Entamoeba moshkovskii is associated with diarrhea in infants and causes diarrhea and colitis in mice

Abstract

Background: Entamoeba moshkovskii is prevalent in developing countries and morphologically indistinguishable from pathogenic Entamoeba histolytica and nonpathogenic Entamoeba dispar. It is not known if E. moshkovskii is pathogenic.

Methods: Mice were intracecally challenged with the trophozoites of each Entamoeba spp. to test the ability to cause diarrhea, and infants in Bangladesh were prospectively observed to see if newly acquired E. moshkovskii infection was associated with diarrhea.

Results: E. moshkovskii and E. histolytica caused diarrhea and weight loss in susceptible mice. E. dispar infected none of the mouse strains tested. In Mirpur, Dhaka, Bangladesh, E. moshkovskii, E. histolytica, and E. dispar were identified in 42 (2.95%), 66 (4.63%), and 5 (0.35%), respectively, of 1426 diarrheal episodes in 385 children followed prospectively from birth to one year of age. Diarrhea occurred temporally with acquisition of a new E. moshkovskii infection: in the 2 months preceding E. moshkvskii-associated diarrhea, 86% (36 of 42) of monthly surveillance stool samples were negative for E. moshkovskii.

Conclusions: E. moshkovskii was found to be pathogenic in mice. In children, the acquisition of E. moshkovskii infection was associated with diarrhea. These data are consistent with E. moshkovskii causing disease, indicating that it is important to reexamine its pathogenicity.

Figure 1.

Entamoeba moshkovskii induced intestinal symptoms and weight loss in CBA/J mice. CBA/J mice were intracecally inoculated with 1 × 10⁶ trophozoites of E. moshkovskii. After infection, diarrhea, colitis, and weight loss were monitored. Normal (A), loose (B), and bloody feces (C) were observed as was indicated in the results. Amoebae were observed in the lumen of the ceca in successfully infected mice (D). Macroscopic and histopathological observations of ceca in mice exhibited bloody diarrhea were shown in panels E and F. Changes in body weight were monitored in successfully infected 15 mice per group (G), in which CBA/J mice were intracecally inoculated with 1 × 10⁶ trophozoites of Entamoeba histolytica (solid squares), E. moshkovskii (solid circles), or medium alone (open diamonds). The study was repeated 3 times with similar results. *P < 1.0 × 10⁻⁶, **P < 1.0 × 10⁻⁵ and ***P < 1.0 × 10⁻⁴ compared with sham-operated mice (Mann–Whitney U test).

Figure 2.

Entamoeba moshkovskii was expelled within 2 weeks in CBA/J Mice. CBA/J (open circles) and C57BL/6 (solid circles) mice were intracecally inoculated with 1 × 10⁶ trophozoites of Entamoeba histolytica (A) or Entamoeba moshkovskii (B). Time course of each Entamoeba spp. infection was then monitored by detection of the parasites in stool by culture and polymerase chain reaction (PCR).