Amoebic dysentery: more than a stomach flu

Amoebic dysentery has been a recurrent agony to the medical community. It goes back to the 6th century BC with records from Assyria, Babylonia, India and Egypt. The casual agent, Entamoeba histolytica, was first observed in in Russia in 1873 by Friedrich Losch.

The lack of symptoms and diagnostic techniques, allied to the poor hygiene conditions around the world, impeded straight identification of amoebiasis patients. Only in 1969, WHO came up with a pre-definition of amoebiasis: “infection with E. histolytica, with or without clinical manifestations”. As the implication that all the strains were potentially pathogenic did not fit in the observation of asymptomatic amoebiasis, in 1993, an old theory of Emily Brumpt stating that there were two very similar species, but only one pathogenic was supported by biochemical, immunological and genetic data and WHO enriched the definition of amoebiasis with the invasive species E. histolytica and the non-invasive species E. dispar. Another morphological identical protozoa E. moshkovskii also infects humans, but little is known about it.

Despite the existence of a fairly effective drug treatment of intestinal ameobiasis symptoms and to clear the cysts housed in the colon, it is still hard to deal with further complications as liver and brain abscesses. Major efforts should be done to aware the population to the importance of hygiene and the danger of this disease.

It is estimated that it affects 10% of the world population. After malaria, schistosomiasis, and leishmaniasis, it has the fourth higher rate of protozoa-associated mortality. Developing countries show a much higher incidence rate due to poor sanitary conditions and climate features, since E. histolytica prefers humid and warm environments. In some tropical countries, antibody prevalence rates are over 50%. However, there are also records of amoebiasis in developed countries, especially around homosexual males, travelers, recent immigrants, HIV-positive individuals and institutionalized people. For instance, according to the CDC-Centers for Disease Control and Prevention, the most affected US states are California and Texas.

Amoebic Dysentery may be hard to diagnose by merely clinical evaluation. Therefore, laboratory tests are of extreme importance since the symptoms are non-specific and it is easy to confuse with bacterial dysenteries. On the other hand, the lack of fever in the majority of the patients may also lead to an incorrect non-infectious intestinal disease diagnosis. Common misdiagnoses are inflammatory bowel disease, giardiasis, irritable bowel disease, lactase deficiency, pyogenic liver abscess, cholangitis, acute hepatitis, appendicitis, pancreatitis, and liver mass.

The major outcome in intestinal dysentery research is to find out effective tools to facilitate clinical diagnosis. Although the current treatment set is fairly efficient, there are still some clinical trials to introduce new and better drugs in the market.

Currently research is trying to clarify the difference in prevalence and persistence rates seen in different parts of the globe as the present data is contradictory. Recent evolution in genomic sequencing is also been used to find any avirulent E. histolytica strains and to implement a specific diagnosis of E. histolytica.

It is understood that the primary way of fighting parasitic infections, particularly those intestinally-based, is through prevention. It is important to equalise hygiene, water supplies, and food handling patterns to reduce the contamination risk and therefore protect the population from these parasites.