Parasitology. Metazoans and Exoparasites Part II. Meatazoans. Three Classes Trematodes (flukes-flat worms) Cestodes (tape worms) Nematodes (round worms). Metazoans. Major Stages of Life Cycle Ova Adult (Mature Parasite). Metazoans. Monecious - having male and
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Metazoans and Exoparasites
Trematodes (flukes-flat worms)
Cestodes (tape worms)
Nematodes (round worms)
Major Stages of Life Cycle
Adult (Mature Parasite)
Monecious - having male and
female reproductive organs in
the same animal.
Diecious - sexually distinct;
denoting species in which
male and female genitals do
not occur in the same
Most trematodes have complex life
cycles, with larval stages parasitizing one or
more species that are different from host of
Larval stages of some medically important
species include miracidium, redia, cercaria,
Most trematodes are endoparasites.
They include several parasites that have an
enormous impact on human populations, such
as human liver flukes and the blood flukes.
causes hepatic portal
disease, very painful,
blood flukes that targets
organs that are fed by
also known as the common liver
fluke or sheep liver fluke, is a
Parasitic flatworm of the class
Platyhelminthes that infects liver
of various mammals, including
Cestoda is a class of parasitic
flatworms, commonly called
Tapeworms live in the digestive
tract of vertebrates as adults and
often in the bodies of various
animals as juveniles.
The beef tapeworm can grow
up to 40 feet long (12 m);
other species may grow to
over 100 feet (30 m).
This infection is caused by
ingestion of eggs shed in the
feces of a human tapeworm
Pigs and humans become
infected by ingesting eggs or
Humans are infected either by
ingestion of food contaminated
with feces containing eggs, or by
Hydatid worm parasitizes the
small intestine of canids as an
adult, but which has important
intermediate hosts such as
livestock and humans, where it
causes hydatid disease.
Hydatid disease is treated with
surgery, taking special care to leave
the cyst intact so new cysts do not
Nematoda , phylum consisting of
about 12,000 known species,
and many more predicted species
of worms (commonly known as
roundworms or threadworms).
Nematodes live in the soil and
other terrestrial habitats as well
as in freshwater and marine
Many are damaging parasites of
plants and animals, including
Ascaris lumbricoides –
fairly long, get together in
balls and start breeding
hook worm. Likes to
penetrate in soft skin
between toes then migrates
from there to other site in
Trichinellosis, also called
trichinosis, is caused by
eating raw or undercooked
meat of animals infected with
Infection occurs commonly in
certain wild carnivorous
(meat-eating) animals but
may also occur in domestic
Lays eggs on the anus.
Causes a very itchy bum and
These don’t really cause
They are responsible for
Insecta (6 legs) – fleas,
Arachnidia (8 legs) – ticks,
Lice are six-legged blood-sucking
parasitic insects that live near the
surface of the skin, often clinging to
the shafts of human hair.
They can travel quickly, up to 10
inches per minute, which explains
why they are so contagious.
Infestation with lice is called
“pediculosis.” In the U.S., head lice
and pubic (crab) lice are the most common forms of pediculosis.
Direct and prolonged head-to-head
contact is the usual mode of head lice
transmission; as such, lice are typically
spread between people who know each
Sharing of inanimate objects that come in
contact with the hair or scalp, such as hats,
scarves, or hairbrushes, may also cause
the spread of head lice, though this is less
Contrary to popular belief, lice cannot
jump from one head to another, and they
cannot survive for long off of the human
Pubic lice (or crab lice) are usually
transmitted sexually and are among
the most contagious of STDs.
Condoms do not prevent the spread
of pubic lice.
Nonsexual transmission of public lice
is also possible.
Body louse claw are adapted for round hair
common with body and head hair.
Crab louse claw is adapted for oval shaped
hair common with pubic hair and eye
Bed bugs, Cimex lectularius , are
blood feeding parasites of humans,
chickens, bats and occasionally
domesticated animals (Usinger
Bed bugs are suspected carriers of
leprosy, oriental sore, Q-fever, and
brucellosis (Krueger 2000) but have
never been implicated in the spread
of disease to humans (Dolling 1991).
Ticks are blood-feeding
parasites that are often found in
tall grass and shrubs where they
will wait to attach to a passing
A tick will attach itself to its host
by inserting its chelicerae
(cutting mandibles) and hypostome
(feeding tube) into the skin.
The hypostome is covered with
recurved teeth and serves as an anchor.
Scabies is a contagious
ectoparasite skin infestation
characterized by superficial
burrows and intense pruritus
It is caused by the mite Sarcoptes
scabiei. The word scabies itself is
derived from the Latin word for
Scabies is highly contagious and can
be spread by scratching, picking up
the mites under the fingernails and
simply touching another person's
They can also be spread onto other
objects like keyboards, toilets,
clothing, towels, bedding, furniture,
and anything else that the mite may
be rubbed off onto, especially if a
person is heavily infested.
The parasite can survive up to 14
days away from a host, but often do
not survive longer than two or three
days away from human skin.[
Insects and arachnids are
much more important as
vectors that as parasites.
Mosquitoes transmit malaria
Ticks transmit Lyme’s disease
Fleas transmit plague