Phylum Nematoda - Chapter 22

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Phylum Nematoda - Chapter 22

• Nematodes or roundworms are among the most
  abundant animals on earth - over 500,000 species
  have been described.
• Majority of nematodes are free-living in every
  conceivable habitat.
• free-living species are commonly microscopic in
  size
• importance? ____________________________

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Phylum Nematoda
Two groups of nematodes are parasitic   (1)
___________________________________ -
cause diseases of medical and veterinary
importance - attract the attention of
parasitologists   (2) ___________________________
________ - may destroy plants resulting in
economic losses - attract the attention of
plant pathologists
3
Characteristics of the Phylum Nematoda

• 1. Body is non-segmented, elongate, and circular
  in cross-section (i.e. the name "roundworms").
• 2. Body wall consists of
• a) outermost noncellular ___________________
  ___________
• b) underlying ___________________________
  that secretes the cuticle
• is a cellular syncytium with nuclei lying in 4
  thickenings

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Characteristics of the Phylum Nematoda

• c) ____________________________________ lies
  below the hypodermis
• contractile and noncontractile regions are
  present
•   no circular muscle is present worm cannot
  shorten or lengthen
• movement is due to undulating motion caused by
  contraction of the longitudinal
  muscles

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Characteristics of the Phylum Nematoda

3. _____________________________________ is body
cavity beneath the musculature.  - cavity is
called a "pseudocoelom" as it is not lined
internally with ______________________________  -
pseudocoelom is filled with a fluid called
pseudocoelomic fluid - reproductive organs are
suspended within the pseudocoelom
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Characteristics of the Phylum Nematoda

Pseudocoelomic fluid has two functions (1)
serves as ________________________________________
_ giving the body rigidity (2) serves as
________________________________________
transporting materials from cell to cell  
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Characteristics of the Phylum Nematoda

• 4. Digestive tract is complete.
•  
• Mouth pharynx esophagus intestine
  anus
•  
• Intestine possesses well-developed microvilli
  for absorption.
• Food - ___________________________________
• ___________________________________
• Little digestion occurs within the nematode
  intestine it is dependent upon the host to
  digest food into an absorbable form.

8
Characteristics of the Phylum Nematoda

5. Nervous system consists of a circumesophageal
nerve ring and 2 or 4 longitudinal nerve
trunks extending the length of the
nematode. Seen only with special staining
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Characteristics of the Phylum Nematoda

6. Excretory system is primitive and consists of
1 or 2 _____________________________ and
excretory ducts Excretory pore is anterior.
No flame cells are present.
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Characteristics of the Phylum Nematoda

7. Nematodes are _______________________ Reproduc
tive system consists of tubular organs lying in
the pseudocoelom. MALE nematodes are generally
smaller in size. Posterior end is often curved
due to presence of _______________________________
_____. Male system is a single tubule. Inner
end is _________________________
___________________________
___________________________
____________________________ supported by
spicules  
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Characteristics of the Phylum Nematoda

FEMALE nematodes are larger in size. The female
reproductive organs are doubled. 2
threadlike ______________________ 2
_________________________ 2 ____________________
_____ single ______________________ _________
________________ (female opening)  

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Characteristics of the Phylum Nematoda

In both the male and female systems, the tubular
organs are continuous and increase in diameter as
they extend to the genital opening.
When viewed in cross-section, the organs are
histologically distinct.

Male
Female
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Characteristics of the Phylum Nematoda

8. Nematode development is similar in all
nematodes.  Consists of 4 larval (juvenile)
stages between the egg and adult. Each stage is
separated by a molt of the cuticle.  
M1 M2
M3 M4 Egg L1
L2 L3 L4
Adult Larval stages may be
passed within the egg, free-living in soil,
parasitic in an intermediate host, or parasitic
in definitive host.

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Ascarid Nematodes Chapter 26
Ascaris lumbricoides Common
parasite of humans. Disease is called
______________________________ Cosmopolitan in
distribution.  - flourishes in warm, moist
climates where the eggs may remain viable in warm
soil for many years.  - use of ___________________
________ to fertilize vegetables is common source
of infection.  - Children are most likely to
become infected by ingesting eggs by eating dirt
or placing soiled fingers or toys into the
mouth.
15
Ascaris lumbricoides
Human is the only definitive host of this
parasite. In the U.S. infections are most
common in _________________________________ Paras
ite is endemic in Wisconsin - prevalence is low -
1.3 in 1976 and 0.5 in 1987.
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Ascaris lumbricoides

• ADULTS are the largest nematode parasites of
  humans.
• Males are ______________ inches in length and 1/8
  inch in diameter.
• posterior end is curved due to presence of
  spicules.
• Females are ______________ inches in length and
  1/4 inch in diameter.

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Ascaris lumbricoides
Anterior end is composed of ___________________
which surround the mouth.
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Ascaris lumbricoides
EGGS are _________________________________________
_ _____________________________________________. E
ggs are unembryonated when passed in the feces.
Embryonation occurs in the soil.  
Unembryonated egg in feces
Embryonated egg in soil
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Life Cycle of Ascaris lumbricoides
1. Adult males and females live in
_______________________ 2. Female releases
200,000 eggs/day which are passed in the
feces. 3. Eggs embryonate in warm, moist shady
soil and __________________stages are passed
within the egg.
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Life Cycle of Ascaris lumbricoides
4. ____________________ is the infective stage
and is ingested by a human. 5. L3 hatches from
egg in the duodenum, penetrates the duodenum,
enters the circulation, travels through the
heart, and reaches the ____________________ via
the pulmonary circulation.  6. In the lungs, the
L3 molts to the L4 stage.
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Life Cycle of Ascaris lumbricoides
7. L4 break into the alveoli, move up the
respiratory tree to the pharynx, and
__________________________   8. L4 move into the
_________________________where they molt to
the adult stage. Become mature in 2
months.   Migratory phase (time from ingestion of
the L3 in egg until L4 reach the small intestine)
is about 25 days.    

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Life Cycle of Ascaris lumbricoides
Adults typically live a year. Why is there this
migratory phase?    

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Pathology of Ascaris lumbricoides
Adults cause (1) _________________________ (due
to toxemia from Ascaris waste products) (2)
__________________________(due to loss of
monosaccharides and amino acids absorbed by the
worms) (3)__________________________________by
large numbers of tangled worms (may be
fatal).

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Pathology of Ascaris lumbricoides
Larvae cause problems in the lungs when they
break through the lung capillaries to enter the
respiratory tree. (1) small hemorrhages are
produced causing plasma to enter alveoli
resulting in ________________________ (2)
inflammatory response to this damage occurs and
__________________ _______________________________
__________ resulting in pneumonia-like symptoms
The more eggs ingested, the more
migrating larvae, the greater the pathology.  

larva
Inflammatory cells
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Ascaris lumbricoides
DIAGNOSIS - ID eggs in feces Eggs have thick,
rough outer shell. Size There is no diagnostic
method for migrating larvae.    

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Treatment of Ascaris lumbricoides

TREATMENT - drug called __________________________
___ is effective against adults. No drug
treatment is available against migrating larvae.
 
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Ascaris suum
___________________________ is the single
greatest cause of economic loss in the swine
industry. Adults of A. suum are nearly identical
to A. lumbricoides in morphology (differences are
visible only with scanning EM). Parasitologists
believe that a single species of Ascaris infected
both humans and pigs at one time but has
now evolved into two separate species -
one infecting humans and one infecting pigs.
     

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Ascaris suum
LIFE CYCLE, PATHOLOGY, DIAGNOSIS, AND TREATMENT
of A. suum is identical to that of A.
lumbricoides except that pigs are the only
hosts.    

Adults in small intestine Unembryonatedd eggs in
feces (identical to A. lumbricoides)
Larval migration in lungs Egg with L3
infective stage
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Ascaris suum
Question? Can Ascaris suum develop into adults
in humans? Difficult to find a volunteer for this
experiment but we did find out an unusual way.
 

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Ascaris suum
 

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Ascaris suum
 

What did we find out from infections in these
volunteers? 1. If eggs of A. suum are ingested
by a human, the ___________ larvae will hatch
from the egg and undergo _________________________
______. 2. The migration is abnormal and
greater pathology occurs in the human lungs
resulting in severe ____________________. A
near-fatal pneumonia occurred in the roommates
3. Adults? _____________________________________

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Toxocara canis and Toxocara cati
Common ascarids in the ___________________________
________________________ Prevalence in dogs and
cats is estimated to be 20 to 100. These
parasites are enzootic in Wisconsin dogs and
cats.  Adults are much smaller than Ascaris.
- males are about ____ inches in length
- females are _____________inches in length
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Toxocara canis Life Cycle
4 aspects to the life cycle 1. Normal cycle in
the dog Dogs are infected by ingestion of
______________________ Larvae undergo migration
through the ___________and are swallowed Reach
adulthood in dog _______________________
1. Normal cycle in dog
L3
L3
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Toxocara canis Life Cycle
2. Addition of a paratenic host (mouse)
If a mouse ingests an infective egg, the
________hatches and migrates to many internal
organs. It develops no further. If mouse is
eaten by a dog, the ________ penetrates the dogs
intestine and undergoes normal migration.  
1. Normal cycle in dog
L3
L3
2. Paratenic host
L3
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3. Transplantal transmission If a bitch becomes
infected, the migrating L3 can cross the placenta
to infect the fetal puppies. When the puppies
are born, they are already infected with adult
worms. Prevalence rates in puppies can reach
100 because of the efficiency of transplacental
transmission.
L3
L3
3. Transplacental transmission
L3
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Toxocara canis Life Cycle
4. Human infection Human infections of Toxocara
cause ____________________________________________
__ This disease results when eggs with L3 are
accidentally ingested by humans.
L3
L3
L3
L3
L3
4. Human

infection
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Toxocara canis Life Cycle
L3 hatch in the human small intestine, penetrate
the intestine, and enter the circulation. L3 are
carried throughout the visceral organs where they
wander randomly - hence, the name "visceral
larva migrans". further development?
___________________________ ______________________
_____
L3
L3
L3
L3
L3
4. Human

infection
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Toxocara canis Life Cycle
Eventually, the human immune system recognizes
the parasite, encapsulates it with
______________________________, and the L3 is
killed.  
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Pathology of Visceral Larva Migrans

• PATHOLOGY - dependent upon which organs are
  invaded by the L3
• ______________________ is commonly invaded -
  hepatomegaly cirrhosis may occur
• __________________________ invasion results in a
  severe tissue reaction that can result in death
• 3. _____________________________may be invaded -
  scar tissue deposition in the retina can result
  in blindness
•  

Scar tissue in retina
L3 in retina
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Tragically, most human cases involve children due
to their close association with pets.  
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Diagnosis and Treatment of Toxocara in Dogs Cats

• DIAGNOSIS
• Adults in dog - Identify egg in feces
• Diagnostic features
• ____________________________
• ____________________________
• ____________________________
• TREATMENT -

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Diagnosis and Treatment of Human Visceral Larva
Migrans
DIAGNOSIS Larvae in human are very difficult to
ID - only way is to ____________________________
________ _________________________________________
___   TREATMENT - _____________________________has
recently been reported to be successful.
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Prevention of Human Infection

• 1. ______________________________________________
  _
• 2. ______________________________________________
  _
• many cities have enacted "pooper scooper" laws
  that require owners to clean up after their pets
• especially important in parks where pet owners
  take animals for walks and children are playing
• 3. ______________________________________________
  __

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Baylisascaris procyonis
Raccoon ascarid - common parasite in the small
intestine of raccoons This parasite has recently
been found to cause ______________________________
__________________ in HUMANS  
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Baylisascaris procyonis
Raccoons are infected by ingestion of
____________________________ Larvae undergo
migration through the __________________________,
are swallowed, and reach adulthood in raccoon
__________________________ .
Egg with L3
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Human Infections of Baylisascaris procyonis
Result from the accidental ingestion of eggs with
L3 L3 hatch in small intestine, penetrate
intestine, and enter circulation L3 have
preference for invading the ______________________
_____________ where they cause a severe tissue
reaction - often fatal.  
Egg with L3
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Human Infections of Baylisascaris procyonis

• Four human fatalities - in Pennsylvania (1983),
  Illinois (1985), and two in 2002 in Minnesota
• occurred in children who had associations with
  raccoons.

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Human Infections of Baylisascaris procyonis

This parasite is a POTENTIAL HEALTH HAZARD IN
WISCONSIN Wisconsin DNR survey indicated that 51
of our raccoons are infected. Highest prevalence
is in the southern half of the state. Juvenile
raccoons have heavy infections What might this
suggest?
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Human Infections of Baylisascaris procyonis

Having a young raccoon as a pet could be a fatal
mistake! Raccoon hunters and trappers should be
aware of this dangerous parasite.
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Anisakis spp.
Anisakis is parasitic in the stomach and small
intestine of ______________ ______________________
______________________________________.
____________________________are 1st intermediate
hosts of this parasite.  Many species of
__________________________serve as 2nd
intermediate hosts of these ascarids - Pacific
salmon, Atlantic cod, haddock, herring,
mackeral
L3 in marine fish
Egg with L2 L2 in copepod or krill
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Anisakis spp.
If marine fish containing Anisakis L3 are eaten
in raw or poorly cooked fish (i.e. sushi,
cerviche, etc.), HUMANS CAN SERVE AS ACCIDENTAL
HOSTS. Disease is called _________________________
_______________  

Human ingests raw fish
Egg with L2 L2 in copepod or krill
L3 in marine fish
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Anisakis spp.
Anisakis L3 from marine fish are about 1 inch
long. L3 normally occur in the fish intestine
but migrate to the musculature when the fish
__________________________ and warm up during
transportation.
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Pathology of Anisakis in humans
PATHOLOGY 1. Larval Anisakis (an L3) burrows
into the wall of the stomach or small intestine
- _______________________is produced around
larva  - causes _________________________________
2. Larva eventually dies (humans are abnormal
hosts) resulting in a ____________________________
___________________ to the dead worm - this
response mimics an ulcer or acute
apppendicitis  - fatalities have occurred.
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Human Cases of Anisakis spp.
U.S. has 12 cases/year - mostly in west coast
and Hawaii  Japan has about 1,000 cases/year
DIAGNOSIS and TREATMENT - find L3 by
______________________________ and remove
it PREVENTION -
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Enterobius vermicularis - Chap. 27
____________________________________ - Humans are
the only host of this parasite. Cosmopolitan
distribution - common in temperate and tropical
climates. In Wisconsin?
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Enterobius vermicularis
Almost anybody can become infected with this
parasite. No social class is exempt. These
parasites soon become "family affairs". Once one
person, usually a child becomes infected, other
family members will undoubtedly also become
infected.  
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Adults of Enterobius vermicularis
Adults live in the _______________________________
________________ (ileum, cecum, appendix, and
colon). They feed on bacteria and dead
intestinal cells - they do not invade
tissue. Pinworms are recognized by 2 structures
1. ____________________________- winglike
extensions of the cuticle at the anterior end  
2. _______________________________- muscular
bulb at end of esophagus

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Adults of Enterobius vermicularis
Males __________________________________________
_____________ ____________________________________
__________________________ Females
__________________________________________________
____ _____________________________________________
_________________ ________________________________
______________________________  

female male
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Adults of Enterobius vermicularis

Female showing esophageal bulb cephalic alae
Male with curved posterior end
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Life Cycle of Enterobius vermicularis
1. Adults copulate in the human digestive tract.
Male dies after copulation. 2. Female migrates
at night to the perianal folds of the anus and
deposits eggs (commonly over 10,000) in the skin
of the ____________________. Female dies after
all eggs have been laid.

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Life Cycle of Enterobius vermicularis
3. Eggs contain L1 larvae when laid, but within
6 hours larvae molt twice in the egg to the
______ stage. 4. ____________________ are
infective and when ingested by a human, the L3
hatch in the small intestine. 5. L3 molt twice
to the adult stage as the worms move into ileum
and large intestine.

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Life Cycle of Enterobius vermicularis
METHODS OF HUMAN INFECTION 1. Infective eggs
may be transmitted _____________
______________________________________________
Deposition of eggs by the female causes
_______________________ 2. Bed clothing and
bedding are contaminated with infective eggs and
ingested. 3. _____________________ - eggs are
inhaled and ingested.

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Life Cycle of Enterobius vermicularis
METHODS OF HUMAN INFECTION cont 4. Infective
eggs can become ______________________ (sweeping
in a bedroom) and can be inhaled and
swallowed. 5. _____________________ - if the
perianal region is not cleaned for some time,
infective eggs may hatch and the L3 wander into
the large intestine and molt to adults.

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Pathology of Enterobius vermicularis
1. Pinworms are generally considered to be
harmless as they do not invade any tissue. They
may cause ___________________ ____________________
______________________________. 2. They do cause
irritation of the anal region resulting
__________________________________________________
. Secondary bacterial infection in areas
scratched raw may occur. 3. Pinworms also cause
______________________________ - mental anguish
and embarrassment of parents whose kids have
"worms" - this often leads to frantic efforts to
eliminate the parasite and its eggs.

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Diagnosis of Enterobius vermicularis
DIAGNOSIS - ______________________is commonly
used. Use of double-stick tape on a tongue
depresser. This is pressed against the perianal
folds where eggs will stick to the tape. Tape
is then stuck onto a microscope slide and
examined for eggs.  

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Diagnosis of Enterobius vermicularis

• DIAGNOSIS - Eggs are distinct.
• football-shaped with one side flattened
• eggshell is smooth
• size -

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Treatment of Enterobius vermicularis
TREATMENT - pinworms are easily killed with drugs
- ________________________________________________
_ To prevent re-infection, treat the whole
family. Wash all bed clothes and bedding in hot
water to kill infective eggs.