[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

CHAPTER 8 The Nematodes
211
Inflammatory
infiltrate
Striated muscle
Coiled larva
Nurse cell
Size range—juvenile: 75-120 m by 4-7 m
Fully developed: up to 1 mm long
A
B
FIGURE 8-21 A, Trichinella spiralis, encysted larva. B, Trichinella spiralis larvae in muscle press. (B from Bowman DD:
Georgis’ parasitology for veterinarians, ed 9, St. Louis, 2009, Saunders.)
TABLE 8-16
Parameter
Description
Average juvenile size 75-120 µm long, 4-7 µm
wide
Average mature size Up to 1 mm in length
Appearance
Colied
Encysted in
Nurse cells of striated muscle
Notable features Inflammatory infiltrate
present around nurse cell
Morphology
Trichinella spiralis
Encysted Larva: Typical
Characteristics at a Glance
Encysted Larvae. The average juvenile encysted
larvae measures from 75 to 120 µm by 4 to 7 µm
(Fig. 8-21; Table 8-16). A fully developed larva
may reach up to a length of 1 mm. These larvae
settle by coiling up in muscle fibers and becoming
encysted. Biopsies of these larvae often reveal a
distinctive inflammatory infiltrate (see Fig.
8-21A) in response to the presence of the larvae.
A striated muscle cell, known as a nurse cell,
surrounds the coiled larva.
TABLE 8-17
Trichinella spiralis Adults:
Typical Characteristics at
a Glance
Characteristic Adult Female Adult Male
Size 4 by 0.5 mm 2 by 0.04 mm
Notable features Blunt, round
posterior
end; single
ovary with
Curved posterior
end with
two rounded
appendages
vulva in
anterior fifth
of body
Common to Both Adult Males and Females
Thin anterior end
Small mouth
Long slender digestive tract
Adults. Although the small T. spiralis adult
worms have rarely been seen, they have been
described (Table 8-17). The female measures 4
by 0.5 mm, whereas the male is significantly
smaller, measuring 2 by 0.04 mm. The typical