Ancylostoma Duodenale and Necator Americanus

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Ancylostoma Duodenale and Necator Americanus

• By Marquetta Valdez

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Some Facts.

• Hookworms infect an estimated 1 billion people
  worldwide, mostly in tropical and sub-tropical
  climates
• A. duodenale and N. americanus are the two
  hookworms that infect humans
• A. duodenale is found in southern Europe,
  northern Africa, India, China, the Middle East,
  and the Americas
• N. americanus can be found in the southeastern
  U.S. and Australia

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Life Cycle and Reproduction

• Eggs are passed in the feces and hatch into
  rhabditiform larvae in about 48 hours in the
  feces or in the soil

• Eggs are generally 57-76 µm by 35-47 µm and are
  oval shaped with a thin shell

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Rhabditiform Larvae (wet mount)
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Life cycle continued

• Juveniles feed on feces for about 3 days then
  molt into 2nd stage juveniles
• They molt again 5-10 days later into filariform
  larvae. Can survive 3-4 weeks outside host.

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Life Cycle

• Infect humans by penetrating skin and then travel
  to the heart and lungs where they penetrate the
  pharynx and are swallowed. When they reach the
  small intestine they attach to the intestinal
  wall and feed on blood.

Cutting plates in N. americanus
Cutting teeth in A. duodenale
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Life Cycle

• Worms molt again two more times to reach maturity
• A. duodenale adult males measure 8-11mm with
  females being 10-13mm
• N. americanus adult males measure 7-9mm and
  females measure 9-11mm
• Adult worms copulate and eggs appear in the feces
  in about 6 weeks (females can produce sever
  thousand eggs in one day)
• Cycle starts over again and adults live 1-2 years

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Life Cycle
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Transmission

• Filariform juveniles wait in soil or feces and
  wave back and forth to increase chances of
  finding a host
• Filariforms then penetrate the skin (usually
  hands or feet)
• Children, elderly people and people who work
  about contaminated soil are at high risk

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Pathogenic Effects

• Asymptomatic until worms have already started
  multiplying
• Symptoms include
• Irritation of skin at site of penetration
• Iron-deficiency anemia
• Abdominal pain
• Diarrhea
• Loss of appetite
• Weight loss
• Tiredness
• Difficulty breathing
• Cardiomegaly
• Irregular heartbeat
• Extreme cases include stunted growth and mental
  retardation

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Diagnosis

• Stool samples showing eggs or actual worms
• Watching for symptoms

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Control and Treatment

• Scientist are trying to develop a vaccine
• In some countries, infections arent treated
  because they are so common
• Drugs of choice are Albendazole, Mebendazole, and
  Pyrantel Pamoate

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Prevention

• Wear shoes
• Monitor the disposal of humans feces

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Works Cited

• "Hookworm Image Library." Division of Parasitic
  Diseases. Center for Disease Control. 29 Sept.
  2006 lthttp//www.dpd.cdc.govgt.
• "Hookworm Infection Fact Sheet." Parasitic
  Disease Infection. Center for Disease Control. 3
  Oct. 2006 ltwww.cdc.govgt.
• "Hookworm." Parasites and Health. Center for
  Disease Control. 29 Sept. 2006 lthttp//www.dpd.cdc
  .gov/DPDx/HTML/Hookworm.htmgt.