106
Protozoa
Legionella
were the first bacteria shown to infect and grow parasitically
within protist hosts commonly found in buildingwater systems and then
also to incidentally infect peopleexposed tobuilding systemwater.The life
cycleof
Legionella
is: 1)Amoebae grazeonbiofilm consumingbacteria for
foodbut are2) infectedby
Legionella
which, 3) growparasiticallyand then
4) overwhelm the protozoan host cell, differentiate into motile cells and
5) cause lysis of the host cell releasing hundreds or thousands of infective
progeny in searchof new amoeba to infect.
Today, we know thatmany other opportunisticwaterborne pathogens
arealsoparasitictoprotozoaandsomeofthemarealsopathogenictopeople
(Table 1). Some of these pathogens are known tobecomemore virulent to
people after growth inside their amoebichosts.
