PHYLUM NEMATODA: Round Worms

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PHYLUM NEMATODA Round Worms II. Taxonomy
G. Ascaris lumbricoides Ascaris suum
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PHYLUM NEMATODA Round Worms II. Taxonomy
G. Ascaris 1. Life cycle

• L3 enters blood ? heart ?
• pulmonary artery ? lungs
• rupture from alveoli ?
• up trachea swallowed
• gut

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PHYLUM NEMATODA Round Worms II. Taxonomy
G. Ascaris 2. Pathology -- most
common helminth of humans esp. in SE
U.S. damage from 3 sources a. Adults in
intestines -- often asymptomatic in
low-level infections -- high level
infections can occlude gut
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PHYLUM NEMATODA Round Worms II. Taxonomy
G. Ascaris 2. Pathology from 3
sources b. Larval migration --
lung damage Loefflers pneumonia --
can become lost in host body transplacental
transmission has been reported

alveolar lumen sec. w/ larvae
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PHYLUM NEMATODA Round Worms II. Taxonomy
G. Ascaris 2. Pathology from 3
sources c. Wandering adults --
perforate gut peritonitis -- into
liver appendix
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PHYLUM NEMATODA Round Worms II. Taxonomy
H. Toxocara canis T. cati common roundworm
of dogs and cats
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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• H. Toxocara canis T. cati
• 1. Life cycle
• -- adults in small intestines of host
• eggs passed in feces
• -- ingested fate depends upon age of host
• -- if in young animal (lt 5 weeks)
• No host immunity
• Eggs hatch larvae
• penetrate gut
• Heart ? lungs ?
• gut migration
• Adults in gut

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• H. Toxocara canis T. cati
• 1. Life cycle
• -- if in older animal (gt 5 weeks)
• some host immunity
• Eggs hatch larvae
• penetrate gut
• Migrate throughout
• tissues hypobiosis
• Larvae reactivated
• by pregnancy
• hormones
• Migrate to placenta
• and mammary glands

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• H. Toxocara canis T. cati
• 2. pathology
• a. In kittens and puppies
• -- pot belly
• -- dull, scruffy coat

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• H. Toxocara canis T. cati
• 2. pathology
• b. In humans (mostly children 1-3 yrs.)
• -- visceral larval migrans

granuloma in liver
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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• H. Toxocara canis T. cati
• 2. pathology
• b. In humans (mostly children 1-3 yrs.)
• -- ocular larval migrans blindness and
  eye loss
• -- mimics retinoblastoma (leading eye
  tumor of children)
• -- up to 37 of retinal disease in
  Atlanta attributed to Toxocara

granuloma
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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• I. Enterobius vermicularis human pinworm

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• I. Enterobius vermicularis human pinworm
• a. Life cycle

Eggs can hatch in perianal region and reinvade
through anus retroinfection
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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• I. Enterobius vermicularis human pinworm
• b. Pathology not a serious parasite, but
  extremely common
• -- causes intense itching
• -- leads to nervousness, irritability
• -- can be introduced into nose
• -- detect with scotch tape method

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• J. Dracunculus medinensis Guinea worm
  fiery serpent of Moses
• -- Middle East and Africa
• -- tissue parasite of humans

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• J. Dracunculus medinensis
• 1. Life cycle
• -- head end of female worm
• protrudes through opening in skin
• uterus extruded through mouth
• -- in presence of water, L1 larvae
• released
• -- L1 ingested by Cyclops
• develop to L3
• -- copepod ingested by DH
• -- L3 penetrates gut migrate
• to skin mature and mate en

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• J. Dracunculus medinensis
• 2. Pathology
• -- damage comes from adult females
• -- extremely painful disfiguring

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• J. Dracunculus medinensis
• 2. Pathology
• -- damage comes from adult females
• -- extremely painful disfiguring

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• J. Dracunculus medinensis
• 3. Treatment Control split-stick method

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Medical symbol Caduceus
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Filtering Drinking Water
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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• K. Filarial worms
• -- many are tissue dwelling parasites
• -- females release microfilaria larvae
• -- insect vector ingests microfilaria
• -- vector transmits L3 when feeding
• -- cause filariasis

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• PHYLUM NEMATODA Round Worms
• II. Taxonomy
• K. Filarial worms
• 1. Wuchereria bancrofti
• -- tissue parasite of humans adults in coiled
  masses in lymphatic tissue
• -- causes Bancroftian filariasis
  elephantiasis
• -- vector ca. 60 spp. Anopheles, Mansonia,
  Culex, Aedes

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a. Life cycle
(6-12 mo. to maturity)
(labium)
(live up to 5-10 yrs.)
sausage stage
(L2 sausage stage)
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 1. Wuchereria
bancrofti b. Pathology damage caused
by adults, not larvae 1)
asymptomatic phase -- patient has
high levels of microfilaria -- but
shows immunological tolerance (hyporesponsiveness)
-- IL- 4 increases suppresses TH1 cells --
TH2 immune responses stimulated -- IFN- ?
depressed -- hyporesponsivenss eventually breaks
down, leading to inflammatory phase
-- in endemic areas, many individuals show
no symptoms and no microfilaria, but
have antibodies to worm antigens
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 1. Wuchereria
bancrofti b. Pathology
2) inflammatory (acute) phase -- due to
antigens of adult worms and bacteria --
lymphedema (chills fever elephantoid fever
acute swelling pain extensive
proliferation of cells lining lymph
vessels) -- orchitis (painful swelling of
testes) -- epididymitis inflammation of
epididymis
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 1. Wuchereria
bancrofti b. Pathology damage due to
adults, not larvae 3) obstructive
(chronic) phase -- results from repeated
acute cycles of infection -- lymph vessels
blocked, fluid accumulates, fibrous tissue
proliferates, granulomas -- lymph varices
(varicose lymph vessels) -- chyluria (lymph in
urine) -- elephantiasis --
persistent build up of
fibrous tissue granulomas -- skin
thickens and cracks
bacterial and fungal invasions
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40 million people suffer from chronic lymphatic
filariasis
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 1. Wuchereria
bancrofti c. Treatment and control
-- Hetrazan ivermectin (Hetrazan fortified
salt) eliminates microfilaria and can kill
adults -- pressure bandages (acute
phase) -- surgical removal of lymphatic
tissue -- control mosquitoes
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 2. Brugia malayi
-- India, Asia
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 3. Onchocerca
volvulus -- Africa Central and South
America -- causes River Blindness
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 3. Onchocerca
volvulus -- vector Simulium (black fly) --
adults occur in nodules under the skin
onchocercoma
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 3. Onchocerca
volvulus a. Life cycle
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 3. Onchocerca
volvulus b. Pathology 1) from
adult worms onchocercomas
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 3. Onchocerca
volvulus b. Pathology 1) from
adult worms hanging groin
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 3. Onchocerca
volvulus b. Pathology 2) from
microfilaria -- severe dermititis --
depigmentation (leopard skin)
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 3. Onchocerca
volvulus b. Pathology 2) from
microfilaria in eye River blindness --
invade cornea sclerosing keratitis (hardening
of cornea) -- invade retina optic nerve
chorioretinopathy -- invade pituitary
dwarfism
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 3. Onchocerca
volvulus c. Treatment and Control
-- treat with Mectizan -- control
blackflies
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 4. Loa loa African
eye worm -- vector Chrysops (deer fly)

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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 5. Dirofilaria
immitis dog heartworm vector Aedes

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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 5. Dirofilaria
immitis dog heartworm a. Life cycle

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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 5. Dirofilaria
immitis dog heartworm b.
pathology
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 5. Dirofilaria
immitis dog heartworm b.
pathology
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PHYLUM NEMATODA Round Worms II. Taxonomy
K. Filarial worms 5. Dirofilaria
immitis dog heartworm c.
treatment