This document provides an overview of parasitic infections, including key terms, types of parasites, how parasites cause disease, and examples of specific parasitic infections. It discusses parasitic protozoa and helminths, how their infections are diagnosed and transmitted, and examples of infections in different parts of the body like the eyes, gastrointestinal tract, and circulatory system. It also covers the life cycles of helminths and medically important arthropods that can transmit parasitic diseases.

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chapter 21 parasitic infections
Science Biology Parasitology
Terms in this set (30)
parasitology study of parasites
parasitism
symbiotic relationship that is of benefit to one part
and detrimental to the other (host)
ectoparasites live on the outside of the hosts body
endoparasites live inside the host
definitive host
if the parasite has more than one host, it is the one
that harbors the adult or sexual stage of the parasite
intermediate host host that harbors the larval or asexual stage
accidental host
one that can serve as the host, but is not the usual
host in the parasites' life cycle
dead-end host
one in which the parasite cannot continue its life
cycle
facultative parasite
an organism that can be parasitic, but does not have
to live as a parasite; is capable of an independent
life
chapter 21 parasitic infections Study

2. obligate parasite
no choice, must inhabit a host or hosts
-most parasites are obligate
how parasites cause disease depends on number of parasites present
toxins or enzymes cause..
physical damage to tissues and organs or occlusion
of blood vessels an other tubular structures
the host immune response
can..
cause more injury than the parasites themselves
parasitic protozoa
-most are unicellular
-classified by mode of locomotion
-not all are parasitic
how has parasitic protozoal
infections diagnosed
by microscopic examination of body fluids, tissue
specimens, or feces
Leishmaniasis
protozoal infection of the skin
-transmitted via the bite of an infected sand fly
-3 forms: cutaneous, mucocutaneous, visceral
protozoal infections of the
eyes
eye
amebic conjunctivitis, ketaconjunctivitis,
toxoplasmosis
toxoplasmosis
caused by Toxoplasma gondii
-can involve the CNS, lungs, muscles, or heart, and
eyes
eye
-serious fetal infections
-acquired by ingesting cysts or oocysts from feces
chapter 21 parasitic infections Study

3. protozoal infections of the GI
tract
-Entamoeba hisolytica
-Balantidium coli
-Cryptosporidim parvum
-Cyclospora cavetanensis
-Giardia lamblia
Giardia lamblia
the trophozoite resembles a face; the nuclei look
like eyes; it has been described as resembling an
eye
owl face, a clown face, and an old man with glasses
Trichomoniasis
protozoal infection of the genitourinary tract
-caused by Trichomonas vaginalis, a flagellate
-a sexually transmitted disease
-usually symptomatic in women only
-T. vaginalis causes about 1/3 of cases in US
protozoal infections of the
circulatory system
-african trypanosomiasis
-american trypanosomiasis (Chagas' disease)
-Malaria
Primary Amebic
Meningoencephalitis
protozoal infection of the CNS, often fatal
-most caused by Naegleria fowleri
-persons become infected by swimming in ameba-
contaminated water
-after it colonizes the nasal tissues, they invade the
brain and meninges by traveling along olfactory
nerves
Helminths
parasitic worm
2 divisions: round worms (nematodes) and flat
worms (Platyhelminthes)
flatworms divisions tapeworms (cestodes) and flukes (trematodes)
chapter 21 parasitic infections Study

4. helminth life cycle
1. egg
2. larva
3. adult worm
helminth infection are acquired
by
ingesting the larvae stage
-in some, larvae enter by penetration of the skin
Helminth infections of the GI
tract
-Ascariasis: Ascaris lumbricoides (N)
-Hookworm infection: Ancylostoma duodenal or
Necator americanus (N)
-Pinworm: Enterobius vermicularis (N)
-Whipworm: Trichuris trichiura (N)
-Strongyloidiasis: Strongyloides stercoralis (N)
-Beef tapeworm: Taenia saginata (C)
-Dog tapeworm: Dipylidium canium (C)
medically important
anthropoids (3 classes)
1. insects (lice, fleas, mosquitoes)
2. arachnids (mites and ticks)
3. crustaceans (crabs, crayfish, Cyclops species)
Arthropods can...
cause, be hosts, or be vectors in the transmission of
certain infectious diseases
chapter 21 parasitic infections Study