Overview
Definition:
Giardiasis is an intestinal infection caused by the protozoan parasite Giardia lamblia (also known as Giardia intestinalis or duodenalis)
Amebiasis is an intestinal infection caused by the protozoan parasite Entamoeba histolytica.
Epidemiology:
Giardiasis is one of the most common waterborne parasitic diseases worldwide, with higher prevalence in areas with poor sanitation and unsafe drinking water
Amebiasis is also globally distributed but is more endemic in tropical and subtropical regions with inadequate sanitation
In children, both are significant causes of diarrheal illness, especially in daycare settings and communities with compromised hygiene.
Clinical Significance:
Both infections can lead to acute or chronic diarrhea, malabsorption, and growth faltering in children, impacting their development and well-being
Differentiating between them is crucial as treatment regimens and potential complications vary significantly, requiring appropriate diagnostic approaches for effective pediatric care and successful DNB/NEET SS examination preparation.
Clinical Presentation
Symptoms:
Giardiasis: Abrupt onset of watery diarrhea, abdominal cramps, bloating, excessive gas, nausea, vomiting, anorexia, and foul-smelling stools
Symptoms can be intermittent
Amebiasis: Mild watery diarrhea to severe dysentery with blood and mucus in stools, abdominal pain (often crampy), fever, tenesmus
Extraintestinal amebiasis (e.g., amebic liver abscess) can present with fever, hepatomegaly, and right upper quadrant pain.
Signs:
Giardiasis: Dehydration, abdominal distension, tenderness
Poor weight gain or weight loss in chronic cases
Amebiasis: Fever, tenderness over the liver if abscess is present, signs of dehydration, severe abdominal tenderness and guarding in invasive disease.
Diagnostic Criteria:
Diagnosis is primarily based on identification of the parasite in stool samples
For Giardiasis, this involves microscopic examination for cysts or trophozoites, antigen detection assays (ELISA), or molecular methods
For Amebiasis, stool microscopy for E
histolytica cysts or trophozoites (often with characteristic ingested red blood cells), antigen detection, serology (for invasive disease), and PCR are used
Imaging (ultrasound, CT) is crucial for suspected extraintestinal amebiasis.
Diagnostic Approach
History Taking:
Key history points include travel history, recent consumption of untreated water or food, exposure to contaminated sources (e.g., daycare, swimming pools), duration and character of diarrhea (watery vs
bloody), associated symptoms like fever, vomiting, abdominal pain, and signs of malabsorption or dehydration
Ask about prior parasitic infections.
Physical Examination:
Assess hydration status carefully
Perform a thorough abdominal examination for tenderness, distension, guarding, and organomegaly (especially liver for amebiasis)
Evaluate for signs of malnutrition or growth faltering.
Investigations:
Stool microscopy for ova and parasites (O&P) is the initial test for both
multiple samples may be needed
Antigen detection tests (e.g., Giardia-specific antigen, E
histolytica antigen) are more sensitive
PCR for Giardia or E
histolytica is highly specific
For suspected invasive amebiasis, consider serological tests (e.g., indirect hemagglutination assay - IHA) and imaging of the liver
Complete blood count may show eosinophilia in Giardiasis and leukocytosis in Amebiasis.
Differential Diagnosis:
Other causes of pediatric diarrhea: bacterial gastroenteritis (Salmonella, Shigella, E
coli, Campylobacter), viral gastroenteritis (Rotavirus, Norovirus), inflammatory bowel disease, malabsorption syndromes (celiac disease, lactose intolerance), irritable bowel syndrome, and other parasitic infections (Cryptosporidiosis, Cyclospora)
Invasive amebiasis must be differentiated from pyogenic liver abscesses.
Management
Initial Management:
Primary goal is rehydration and nutritional support
Oral rehydration solution (ORS) is the mainstay for mild to moderate dehydration
Severe dehydration requires intravenous fluid resuscitation
Identify and treat nutritional deficiencies, especially in cases of chronic diarrhea or malabsorption.
Medical Management:
Giardiasis: First-line treatment is usually Tinidazole (5-10 mg/kg/day once daily for 3 days) or Metronidazole (15 mg/kg/day divided into 3 doses for 5-7 days, max 750 mg/day)
Alternative agents include Nitazoxanide (100-200 mg BID for 3 days in children >12 years or 5 mg/kg BID for 3 days in children <12 years)
Amebiasis: Asymptomatic cyst passers: Diloxanide furoate (20 mg/kg/day divided into 3 doses for 10 days) or Iodoquinol
Symptomatic intestinal amebiasis: Metronidazole (35-50 mg/kg/day divided into 3 doses for 10 days, max 2-3 g/day), followed by a luminal agent (Diloxanide furoate or Iodoquinol)
Invasive amebiasis (extraintestinal or severe intestinal): Metronidazole, followed by a luminal agent
For amebic liver abscess, drainage may be necessary along with medical therapy.
Surgical Management:
Rarely indicated for intestinal amebiasis unless complications like perforation or toxic megacolon occur
Surgical intervention may be required for large or complicated amebic liver abscesses that do not respond to medical management or have complications like rupture.
Supportive Care:
Maintain adequate fluid and electrolyte balance
Monitor for signs of dehydration and complications
Ensure appropriate nutritional intake, considering temporary lactose restriction if symptoms persist
Educate caregivers on hygiene practices to prevent transmission.
Complications
Early Complications:
Giardiasis: Severe dehydration, electrolyte imbalances, reactive arthritis (rare)
Amebiasis: Profuse bloody diarrhea, toxic megacolon, bowel perforation, peritonitis, fulminant amebic colitis
Early extraintestinal complications include amebic liver abscess, amebic lung abscess, or amebic brain abscess.
Late Complications:
Giardiasis: Chronic diarrhea, malabsorption, weight loss, failure to thrive, post-infectious irritable bowel syndrome
Amebiasis: Residual liver abscesses, fistulas, strictures, appendicitis (due to amoebomas), increased risk of colorectal cancer with chronic infections.
Prevention Strategies:
Emphasize good personal hygiene (handwashing), safe water practices (boiling, filtering, treating water), proper food handling and preparation, and effective sanitation systems
Vaccination is not available for either infection
Prompt diagnosis and treatment of infected individuals are crucial to limit spread.
Prognosis
Factors Affecting Prognosis:
Host immune status, nutritional status, severity of infection, timeliness of diagnosis and treatment, and presence of complications
Children with underlying immunocompromise or malnutrition have a poorer prognosis.
Outcomes:
With appropriate antiparasitic treatment and supportive care, most children with uncomplicated giardiasis and intestinal amebiasis recover fully
Chronic or complicated cases, especially with extraintestinal involvement, can have a prolonged recovery and may require multidisciplinary management.
Follow Up:
Follow-up is important for children with chronic symptoms, malabsorption, or failure to thrive
Repeat stool examinations may be necessary to confirm eradication
Monitor growth and development closely
Patients with amebic liver abscesses require prolonged follow-up and imaging to ensure complete resolution and rule out recurrence.
Key Points
Exam Focus:
Distinguishing clinical features and first-line treatment options for giardiasis vs
amebiasis in children
Management of asymptomatic cyst passers versus symptomatic patients in amebiasis
Recognition and initial management of amebic liver abscess
Importance of luminal agents after systemic treatment for invasive amebiasis
Role of hydration and nutrition in all pediatric diarrheal illnesses.
Clinical Pearls:
Always consider both Giardia and Entamoeba in children with persistent or recurrent diarrhea, especially with a history of travel or exposure to contaminated water
A high index of suspicion for amebiasis is warranted in endemic areas or in immunocompromised individuals
Remember that some patients with E
histolytica can be asymptomatic carriers but still excrete infectious cysts
Metronidazole is a cornerstone for amebiasis treatment but does not eradicate cysts
hence, a luminal agent is essential.
Common Mistakes:
Mistaking amebic dysentery for bacterial dysentery and using antibiotics instead of antiparasitics
Failing to treat asymptomatic E
histolytica carriers, leading to continued transmission
Inadequate treatment of amebic liver abscesses (e.g., omitting luminal agents or failing to drain)
Overlooking dehydration and nutritional deficiencies in pediatric diarrheal illnesses
Relying on a single stool O&P examination for diagnosis, as sensitivity can be low.