Order Trichiurida
Order Trichiurida
• Trichuris trichiura
– Whipworm
• Trichinella spiralis
Trichuris trichiura
• 30-50 mm
• Long esophagus
surrounded by stichocytes
(glands)
– Stichosome
• Single gonad
• Males have single spicule
• Eggs have characteristic
shape 50-54 X 22-23 μm
• Direct Life Cycle
• Adults live in
cecum and
ascending colon
• Release eggs with
feces
• Eggs embryonate
in soil (21 days)
• Eggs ingested
• Hatch
• Juveniles enter
crypts of
Lieberkühn
Crypts of Lieberkühn
Tubular glands at base
of villi
• Juveniles enter
crypts of
Lieberkühn
(large intestine)
• Penetrate cells
• As they grow,
tunnel in
epithelium.
Posterior end
enters lumen
• Mating
• Egg production
Symptoms and Pathology
• Most symptom-less
• > 100 worms
– Heavy infections common (200 to over 1000 worms)
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Dysentery
Anemia
Growth retardation
Finger clubbing
Reduce cognitive function in children
Trichuris trichiura
• 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
• Rectal prolapse
Symptoms and Pathology
• Anterior end buried in mucosa
– Physical damage
– Fibrosis
– Chronic hemorrhage  anemia
Diagnosis
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Look for eggs in feces
Adult worms
Frank blood in feces
Treatment difficult
Mebendazole
Epidemiology
• Cosmopolitan
• Prevalence
– SE U.S. 20-25% in children
– U.S. 1.2%
• 902 million infected worldwide
Prolific
• Females produce 3,000-20,000 eggs per day
• Sensitive to environmental conditions
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High rainfall
Moisture retaining soil
Shade
Warm climate
Epidemiology
• Ingest Eggs with Juveniles!
– Very similar to Ascaris epidemiology
Trichinella spiralis
• Males 1.5 mm, Females 3
mm
• Short esophagus
• Stichosome
• Psuedobursa
• No copulatory spicule
• Single gonad
• Uterus contains fully
developed eggs
Trichinella spiralis
• Parasites of carnivorous mammals
• Causes Trichinosis
• Unusual life cycle
– Same individual host is both definitive and intermediate
host
– Adults in small intestine
– Juveniles inside muscle cells
• Largest intracellular parasite
• Def. host is infected
by ingesting juveniles
in the muscle of other
hosts
• Juveniles enter
intestinal mucosa
• 4 molts
• Growth
• Copulation
• Within 32 hours after
ingestion
Adults in small intestine
• Thread throughout
intestinal cells
• Females release
juveniles into
mucosa
• Thousands over 416 weeks
• Juveniles enter
hepatoportal system
• Carried to liver,
heart, lungs, then
arterial system
• Distributed
throughout body
• Penetrate cells of
skeletal muscle
• Grow to about 1 mm
• Infective in 4-6 weeks
• How do the juveniles fit inside a muscle
cell?
• How do juveniles survive inside a muscle
cell?
Nurse Cell
• Juveniles take over cell
– Redirect cell activities to their survival
• Alter gene expression
– From a contractile fiber
– To a cell that nourishes the worm
• Cell becomes encapsulated with
collagen
• Blood vessels form around the cell
• Juveniles arrest development
• Live for months-years and up to 39
years
• Die from calcification
Which muscles?
• Commonly
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Eye
Tongue
Masticatory
Diaphragm
Intercostals
Heavy muscles of arms and legs
Diagnosis and Treatment
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Most cases go undetected
Difficult to diagnose
Symptoms are vague
Difficult to find juveniles in tissue
– Muscle biopsy
– But too late
• No treatment to kill parasites
– Shielded from drugs
• Treat symptoms
Epidemiology
• Cosmopolitan
– Circumboreal (northern areas of North America and
Eurasia)
– Less common in tropical areas
• Common in U.S.
– 1940-1950 high prevalence
– Decreased until 1980
– Asian immigrants consuming raw pork
• Transmission cycles
– Domestic
– Sylvatic
Domestic Cycle
PIG
Nip tails
RAT
RAT
PIG
Cannibalism
Scavenging
Scavenging,
Eating human
garbage
DEAD END
Eat
undercooked
pork
Humans
Feed garbage
to pigs
Raise pigs
Create rat habitat
Keep infection cycle going
Eats rats
Sylvatic Cycle
Sylvatic Cycle
• Humans less commonly involved
• Hunting and eating wild game
Control and Prevention
• Cook meat thoroughly
– Pork
– Wild game
• Raw sausage is delicacy
– Mixture of different animals
• Freeze meat
– -15 C
Has trichinosis caused us to modify our
behavior?
• Cook pork thoroughly
• Pork uncommon in fast food restaurants
Order Oxyurida
• Enterobius vermicularis
– Pinworms
– Enterobiasis
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Large esophageal bulb
Sharp, pointed tail
Alae at anterior end
Cosmopolitan
Common in people
Relatively unpathological
• Direct life cycle
• Adults live in ileocecal
region of intestine
(wander throughout gut)
• Feed on bacteria and
organic material from
cells
• At night, females
migrate to anus and lay
eggs (up to 16,000 each)
• Embryonates within 6
hours
• Infection via ingestion of
embryonated eggs
• Or may hatch on
perianal folds and
wander up intestine
Symptoms and Pathology
• 1/3 asymptomatic
• Pruritus
• Lesions from feeding not significant
– Secondary infections can occur
• Itching can lead to secondary infections
Pinworm Neurosis
• Nervousness
– Fidgeting, restlessness, irritable, nail biting,
nose picking
– Due to toxemia and damage of epithelium
• Children
• Parents
– Obsessive cleaning
Diagnosis
• Scotch tape test
• Flashlight test
• Mebendazole
• Treat entire family
Diagnosis of Enterobius vermicularis
DIAGNOSIS -
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.
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.
Epidemiology
• Very Prolific
• Eggs build up fast
– Clothing and bedding
– Eggs very light and float
– Easily distributed
• Eggs viable for up to a
week
Prevention and Control
• Not very serious
• Good hygiene