Trichurid Nematodes Chapter 23 Trichuris trichiura

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Trichurid Nematodes - Chapter 23Trichuris
trichiura
Common name - ______________________________ Cosmo
politan. Most common in warm climates.
- In southeastern U.S. - prevalence rates of 20
to 25 in children - In Wisconsin?
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Trichuris trichiura
ADULTS measure 30 to 50 mm in length. - Anterior
end is narrow and threadlike consists of a long
glandular esophagus called the ___________________
_____ - Posterior end is thickened and contains
the intestine and tubular reproductive organs.
Male has coiled posterior end due to spicule.  
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Trichuris trichiura
EGGS are diagnostic in human feces Characteristic
s -
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Life Cycle of Trichuris trichiura
1. Adults live in the human _____________________
_______________________________ 2. Female
releases 1000 to 7000 unembryonated
double-plugged eggs each day. 3. Eggs are
deposited onto warm, moist shady soil where they
embryonate to the L1 stage.  
Egg with L1
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Life Cycle of Trichuris trichiura
4. ________________________ is the infective
stage and is ingested. 5. L1 hatch from the egg
in the small intestine and burrow into the mucosa
where they _______________________________________
_____________ 6. Adults migrate to the ileocecal
and colon regions. __________________________
is inserted into the wall of the intestine
penetrating through the mucosa and into the
submucosa where blood is ingested.
Egg with L1
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Pathology of Trichuris trichiura
Fewer than 100 worms cause little pathology -
asymptomatic to minor intestinal pain.
Heavy infections cause serious problems  (1)
__________________________________________-
hemorrhaging occurs as worms penetrate into the
submucosal region and feed on blood. Fatalities
common in children. Results  
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Pathology of Trichuris trichiura
(2) _____________________________________ - worms
cause loss of muscle tone in wall of rectum and
it everts out the anus whipworms are often seen
attached to the rectal tissue

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Trichuris trichiura
TREATMENT PREVENTION -
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Other species of Trichuris

• Many other species of Trichuris infect mammals
• Trichuris vulpis is common parasite of
  __________________
• see demo. in lab
• Trichuris suis occurs in ________________
• Trichuris ovis occurs in ____________________.

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Other species of Trichuris

• Trichuris suis occurs in pigs.
• research is underway to use T. suis as a
  treatment of Crohns Disease in humans
• Crohns disease involves inflammation of large
  intestine due to high T helper cell response
• T. suis dampens the T cell response and reduces
  inflammation
• Because humans are abnormal hosts, the parasites
  do not reproduce and eventually die
• Recent paper Trichuris suis appears safe and
  effective in the treatment of inflammatory bowel
  disease A possible example of TH2 conditions of
  the mucosal immune response

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Trichinella spiralis
Causative agent of trichinosis in humans and many
other mammals. Trichina worms were described in
1835 from a human autopsy.  Young Jim Paget, a
first year medical student at London Hospital
Medical School, rushed into the autopsy room. The
51 yr-old Italian bricklayer who had died of
tuberculosis, and that they were now dissecting,
also had "sandy diaphragm," a condition that
dulled even the sharpest of scalpels. Well,
anyway, when they had all cleared the room, Jim
quietly stole back in and removed a small bit of
muscle tissue from the diaphragm. He was more
than curious as to the nature of "sandy
diaphragm". He first examined it with his trusty
hand lens he carried for just such a situation.
He thought he saw small worms coiled up inside
each nodule. Upon even higher magnification, the
presence of coiled worms was revealed.
(From www.trichinella.org)
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Trichinella spiralis
Jim Paget Worms in the
sandy diaphragm
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Trichinella spiralis
Trichina worms were observed in pork in 1846 by
Joseph Leidy. He saved hundreds of lives by
recommending cooking pork at a high enough
temperature to kill the organism.  
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Life Cycle worked out in 1850s
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Distribution of Trichinella spiralis
Trichinosis is most common in temperate and
arctic climates - 2 strains - high prevalence in
pork-eating areas of the world  - in U.S. and
Wisconsin?
arctic
temperate
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Cases of Trichinella spiralis
Number of cases in U.S. has steadily
decline Large outbreaks occur on occasion



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Outbreak of Trichinella spiralis in Wisconsin



April 1991
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Adults of Trichinella spiralis
Adults are very small, _______mm in
length. _________________________ forms first
half of the worm. Female is identified by
presence of ___________________________________.
Eggs hatch in utero and females give birth
to_________________
stichosome
Hatched L1
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Adults of Trichinella spiralis
Male is recognized by long _______________________
_ and 2 caudal _____________________________.
stichosome
Copulatory appendages
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Trichinella spiralis
HOSTS - __________________________________________
can serve as hosts of Trichinella spiralis Hosts
include pigs, rats, bear (all types including
polar bear), canids, felids, mustelids, and
marine mammals. Why is life cycle unusual?
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Life Cycle of Trichinella spiralis
1. Mammal eats another mammal containing
____________________________ 2. Cyst wall is
digested in the stomach and the larvae (L1) are
released. They molt 4 times to the
________________________ 3. Adults occur in the
___________________________. Adults copulate
(male dies) and the female migrates into the
intestinal mucosa to release her larvae. 4.
Female gives birth to 1500 larvae over period of
1 - 4 months.
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Life Cycle of Trichinella spiralis

• 5. L1 enter the circulation and are carried to
  all organs of the body.
• 6. L1 eventually reach the ______________________
  _______and become encapsulated by host tissue
  within a muscle cell.
•   Trichina cysts may become calcified by the host
  after 9 mo.
• Cysts can remain viable for many years.
• 7. If this mammal with trichina cysts is eaten
  by another mammal, the cycle begins all
  over.

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Life Cycle of Trichinella spiralis
Adult female in mucosa of small
intestine Trichina cysts in skeletal muscle
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Life Cycle of Trichinella spiralis
MAINTENANCE CYCLES 1. ____________________________
_- pigs are fed household garbage containing pork
scraps infected with trichina cysts or by
tail-biting. 2. _____________________________-
pigs eat dead or dying rats. 3.
_____________________________- cannabalism common
in rats 4. _____________________________- occurs
commonly in nature
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Life Cycle of Trichinella spiralis

• SOURCES OF HUMAN INFECTIONS
• 1. Most causes of human trichinosis are from
  ingestion of _____________________________________
  _
•   U.S. pigs have a 0.7 prevalence of this
  parasite it is NOT inspected for
  by USDA inspectors.
• 2. Some cases are from ingestion of poorly
  cooked ______________________________
• 3. Few cases are from ingestion of raw or poorly
  cooked ______________________________(recent
  outbreak in France)
• 4. Rare cases from eating unusual carnivores -
  recent case from cougar jerky
• Read case reports of these
  in lab

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Pathology of Trichinella spiralis

• Majority of infections are light and produce only
  mild symptoms - commonly misdiagnosed as the flu.
• 4 stages of pathology in heavy infections
• 1. Invasion - ______________________________
• __________________________________
• first symptoms appear 12 hours to 2 days
  following ingestion of trichina cysts
• inflammation of mucosa
• symptoms - _________________________
• _______________________________
•  

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Pathology of Trichinella spiralis

• 2. migration of larvae
• damage to blood vessels causes
  ______________________ (symptoms are puffy face
  and hands)
• damage to ____________________ by wandering
  larvae (abnormal EKG's)
• hypereosinophilia

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Pathology of Trichinella spiralis
3. penetration and encystment in skeletal
muscles - _______________________________ -
_______________________________ -
_______________________________ - difficulty in
breathing and swallowing respiratory muscles -
intercostals and diaphragm) and tongue are
heavily parasitized) - death may occur between
the 4th and 6th weeks due to _____________________
_ _________________________________  


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Pathology of Trichinella spiralis

4. calcification (if one survives stage 3!) -
occurs 9 months after infection - calcium is
deposited around the cysts - L1 eventually die
in a year or so

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Pathology of Trichinella spiralis

• In human infections, 5 larvae/gram body weight
  are fatal.
•  (i.e., in a 150 lb. person x 454 g/lb x 5 larvae
  340,500 larvae)
• Heavy infections in pork are common, as 1 oz. of
  infected sausage may contain 100,000
  trichina cysts
• If half are females (50,000), each producing
  1500 larvae, 75 million larvae can be
  produced. Death occurs.
• Pigs can tolerate 10 larvae/ gm body wt.
•  
• Rats can tolerate 30 larvae/ gm body wt.

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Diagnosis of Trichinella spiralis



No method to diagnose adults. 2 methods to
diagnose larvae 1. _____________________________
__ - trichina cysts can be seen with
microscope 2. ELISA to identify Trichinella
_______________________
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Treatment of Trichinella spiralis



Drug treatment is not effective. Why?
___________________________________________
________________________________________________
Many drugs are effective against adults, but
trichinosis is not suspected until larvae are in
the muscles.
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Prevention of Trichinella spiralis

• 1. Thorough cooking of __________________________
  ____ (temperature above 58o C. or 137o F.)
• - microwave cooking of pork roasts and chops
  (with bone) is NOT efective in killing trichina
• federal inspection? ______________________________
  ___

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Prevention of Trichinella spiralis
2. _______________________________ at -5o F. for
20 days will kill temperate climate strain -
BUT freezing is NOT effective against the arctic
strain (several expeditions to the north pole
ended in disaster due to trichinosis in the
explorers from eating poorly cooked polar bear or
walruses) - smoking, salting, and drying pork,
bear or other meat will NOT kill
trichina larvae



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Prevention of Trichinella spiralis



3. ____________________________________________  
- Do not feed pork scraps in garbage to pigs
(many states have laws requiring
heat treatment of garbage if it is fed to pigs)
- clip pig tails after birth - eliminate rats in
areas where pigs are kept
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