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114 CHAPTER 4

MANSONELLA OZZARDI
MICROSCOPIC DIAGNOSTIC
FEATURE Mansonella ozzardi is the only filarial infection by nema-
todes in the New World, and is found primarily in Central
America and South America as well as in the Caribbean
General Islands. The organism invades the body cavities and the
Classification—Nematode (tissue) fatty tissue of the viscera and mesentery of and around
the organs of the abdomen.
Organism Mansonella
streptocerca
Specimen Required Skin snips soaked in Morphology
saline
The adult female worms of M. ozzardi measure 65 to
Stage Adult
80 mm, whereas the male most often ranges from only
Size Adults are 180–240 μm
in length 24 to 28 mm in length. The microfilariae are unsheathed
but migrate through the tissues of the skin before enter-
Shape Unsheathed
microfilariae ing the blood circulation. The larvae are nonperiodic
and are roughly 88 μm in length.
Body nuclei Continuous in a single
column to tip of tail
Other Features Partial coil of tail is Symptoms
known as “shepherd’s
crook” Most victims of this infection are asymptomatic or ex-
perience rather mild symptoms. As with other filarial
disorders, symptoms may be exaggerated in those who
are not natives of the endemic area. Rarely, lympha-
is a side effect of both of these drugs. In endemic areas, denopathy, fever, marked eosinophilia, pruritis, and
vector control would be advisable, but is rarely practiced. skin lesions are experienced by the victims of M. ozzardi
Insect repellent may prevent a great number of the bites infections.
but bed netting to prevent bites from the infected midges
is not very effective as the midges are so small they can Life Cycle
pass through the netting.
The mature worms of M. ozzardi inhabit the mesentery
SEROUS CAVITY FILARIASIS and visceral fat surrounding the abdominal organs. The
mature female worms produce unsheathed microfilariae,
Two species of filarial parasites primarily infect the se- which migrate through tissues of the skin and enter the
rous cavities of the human body. The two species that are circulating blood, are ingested by the feeding midge (genus
considered to be parasites of serous cavities are: Man- Culicoides) and are not periodic in their times of activity or
sonella perstans and Mansonella ozzardi. Mansonella appearance. In some regions, the blackflies (Simulium) are
perstans is another human filarial nematode transmitted the primary vectors for the organism. Inside the insect the
by a fly called a midge, an extremely tiny bloodsucking infective larvae ingested from the host undergo further de-
fly. Mansonella perstans is one of the two parasites that velopment and are then passed on to the next host. Again,
lead to “serous cavity filariasis” in humans. Mansonella humans are the only known host for this organism.
ozardi is the other parasite that produces serous cavity
filariasis. Infections by M. perstans produce more benign Disease Transmission
conditions than those of W. bancrofti, B. malayi, and
Loa loa. Mansonella perstans is prevalent in Sub- Saharan M. perstans infection rates are high in endemic areas. The
Africa, as well as areas of the New World (Central and disease is acquired when bitten by an infected midge of
South America, Caribbean) but both species occupy the genus Cullicoides, except in the Amazon River basin
areas of the Congo River basin of West Africa. where the vector is the blackfly.