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Intestinal Nematodes 153

MICROSCOPIC DIAGNOSTIC

FEATURE

General Classification—Hookworm adult
Organism A. duodenale and Source: Centers for Disease Control and Prevention (CDC)
N. americanus
Specimen Required Feces
Stage Adult
Size Females 10–12 mm in
length; male slightly
shorter FIGURE 6-13 Egg of Ancylostoma duodenale or
Shape Round and elongated Necator americanus hookworm
with a long pointed
tail may help to avoid infecting humans. Some canine
Motility Not reported and feline hookworms, such as caninum, known
Other Features Well-developed as the common dog hookworm, may in rare cases
mouthparts for develop to adulthood in humans and when they
attaching to do, they may result in eosinophilic enteritis in
intestinal mucosa people. Their invasive larvae can also cause an
itchy rash called cutaneous larva migrans on the
skin of humans.

Source: Centers for Disease Control and Prevention (CDC) DIFFERENTIATING FROM
STRONGYLOIDES STERCORALIS,

HOOKWORM LARVAE

Since it is sometimes difficult to differentiate between the
eggs of Ancylostoma duodenale and Necator americanus
along with most other hookworm species in order to
identify the genus, additional steps may be necessary. The
eggs must be placed in an appropriate environment in the
lab to allow the larvae to hatch out, at which time the larvae
are easier to identify due to the morphology exhibited. If
FIGURE 6-12 Hookworm infection by direct contact the fecal sample is left for a day or more under simulated
with contaminated soil tropical conditions, the larvae will have hatched out,
allowing speciation, and eggs might no longer be evident.
■ Do not use human excrement or raw sewage as It is paramount to distinguish hookworm larvae from
fertilizer in agricultural practices. This is practiced S. stercoralis larvae, because infection with S. stercoralis has
in some cultures and is called “night soil.” Fruits
a more serious impact on the victim and requires different
and vegetables that are normally eaten raw and treatment. This species also is known as threadworms
come from developing countries are a ready source
and are capable of living in the small intestine or as a free-
of parasitic infections and mere rinsing of the food living worm (Figure 6-14). Although the larvae of the two
is not sufficient to remove or destroy the organisms.
hookworm species, A. duodenale and N. americanus,
■ Deworming of the family pets, both dogs and can be distinguished microscopically, this is not typically
cats, will aid the pets in remaining healthy and done except for research purposes. Adult worms would