[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 9 The Filariae
Tip of tail free of nuclei
No sheath
Approximate length: 88 m
FIGURE 9-9 Mansonella ozzardi microfilaria.
average of 70 mm. The posterior section of the
adult male worm, measuring approximately
32 mm in length, has been recovered and documented
from humans. The location of the adults
in humans is currently unknown.
Laboratory Diagnosis
M. ozzardi microfilariae may be recovered in
peripheral blood. The organism is nonperiodic
because there is no known optimum time for
collecting the blood sample. Giemsa-stained
microscopic examination is necessary to identify
the characteristic microfilariae.
Life Cycle Notes
M. ozzardi is transferred by the injection of infective
larvae to the human definitive host. This
transmission is carried out by the Culicoides
sucking midge or, depending on the geographical
location, the Simulium blackfly. The microfilariae
are found in the blood as well as in the capillaries
and intravascular spaces of the skin. The
emerging adults may take up residence in the
body cavities, visceral fat, and mesenteries but is
still undocumented.
by Culicoides midges or Simulium blackflies,
depending on the geographic location.
Clinical Symptoms
Although asymptomatic infections are common,
symptoms such as urticaria, lymphadenitis, skin
itching, and arthralgias may occur. As with
several of the other microfilariae, eosinophilia is
common. The adult worms cause minimal
damage to the areas they inhabit.
Treatment
Asymptomatic infections are not typically treated.
Individuals who require treatment usually
receive ivermectin. Diethylcarbamazine (DEC)
has proven to be ineffective against M. ozzardi.
Prevention and Control
Controlling the sucking midge and Simulium
populations is crucial to halting M. ozzardi.
Unfortunately, there are no known control programs
in place at this time. Both vectors are so
small that they are not deterred by nets or screening
equipment.
Epidemiology
Found exclusively in the Western Hemisphere, M.
ozzardi is known to exist in North America and
Central and South Americas, as well as in parts of
the West Indies and Caribbean. Specific countries
known to harbor this organism include Bolivia,
Colombia, Peru, Haiti, the Dominican Republic,
and Puerto Rico. The parasite may be transmitted
Quick Quiz! 9-12
How are the microfilariae of Mansonella ozzardi
differentiated from those of Ochocerca volvulus?
(Objective 9-13)
A. Location of the microfilariae
B. Absence of a sheath
C. Lack of terminal nuclei in the tail
D. Presence of a sheath