Parasit Amoba 1r6l2

Amobiasis

Introduction  Several

protozoan species in the genus Entamoeba colonize humans, but not all of them are associated with disease.  Entamoeba histolytica is well recognized as a pathogenic ameba, associated with intestinal and extraintestinal infections.  The other species are important because they may be confused with E. histolytica in diagnostic investigations

Geographic Distribution:  Worldwide,

with higher incidence of amebiasis in developing countries.  In industrialized countries, risk groups include:  Male

homosexuals  Travelers  Recent immigrants  Institutionalized populations

Life cycle 1. 2.

3. 4. 5.

Cysts and trophozoites are ed in feces Cysts are typically found in formed stool, whereas trophozoites are typically found in diarrheal stool. Infection by entamoeba histolytica occurs by ingestion of mature cysts In fecally contaminated food, water, or hands. Excystation occurs in the small intestine and trophozoites are released, Which migrate to the large intestine. The trophozoites multiply by binary fission and produce cysts

eC E. H ycle of isto lyt i ca  Because

of the protection conferred by their walls, the cysts can survive days to weeks in the external environment and are responsible for transmission.  Trophozoites ed in the stool are rapidly destroyed once outside the body, and if ingested would not survive exposure to the gastric environment.  In many cases, the trophozoites remain confined to the intestinal lumen

1.

2.

3.

Noninvasive infection of individuals who are asymptomatic carriers, ing cysts in their stool. In some patients the trophozoites invade the intestinal mucosa (intestinal disease). Through the bloodstream, extraintestinal sites such as the liver, brain, and lungs (extraintestinal disease), with resultant pathologic manifestations.

f o e l c y Life C a c i t y l o t s E. H i

Clinical Features: 1. 2.

A wide spectrum, from asymptomatic infection ("luminal amebiasis"), Invasive intestinal amebiasis: 1. 2. 3. 4. 5.

3.

Dysentery Colitis Appendicitis toxic megacolon amebomas),

Invasive extraintestinal amebiasis 1. 2. 3. 4. 5.

liver abscess Peritonitis pleuropulmonary abscess cutaneous genital amebic lesions

Laboratory Diagnosis:  Differentiation

is possible, but not always easy, based on morphologic characteristics of the cysts and trophozoites.  The nonpathogenic Entamoeba dispar, however, is morphologically identical to E. histolytica, E. polecki and differentiation must be based on isoenzymatic or immunologic analysis.

Laboratory Diagnosis:  Microscopic

identification of cysts and trophozoites in the stool is the common method for diagnosing E. histolytica.  This can be accomplished using:  Fresh

stool: wet mounts and permanently stained preparations (e.g., trichrome).  Concentrates from fresh stool: wet mounts, with or without iodine stain, and permanently stained preparations (e.g., trichrome). Concentration procedures, however, are not useful for demonstrating trophozoites.  In addition, E. histolytica trophozoites can also be identified in aspirates or biopsy samples obtained during colonoscopy or surgery

Diagnostic findings: 1. 2. 3. 4. 5.

Microscopy Immunodiagnosis Molecular methods for discriminating between E. histolytica and E. dispar Morphologic comparison with other intestinal parasites Bench aid for E. histolytica

Treatment: 1.

For asymptomatic infections: 1. 2. 3.

2.

Iodoquinol Paromomycin Diloxanide furoate (not commercially available in the U.S.) are the drugs of choice.

For symptomatic intestinal disease, or extraintestinal, infections (e.g., hepatic abscess), the drugs of choice are; 1. 2.

Metronidazole or tinidazole Immediately followed by treatment with iodoquinol, paromomycin, or diloxanide furoate.

Giardiasis

Causal Agent:  Giardia

intestinalis is a protozoan flagellate (Diplomonadida).  This protozoan was initially named Cercomonas intestinalis by Lambl in 1859 and renamed Giardia lamblia by Stiles in 1915, in honor of Professor A. Giard of Paris and Dr. F. Lambl of Prague.  However, many consider the name, Giardia intestinalis, to be the correct name for this protozoan. The International Commission on Zoological Nomenclature is reviewing this issue.

Life Cycle:

Life Cycle:

Life Cycle: 1.

2.

3.

Cysts are resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the feces (diagnostic stages) The cysts are hardy and can survive several months in cold water. Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites) In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites)

Life Cycle: 4.

5.

Trophozoites multiply by longitudinal binary fission, remaining in the lumen of the proximal small bowel where they can be free or attached to the mucosa by a ventral sucking disk Encystation occurs as the parasites transit toward the colon. The cyst is the stage found most commonly in nondiarrheal feces

Geographic Distribution: 

Worldwide, more prevalent in warm climates, and in children.

Clinical Features: 1. 2.

3.

The spectrum varies from asymptomatic carriage to severe diarrhea and malabsorption. Acute giardiasis develops after an incubation period of 1 to 14 days (average of 7 days) and usually lasts 1 to 3 weeks. Symptoms include: 1. 2. 3. 4.

4.

Diarrhea Abdominal pain Bloating Nausea, and vomiting.

In chronic giardiasis the symptoms are recurrent and malabsorption and debilitation may occur.

Laboratory Diagnosis:

1.

2. 3.

4.

Giardiasis is diagnosed by the identification of cysts or trophozoites in the feces, using direct mounts as well as concentration procedures. Repeated samplings may be necessary. In addition, samples of duodenal fluid (e.g., Enterotest) or duodenal biopsy may demonstrate trophozoites. Alternate methods for detection include antigen detection tests by enzyme immunoassays, and detection of parasites by immunofluorescence.

Treatment

1.

2.

Several prescription drugs are available to treat giardiasis including metronidazole and tinidazole. Nitazoxanide has provided some encouraging results in the management of giardiasis in children.