Download Lecture 9 Roundworms - NGHS

Pseudocoelomate Animals
• body cavity present but incompletely
lined with mesoderm
• body cavity is fluid filled and acts like
a hydrostatic skeleton
• complete digestive tract with
2 openings
What is a Roundworm?
• Widely distributed - live in soil, saltwater
and freshwater environments
• Most are parasitic
• Smaller than tapeworms with a thick
outer covering that keeps them from
being digested
• Tapered at both ends
Phylum Nematoda - the Roundworms
•
•
smooth, long, tubular body
move with longitudinal muscles in body
wall
• dioecious
• fluid filled pseudocoel – hydrostatic
skeleton
Long, smooth and tubular
• rigid cuticle covering body
• paired nerve cords – dorsal and
ventral sides
• free
living and parasitic worms are in
the phylum
•
15,000 species have been named; estimated
500,000 species exist
More than half a million types of round
worms exist in the world.
•
– large human roundworm
• Southeastern US – more common
• Intestinal worm – 30 cm long
• eggs are in human feces and can
directly infect another person via food
• larvae develop and are carried by
the blood to the lungs –
cough/swallow
Ascaris
Can cause pneumonia and intestinal blockage
• Fully embryonated
eggs are swallowed
and L2 hatches in the
stomach and
penetrate stomach or
duodenal mucosa
• Larvae enter blood
stream and leave
through alveoli into
lung
• Larvae molt several
times in the lungs
L3/L4 move up and
get swallowed
• 2-3 months after
infection the adult
worms start laying
eggs (200,000 daily)
• Eggs are shed with
the feces and
embryonate within 2-3
weeks
Female posterior
Ascaris
Male posterior
characteristic hooked
end
dioecious
Female vs. Males
Females are larger
than males
They can produce
200000 eggs a
day.
Ascaris female x.s.
Ascaris male x.s.
Ascaris Dissection
Ascaris Dissection 2
Larval stage forms calcified cysts
in muscle of host ( human or pig/bear )
Trichinosis –
contracted from
undercooked infected
pork
Dirofliaria immitis
• a parasitic nematode that can kill your dog
• ingested worms travel to
intestines,
• then to lungs in bloodstream
• worms are coughed up and
swallowed
• and become adult worms in
intestines
Common in
southern states
•larvae hatch in soil and penetrate
bare skin
•adult worms live in intestines and
suck blood
•eggs leave in human wastes
•larvae hatch in soil and penetrate
bare skin
Hookworm
mouth
hooks
• Adult worms live in the small
intestine and female lay 510000 eggs a day over 5 years
• Eggs are passed with the feces
• Larvae develop outside the
body and molt twice
• The filariform or L3 larvae
move to the surface in search
for a host
• If they come into contact with
the host they penetrate the
skin, enter blood vessels and
leave the circulatory system
into the alveoli
• The lavae move up the trachea
into the esophagus, are
swallowed and finally reach the
intestine, where they molt twice
more before they reach
maturity
– itchy butt worms
Fecal samples are used
to diagnose
most digestive system
parasites
Pinworms
• The most common worm infection in the US
• Common in young children
– FYI: spread from child to child on clothing, bedding
toys… then they put their fingers in their mouth
Pinworms
• Life cycle
– adults live in large intestine
– Female: migrate to outside the anus (at night) to lay
eggs
• Symptoms
–
–
–
–
–
Itchiness around anus
Restless sleep
Irritability
Loss of appetite
Many affected people have no symptoms
Life cycle depends on a small “water flea”
crustacean
Infected “fleas” have worm larvae and get
swallowed in drinking water
Male and female worms grow and
mate in host
Female worm migrates to body surface
to release eggs
Worm under
skin
Guinea worm being “wound” out of skin
Loa loa does not often get noticed unless it
wanders across the eyeball. See arrow above.
River blindness is caused by immature filarial worms
that enter eye, die, and cause masses of connective
tissue with calcium deposits to form.
Filiarial worms
• Tropical countries
• Symptoms
– Obstruct lymph vessels
• FYI… quick review on the lymphatic system
• The lymphatic system is like the blood circulation…
– tubes branch through all parts of the body LIKE the arteries
and veins that carry blood EXCEPT that the lymphatic
system carries a colorless liquid called 'lymph'.
– Lymph is a clear fluid that circulates around the body tissues.
It contains a high number of WBC’s. Plasma leaks out of the
capillaries to surround and bathe the body tissues. This then
drains into the lymph vessels.
Elephantiasis – caused by Wuchereria microfilarial
blockage of lymph vessels; this blockage in turn
causes masses of connective tissues to form.
Transmission via mosquito bites – usually after
repeated exposures.