Amoebiasis: Difference between revisions

Asymptomatic human infections are usually diagnosed by finding cysts shed in the stool. Various [[flotation process|flotation]] or sedimentation procedures have been developed to recover the cysts from fecal matter and stains help to visualize the isolated cysts for microscopic examination. Since cysts are not shed constantly, a minimum of three stools should be examined. In symptomatic infections, the motile form (the trophozoite) can often be seen in fresh feces. [[serology|Serological]] tests exist and most individuals (whether with symptoms or not) will test positive for the presence of [[antibody|antibodies]]. The levels of antibody are much higher in individuals with [[liver abscess]]es. Serology only becomes positive about two weeks after infection. More recent developments include a kit that detects the presence of amoeba proteins in the feces and another that detects ameba [[DNA]] in feces. These tests are not in widespread use due to their expense.

 

 

Microscopy is still by far the most widespread method of diagnosis around the world. However it is not as sensitive or accurate in diagnosis as the other tests available. It is important to distinguish the ''E. histolytica'' cyst from the cysts of nonpathogenic intestinal protozoa such as ''[[Entamoeba coli]]'' by its appearance. ''E. histolytica'' cysts have a maximum of four nuclei, while the [[commensalism|commensal]] ''Entamoeba coli'' cyst has up to 8 nuclei. Additionally, in ''E. histolytica,'' the [[endosome]] is centrally located in the nucleus, while it is usually off-center in ''Entamoeba coli.'' Finally, [[chromatoidal bodies]] in ''E. histolytica'' cysts are rounded, while they are jagged in ''Entamoeba coli''. However, other species, ''[[Entamoeba dispar]]'' and ''E. moshkovskii'', are also commensals and cannot be distinguished from ''E. histolytica'' under the microscope. As ''E. dispar'' is much more common than ''E. histolytica'' in most parts of the world this means that there is a lot of incorrect diagnosis of ''E. histolytica'' infection taking place. The WHO recommends that infections diagnosed by microscopy alone should not be treated if they are asymptomatic and there is no other reason to suspect that the infection is actually ''E. histolytica''.