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Microbiology · Nematodes

Mansonella ozzardi / Mansonella perstans !

  • Parasite
  • For completeness

An Amazonian filaria spread by biting midges. It rarely causes symptoms, but its microfilariae show up on thick smears and must be told apart.

Updated 2026-11-01

Also called: mansonellosis

At a glance

Shape
Threadlike adults in subcutaneous tissue or serous cavities
Family
Onchocercidae
Type
Filarial nematode (tissue)
Stain
Giemsa thick smear: unsheathed microfilariae without marked periodicity
Size
Small, unsheathed microfilariae

Morphology

  • Unsheathed microfilariae circulating in blood day and night.
  • M. ozzardi: adults in subcutaneous tissue.
  • M. perstans: adults in the peritoneum or pleura, rarely the pericardium.

Transmission

  • Bites of infected biting midges (Culicoides).
  • For M. ozzardi in parts of South America, also blackflies (Simulium).

Reservoir: Humans

Vector: Biting midges of the genus Culicoides; in South America, also Simulium for M. ozzardi.

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Life cycle

  1. A midge (Culicoides) or, for M. ozzardi, a blackfly (Simulium) leaves L3 larvae on the skin while biting.
  2. The larvae mature: M. ozzardi in subcutaneous tissue; M. perstans in the peritoneum or pleura.
  3. Females release unsheathed microfilariae that circulate in the blood without marked periodicity.
  4. Another insect swallows them while biting; in its thoracic muscles they become L3 and move to the proboscis.

Virulence factors

  • Usually of low pathogenicity and unnoticed.
  • May be linked to fever, joint pain, itch and eosinophilia.
  • Its practical importance is diagnostic confusion with other filariae on thick smears.

Diseases it causes

  • Mansonellosis: usually asymptomatic; sometimes fever, joint pain, itch and eosinophilia

Clinical picture

  • Microfilariae found on a thick smear taken to look for malaria.
  • Unexplained eosinophilia in Amazon residents.
  • Mild nonspecific symptoms.

Diagnosis

  • Unsheathed microfilariae on Giemsa thick and thin smears, at any hour.
  • Concentration methods (Knott, filtration) raise sensitivity.
  • PCR or LAMP in research and reference centres.
  • Serology is of little use because of cross-reactions with other filariae.

Treatment

M. ozzardi responds to ivermectin; M. perstans responds better to doxycycline, which targets Wolbachia. Diethylcarbamazine has little effect.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Repellents and covering clothing at dawn and dusk.
  • Fine-mesh bed nets.
  • Control of midge breeding sites.

Test yourself

Think of the answer, then tap the question to see it.

How are Mansonella microfilariae told apart from W. bancrofti?

Mansonella microfilariae are unsheathed and circulate without marked periodicity; W. bancrofti are sheathed and nocturnal.

Which insect mainly transmits Mansonella?

Biting midges of the genus Culicoides.

In which region of Colombia is M. ozzardi endemic?

In the Amazon, especially in communities of Vaupés and Amazonas.

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Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: CDC - DPDx - Mansonellosis (CDC, 2019); Parasitosis humanas (Corporación para Investigaciones Biológicas (CIB), 2019).

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Representative model, for educational purposes only.