[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

CHAPTER 9 The Filariae
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Philippines, Indonesia, Sri Lanka, New Guinea,
Vietnam, Thailand, and specific regions of Japan,
Korea, and China. Although humans are considered
to be the primary definite host, B. malayi is
also known to infect felines and monkeys.
Clinical Symptoms
Infections with B. malayi are often asymptomatic
even with the presence of microfilariae in the
blood. Fevers may take months to years to
develop after the inital infection. Additional
symptoms include the formation of granulomatous
lesions following microfilarial invasion into
the lymphatics, chills, lymphadenopathy, lymphangitis,
and eosinophilia. Eventually the result
is elephantiasis of the legs. Elephantiasis of the
genitals is possible but less common.
Treatment
Treatment for B. malayi is similar to that for W.
bancrofti, with the most useful medication being
diethylcarbamazine (DEC). Inflammatory reactions
are more common after treatment and can
be severe. Therefore, anti-inflammatory drugs
may be necessary.
Prevention and Control
The prevention and control measures for B.
malayi are identical to those for W. bancrofti.
Notes of Interest and New Trends
In addition to B. malayi, Malayan filariasis may
also be caused by another species of Brugia,
Brugia timori, first isolated in 1964 on the island
of Timor. Readily distinguishable from B. malayi,
the microfilariae of B. timori measure approximately
310 µm. The organism has a sheath,
which is difficult to observe using Giemsa stain
and distinct nuclei in the tip of the tail. The body
tissue of this organism does not bulge around the
two nuclei like that of B. malayi.
A condition called tropical eosinophilia or
occult (meaning hidden or not apparent) filariasis
is known to occur in persons who reside in
the areas of the world in which both B. malayi
and W. bancrofti are endemic. These patients
experience a number of pulmonary and asthmatic
symptoms. On thorough examination of
infected patients, no microfilariae are found in
their blood. It is suspected that a filarial parasite
is present and is responsible for this condition
but remains hidden deep in the body such as in
the lungs. The signs and symptoms may be due
to the body’s inflammatory response. Successful
resolution of symptoms with DEC therapy confirms
the diagnosis of filarial infection but failure
to respond to DEC suggests another cause for the
symptoms.
Quick Quiz! 9-6
Which of the following can be used in the differentiation
and identification of Brugia malayi? (Objective
9-13)
A. Absence of a sheath
B. Absence of nuclei in the tail
C. Presence of a sheath that is very difficult to observe
on Giemsa stain
D. Presence of two terminal nuclei in the tail
Quick Quiz! 9-7
Select the ideal time period to collect blood samples
for examination for the presence of the microfilariae
of Brugia malayi. (Objective 9-8)
A. 10:00 p.m. to 4:00 a.m.
B. 10:00 a.m. to 4:00 p.m.
C. 4:00 p.m. to 8:00 p.m.
D. Any time of the day or night
Loa loa
(lo’uh/lo’uh)
Common name: Eye worm (African).
Common associated disease and condition
names: Loiasis.
Morphology
Microfilariae. The sheathed Loa loa microfilaria
usually measures 248 to 300 µm in length