation. Rectal examination should reveal heme-negative stools. In severe cases, evidence of dehydration or wasting may be present.