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Mansonellosis

[Mansonella ozzardi] [Mansonella perstans] [Mansonella streptocerca]

Life Cycle

During a blood meal, an infected arthropod (midges, genus Culicoides, or blackflies, genus Simulium) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound The number 1. They develop into adults that commonly reside in subcutaneous tissues The number 2. Adult worms are rarely found in humans. The size range for females worms is 65 to 81 mm in length and 0.21 to 0.25 mm in diameter but unknown for males. Adults worms recovered from experimentally infected Patas monkeys measured 24 to 28 mm in length and 70 to 80 µm in diameter (males) and 32 to 62 mm in length and .130 to .160 mm in diameter (females). Adults produce unsheathed and non-periodic microfilariae that reach the blood stream The number 3. The arthropod ingests microfilariae during a blood meal The number 4. After ingestion, the microfilariae migrate from the arthropod’s midgut through the hemocoel to the thoracic muscles The number 5. There the microfilariae develop into first-stage larvae The number 6 and subsequently into third-stage infective larvae The number 7. The third-stage infective larvae migrate to arthropod’s proboscis The number 8 and can infect another human when the arthropod takes a blood meal The number 1.

During a blood meal, an infected midge (genus Culicoides) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound The number 1. They develop into adults that reside in body cavities, most commonly the peritoneal cavity or pleural cavity, but less frequently in the pericardium The number 2. The size range for female worms is 70 to 80 mm in length and 120 µm in diameter, and the males measure approximately 45 mm by 60 µm. Adults produce unsheathed and subperiodic microfilariae, measuring 200 by 4.5 µm that reach the blood stream The number 3. A midge ingests microfilariae during a blood meal The number 4. After ingestion, the microfilariae migrate from the midge’s midgut through the hemocoel to the thoracic muscles of the arthropod The number 5. There the microfilariae develop into first-stage larvae The number 6 and subsequently into third-stage infective larvae The number 7. The third-stage infective larvae migrate to the midge’s proboscis The number 8 and can infect another human when the midge takes a blood meal The number 1.

During a blood meal, an infected midge (genus Culicoides) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound The number 1. They develop into adults that reside in the dermis, most commonly less than 1 mm from the skin surface The number 2. The females measure approximately 27 mm in length. Their diameter is 50 µm at the level of the vulva (anteriorly) and ovaries (near the posterior end), and up to 85 µm at the mid-body. Males measure 50 µm in diameter. Adults produce unsheathed and non-periodic microfilariae, measuring 180 to 240 µm by 3 to 5 µm, which reside in the skin but can also reach the peripheral blood The number 3. A midge ingests the microfilariae during a blood meal The number 4. After ingestion, the microfilariae migrate from the midge’s midgut through the hemocoel to the thoracic muscles The number 5. There the microfilariae develop into first-stage larvae The number 6 and subsequently into third-stage larvae The number 7. The third-stage larvae migrate to the midge’s proboscis The number 8 and can infect another human when the midge takes another blood meal The number 1.

 

 

Microfilariae of Mansonella perstans.

 

Microfilariae of Mansonella perstans are unsheathed and measure 190-200 µm in stained blood smears and 180-225 µm in 2% formalin. The tail is blunt and nuclei extend to the tip of the tail. Microfilariae circulate in the blood.

Figure A: Microfilaria of M. perstans in a thick blood smear stained with Giemsa, from a patient from Cameroon.

Figure B: Microfilaria of M. perstans in a thick blood smear stained with Giemsa, from a patient from Cameroon.

Figure C: Microfilaria of M. perstans in a thick blood smear stained with Giemsa, from a patient from Cameroon.

Figure D: Microfilaria of M. perstans in a thin blood smear from the same specimen as Figures A-C.

Figure E: Microfilaria of M. perstans in a thin blood smear from the same specimen as Figures A-D.

Figure F: Microfilaria of M. perstans in a thick blood smear stained with Giemsa. Image courtesy of the Parasitology Department, Public Health Lab, Ontario Agency for Health Protection and Promotion, Canada.

Microfilariae of M. ozzardi.

 

Microfilariae of Mansonella ozzardi are unsheathed and measure 160-205 µm in stained blood smears and 200-255 µm in 2% formalin. The tail tapers to a point and the nuclei end well before the end of the tail. The end of the tail is also bent in a small hook-like shape. Microfilariae circulate in blood.

Figure A: Microfilaria of M. ozzardi in a thick blood smear, stained with Giemsa.

Figure B: Microfilaria of M. ozzardi in a thick blood smear, stained with Giemsa.

Figure C: Microfilaria of M. ozzardi in a thick blood smears, stained with Giemsa.

Figure D: Microfilaria of M. ozzardi in a thick blood smear, stained with Giemsa. Note the hook-like end to the tail in this figure.

Microfilariae of M. streptocerca.

 

Microfilariae of Mansonella streptocerca are unsheathed and measure 180-240 µm. The tail is been into a hook-like shape and the nuclei extend to the end of the tail. Microfilariae are found in skin and do not circulate in the blood.

Figure A: Microfilaria of M. streptocerca, fixed in 2% formalin and stained with hematoxylin.

Laboratory Diagnosis

Mansonella perstans and M. ozzardi are usually diagnosed by the finding of microfilariae circulating in blood. Neither species exhibits periodicity. Mansonella streptocerca is usually diagnosed by finding microfilariae in skin snips.

Skin snips should be think enough to include the outer part of the dermal palpillae but not so thick as to produce bleeding. Skin snips should be placed immediately in normal saline or distilled water, just enough to cover the specimen. Microfilariae tend to emerge more rapidly in saline, however in either medium the microfilariae typically emerge in 30-60 min and can be seen in wet mount preparations. For a definitive diagnosis, allow the wet mount to dry, fix in methanol, and stain with Giemsa or hematoxylin-and-eosin.

Treatment Information

For information about treatment please contact CDC-INFO.

DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/.

  • Page last reviewed: December 29, 2017
  • Page last updated: December 29, 2017
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