[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 10 The Cestodes
TABLE 10-4
Parameter
Scolex
Number of suckers
Rostellum
Hooks
Gravid Proglottid
Size
Appearance
Hymenolepis diminuta
Adult: Typical
Characteristics at a Glance
Description
Four
Present
Absent
Twice as wide as long
Saclike uterus filled with
eggs
Sac-like uterus filled with eggs
bladder-like cyst that contains little or no fluid
that emerges from select tapeworm eggs, occurs
in this host. Consumption by a rat of infected
insects, which typically reside in grains or
cereal, results in the development of an adult
worm. Eggs are produced in the infected rat
and are excreted in its droppings, thus setting
the stage for a new cycle. Human infection with
H. diminuta is considered to be an accidental
parasitic disease that normally infects animals
but can also infect humans, known as a zoonotic
occurrence, or zoonosis. In this case, the
human takes the place of the rat in the parasite
life cycle.
Epidemiology
The distribution of H. diminuta is worldwide.
Areas in which foodstuffs such as grain or cereal
are not protected from rats and insects are at risk
of transmitting the parasite.
FIGURE 10-9 Hymenolepis diminuta proglottid.
of a saclike uterus filled with eggs that occupy
most of the available space.
Laboratory Diagnosis
Laboratory diagnosis is based on the recovery of
the characteristic eggs in stool specimens. It is
interesting to note that the proglottids are typically
not found in stool because they usually
disintegrate in the human gut. Similarly, the
scolex is rarely seen in these samples.
Life Cycle Notes
H. diminuta is primarily a parasite of rats. Contaminated
droppings from infected rats are the
source of parasite transmission into an intermediate
host, such as the grain beetle or flea.
Development of the cysticercoid larva, a larval
stage consisting of a scolex surrounded by a
Clinical Symptoms
Asymptomatic. Many patients infected with
H. diminuta remain asymptomatic.
Hymenolepiasis: Rat Tapeworm Disease. Persons
infected with H. diminuta usually present
with mild symptoms such as diarrhea, nausea,
abdominal pains, and anorexia.
Treatment
The treatment of choice against H. diminuta is
praziquantel. Niclosamide is an effective alternative
therapy; however, it is not yet readily available
in the United States.
Prevention and Control
There are three primary prevention and control
measures against the spread of H. diminuta.
First, administering effective rodent control
measures is crucial to ensure the halt of the
normal parasite life cycle, thus preventing rats
from contaminating foodstuffs such as grains
and cereals. Second, protection of these foods