Entamoeba histolytica

Test code: X0048 - Ultrasensitive qualitative detection and differentiation of Entamoeba histolytica by real time PCR.

Entamoeba histolytica is a single-celled, anaerobic parasitic protozoan (amoebozoan) that primarily infects humans and other primates, causing the disease known as amebiasis (or amoebic dysentery). This parasite is morphologically similar to non-pathogenic species like E. dispar, E. moshkovskii, and E. Bangladeshi, so that it is difficult to visually differentiate these species.

This parasite’s life cycle consists of a trophozoite stage and a cyst stage. Infection starts when mature cysts are ingested from contaminated sources. In the small intestine, these excyst to release trophozoites, which then migrate to the large intestine. Trophozoites can multiply by binary fission. They can either remain in the intestinal lumen causing asymptomatic infection and cyst passage, or invade the intestinal mucosa leading to disease. They can also spread through the bloodstream to extraintestinal sites like the liver. Both cysts and trophozoites are shed in feces, but only cysts can survive outside the body for days to weeks.

Transmission of this parasite is primarily through the fecal-oral route through ingestion of cysts in contaminated food and water. It can also transmit through sexual contact involving fecal exposure. The parasite is found worldwide, with higher prevalence in developing countries where sanitation is poor.

Most infections are asymptomatic. However, some infected people may develop invasive intestinal amebiasis (amebic colitis); symptoms can include diarrhea (often bloody), abdominal pain, weight loss, constipation, and dysentery. Complications include peritonitis, perforations, amebomas (granulomas), and extraintestinal issues like liver abscesses, pleuropulmonary abscesses, or brain abscesses.

Microscopic identification in fecal smears has low sensitivity and specificity. Because this parasite is morphologically similar to other non-pathogenic Entamoeba species, diagnosis of E. histolytica often requires other confirmation. Polymerase chain reaction (PCR) is increasingly being used to diagnose this parasitic infection due to its high specificity and sensitivity (Blessmann et al., 2002; Kebede et al., 2004).

Utilities:

• Help confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of Entamoeba histolytica infection
• Help ensure that animal groups are free of Entamoeba histolytica
• Early prevention of spread of Entamoeba histolytica between animals
• Minimize human exposure to Entamoeba histolytica

References:
Blessmann J, Buss H, Nu PA, Dinh BT, Ngo QT, Van AL, Alla MD, Jackson TF, Ravdin JI, Tannich E. Real-time PCR for detection and differentiation of Entamoeba histolytica and Entamoeba dispar in fecal samples. J Clin Microbiol. 2002 Dec;40(12):4413-7.

Specimen requirement: 0.2 ml feces, or rectal swab, or 0.2 ml soil

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time PCR

Normal range: Nondetected