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Helminthiasis
Helminthiasis
• Helminthiasis is a macroparasitic disease of
humans and animals in which a part of the body is
infested with parasitic worms such
as pinworm, roundworm, or tapeworm. Typically,
the worms reside in the gastrointestinal tract but
may also burrow into the liver or other organs.
• Helminthiasis can have immunomodulatory effects
on the host,[1] with implications for
any coinfecting pathogens.
Hymenolepiasis is caused by two
cestodes (tapeworm) species,
 Hymenolepis nana (the dwarf
tapeworm, adults measuring 15 to
40 mm in length) and
 Hymenolepis dimnuta (rat
tapeworm, adults measuring 20
to 60 cm in
length). Hymenolepis
diminuta is a cestode of rodents
infrequently seen in humans and
frequently found in rodents.
Hymenolepis Nana - Dwarf Tapeworm
• Hymenolepis nana is the most
common tapeworm in humans.
It is also known as the dwarf
tapeworm due to its particularly
small size (adults are only 15–40
mm long). The disease,
hymenolepiasis is found
worldwide. In temperate zones
children and institutionalized
people are infected more often.
The disease is somewhat
common in the eastern Europe.
Hymenolepis nana is the most common cause of all cestode infections,
and is encountered worldwide. In temperate areas its incidence is
higher in children and institutionalized groups. Hymenolepis
diminuta, while less frequent, has been reported from various areas of
the world.
Egg
• H. nana egg is colourless, almost
transparent, oval, 30–50 µm
(micrometers) in diameter, has polar
filaments. When shed in stool they are
immediately infective and survive up to
10 days in the external environment,
they are embryonated and have a 6hooked oncospheres inside the shells.
Shell consists of two distinct
membranes. On inner membrane there
are two small "knobs" or poles from
which 4–8 filaments arise and spread
out between the two membranes.
Scolex
• Scolex is small, 0.3
mm in diameter,
globular (rounded),
cup-like, situated at
the anterior end, has
four suckers and
retractile rostellum
with a single row of
20–30 hooks.
Proglottids.
• Gravid (mature, full of
eggs) proglottids are 0.2–0.3 mm
long and 0.8–0.9 mm wide.
Proglottid is filled with eggs, uterus
is not visible. Each proglottid has
both male and female reproductive
organs making Hymenolepis
nanahermaphroditic. A proglottid
copulates with itself or with other
segments of the same individual or
nearbyHymenolepis
nana tapeworms. Proglottids
usually disintegrate in the
gastrointestinal tract and are rarely
present in the feces.
Life Cycle:
Hymenolepis nana
• 1.Eggs of Hymenolepis nana are immediately infective when passed with the stool and
cannot survive more than 10 days in the external environment .
.
• 2.When eggs are ingested by an arthropod intermediate host
• 3.(various species of beetles and fleas may serve as intermediate hosts), they develop into
cysticercoids, which can infect humans or rodents upon ingestion
• 4. and develop into adults in the small intestine. A morphologically identical variant, H.
nana var. fraterna, infects rodents and uses arthropods as intermediate hosts. When eggs
are ingested
• 5.(in contaminated food or water or from hands contaminated with feces), the oncospheres
contained in the eggs are released. The oncospheres (hexacanth larvae) penetrate the
intestinal villus and develop into cysticercoid larvae .
• 6.Upon rupture of the villus, the cysticercoids return to the intestinal lumen, evaginate
their scoleces ,
• 7.attach to the intestinal mucosa and develop into adults that reside in the ileal portion of
the small intestine producing gravid proglottids .
• 8.Eggs are passed in the stool when released from proglottids through its genital atrium or
when proglottids disintegrate in the small intestine .
• 9.An alternate mode of infection consists of internal autoinfection, where the eggs release
their hexacanth embryo, which penetrates the villus continuing the infective cycle without
passage through the external environment . The life span of adult worms is 4 to 6 weeks,
but internal autoinfection allows the infection to persist for years.
Hymenolepis diminuta
1.
Eggs of Hymenolepis diminuta are passed out in the feces of the
infected definitive host (rodents, man) .
2. The mature eggs are ingested by an intermediate host (various
arthropod adults or larvae) ,
3. and oncospheres are released from the eggs and penetrate the
intestinal wall of the host ,
4. which develop into cysticercoid larvae. Species from the
genus Triboliumare common intermediate hosts for H. diminuta. The
cysticercoid larvae persist through the arthropod's morphogenesis to
adulthood. H. diminuta infection is acquired by the mammalian host after
ingestion of an intermediate host carrying the cysticercoid larvae .
5. Humans can be accidentally infected through the ingestion of insects
in precooked cereals, or other food items, and directly from the
environment (e.g., oral exploration of the environment by children). After
ingestion, the tissue of the infected arthropod is digested releasing the
cysticercoid larvae in the stomach and small intestine. Eversion of the
scoleces
6. occurs shortly after the cysticercoid larvae are released. Using the
four suckers on the scolex, the parasite attaches to the small intestine
wall. Maturation of the parasites occurs within 20 days and the adult
worms can reach an average of 30 cm in length .
7. Eggs are released in the small intestine from gravid proglottids
8. that disintegrate after breaking off from the adult worms. The eggs
are expelled to the environment in the mammalian host's feces .
Hymenolepiasis is usually asymptomatic in adults. But prolonged infection or
multiple tapeworms especially in children can cause more severe symptoms. The
worms eat your food and cause inflammation of the intestinal mucosa. The
inflamed tissue will have a reduced ability to absorb nutrients. People with little
food to begin with and those who are weakened by other diseases suffer the most.
Hymenolepiasis symptomssometimes include:
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anal itching
diarrhea (can be bloody)
headache
increased appetite or loss of appetite
insomnia
muscle spasms
nausea
nervousness
seizures
stomach ache
vomiting
weakness
weight loss.
Diagnosis:
• Your health care provider makes the diagnosis by identifying
tapeworm eggs in stool. Sometimes many stool specimens are
needed to make the diagnosis. Hymenolepis nana starts laying eggs
within a few weeks of the start of the infection and only after that it
is possible to find eggs. Alternatively adult worm can be identified
during endoscopic examination.
Hymenolepis Nana, adult, stained mount.
Treatment:
• Hymenolepiasis is usually treated with a prescription drug called
praziquantel which causes the tapeworm (both adults and larvae)
to dissolve. A single dose of praziquantel has an efficacy of 96 %. If
praziquantel is not available, niclosamide or albendazole can be
used instead.
To prevent getting
infected:
 Wash, peel or cook all fruits and
vegetables.
 Wash hands with water and soap
after using the toilet and before
preparing food or eating.
 Quit the habit of putting fingers in
your nose and mouth. The
microscopic parasite eggs are
sometimes found under fingernails
and can easily be ingested.
Enterobiosis.
• Enterobius
vermicularis, a small
nematode, is a common
cause of helminthic
infestation in the United
States. The female
nematode averages 10
mm X 0.7 mm, whereas
males are smaller. All
socioeconomic levels are
affected. Infestation often
occurs in family clusters.
Infestation does not
equate with poor home
sanitary measures (an
important point when
discussing therapy).
Pathophysiology
• E vermicularis is an obligate parasite; humans are the only
natural host. Fecal-oral contamination via hand-mouth
contact or via fomites (toys, clothes) are common methods of
infestation. After ingestion, eggs usually hatch in the
duodenum within 6 hours. Worms mature in as little as 2
weeks and have a life span of approximately 2 months.
• Adult worms normally inhabit the terminal ileum, cecum,
vermiform appendix, and proximal ascending colon. The
worms live free in the intestinal lumen. Little evidence
supports invasion of healthy tissue under normal conditions.
The female worm migrates to the rectum after copulation and,
if not expelled during defecation, migrates to the perineum
(often at night) where an average of 11,000 eggs are released.
Eggs become infectious within 6-8 hours and, under optimum
conditions, remain infectious in the environment for as long
as 3 weeks.
• See the image below.
Epidemiology
• Frequency
• United States
• Prevalence is approximately 5-15% in the general population; however, this rate has
declined in recent years. Prevalence rates are probably higher in institutionalized
individuals. Humans are the only known host.
• International
• E vermicularis infestation occurs worldwide. Prevalence data vary by country.
• Mortality/Morbidity
• Secondary bacterial skin infection may develop from vigorous scratching to relieve
pruritus. Reinfestation is common. Infection can develop as long as female pinworms
continue to lay eggs on the skin. Restless sleeping may be due to pruritus ani. Infestation
has been reported to cause enuresis.
• Immunocompromised
• Although other helminthic infection rates are shown to be higher in patients with HIV,
studies to date have not shown a statistically significant difference forEvermicularis.[1]
• Race
• All races are subject to infestation.
• Sex
• Infestation can occur in males and females.
• Age
• The prevalence is greatest in children aged 5-9 years, but all ages can be affected
Symptoms
• Patients with enterobiasis are often asymptomatic. Worms may be incidentally discovered
when they are seen in the perineal region.
• If patients are symptomatic, pruritus ani and pruritus vulvae are common presenting
symptoms. However, one study failed to find an increase of these symptoms in infested
children compared with matched control subjects.
• Restlessness during sleep is noted by the parents of many patients.
• Enuresis may be a symptom in children with pinworms.
• Patients often have excoriation or erythema of the perineum, vulvae, or both, but
infestation can occur without these signs.
• Visual sighting of a worm by a reliable source (eg, a parent) is usually accepted as evidence
of infestation and grounds for treatment.
• Worms can be found in stools or on the patient's perineum before bathing in the morning.
• Occasionally, the gravid female worm may aberrantly migrate into the female genitalia and
produce vaginitis.[2] Incidental recovery at necropsy or surgery of small granulomatous
lesions surrounding the worm, larvae, or eggs in the salpinx and peritoneum demonstrates
the worm's ability to ascend the female genital tract.
• Abdominal pain may sometimes be severe and can mimic acute appendicitis.
Differentials
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Appendicitis
Ascariasis
Cervicitis
Contact Dermatitis
Giardiasis
Laboratory Studies
• Without a visual report, diagnosis of enterobiasis can be
confirmed using the knowledge that eggs are normally
deposited in great quantities on the perineum at night.
• Wide (2 inch) transparent tape is pressed against the
perineum at night or in the morning before the patient bathes
to capture eggs.[4] Three such specimens are usually
consecutively collected.
• Diagnosis is made by identifying eggs under the low-power
lens of microscope. Dilute sodium hydroxide or toluene
should be added to the slide.
Medical Care
• Fear, disgust, and guilt are
common parental reactions to a
parasitic worm infestation, such
as enterobiasis. Many families
present to the emergency
department or their pediatrician
with misconceptions about
pinworms. In addition to
prescribing medications,
educating families about
pinworms (see Patient
Education) is helpful.
• Thorough and regular
handwashing is effective in
preventing disease
transmission.
Medication Summary
• Mebendazole or albendazole are recommended as first-line treatment of
pinworms. A second dose given 2 weeks after the initial dose helps prevent
reoccurrences from reinfection.
• Because asymptomatic infestation of other members in a household is
frequent, simultaneously treating all household members may be
reasonable. Families should be informed that repeat infestations are
common. Reinfestation is treated with the same medications as the initial
infestation.
• Symptomatic relief of pruritus can be obtained by applying an antipruritic
ointment or cream topically to the affected (usually perianal) region.
• Anal albendazole may help with symptoms of pruritus ani. A recent letter to
the editor stated a “local application of albendazole using an ear bud soaked
with the residual albendazole suspension in the vial” in addition to the
recommended oral dose of albendazole provided dramatic relief of pruritus
ani.[5]
• Ivermectin has been shown to have decreased efficacy as a single agent,
compared with albendazole.[6] However, it may possess efficacy when given
as an adjunct.
Anthelmintics
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Class Summary
Parasite biochemical pathways are different from the human host, thus toxicity is directed to the parasite,
egg, or larvae. Mechanism of action varies within the drug class.
•
Pyrantel pamoate (Antiminth, Pin-Rid, Pin-X)
•
Depolarizing neuromuscular blocking agent and inhibits cholinesterases, resulting in spastic paralysis of
the worm. Purging not necessary. May be taken with milk or fruit juices.
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Mebendazole (Vermox)
•
Causes worm death by selectively and irreversibly blocking uptake of glucose and other nutrients in
susceptible adult intestine where helminths dwell.
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Albendazole (Albenza)
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A benzimidazole carbamate drug that inhibits tubulin polymerization, resulting in degeneration of
cytoplasmic microtubules. Decreases ATP production in worm, causing energy depletion, immobilization,
and finally death. Converted in the liver to its primary metabolite, albendazole sulfoxide. Less than 1% of
the primary metabolite is excreted in the urine. Plasma level is noted to rise significantly (as much as 5fold) when ingested after high-fat meal. Experience with patients < 6 y is limited.
To avoid inflammatory response in CNS, patient must also be started on anticonvulsants and high-dose
glucocorticoids.
•
Inpatient & Outpatient Medications
• An antihelminthic medication should be
prescribed to patients with enterobiasis .
• Application of an antipruritic ointment or
albendazole may help control scratching.[5]
Complications
• Beware of skin infection from vigorous scratching to
relieve pruritus.
• Pinworms have been associated with appendicitis.[7,
8] However, small and large intestine ulcerations,
perianal abscesses, intestinal pain, transient
synovitis, or enuresis is believed to be coincidental
and not causal.[9]
• If a patient with enterobiasis is refractory to
treatment, consider the possibility of an infestation
with Dipylidium caninum, which is a common
tapeworm that infects domestic cats and dogs.[10]
Patient Education
• Inform families that dogs and cats do not harbor E vermicularis.
• Inform families that infestation may occur in spite of proper child and
household hygiene.
• Counsel families to avoid overreaction through aggressive sanitary
measures. Because infectious eggs may be in bedclothes and dust and
remain infectious for 20 days, wet-mopping floors or vacuuming carpets
and washing bedclothes are prudent precautions.
• Reassuring families that pinworms are not a sexually transmitted disease
and are not evidence of child abuse may be helpful.
• Keeping the patient's fingernails trimmed to prevent excoriations is helpful.
• Avoid scratching the area and nail biting because this is a cause of
autoinfection.
• Encourage the patient to bathe in the morning, this significantly reduces
the number of eggs.
• Children may return to school once they have received a dose of medication,
bathed, and have nails trimmed.
• Bed linens should be washed in hot, soapy water.
Enterobiasis and
child
• Enterobiasis is a disease caused by tiny
parasitic worms - pinworms or Enterobius
vermicularis. Pinworms do not exceed 1 cm at
length. Usually one end of this worm is pointed
(hence comes the name) and the other rounded.
Parasites may have different color: from
thewhitish or yellow to dark or even black.
Living pinworms may crawl or squirm.
Pinworms are nocturnal animals: it is at night
when the females of pinworms go into the
rectum and skin around the anus, causing
discomfort and itching. They lay eggs in the folds
of the skin and die.
• Infection is transmitted through dirty
hands or contaminated objects. Child,
combing or touching the skin of the perineum,
contaminate hands with the worm eggs. After
contaminated hands contact the bed or
underwear eggs come from the body of a patient.
The role of flies andcockroaches in the
transference of pinworm eggs is proven. A reinfection when mature pinworm moves from
the skin into the anus is not very rare.
Enterobiasis is very common human parasitic
disease and it is considered to be the most
common infections worldwide. In some baby
groups up to 100% of children are infected with
pinworms.
Syptoms
• The period from contamination to onset of
symptoms at enterobiasis is 12 - 14 days. This is the
time when pinworms reach maturity age. The main
symptoms of the disease is itching ordiscomfort in
the anus, redness around the anus or perineum
especially after defecation, the increased interest of
the child to his genitals, masturbation. In girls, in
addition, pinworms can creep in genital tract,
causing inflammation and infections
(vulvovaginitis, urethritis, thrush). Also the child
becomes an excitable in the evening and very
moody. For a long time a child can not fall asleep,
sleeping restlessly - often wakes up and screams
during sleep, crying, tossing on the bed.
Simultaneously a daytime sleep may be
normal. These symptoms may occur not every
day, if there's a bit worms in the gut. But when the
number of parasites increases - the described
discomfort may become permanent. In addition,
pinworms, like any other focus of chronic infection
can cause a malfunction in the bowel (abdominal
pain, excessive
flatulence, constipation ordiarrhea, food
maldigestion, etc.), allergic
reactions, intoxication (lethargy, fatigue, irritabilit
y, teeth grinding or bruxism), lead to
intestinal dysbacteriosis.
Diagnosis
• The diagnosis of enterobiasis isn't very difficult,
especially if pinworms are found. They can be
seen in the evening or at night near the anus
or on the skin folds or on the bedclothes.
Sometimes you can see the worms in the
excrements. A special study for the detection of
pinworm eggs - scraping on enterobiasis (smearing of skin folds around the anus, or
sticking this area with adhesive tape) sometimes
can not reveal the disease if a pinworm had not
laid eggs before. Hence, scraping on enterobiasis
should be conducted in the morning after a night
when a child could not sleep or slept restless. An
important moment - you shouldn't wash a
child before scraping. If you receive a negative
result, repeat the scraping for several times
during 1 - 2 weeks.With a strong suspicion about
enterobiasis a treating should be started even if
pinworms or their eggs are not found!