R

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R
oundworms
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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

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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

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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
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• 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

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More than half a million types of round worms
exist in the world.

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Ascaris
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

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Ascaris
Can cause pneumonia and intestinal blockage
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• 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

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Male posterior characteristic hooked end
Female posterior
Ascaris
dioecious
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Female vs. Males

• Females are larger than males
• They can produce 200000 eggs a day.

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Ascaris female x.s.
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Ascaris male x.s.
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Ascaris Dissection
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Ascaris Dissection 2
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Trichina worm
Larval stage forms calcified cysts in muscle of
host ( human or pig/bear )
Trichinosis contracted from undercooked
infected pork
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Dog Heartworm
Dirofliaria immitis

• a parasitic nematode that can kill your dog

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Hookworms

• ingested worms travel to intestines,
• then to lungs in bloodstream
• worms are coughed up and swallowed
• and become adult worms in intestines

• 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

Common in southern states
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hooks
Hookworm mouth
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• Adult worms live in the small intestine and
  female lay 5-10000 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

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Pinworms
itchy butt worms
Fecal samples are used to diagnose
most digestive system parasites
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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

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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

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The Guinea Worm
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
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Worm under skin
Guinea worm being wound out of skin
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Loa loa does not often get noticed unless it
wanders across the eyeball. See arrow above.
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River blindness is caused by immature filarial
worms that enter eye, die, and cause masses of
connective tissue with calcium deposits to form.
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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 WBCs.
  Plasma leaks out of the capillaries to surround
  and bathe the body tissues. This then drains into
  the lymph vessels.

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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.