[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 1 Introduction
BOX 1-1
Populations at Risk for
Contracting Parasites
Individuals in underdeveloped areas and countries
Refugees
Immigrants
Visitors from foreign countries
Individuals who are immunocompromised
Individuals living in close quarters (e.g., prisons)
Children who attend day care centers
BOX 1-2 Modes of Parasite Transmission
Ingestion of contaminated food or drink (primarily water)
Hand-to-mouth transfer
Insect bite
Entry via drilling through the skin
Unprotected sexual relations
Mouth-to-mouth contact
Droplet contamination
Eye contact with infected swimming water
underdeveloped tropical and subtropical countries
such as Haiti, Guatemala, and Myanmar
(Burma) and countries on the African continent.
Increased population den sity, poor sanitation,
marginal water sources, poor public health practices,
and environmental changes affecting vector
breeding areas account for the prevalence of parasites.
The habits and customs of the people living
in these regions are also contributing factors.
The increased prevalence of global travel
likely accounts for parasitic infections being
spread to areas other than where these infections
originated. Individuals who travel to endemic
areas are at risk of contracting parasitic infections.
Refugees, immigrants, and foreign visitors
may bring parasites with them when entering a
nonendemic area.
Representative additional human populations
at risk of contracting a parasitic infection are
listed in Box 1-1. Historically, a dramatic increase
in parasite infection incidence occurred in the
homosexual population but it is now also occurring
more in the heterosexual population. More
recently, parasitic infections have become more
prevalent in underdeveloped countries, regardless
of a person’s sexual orientation.
The means whereby a parasite gains entry into
an unsuspecting host, referred to as mode of
transmission, vary by specific parasite species
and those associated with the parasites covered
in this text are summarized in Box 1-2. Consuming
contaminated food or water and hand-tomouth
transfer are common ways of transmitting
select parasites. Others require an insect (arthropod)
vector through which a parasite is passed
on to an uninfected host, most often via a blood
meal (bite). Still others will drill their way
into the body via the skin through an unprotected
bare foot or when an unsuspecting human
is swimming in contaminated water. Sexual
transmission, mouth-to-mouth contact through
kissing, droplet contamination, and eye contact
with infected swimming water also serve as
routes for parasite transmission.
Quick Quiz! 1-2
Which of the following people may be at risk for
contracting a parasitic infection? (Objective 1-5)
A. A toddler who attends an all-day preschool or day
care center
B. A 25-year-old man who lives on his own in an
apartment complex
C. A 37-year-old South American refugee
D. More than one of these: _______________
(specify)
PARASITE-HOST RELATIONSHIPS
The study of parasite-host relationships is over
100 years old. The main focus of this research
has been threefold: (1) recognition of these relationships;
(2) search for patterns of the relationships;
and (3) development of methodologies to
study these patterns. Table 1-1 lists the terms
associated with parasite-host relationships, along
with their definitions.
There are several types of parasites that may
be members of a parasite-host relationship. An