[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

APPENDIX B Answers to Case Studies: Under the Microscope
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CHAPTER 8
Case Study 8-1: Under the Microscope
1. Trichuris trichiura egg.
2. Whipworm.
3. Ingestion of infective eggs.
4. Trichuriasis; whipworm infection.
5. Adult worms.
Case Study 8-2: Under the Microscope
1. Ascaris lumbricoides. Figure A, adult pregnant
female; Figure B, mature egg.
2. Large intestinal roundworm, human
roundworm.
3. The life cycle of A. lumbricoides is relatively
complex compared with the parasites presented
thus far. Infection begins following the
ingestion of infected eggs that contain viable
larvae. Once inside the small intestine, the
larvae emerge from the eggs. The larvae then
complete a liver-lung migration by first entering
the blood via penetration through the
intestinal wall. The first stop on this journey
is the liver. From there, the larvae continue
the trip via the bloodstream to the second
stop, the lung. Once inside the lung, the larvae
burrow their way through the capillaries into
the alveoli. Migration into the bronchioles
then follows. From here, the larvae are transferred
through coughing into the pharynx,
where they are then swallowed and returned
to the intestine.
The larvae then mature, 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. The resulting embryonated eggs
are the infective stage for a new host and,
when consumed by a human host, initiate a
new cycle.
4. The avoidance of using human feces as fertilizer,
as well as exercising proper sanitation
and personal hygiene practices, are critical
measures for breaking the life cycle of Ascaris.
CHAPTER 9
Case Study 9-1: Under the Microscope
1. Loa loa
2. Loa loa, is known to inhabit areas of Africa
especially the rain forest belt and as such is
referred to as the African Eye Worm. It is
estimated that the infection rates may be over
70% in the areas in which a large vector
population exists.
3. Yes, the blood sample was drawn at the
appropriate time. Samples collected between
10:15 am and 2:15 pm yield the best recovery
rate of Loa loa microfilariae. This parasite
exhibits diurnal periodicity.
4. Surgical removal is the treatment of choice for
the removal of adult Loa loa worms. The
medication of choice for the treatment of Loa
loa is diethylcarbamazine (DEC).
Case Study 9-2: Under the Microscope
1. The organism observed in the stained blood
smear in this case is that of a Wuchereria
bancrofti microfilaria.
2. Technically, the timing of the blood collection
was not optimal for the best recovery of
microfilariae. Wuchereria bancrofti generally
exhibits nocturnal periodicity. The organism
can also exhibit subperiodic periodicity and
can be prevalent in the late afternoon. This
may explain why the organism was detected
in Sir Thomas’ blood even though the timing
of his blood collection was not optimal.
3. The vectors responsible for parasite transmission
in this case consist of Culex, Aedes, and
Anopheles spp. of mosquitoes.
4. Sir Robert is exhibiting the signs and symptoms
of Bancroft’s filariasis or elephantiasis.
5. Prevention and control strategies that Sir
Robert should have implemented on his
adventure include using personal protection
when entering known endemic areas, avoiding
mosquito infested areas, and using mosquito
netting and insect repellants.