Ascaris Lumbricoides

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Ascaris Lumbricoides
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Ascaris Lumbricoides

• -Ascariasis is caused by the parasitic roundworm
  Ascaris lumbricoides. Perhaps as many as one
  quarter of the world's people are infected. It is
  the largest of the intestinal nematodes
  parasitizing humans.
• -It is the most common worm found in human ,and
  it is worldwide in distribution and most
  prevalent in tropic areas with more prevalent
  in the countryside than in the city

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Adult worm of A. lumbricoides
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• Factors favoring the spread of the transmission
• 1.  Simple life cycle.
• 2. Enormous egg production ( 240,000 eggs/ day/
  female).
• 3. These eggs are highly resistant to ordinary
  disinfectants.The eggs may remain viable for
  several years.
• 4. Social customs and living habits.
• 5. Disposal of feces is unsuitable.

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Life Cycle 1. Site of
inhabitation small intestine 2.
Infetive stage embryonated eggs 3.
Route of infection by mouth 4. No
intermediate and reservoir hosts 5.
Life span of the adult worm about 1 year-This
worm lives in the lumen of small intestine,
feeding on the intestinal contents, where the
fertilized female lays eggs. An adult female can
produce approximately 200,000 eggs per day, which
are passed in feces. When passed, the eggs
require outside development of about three weeks
until a motile embryo is formed within the
egg.
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• - After the ingestion of embryonated eggs
  (infective) in contaminated food or drink or from
  contaminated fingers, host digestive juices acts
  on the egg shell and liberate the larva into the
  small intestine.
• -These larvae penetrate the intestinal mucosa and
  enter lymphatics and mesenteric vessels. They are
  carried by circulation to the liver, heart and
  finally to the lungs where they penetrate the
  capillaries into the alveoli in which they molt
  twice and stay for 10-14days.
• -Then they are carried, or migrate, up the
  bronchioles, bronchi, and trachea to the thorate.
  When swallowed, the larvae pass down into the
  small intestine where they develop into adults.
• -The time from the ingestion of embryonated eggs
  to oviposition by the females is about 60-75
  days. The adult worms live for about one-two
  year.

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Pathogenesis

• There are two phase in ascariasis
• 1. The blood-lung migration phase of the larvae
  During the migration through the lungs, the
  larvae may cause a pneumonia. The symptoms of the
  pneumonia are low fever, cough, blood-tinged
  sputum, asthma. Large numbers of worms may give
  rise to allergic symptoms. Eosionophilia is
  generally present. These clinical manifestation
  is also called Loefflers syndrome.

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• 2. The intestinal phase of the adults.
• The presence of a few adult worms in the lumen of
  the small intestine usually produces no symptoms,
  but may give rise to vague abdominal pains or
  intermittent colic, especially in children. A
  heavy worm burden can result in malnutrition.
• -More serious manifestations have been observed.
  Adults worm may block the the common bile duct
  and even perforate the intestinal wall.
• -Thus complications of ascariasis, that may occur
  include intestinal obstruction, appendicitis,
  biliary ascariasis, perforation of the intestine,
  pancreatitis and peritonitis, enlargement of the
  liver or spleen, etc.
• -other complications, sometimes fatal, include
  obstruction of the bowel by a bolus of worms
  (observed particularly in children). More than
  796 Ascaris lumbricoides worms weighing 550 g 19
  ounces were recovered at autopsy from a
  2-year-old South African girl. The worms had
  caused torsion and gangrene of the ileum, which
  was interpreted as the cause of death.

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• Source
• Ingestion of infective eggs from soil
  contaminated with human feces or transmission and
  contaminated vegetables and water is the primary
  route of infection.
• -Intimate contact with pets which have been in
  contact with contaminated soil may result in
  infection, while pets which are infested
  themselves by a different type of roundworm can
  cause infection with that type of worm.
• -Transmission also comes through municipal
  recycling of wastewater into crop fields. This is
  quite common in emerging industrial economies,
  and poses serious risks for not only local crop
  sales but also exports of contaminated
  vegetables. A 1986 outbreak of ascariasis in
  Italy was traced to irresponsible wastewater
  recycling used to grow vegetable exports .
• -Transmission from human to human by direct
  contact is impossible.

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Diagnosis

• The confirmative diagnosis depends on the
  recovery and identification of the worm or its
  egg.
• 1. Ascaris pneumonitis examination of
  sputum for Ascaris larvae is sometimes
  successful.
• 2. Intestinal ascariasis feces are examined
  for the ascaris eggs.
• (1) direct fecal film it is simple and
  effective. The eggs are easily found using this
  way due to a large number of the female
  oviposition, approximately 240,000 eggs per worm
  per day. So this method is the first choice.
• (2) recovery of adult worms when adults
  or adolescents are found in feces or vomit and
  tissues and organs from the human infected with
  ascarids , the diagnosis may be defined.
• (3) On X-ray, 1535 cm long filling
  defects, sometimes with whirled appearance
  (bolus of worms).

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• Treatment
• Drugs that are used to kill roundworms are called
  ascaricides and include
• 1-Benzimidazole derivatives
• a-Mebendazole
• Causes slow immobilization and death of the worms
  by selectively and irreversibly blocking uptake
  of glucose and other nutrients in susceptible
  adult intestine.
• Drug interactions
• -Carbamazepine and Phenytoin lowers serum levels
  of mebendazole. Cimetidine raises serum
  mebendazole levels, increasing its effectiveness.
• -Stevens-Johnson syndrome (toxic epidermal
  necrolysis) when Mebendazole is combined with
  high doses of Metronidazole.

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• b-Albendazole
• A broad-spectrum antihelminthic agent that
  decreases ATP production in the worm, causing
  energy depletion, immobilization, and finally
  death.
• -It causes degenerative alterations in the
  intestinal cells of the worm by binding to the
  colchicine-sensitive site of tubulin, thus
  inhibiting its polymerization or assembly into
  microtubules. The loss of the cytoplasmic
  microtubules leads to impaired uptake of glucose
  by the larval and adult stages of the susceptible
  parasites, and depletes their glycogen stores.
  Degenerative changes in the endoplasmic
  reticulum, the mitochondria of the germinal
  layer, and the subsequent release of lysosomes
  result in decreased production of adenosine
  triphosphate (ATP), which is the energy required
  for the survival of the helminth. Due to
  diminished energy production, the parasite is
  immobilized and eventually dies.
• -Contraindicated during pregnancy and children
  under 2 years.

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• 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, easy bruising, mental/mood changes,
  very stiff neck, change in amount of urine.
  Allergic reactions are also possible.
• -CBC and hepatic functions have to be obtained
  regularly in patients receiving Albendazole.

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• c-Thiabendazole
• This may cause migration of the worm into the
  esophagus, so it is usually combined with
  piperazine.

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• 2-Piperazine
• -Piperazines were originally named because of
  their chemical similarity with piperidine, a
  constituent of piperine in the black pepper plant
  
• -Generally it acts by paralysing parasites, which
  allows the host body to easily remove or expel
  the invading organism. This action is mediated by
  its agonist effects upon the inhibitory GABA
  receptor. Its selectivity for helminths is
  because vertebrates only use GABA in the CNS and
  the helminths' GABA receptor is a different
  isoform to the vertebrate's one.
• -(i.e) It is a flaccid paralyzing agent that
  causes a blocking response of ascaris muscle to
  acetylcholine. The narcotizing effect immobilizes
  the worm, which prevents migration when treatment
  is accomplished with other drugs such as
  albendazole. If used by itself it causes the worm
  to be passed out in the feces.

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• 3-Pyrantel pamoate
• It is a combination of pyrantel and pamoic acid.
• -Pyrantel pamoate acts as a depolarizing
  neuromuscular blocking agent, thereby causing
  sudden contraction, followed by paralysis, of the
  helminths. This has the result of causing the
  worm to "lose its grip" on the intestinal wall
  and be passed out of the system by natural
  process. Since Pyrantel is poorly absorbed by the
  hosts intestine, the small dosage of medication
  used is completely ineffective to the host.
• -Spastic (tetanic) paralyzing agents, in
  particular pyrantel pamoate, may induce complete
  intestinal obstruction in a heavy worm load.
• -Worms usually pass in normal stool or with
  diarrhea, straining, and occasional vomiting.
• -P.S. Pyrantel pamoate is considered a
  Pregnancy category C drug for use during
  pregnancy for humans