LESSON 5: NEMATODA Flashcards
(152 cards)
1
Q
(Gr., nematos, thread) occur in nearly every conceivable kind of ecological niche.
A
Nematodes
2
Q
may contain billions of nematodes per acre
A
Good topsoil
2
Q
Nematodes: Approximately _____________ have been named, but most estimates
predict well over one million species exist.
A
25,000 species
3
Q
Nematodes also ____________ virtually every type of animal and many plants.
A
parasitize
4
Q
The effects of nematode infestation on crops, domestic animals, and humans make this phylum
A
one of the most important of all parasitic
animal groups.
5
Q
A
6
Q
Most nematodes are less than__________, and many are _________, but some parasitic nematodes are over a meter in length.
A
- 5 cm in length
-microscopic
7
Q
Nematodes: Use of the __________nas a hydrostatic skeleton is a conspicuous
feature of nematode
A
pseudocoelom
7
Q
Nematodes: The outer body covering is a relatively thick, ____________-,
secreted by the underlying epidermis .
A
non cellular cuticle
8
Q
Nematode: underlying epidermis
A
Hypodermis
9
Q
Nematodes: is of great functional importance, serving to contain the high
hydrostatic pressure exerted by fluid in the pseudocoelom
A
Cuticle
10
Q
Nematodes: Beneath the hypodermis is a layer of
A
Longitudinal muscles
11
Q
Nematodes: Layers of the cuticle are primarily composed of
A
Collagen
12
Q
Nematodes: The muscles are arranged in ________________, separated by
four epidermal cords that project inward to the pseudocoelom
A
four bands, or quadrants
12
Q
Nematodes: There are __________in the body wall
A
no circular muscles
13
Q
Most nematodes are __________.
A
dioecious
13
Q
Nematodes: Another unusual feature of body-wall muscles in nematodes is that
the _______ extend processes to synapse with nerve cords, rather
than nerves extending an axon to synapse with muscle
A
muscles
14
Q
Males are ________ than females, and their posterior end usually bears a pair
of ____________
A
-smaller
-copulatory spicules
15
Q
Nematodes: After embryonic development, a _____________ hatches from an egg
A
juvenile worm
16
Q
Nematodes: Fertilization is __________, and shelled zygotes or embryos are stored in the
uterus until deposition.
A
internal
17
Q
-one of the most common worm parasites of
humans
-now uncommon to US
A
Ascaris lumbricoides (Large Roundworm of
Humans)
18
Q
A. lumbricoides occurs in places that are:
A
warm, humid regions
19
Q
a parasite of pigs, is morphologically similar to A. lumbricoides and was long considered the same species
A
Ascaris suum
20
Q
Adult Ascaris worms live in the ________of their host
A
small intestine
21
Ascaris females may reach ______ in length and can produce _________ a day
-30 cm
- 200,000 eggs
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Ascaris: Fertilized eggs leave the host's body with the feces and are amazingly
tolerant to _______________, but are killed by ________________
-desiccation or lack of oxygen
-direct sunlight and high temperature.
23
Ascaris: In the absence of a sewage system, _________onto soil allows the life cycle
to continue
defecation
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Ascaris: Given suitable soil conditions, embryos develop into infective juveniles within _______
two weeks
23
Ascaris: Shelled juveniles can remain viable for many months or even years in soil,
so they may be transmitted to a new host by __________________________
consumption of contaminated
vegetables or ingestion of soil
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Ascaris: ___________ hatch from the shelled eggs once they are swallowed by
a host.
Tiny juveniles
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Ascaris: They burrow through the host's _____________ entering the blood or
lymph and then traveling to the heart
intestinal wall
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Pathway of Ascaris in human body after ingestion
Intestinal Walls--->blood/lymph--->heart--->lungs--->alveoli--->trachea---> swallowed back to intestines
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Ascaris: If abundant in the lungs, they may cause a serious __________ at this stage
pneumonia
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Ascaris: __________ after being ingested as shelled juveniles, the worms feed
on intestinal contents and mature
Two months
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Ascaris in the intestines may cause:
-abdominal symptoms
-allergic reactions
-intestinal blockage (in large numbers)
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Life Cycle of Ascaris
1. Ingestion
2. Larval Migration
3. Lung Phase
4. Maturation
5. Excretion
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Humans ingest infective eggs from contaminated food, water,
or soil
Ingestion
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Eggs hatch in the small intestine.
Larvae penetrate the intestinal wall → enter the bloodstream.
Travel to the liver, heart, and then to the lungs
Larval Migration
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In the lungs, larvae break into alveoli, mature further.
They migrate up the bronchi and trachea.
Coughed up and swallowed back into the intestines.
Lung phase
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Back in the small intestine, they mature into adult worms.
Adults live there, mate, and females lay thousands of eggs daily.
Maturation
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Eggs are passed in feces to contaminate the environment
Excretion
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Ascaris: Total time: Around __________ from egg ingestion to egg-laying adult.
2–3 months
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Transmission of Ascaris
-Fecal-oral transmission
-poor hygiene
-lack of sanitation
-eating unwashed vegetable
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Clinical features of Ascaris: Light Infections
Asymptomatic
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Clinical features of Ascaris: Heavy Infections
* Intestinal blockage (can be fatal).
* Nutritional deficiencies and growth retardation in children.
* Pulmonary symptoms (during lung migration phase):
* Cough, wheezing, shortness of breath ("Löffler’s syndrome").
* Abdominal pain, nausea, vomiting.
* Rare complications: worms migrating into the bile ducts, liver, pancreas.
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Diagnosis of Ascaris is through:
-Stool examination
-Imaging
-Blood tests (eosinophilia during migratory phase)
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Treatment for Ascaris infection
-Anthelmintic drugs
-Surgery
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Anthelmintic drug includes:
-Albendazole
-Mebendazole
-Ivermectin
40
Classification of Ascaris lumbricoides
* Kingdom: Animalia
* Phylum: Nematoda
* Class: Secernentea
* Order: Ascaridida
* Family: Ascarididae
* Genus: Ascaris
* Species: A. lumbricoides
40
Morphology of A. lumbricoides
* Color: Creamy white to pink.
* Shape: Cylindrical body, tapering at both ends.
* Surface: Covered by a tough, flexible cuticle.
*Distinct Features:
* Males have a curved posterior end.
* Females are straight and larger
40
Ascaris: Species of ____________ infect cats and dogs
Toxocara
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Toxocara: Their life cycle is generally similar to that of Ascaris, but juveniles
often do not _______________ in adult dogs, remaining
in the host's body in a stage of arrested development.
complete their tissue migration
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Toxocara: Pregnancy in the female dog, however, stimulates juveniles to wander, and
they infect the _______________
embryos in the uterus
41
Toxocara: These ascarids also survive in humans but do not complete their
development, leading to an occasionally serious condition in children called
______________
visceral larva migrans
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are so named because their anterior end curves dorsally, suggesting a hook.
Hookworm
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The most common species of hookworm is ________________ (L. necator, killer),
whose females are up to _____. Males can reach __________.
-Necator americanus
-Females: 11 mm in length
-Males: 9 mm in length
43
Hookworm: ____________ in the mouth cut into the intestinal mucosa of the host,
where they suck blood and pump it through their intestine, partially
digesting it and absorbing the nutrients
Large plates
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Hookworm: They suck much more blood than they need for food, and heavy
infections cause _______in the patient
anemia
45
Hookworm: Shelled embryos leave the host's body in feces, and juveniles hatch in
the soil, where they live on ________.
bacteria
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Hookworm disease in children may:
-retard mental
-physical growth
-general loss of energy
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Hookworm: When human skin contacts ____________, the juveniles burrow through
the skin to the blood, reaching the lungs and finally the intestine in a
manner similar to that described for Ascaris.
infested soil
47
Classification of Hookworm
* Kingdom: Animalia
* Phylum: Nematoda
* Class: Secernentea
* Order: Strongylida
* Family: Ancylostomatidae
* Genera:
Ancylostoma (e.g., A. duodenale)
Necator (e.g., N. americanus
47
The major species of hookworm infecting humans:
-Ancylostoma duodenale
-Necator americanus
48
Morphology of Hookworm:
* Color: Whitish or grayish.
* Shape: Slender, cylindrical body; anterior (head) end is bent dorsally like a
"hook" — hence the name.
*Mouth Parts:
Ancylostoma: Has teeth (2 pairs) for cutting intestinal tissue.
Necator: Has cutting plates instead of teeth
49
Infective stage (hookworm): Rhabditiform larvae molt into __________ (infective stage). And can survive in soil for weeks
filariform larvae
50
Life cycle of hookworm
1. Eggs in Feces
2. Development in Soil
3. Infective stage
4. Skin Penetration
5. Larval Migration
6. Maturation
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Development in Soil (hookworm): Eggs hatch into ____________ (non-infective) in warm, moist soil
rhabditiform larvae
52
Larval migration of hookworm:
Feet (skin)-->bloodstream → heart → lungs → Break into alveoli → climb up trachea → swallowed → reach small
intestine
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Entire cycle of hookworm infection to egg production
approx. 5-9 weeks
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Transmission of Hookworm
-walking barefoot
-poor sanitation
-contaminated environment
54
Epidemiology of hookworm
Common in:
* Tropical and subtropical climates (e.g., Sub-Saharan Africa, South
Asia, Latin America).
* Areas with poor hygiene and warm, moist soil.
* Over 400 million people infected globally.
55
Clinical Features of hookworm: Light infections
Asymptomatic
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Clinical features of hookworm: heacy infections
* Skin: "Ground itch" — itchy, red rash at site of larval penetration.
* Lungs: Mild cough, wheezing during pulmonary migration
Intestines:
* Abdominal pain, diarrhea, nausea.
* Iron-deficiency anemia from blood loss.
* Fatigue, pallor, weakness.
* Protein loss → edema (swelling).
57
Diagnosis for hookworm
-stool examination
-blood tests (hypochromic, microcytic anemia)
58
Treatment for hookworm
-Anthelminthic drug (Albendazole, mebendazole)
-Iron Supplement (for anemia)
-Nutritional support
59
Hookworm: ________________ can also infect orally (larvae swallowed directly)
Ancylostoma duodenale
60
Hookworm: Each adult worm can cause a daily blood loss of___________ per worm
0.03–0.2 mL
61
Female hookworms can produce up to ____________ per day
30,000 eggs
62
Severe chronic hookworm infections in children have been called
___________________ because of their impact on growth and mental development
"neglected causes of poverty"
63
Common in: Middle East, India,, Europe
Method of Infection: Skin and Oral
Size: Larger
Mouth Structure: teeth
Blood loss per worm: more than the other type
Ancylostoma duodenale
64
Common in: Americas, Africa, Asia
Method of Infection: Mainly skin
Size: Smaller
Mouth Structure: Cutting Plates
Blood loss per worm: lesser than the other type
Necator americanus
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-(Gr. trichinos, of hair, + -ella, diminutive) is one of the species of tiny small parasitic nematodes responsible for the potentially lethal disease trichinosis.
Trichinella spiralis
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Trichina: Adult worms burrow in the __________ of the host's small intestine,
where females produce living young
mucosa
66
Trichinella spiralis is responsible for the disease
trichinosis
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Trichina: Juveniles penetrate blood vessels and are carried throughout the
body, where they occupy almost any____________
tissue or body space
68
Trichina: Eventually, they penetrate skeletal
muscle cells, becoming one of the
largest known
Intracellular parasites
69
Trichina: Juveniles cause astonishing ____________________ in their host cell, which loses its striations and becomes
a nurse cell that nourishes the worm
redirection of gene expression
70
Trichina: When_____________ is
swallowed, the worms are liberated
into the host's intestine, where they
mature.
meat containing live juveniles
70
can infect a wide variety of mammals in addition to
humans, including pigs, rats, cats, and dogs
Trichinella spp.
71
Pigs become infected with Trichina by eating __________________ or by eating ________.
-pork scraps infested with juveniles
-infected rats
71
Trichina: Heavy infections may cause _______, but lighter infections are much
more common.
death
72
Trichinella spiralis has _______________, which differ in geographic
distribution, infectivity to different host species, and freezing
resistance.
four sibling species
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Trichina: Recent cases of infection come from ____________or from ______raised in
close proximity to wild animals
-wild boar
- hogs
73
Trichina: In northern California, ___ people were infected in 2008 after
consuming black bear meat.
30
74
Classification of Trichinella spiralis
* Kingdom: Animalia
* Phylum: Nematoda
* Class: Enoplea
* Order: Trichocephalida
* Family: Trichinellidae
* Genus: Trichinella
* Species: T. spiralis (most important for humans)
74
Morphology of Trichinella spiralis
Adult Worms:
* Very tiny: Males ~1.5 mm, Females ~3–4 mm long.
* Slender, thread-like bodies.
Larvae:
* Coiled larvae (encysted) are found in muscle tissue.
* Encysted larvae are about 0.4 mm long, visible under a microscope
74
a serious disease
resulting from eating raw or undercooked meat (especially pork)
containing larvae.
Trichinosis (also called as trichinellosis)
75
Life Cycle of Trichinella spiralis
1. Ingestion
2. Release in Intestine
3. Maturation
4. New Born Larvae
5. Larval migration
6. Encystment
75
Unique among nematodes: Trichinella spiralis uses the ___________ for all
stages
same host
76
Trichina: maturation
* Larvae mature into adults within 1–2 days.
* Adults mate; males die after matin
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Trichina: Release in Intestine
Stomach acid releases larvae → they migrate to the small intestine
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Female trichina give birth to live larvae, meaning it is a ________ reproduction
viviparous
76
Transmission of trichina is only through
Eating infected meat
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Trichina: Encystment
1. Larvae coil and encyst in muscle fibers.
2. They can remain alive in cysts for years
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Trichina: Larval migration
* Newborn larvae enter lymphatic system or bloodstream.
* They are carried to striated muscle tissue (skeletal muscles).
78
(Gr. enteron, intestine, + bios, life),
cause relatively little disease, but they are the most common worm
parasite in the United States, occurring in an estimated 30% of
children and 16% of adult
Pinworms (Enterobius vermicularis)
79
Pinworm: Adult parasites occupy the
Large intestine and cecum
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Pinworm: Eggs develop rapidly and become infective within __________ at body
temperature
6 hours
79
Pinworm: Scratching the ___________ effectively contaminates hands and
bedclothes
resultant itch
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Pinworm: Females reach
about _____ in length and migrate to the anal region at night to lay
their eggs
12 mm
80
Pinworm: After they are swallowed, they hatch in the _________, and the
worms mature in the ____________.
-duodenum
-large intestine
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Pinworm: Members of this order of nematodes have __________, a
characteristic shared with a few other animal groups, notably many
hymenopteran insects
haplodiploidy
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Pinworm: Males are haploid and are produced ___________
parthenogenetically
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Pinworm: females are
diploid and arise from ______________
fertilized eggs
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Pinworms are _______________________ that
infect the human intestine
small, white, thread-like parasitic roundworms
82
Pinworm cause condition known as
enterobiasis (also called as oxyuriasis
82
Classification of Pinworm
* Kingdom: Animalia
* Phylum: Nematoda
* Class: Secernentea
* Order: Oxyurida
* Family: Oxyuridae
* Genus: Enterobius
* Species: E. vermicularis
83
Morphology of Pinworm
Adults:
* Females: ~8–13 mm long (larger than males).
* Males: ~2–5 mm long.
* Slender, pointed tails (hence “pinworm”).
* Color: White and thin, like a tiny thread.
Eggs:
* Oval, flattened on one side.
* Translucent and very light, allowing easy airborne spread
83
It’s the most common helminth infection in children in developed
countries like the USA and Europe
Pinworm
84
Life cycle of Pinworm
1. Ingestion
2. Larvae Hatch
3. Maturation
4. Reproduction
5. Egg Laying
85
Maturation of pinworm happens in the
large intestine or cecum
85
Pinworm eggs hatch in the
small intestine
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Pinworm: _________(full of eggs) migrate at night to the ______________ (skin
around the anus) to lay eggs.
-Gravid females
-perianal region
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Pinworm males after mating
They die
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Each female pinworm lay up to
10, 000 eggs
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Total cycle time of pinworm
1-2 month
87
Transmission of Pinworm
-fecal-oral route
-airborne eggs
-autoinfection is common
87
Diagnosis of Pinworm is through
-Scotch tape test (cellophane tape test)
-Direct observation
88
Treatment for Pinworm
-Antiparasitic drug (mebendazole, albendazole, pyrantel pamoate)
-Household treatment
-environmental cleaning
88
Pinworm: A second dose ____________ is recommended to kill newly hatched worms.
2 weeks later
88
At least eight species of ____________infect humans, and some
cause major diseases.
filarial nematodes
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Filarial worm: Some 120 million people in tropical countries are infected with
________________ (named for Otto Wucherer) or _____________ (named for S. L. Brug), placing these species among the scourges of
humanity
-Wuchereria bancrofti or Brugia malayi
89
Pinworm eggs are not often found in _______ because females deposit them on the skin around the anus.
feces
90
Filarial Worm: The worms infect the _______________, and females may be as long
as ______-.
-lymphatic system
-100 mm
91
Filarial worm: Disease symptoms include _________________________________________
inflammation and obstruction of the
lymphatic system
92
Filarial Worm: Female worms release tiny living _________________ into the blood and
lymph of the host
microfilariae
92
Filarial Worm: When the mosquito again feeds on a human, the microfilariae escape
from the mosquito and penetrate the _________made by the mosquito
bite
wound
92
Filarial Worm: These microfilariae are then ingested by ___________as the insects
feed, and they develop in to the ____________
-mosquitos
-infective stage
93
Long and repeated exposure to
filarial worms can lead to
_______________, a condition
marked by excessive growth of
connective tissue and enormous
swelling of affected parts, such
as the scrotum, legs, arms, and
more rarely, the vulva and
breast
elephantiasis
93
Another filarial worm causes river blindness (____________) and is carried by ___________
-onchocerciasis
-blackflies
94
Diseases caused by filarial worms fall into the Centers for Disease
Control (CDC) category ____________________
“Neglected Tropical Diseases.”
95
The most common filarial worm in the United States is probably the dog
heartworm,
Dirofilaria immitis
96
Life Cycle of Filarial Worms (General Pattern)
1. Infective Larva (L3 Stage)
2. Larval Migration
3. Maturation
4. Mating
5. Insect Ingestion
6. Development of Infective larvae
7. Cycle repeats after next bite
96
Disease: River Blindness (onchocerciasis)
Vector: Blackflies
Onchocerca volvulus
96
Classification of Pinworm
* Kingdom: Animalia
* Phylum: Nematoda
* Class: Secernentea
* Order: Spirurida
* Superfamily: Filarioidea
96
Pinworm: This worm causes a very serious disease among dogs, and no responsible
owner should fail to provide ______________for a dog during mosquito
season
“heartworm pills”
97
Disease: Mansonelliasis
Vector: Midges and Blackflies
Mansonella spp.
97
Disease: Lymphatic filariasis
Vector: Mosquitoes
-Wuchereria bancrofti
-Brugia malayi
-Brugia timori
97
Disease: African eye worm (loiasis)
Vector: Deerflies
Loa loa
98
Wuchereria and Brugia preferred to migrate in ________________
Lymphatic vessesl
99
Onchocerca and Loa loa preferred to migrate in the ______________
Subcutaneous tissues
100
Prevention for Filarial worm infection
-Vector Control
- Mass Drug Administration
-Protective clothing and insect repellant
