Biology Reference
In-Depth Information
Chapter 7
Shigella
and enteroinvasive
Escherichia coli
: Paradigms for
pathogen evolution and host-
parasite interactions
Anthony T. Maurelli
Uniformed Services University, Bethesda, MD, USA
BACKGROUND
Bacillary dysentery or shigellosis is caused by members of the
Shigella
genus
and a group of pathogenic strains of
Escherichia coli
known as enteroinvasive
E. coli
(EIEC). Dysentery was the term used by Hippocrates to describe an
illness characterized by frequent passage of stools containing blood and mucus
accompanied by painful abdominal cramps. This disease has had a tremendous
impact on human society over the centuries with perhaps one of the greatest
effects being its powerful influence in military operations. Long, protracted
military campaigns and sieges almost always spawned epidemics of dysentery
and caused large numbers of military and civilian casualties. The Napoleonic
campaigns and the American Civil War were 19th century examples of the
devastation caused by dysentery. This capacity of dysentery to factor in the
outcome of nation-shaping events continues in the modern era. Soldiers were
stricken with the disease in essentially all major conflicts of the 20th century,
including both World Wars, Korea, Vietnam, and the first Gulf War. Indeed,
this ancient disease goes hand in hand with political and socio-economic strife
as dysentery continues to claim the lives of hundreds of thousands of people
living in the unsanitary conditions brought on by war and poverty. The low
infectious dose required to cause disease coupled with oral transmission of the
bacteria via fecally contaminated food and water, accounts for the spread of
dysentery caused by
Shigella
spp. in the wake of many natural (earthquakes,
floods, famine) as well as man-made (war) disasters. For example, refugees of
a recent conflict in Zaire suffered high morbidity and mortality rates brought
on by bacillary dysentery (
Kim et al., 2009
). Even apart from these special
circumstances, shigellosis remains an important disease in developed countries
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