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Epidemiology and Conditions Leading to Parasitic Infestations 19

resulting from a spirochetal infection, in which the infec-
tive organism is spread by insects and arachnids.
There are a number of anatomical forms of “worms”
that are known to invade the human body. Certain
intestinal organisms called flukes may cause severe dis-
ease of the gastrointestinal tract, bladder, or liver and may
also destroy large numbers of blood cells. Some parasitic
worms have the ability to fool bodies into thinking they
are normal part of the tissue or organ and the immune
system will not fight off the intruders. A number of worm-
caused infections can cause physical trauma by perforat-
ing (burrowing) into the intestines, the circulatory system,
Source: Centers for Disease Control and Prevention (CDC) forming clumps as balls or tumors, and sometimes are
the lungs, the liver, or the skin of body (Figure 2-5). They
can break down, damage, or block organs of the body by

even mistaken for cancer tumors. A number of species
are also able to travel to the brain, heart, and lungs, where
they invade the tissues of these vital organs.

Eosinophilia

in a common blood test is found in the CBC (complete
blood count), which includes a count of the percentages of
FIGURE 2-3 Edema exhibited by this African child An important clinical finding that is sometimes discovered
was brought on by nephrosis associated with malaria certain white blood cells that might show an increase in a
white blood cell called the eosinophil. Eosinophils are white
blood cells that normally comprise only a small percentage
Source: Centers for Disease Control and Prevention (CDC) toplasmic granules that stain an orange color when an acid
of up to 3 percent of the leukocytes in the blood. The eo-
sinophils have a polymorphic nucleus and pronounced cy-

stain is used. They increase significantly in many allergic
responses and during extremely serious allergic reactions
that include bronchoconstriction as often found in asthma,

FIGURE 2-4 Trichinella spiralis cyst seen embedded
in a muscle tissue specimen

and lymphatic system, and as do parasites, may invade Source: Centers for Disease Control and Prevention (CDC)
the tissues of the host. The hosts or carriers, sometimes
called vectors, are usually lice, ticks, fleas, mites, and fly-
ing insects, which then transmit the parasites to humans
and other mammals. Parasitic spirochetes are responsi-
ble for relapsing fever, infectious jaundice, Lyme disease,
sores, ulcers, Vincent’s angina (a disease that causes FIGURE 2-5 Subcutaneous emergence of a female
destruction of the gums), and Wyles disease, a condition Guinea worm