.

1. Ancylostoma Duodenale and
Necator Americanus
By Marquetta Valdez

2. 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

3. 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
A. duodenale N. americanus
• Eggs are generally 57-76 µm by 35-47
µm and are oval shaped with a thin shell

4. Rhabditiform Larvae (wet mount)

5. 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.

6. 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

7. 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

8. Life Cycle

9. 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

10. 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

11. Diagnosis
 Stool samples showing eggs or
actual worms
 Watching for symptoms

12. Control and Treatment
 Scientist are trying to develop a
vaccine
 In some countries, infections aren’t
treated because they are so
common
 Drugs of choice are Albendazole,
Mebendazole, and Pyrantel Pamoate

13. Prevention
 Wear shoes
 Monitor the disposal of humans
feces

14. Works Cited
 "Hookworm Image Library." Division of
Parasitic Diseases. Center for Disease
Control. 29 Sept. 2006
<http://www.dpd.cdc.gov>.
 "Hookworm Infection Fact Sheet."
Parasitic Disease Infection. Center for
Disease Control. 3 Oct. 2006
<www.cdc.gov>.
 "Hookworm." Parasites and Health. Center
for Disease Control. 29 Sept. 2006
<http://www.dpd.cdc.gov/DPDx/HTML/Ho
okworm.htm>.