Video: Killer amoeba chews on living gut cells

Nasty gnawer (Image: CDC-Moser/Phanie/REX)

It’s a killer amoeba. More than 100,000 people die each year from amoebic dysentery, mostly in developing countries where sanitation is poor. But only 10 per cent of people who carry the amoebic parasite ever show symptoms, leaving scientists mystified as to how it preys on the body.

Now Katherine Ralston and William Petri of the University of Virginia, Charlottesville, have found that Entamoeba histolytica has a unique – and gruesome – strategy. It gnaws away at the gut wall, ripping and ingesting chunks off living cells, killing them in the process.


It’s “purely malevolent”, says Michael Blennerhassett of Queen’s University in Ontario, Canada, because the amoeba aren’t interested in the cells once they’re dead. This suggests they don’t need to eat them for the nutrients they contain, says Blennerhasset, who was not involved in the study. “This is a previously unsuspected method of attack.”

Ralston and Petri labelled mouse intestines using fluorescent dyes, in order to follow their fate. Most amoebas kill cells by attaching themselves to them, but E. histolytica tears at its targets. “We saw that the amoeba ingested bites of the fluorescent membranes of the intestinal cells,” says Ralston. “They are impressively ravenous.”

If E. histolytica is constantly grazing throughout the gut, it may be able to lurk inside a host for years without wreaking enough damage to cause inflammation or disease.

“The way it samples bits and pieces of the cell suggests this may be going on all the time, and only when a certain balance is broken does the disease set in,” says Kris Chadee, a microbiologist from the University of Calgary in Alberta, Canada. “The parasite needs to attach to the cell to rip off little pieces, so if you could get blocking antibodies in the place where it attaches, that would be a potential target for drug development.”

Journal reference: Nature, DOI: 10.1038/nature13242