Giardiasis (Giardia Lambia)- Symptoms, Treatment



Giardiasis, a common intestinal infection caused by the parasite Giardia lamblia, affects millions worldwide.

What is Giardiasis?

Giardiasis is an infectious disease primarily affecting the small intestine. It is caused by the microscopic parasite Giardia lamblia, also known as Giardia intestinalis or Giardia duodenalis. Giardia lamblia is a flagellated protozoan parasite belonging to the genus Giardia. It exists in two forms: cysts, which are the dormant, infective stage, and trophozoites, which are the active, multiplying stage.


The main cause of giardiasis is the ingestion of Giardia cysts through contaminated food or water. Cysts can survive in various environments and are resistant to chlorine disinfection, making them prevalent in untreated or inadequately treated water sources. Poor hygiene, including inadequate handwashing, also contributes to transmission.

Signs and Symptoms:

Giardiasis, caused by the parasite Giardia lamblia, presents with a variety of signs and symptoms that can range from mild to severe. Let’s see both acute and long term giardiasis symptoms:

Acute Giardiasis Symptoms:

During the acute phase of giardiasis, which typically lasts for 1 to 3 weeks after infection, individuals may experience the following symptoms:

1. Diarrhea:
Watery, foul-smelling diarrhea is a hallmark symptom of acute giardiasis. The frequency and severity of diarrhea may vary but often persist for several days or weeks.

2. Abdominal Cramps:
Abdominal cramps and discomfort are common during the acute phase of giardiasis. These cramps may range from mild to severe and are often accompanied by bloating.

3. Bloating and Gas:
Bloating, characterized by a feeling of fullness or tightness in the abdomen, is prevalent in acute giardiasis. Excessive gas (flatulence) may also contribute to discomfort.

4. Nausea:
Nausea and occasional vomiting are common symptoms during the acute phase of giardiasis. Individuals may experience a reduced appetite and food aversions.

5. Fatigue:
Fatigue is a common complaint during acute giardiasis. The combination of dehydration, nutrient malabsorption, and the body’s immune response to the infection can result in feelings of weakness and exhaustion.

6. Weight Loss:
Unintentional weight loss may occur during acute giardiasis, particularly in cases of severe or prolonged diarrhea. Malabsorption of nutrients can lead to reduced calorie absorption and subsequent weight loss.

Long-Term Giardiasis Symptoms:

In some cases, giardiasis may persist beyond the acute phase, leading to long-term symptoms that can last for weeks or months. These may include:

1. Chronic Diarrhea:
Some individuals may continue to experience diarrhea even after the acute phase has resolved. Chronic diarrhea can contribute to ongoing discomfort and dehydration.

2. Abdominal Discomfort:
Chronic abdominal discomfort, including bloating and cramping, may persist in individuals with long-term giardiasis. This can affect quality of life and daily activities.

3. Malabsorption Issues:
Persistent giardiasis can lead to malabsorption of nutrients, resulting in deficiencies and related symptoms such as weight loss, fatigue, and weakness.

4. Recurrent Infections:
In some cases, individuals may experience recurrent episodes of giardiasis, especially if underlying risk factors such as poor sanitation or untreated water sources are not addressed.

Life Cycle of Giardia:

To know Giardiasis nicely and also to prevent the infection, we must understand the life cycle of giardia lambia.

Life cycle of giardia lambia - Giardiasis - Modern HealthMe, Healthline, WebMD
Life cycle of giardia lambia

1. Cyst Stage:

The life cycle of Giardia begins with the cyst stage, which is the dormant, environmentally resistant form of the parasite. Cysts are passed in the feces of an infected individual and can survive in various environments, including water and soil, for extended periods. Giardia cysts are resistant to chlorine disinfection, making them prevalent in untreated or inadequately treated water sources.

2. Ingestion:

Upon ingestion of contaminated food or water, Giardia cysts reach the small intestine of the host. This typically occurs through the consumption of untreated water from lakes, streams, or wells, or the ingestion of food contaminated with Giardia cysts.

3. Excystation:

Once inside the host’s small intestine, the cysts undergo excystation, a process in which they transform into the active, motile form of the parasite known as trophozoites. This transformation is triggered by the acidic environment of the stomach and the presence of bile in the small intestine.

4. Trophozoite Stage:

Trophozoites are the active, multiplying stage of Giardia lamblia. These pear-shaped organisms possess flagella, which they use for movement and attachment to the intestinal wall. Trophozoites reproduce by binary fission, rapidly multiplying and colonizing the surface of the small intestine.

5. Attachment and Colonization:

Once attached to the intestinal wall, trophozoites interfere with nutrient absorption and cause damage to the epithelial cells lining the intestine. This disruption leads to the characteristic symptoms of giardiasis, including diarrhea, abdominal cramps, and bloating.

6. Encystation:

As the infection progresses, some trophozoites undergo encystation, transforming back into cysts. Encystation typically occurs in the lower part of the small intestine as trophozoites transit towards the colon. Cysts are then excreted in the feces, completing the life cycle of Giardia lamblia.

Risk Factors

Several factors increase the risk of contracting giardiasis, including:

  1. Drinking untreated water from lakes, streams, or wells
  2. Consuming food contaminated with Giardia cysts
  3. Engaging in activities such as camping or hiking where access to clean water may be limited
  4. Living in or traveling to areas with poor sanitation and hygiene practices

Diagnosis of Giardiasis

Accurate diagnosis of giardiasis is crucial for initiating timely treatment and preventing the spread of the infection. Several methods are used to diagnose this intestinal illness.

1. Stool Sample Analysis:

  • Microscopic examination of stool samples is a common and effective method for diagnosing giardiasis.
  • Laboratory technicians look for the presence of Giardia cysts or trophozoites in the stool under a microscope.
  • Concentration techniques, such as using zinc sulfate flotation or formalin-ethyl acetate sedimentation, may enhance the detection of Giardia organisms.

2. Antigen Tests:

  • Rapid diagnostic tests (RDTs) that detect Giardia antigens in stool samples are available.
  • These tests are often used in clinical settings for quick and convenient diagnosis, providing results within a short period, usually less than an hour.
  • Antigen tests offer high sensitivity and specificity, making them valuable tools for diagnosing giardiasis.

3. Polymerase Chain Reaction (PCR):

  • PCR assays can detect Giardia DNA in stool samples with high sensitivity and specificity.
  • This molecular diagnostic technique amplifies specific DNA sequences of the parasite, allowing for the sensitive detection of Giardia lamblia even in low concentrations.
  • PCR is particularly useful in cases where traditional microscopy may yield false-negative results.

4. Serological Tests:

  • Serological tests, such as enzyme-linked immunosorbent assays (ELISA) or indirect fluorescent antibody (IFA) tests, detect antibodies produced by the host’s immune system in response to Giardia infection.
  • While serological tests can indicate past or recent exposure to Giardia lamblia, they are not routinely used for diagnosing acute giardiasis due to the time delay in antibody production.

5. Duodenal Aspiration:

  • In some cases, especially when other diagnostic methods have been inconclusive, healthcare providers may perform a duodenal aspiration to obtain fluid from the upper part of the small intestine.
  • The fluid sample is then examined under a microscope for the presence of Giardia trophozoites.
  • Duodenal aspiration is an invasive procedure and is typically reserved for specialized cases.

Giardiasis Treatment:

Treating giardiasis aims to eliminate the parasite Giardia lamblia from the body and alleviate associated symptoms. In addition to specific medications, supportive treatments play a crucial role in managing this intestinal infection.

1. Antiparasitic Medications:

  • Metronidazole (Flagyl): This is the most commonly prescribed medication for giardiasis. It disrupts the DNA of the Giardia parasite, leading to its death.
  • Tinidazole (Tindamax): Similar to metronidazole, tinidazole is effective in treating giardiasis and is preferred for its shorter treatment duration.
  • Nitazoxanide (Alinia): Nitazoxanide interferes with the energy metabolism of Giardia parasites, causing their death.
  • Paromomycin: This antibiotic inhibits protein synthesis in Giardia parasites and is used in cases of metronidazole-resistant infections.

2. Supportive Treatment:

  • Rehydration: Diarrhea and vomiting associated with giardiasis can lead to dehydration. Oral rehydration solutions containing electrolytes and fluids can help replenish lost fluids and prevent dehydration. In severe cases, intravenous fluids may be necessary.
  • Nutritional Support: Malabsorption of nutrients due to giardiasis can lead to weight loss and nutritional deficiencies. Consuming easily digestible foods and drinks, such as broth, bananas, rice, and oral nutritional supplements, can help maintain adequate nutrition during the recovery period.
  • Probiotics: Probiotics, such as Lactobacillus and Saccharomyces boulardii, may help restore the balance of beneficial bacteria in the gut and alleviate gastrointestinal symptoms.
  • Symptomatic Relief: Over-the-counter medications, such as anti-diarrheals (e.g., loperamide) and anti-nausea medications (e.g., ondansetron), may provide symptomatic relief and improve comfort during the acute phase of giardiasis.

3. Hygiene and Prevention:

  • Hand Hygiene: Proper handwashing with soap and water after using the bathroom and before handling food is essential for preventing the spread of giardiasis.
  • Water Treatment: Boiling, filtering, or chemically treating water from potentially contaminated sources can help reduce the risk of giardiasis transmission.
  • Food Safety: Practicing safe food handling and preparation techniques, such as washing fruits and vegetables thoroughly and cooking food to appropriate temperatures, can minimize the risk of ingesting Giardia cysts.


While giardiasis often resolves without complications, prolonged or severe cases can lead to:

  1. Dehydration
  2. Malabsorption
  3. Weight loss
  4. Failure to thrive in children

Prompt diagnosis and treatment are essential to prevent complications and promote recovery.


Giardiasis, caused by the Giardia lamblia parasite, is a prevalent intestinal infection with significant global impact.

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