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Protozoal Microorganisms as Intestinal Parasites 39

2

The cyst is the infectious
stage and is acquired by Some trophozoites invade
the host through ingestion the wall of the colon.
of contaminated food or
water.

i = Infective Stage i d
Cyst
Source: Centers for Disease Control and Prevention (CDC)
d = Diagnostic Stage 1

3 4 5

Cyst Trophozoite

FIGURE 3-2 B. coli Life Cycle

Disease Transmission contact with humans. The parasite B. coli is commonly
an infection found in a wide group of mammals that
The infection most frequently occurs in areas where includes monkeys and pigs. In areas where pigs are han-
certain animals that harbor the organism come in dled by humans on a daily basis, the infection rate has