[Last Modified: ]

November 2004
Answer to Case 144
This was a case of filariasis caused by Mansonella ozzardi (also known as Ozzard's filariasis or mansonelliasis).  Morphologic features seen in the images were:

• No evidence of a sheath.
• Size range is consistent with M. ozzardi (180-200 micrometers).  Note that M. perstans microfilariae are in the same size range as M. ozzardi.
• Nuclear column terminates well before the end of the tail, which is long and tapered to a point.  M. perstans has a nuclear column that extends to the tip of the tail and the terminal nucleus is frequently larger than the preceding nuclei, giving a knob-like appearance to the tail.
• Anterior nuclei in M. ozzardi are elongated and the last 2 or 3 either overlap, or are side-by-side.

Microfilaria of M. ozzardi are nonperiodic, therefore they may be observed in blood specimens drawn from infected individuals regardless of whether the specimen was collected during the day or at night.  Incubation period in humans has not been determined and clinical presentation varies in different populations.

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