[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

200
CHAPTER 8 The Nematodes
Prominent incurved tail
Anus
Spicule
Lateral line
Cuticle
Mouth
Average size: length is seldom up to 30 cm
FIGURE 8-9 Ascaris lumbricoides, adult male.
Anus
Lateral line
Genital girdle
Cuticle
Mouth with
three lips
Average size: 22-35 cm long
B
FIGURE 8-10 A, Ascaris lumbricoides, adult female.
B, Ascaris lumbricoides, adult female.
From here, the larvae are transferred through
coughing into the pharynx, where they are swallowed
and returned to the intestine.
Maturation of the larvae occurs, resulting
in adult worms, which take up residence in
the small intestine. The adults multiply and a
number of the resulting undeveloped eggs (up to
250,000/day) are passed in the feces. The outside
environment, specifically soil, provides the necessary
conditions for the eggs to embryonate.
Infective eggs may remain viable in soil, fecal
matter, sewage, or water for years. It is important
to note that these eggs may even survive in 10%
formalin fixative used in stool processing. The
longevity of these eggs is partly because they are
not easily destroyed by chemicals. The resulting