Entamoeba dispar: A Rare Case of Enteritis in a Patient Living in a Nonendemic Area

Entamoeba dispar, a common noninvasive parasite, is indistinguishable in its cysts and trophozoite forms from Entamoeba histolytica, the cause of invasive amebiasis, by microscopy. To differentiate the two species seems to be a problem for laboratory diagnosis. Recent experimental studies showed that？？E. dispar can be considered pathogenic too. We present a rare case of enteritis due to E. dispar. 1. Introduction Entamoeba histolytica and Entamoeba dispar are two distinct but morphologically identical species living in the human colon [1, 2]. E. histolytica causes amebiasis. Amebiasis is one of the most common causes of death from protozoan parasitic disease, second only to malaria, with approximately 50 million cases and 100？000 deaths annually, as reported by the WHO [3] and in areas where invasive amebiasis is common; E. dispar is by far the more prevalent species [4]. Until a few years ago, several studies distinguished between infections caused by E. histolytica, with invasive intestinal and extraintestinal disease, and those by E. dispar and E. moshkovskii, which were not considered pathogenic [5]. Recent studies showed E. dispar trophozoites to produce focal lesions in experimental animal models and to have lytic activity in cultured monolayer epithelial cells [6]. In 2012 Dolabella et al. described E. dispar trophozoites from the ICB-ADO strain (zymodeme I-nonpathogenic), inoculated intrahepatically in hamsters, which produced amoebic liver abscess [7]. Antigen detection, culture, and polymerase chain reaction are employed to distinguish E. histolytica from E. dispar. We report a case of enteritis due to E. dispar. 2. Case Report An Italian 81-year-old woman suffered of abdominal pain and chronic diarrhea. She evacuated unformed stools three times a day for 10 days. She had not been hospitalized in the last year nor had she traveled to tropical countries. Blood biochemistry and liver function tests were normal, and she was serologically negative for human immunodeficiency virus (HIV). Multiple stool cultures for bacterial pathogens, including Salmonella, Shigella, and Campylobacter, enterotoxigenic and other pathogenic E. coli and C. difficile toxin A/B were negative. Stools collected for parasites were negative for ova and larvae by microscopy and for Giardia intestinalis and Cryptosporidium parvum by immunochromatographic test (CerTest Biotec S.L. Zaragoza—Spain). Entamoeba histolytica/dispar/moshkovskii cysts were detected by microscopy at wet smear preparation with a 400x phase-contrast objective (Figure 1). Figure 1: Entamoeba