Trichurid Nematodes - Chapter 23
Trichuris trichiuraCommon name - ______________________________
Cosmopolitan. Most common in warm climates.
- In southeastern U.S. - prevalence rates of 20 to 25% in children
- In Wisconsin?
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.
Trichuris trichiura
EGGS are diagnostic in human feces:
Characteristics -
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
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
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:
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
Trichuris trichiura
TREATMENT –
PREVENTION -
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 ____________________.
Other species of Trichuris
Trichuris suis occurs in pigs.
• research is underway to use T. suis as a treatment of Crohn’s Disease in humans
• Crohn’s 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
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)
Trichinella spiralis
Jim Paget Worms in the “sandy diaphragm”
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.
Life Cycle worked out in 1850’sRudolph Virchow. the famous German pathologist, is generally acknowledged as the person who, through basic laboratory experimentation, deciphered the essentials of the life cycle of Trichinella spiralis. To do so, Virchow took advantage of serendipity; an old dog and a fresh cadaver whose muscle tissue was riddled with white flecks. Microscopic examination confirmed that the flecks were, indeed, Trichinella spiralis larvae just waiting to be eaten. Rudolph fed his poor unsuspecting canine a large quantity of this infected human muscle tissue. Days later, when he autopsied the now dead dog, he observed the adult worm in the small intestine, and concluded correctly that trichinella may cause disease in humans as well.
Needless to say, Rudolph’s reputation as a pathologist grew faster after this incident, and as the result, he became more and more pro-active. He even went so far as to become a member of the prestigious Rathause. While expounding one day before that distinguished political body, he inadvertently managed to argue against a policy coveted by none other than Baron von Bismarck. As the offended person, the good Baron challenged Virchow to a duel, and this gave Virchow the first choice of weapons. The story goes on that Rudolph chose sausages, one with and one without you-know-who. Upon explaining the potential lethality of his weaponry to Bismarck, the now enraged and thoroughly frustrated Baron less-than-politely declined to dine.
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
Cases of Trichinella spiralis
Number of cases in U.S. has steadily decline
Large outbreaks occur on occasion
Outbreak of Trichinella spiralis in Wisconsin
April 1991
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
Adults of Trichinella spiralis
Male is recognized by long ________________________ and 2 caudal _____________________________.
Copulatory appendages
stichosome
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?
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.
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.
Life Cycle of Trichinella spiralis
Adult female in mucosa of small intestine
Trichina cysts in skeletal muscle
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
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
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 - _________________________
_______________________________
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
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 ______________________
_________________________________
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
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.
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 _______________________
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.
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? _________________________________
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
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
