Giardia lamblia On the Web
American Roentgen Ray Society Images of Giardia lamblia
Giardia cell, SEM
Higher Order Classification
Eukaryota, Diplomonadida group, Diplomonadida, Hexamitidae, Giardiinae, Giardia, G. lamblia
- Giardia affects humans and animals, such as cats, dogs, cows, beavers, deer, and sheep.
- Giardia lamblia is a flagellated, microaerophilic parasite.
- The trophozoite form of G. lamblia is pear-shaped and has a unique morphology that includes two identical nuclei, a ventral disc for adhesion to the host intestine, and flagella.
- G. lamblia genome consists of 1.2 million base pairs (average GC content: 46%).
- The genome pairs are distributed across five linear chromosomes.
- Similar to other eukaryotes, each chromosome is flanked by the telomere sequence (5’TAGGG3’).
Giardia belongs among the diplomonads.
- The life cycle begins with a noninfective cyst being excreted with faeces of an infected individual. Once out in the environment, the cyst becomes infective.
- A distinguishing characteristic of the cyst is 4 nuclei and a retracted cytoplasm.
- Once ingested by a host, the trophozoite emerges to an active state of feeding and motility.
- After the feeding stage, the trophozoite undergoes asexual replication through longitudinal binary fission.
- The resulting trophozoites and cysts then pass through the digestive system in the feces.
- While the trophozoites may be found in the feces, only the cysts are capable of surviving outside of the host.
- Distinguishing features of the trophozoites are large karyosomes and lack of peripheral chromatin, giving the two nuclei a halo appearance.
Giardia lamblia infection must be differentiated from other causes of viral, bacterial, and parasitic gastroentritis.
|Organism||Age predilection||Travel History||Incubation Size (cell)||Incubation Time||History and Symptoms||Diarrhea type8||Food source||Specific consideration|
|Fever||N/V||Cramping Abd Pain||Small Bowel||Large Bowel||Inflammatory||Non-inflammatory|
|Viral||Rotavirus||<2 y||-||<102||<48 h||+||+||-||+||+||-||Mostly in day cares, most common in winter.|
|Norovirus||Any age||-||10 -103||24-48 h||+||+||+||+||+||-||Most common cause of gastroenteritis, abdominal tenderness,|
|Adenovirus||<2 y||-||105 -106||8-10 d||+||+||+||+||+||-||No seasonality|
|Astrovirus||<5 y||-||72-96 h||+||+||+||+||+||Seafood||Mostly during winter|
|Bacterial||Escherichia coli||ETEC||Any age||+||108 -1010||24 h||-||+||+||+||+||-||Causes travelers diarrhea, contains heat-labile toxins (LT) and heat-stable toxins (ST)|
|EPEC||<1 y||-||10†||6-12 h||-||+||+||+||+||Raw beef and chicken||-|
|EIEC||Any ages||-||10†||24 h||+||+||+||+||+||Hamburger meat and unpasteurized milk||Similar to shigellosis, can cause bloody diarrhea|
|EHEC||Any ages||-||10||3-4 d||-||+||+||+||+||Undercooked or raw hamburger (ground beef)||Known as E. coli O157:H7, can cause HUS/TTP.|
|EAEC||Any ages||+||1010||8-18 h||-||-||+||+||+||-||May cause prolonged or persistent diarrhea in children|
|Salmonella sp.||Any ages||+||1||6 to 72 h||+||+||+||+||+||Meats, poultry, eggs, milk and dairy products, fish, shrimp, spices, yeast, coconut, sauces, freshly prepared salad.||Can cause salmonellosis or typhoid fever.|
|Shigella sp.||Any ages||-||10 - 200||8-48 h||+||+||+||+||+||Raw foods, for example, lettuce, salads (potato, tuna, shrimp, macaroni, and chicken)||Some strains produce enterotoxin and Shiga toxin similar to those produced by E. coli O157:H7|
|Campylobacter sp.||<5 y, 15-29 y||-||104||2-5 d||+||+||+||+||+||Undercooked poultry products, unpasteurized milk and cheeses made from unpasteurized milk, vegetables, seafood and contaminated water.||May cause bacteremia, Guillain-Barré syndrome (GBS), hemolytic uremic syndrome (HUS) and recurrent colitis|
|Yersinia enterocolitica||<10 y||-||104 -106||1-11 d||+||+||+||+||+||Meats (pork, beef, lamb, etc.), oysters, fish, crabs, and raw milk.||May cause reactive arthritis; glomerulonephritis; endocarditis; erythema nodosum.|
|Clostridium perfringens||Any ages||> 106||16 h||-||-||+||+||+||Meats (especially beef and poultry), meat-containing products (e.g., gravies and stews), and Mexican foods.||Can survive high heat,|
|Vibrio cholerae||Any ages||-||106-1010||24-48 h||-||+||+||+||+||Seafoods, including molluscan shellfish (oysters, mussels, and clams), crab, lobster, shrimp, squid, and finfish.||Hypotension, tachycardia, decreased skin turgor. Rice-water stools|
|Parasites||Protozoa||Giardia lamblia||2-5 y||+||1 cyst||1-2 we||-||-||+||+||+||Contaminated water||May cause malabsorption syndrome and severe weight loss|
|Entamoeba histolytica||4-11 y||+||<10 cysts||2-4 we||-||+||+||+||+||Contaminated water and raw foods||May cause intestinal amebiasis and amebic liver abscess|
|Cryptosporidium parvum||Any ages||-||10-100 oocysts||7-10 d||+||+||+||+||+||Juices and milk||May cause copious diarrhea and dehydration in patients with AIDS especially with 180 > CD4|
|Cyclospora cayetanensis||Any ages||+||10-100 oocysts||7-10 d||-||+||+||+||+||Fresh produce, such as raspberries, basil, and several varieties of lettuce.||More common in rainy areas|
|Helminths||Trichinella spp||Any ages||-||Two viable larvae (male and female)||1-4 we||-||+||+||+||+||Undercooked meats||More common in hunters or people who eat traditionally uncooked meats|
|Taenia spp||Any ages||-||1 larva or egg||2-4 m||-||+||+||+||+||Undercooked beef and pork||Neurocysticercosis: Cysts located in the brain may be asymptomatic or seizures, increased intracranial pressure, headache.|
|Diphyllobothrium latum||Any ages||-||1 larva||15 d||-||-||-||+||+||Raw or undercooked fish.||May cause vitamin B12 deficiency|
8Small bowel diarrhea: watery, voluminous with less than 5 WBC/high power field
Large bowel diarrhea: Mucousy and/or bloody with less volume and more than 10 WBC/high power field
† It could be as high as 1000 based on patient's immunity system.
|Diverticulitis||Abdominal CT scan with oral and intravenous (IV) contrast||bowel rest, IV fluid resuscitation, and broad-spectrum antimicrobial therapy which covers anaerobic bacteria and gram-negative rods|
|Ulcerative colitis||Endoscopy||Induction of remission with mesalamine and corticosteroids followed by the administration of sulfasalazine and 6-Mercaptopurine depending on the severity of the disease.|
|Entamoeba histolytica||cysts shed with the stool||detects ameba DNA in feces||Amebic dysentery
For amebic liver abscess:
- Le Blancq SM, Kase RS, Van der Ploeg LH (1991). "Analysis of a Giardia lamblia rRNA encoding telomere with [TAGGG]n as the telomere repeat". Nucleic Acids Res. 19 (20): 5790. PMC 328996. PMID 1840670.
- "Public Health Image Library (PHIL)".
- Konvolinka CW (1994). "Acute diverticulitis under age forty". Am J Surg. 167 (6): 562–5. PMID 8209928.
- Silverberg MS, Satsangi J, Ahmad T, Arnott ID, Bernstein CN, Brant SR; et al. (2005). "Toward an integrated clinical, molecular and serological classification of inflammatory bowel disease: report of a Working Party of the 2005 Montreal World Congress of Gastroenterology". Can J Gastroenterol. 19 Suppl A: 5A–36A. PMID 16151544.
- Satsangi J, Silverberg MS, Vermeire S, Colombel JF (2006). "The Montreal classification of inflammatory bowel disease: controversies, consensus, and implications". Gut. 55 (6): 749–53. doi:10.1136/gut.2005.082909. PMC 1856208. PMID 16698746.
- Haque R, Huston CD, Hughes M, Houpt E, Petri WA (2003). "Amebiasis". N Engl J Med. 348 (16): 1565–73. doi:10.1056/NEJMra022710. PMID 12700377.