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Tapeworm Infection
Tapeworm Infection
-It is the infection of the digestive tract by adult parasitic
flatworms called cestodes or tapeworms.
-It is caused by ingesting food or water contaminated with
tapeworm eggs or larvae cysts.
-Tapeworm larvae develop into adult tapeworms in the
intestines (intestinal tapeworm infection). However, some
tapeworms can also migrate outside the intestines and form
cysts in body tissues and organs (invasive tapeworm
infection).
-Intestinal tapeworm infections are usually mild, but invasive
tapeworm infections can cause serious complications.
An adult tapeworm consists of a head, neck and chain of segments
called proglottids which contain eggs. An intestinal tapeworm head
adheres to the intestine wall, and the proglottids grow and produce
eggs. Adult tapeworms can live for up to 20 years in a host.
Common types
The most common types of tapeworm infections in
humans are:
-Pork tapeworm (Taenia solium)
-Beef tapeworm (Taenia saginata)
-Dwarf tapeworm (Hymenolepis nana)
-Fish tapeworm (Diphyllobothrium latum)
Most occurrences are found in areas which lack
adequate sanitation and include Southeast Asia
and East Africa.
Transmission
1-Ingestion of eggs
Tapeworm eggs are generally ingested through food, water or soil
contaminated with human or animal (host) feces. For example, if a
pig is infected with a tapeworm, it may pass eggs or segments
(proglottids: egg bearing parts) of the adult tapeworm through its
feces into soil. Each segment contains thousands of microscopic
tapeworm eggs. These eggs can be ingested via food contaminated
with the feces. Once the eggs have been ingested, they develop into
larvae, which either grow to adult worm in the intestine (Taeniasis)
or these larava can migrate out of the intestines and form cysts in
other tissues such as the lungs or liver or the brain . This type of
infection is not common with beef or fish tapeworms, but can occur
with the pork tapeworm — causing what is called Cysticercosis —
(i.e) For the pork tapeworm only, people who ingest the eggs can
become an intermediate host.
Cont. Transmission
Ingestion of larvae cysts in meat or muscle tissue
-Untreated infected human waste when released into the environment, the
eggs may be ingested by intermediate hosts, such as pigs, cattle, or (in the
case of fish tapeworms) small crustaceans, which are in turn ingested by
fish. The eggs hatch into larvae in the intermediate host. The larvae invade
the intestinal wall and are carried through the bloodstream to skeletal
muscle and other tissues, where they form cysts.
-Eating raw or undercooked meat from an animal or a fish that has the larval of
the tapeworm in form of cysts in its muscle tissue lead to tapeworm
infection.
-Once ingested, the larvae is released ,and then develop into adult tapeworms
in the intestines of the human host. Adult tapeworms can measure up to 50
feet long and can survive as long as 20 years. Some tapeworms attach
themselves to the walls of the intestine, where they cause irritation or mild
inflammation, while others may pass through to the stool and exit the body.
Symptoms
Intestinal tapeworms in the intestine usually cause no symptoms, some people
experience the following:
-Nausea
-Weakness
-Loss of appetite
-Abdominal pain
-Diarrhea
-Weight loss and inadequate absorption of nutrients from food
-Occasionally, a person with a tapeworm can feel a piece of the worm move out
through the anus or see part of the ribbon-like tapeworm in stool.
-The fish tapeworm (Diphyllobothrium latum) can cause anemia because it
absorbs vitamin B12, which is necessary for red blood cells to mature.
If tapeworm larvae have migrated out of the intestines
and formed cysts in other tissues, as in the brain and the
tissues covering the brain (meninges) it will cause
cysticercosis and result in neurological symptoms as:Headaches ,
-confusion
-Seizures
-Fever
-Cystic masses or lumps
-Allergic reactions to the larvae
P.S.: It can take years of development before the patient
has those symptoms of the brain.
-Rarely, cysts develop in the eyes, sometimes causing
blindness, or in the spinal cord, sometimes causing
muscle weakness or paralysis.
Diagnosis
-Diagnoses of intestinal tapeworm infection is microscopic
identification to check for eggs or tapeworm segments in
the feces. Because the eggs and segments are passed
irregularly, the lab may need to collect two to three
samples over a period of time to detect the parasite.
-Eggs are sometimes present at the anus, so the doctor
may use the "Scotch tape test," in which a piece of
transparent tape is pressed to the anus to collect eggs
for microscopic identification.
-In people with cysticercosis, cysts in the brain or other
tissues can be seen using computed tomography (CT) or
magnetic resonance imaging (MRI). Blood tests for
antibodies to the pork tapeworm may also be helpful.
Prevention
1-The first line of defense against tapeworms is thoroughly
cooking meat and freshwater fish.
2-Prolonged freezing can also kill cysts. Thus, freshwater
fish should not be served as sushi, and should be eaten
only after it has been cooked, or properly froze(Smoking
and drying do not kill cysts).
3-Another line of defense is careful evaluation of meat and
fish by trained inspectors. As cysts are visible in infected
meat.
4-Adequate treatment of human waste interrupts the life
cycle and thus helps prevent cysticercosis
Treatment
Tapeworms are treated with medications
taken by mouth, usually in a single dose.
The drug of choice for tapeworm infections
is niclosamide. Praziquantel is also
effective ,and albendazole (mainly for cerebral
cysticercosis) are also being used
Niclosamide
Mechanism of action
Niclosamide uncouples oxidative phosphorylation in the
tapeworm As it inhibits the mitochondrial A laxative should
be taking before and during drug administration to avoid
disintegration of died worm and the release of the eggs
with increasing possibility of cycticercosis anaerobic
phosphorylation of ADP to ATP.
Adverse Effects
The medication can have side effects such as abdominal
pain, anorexia, diarrhea, and emesis. Rarely, dizziness,
skin rash, drowsiness, perianal itching, and an unpleasant
taste.
Praziquantel
Mechanism of action
It increases the permeability of the membranes of
parasite cells for calcium ions. The drug thereby
induces contraction of the parasites resulting in
paralysis in the contracted state. The dying
parasites are dislodged from their site of action in
the host organism and may enter systemic
circulation or may be destroyed by host immune
reaction (phagocytosis).
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Side effects
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The majority of side-effects develop due to the release of the
contents of the parasites as they are killed and the consequent host
immune reaction.
Drowsiness ,dizziness, headache, and malaise fatigue, and vertigo
have also been seen.
Almost all patients with cerebral cysticercosis experience CNS side
effects related to the cell-death of the parasites (headache,
worsening of preexisting neurological problems, seizures). These
side effects may be life-threatening and can be reduced by
coadministration of corticosteroids. It is strongly recommended that
all patients with cerebral cysticercosis are hospitalized during
treatment.
Approximately 90% of all patients have abdominal pain or cramps
with or without nausea and vomiting.
Urticaria, rash, and pruritus.
Fever, sweating, various cardiac arrhythmias, and hypotension
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Albendazole
Mechanism of Actions:
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Albendazole and its metabolite albendazole sulfoxide are thought to
act by inhibiting microtubule synthesis in the worm , thus irreversibly
impairing glucose uptake. As a result, parasites are immobilized or
die slowly, and their clearance may not be complete until several
days after treatment.
Albendazole also has been shown to inhibit the enzyme fumarate
reductase, which is helminth-specific. This action may be
considered secondary to the effect on the microtubules due to the
decreased absorption of glucose. This action occurs in the presence
of reduced amounts of nicotinamide-adenine dinucleotide in reduced
form (NADH), which is a coenzyme involved in many cellular
oxidation-reduction reactions.
Patients being treated for neurocysticercosis should receive
appropriate steroid and anticonvulsant therapy as required. Oral or
intravenous corticosteroids should be considered to prevent cerebral
hypertensive episodes during the first week of treatment.
Adverse Reactions
 Albendazole may cause dizziness, headache, fever,
nausea, vomiting, or temporary hair loss.
 In rare cases it may cause persistent sore throat,
severe headache, seizures, vision problems,
yellowing eyes or skin, dark urine, stomach pain,
mental/mood changes.
 CBC and hepatic functions have to be obtained
regularly in patients receiving Albendazole.
 The drug, which is teratogenic and embryotoxic
(even do not become pregnant for one month after
taking this drug).
Treatments for invasive tapeworm infection
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Treating an invasive infection depends on the location and effects of
the infection.
Anthelmintic drugs. Albendazole can shrink some tapeworm cysts.
Monitoring the cysts periodically using ultrasound or X-ray (to be
sure the drug is effective )is needed.
Anti-inflammatories.
Anti-epileptic therapy.
Shunt placement. One type of invasive infection can cause too
much fluid on the brain, called hydrocephalus. Placing a permanent
shunt, or tube, in the head of the patient to drain the fluid is required.
Surgery. Whether cysts can be removed surgically depends on their
location and symptoms. Those that develop in the eyes are typically
removed, since they can eventually threaten organ function.