[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Nematodes](https://durgical.com/en/microbiology/groups/nematodes/) › Mansonella ozzardi / Mansonella perstans

[Microbiology](https://durgical.com/en/microbiology/) · [Nematodes](https://durgical.com/en/microbiology/groups/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

## Key points

- Unsheathed microfilariae without periodicity (W. bancrofti: sheathed and nocturnal).
- Vectors: Culicoides midges and, in the Amazon (Colombia included), Simulium blackflies.
- Present in the Colombian Amazon.
- Usually benign; an incidental find on a malaria thick smear.

## 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

- A midge (Culicoides) or, for M. ozzardi, a blackfly (Simulium) leaves L3 larvae on the skin while biting.
- The larvae mature: M. ozzardi in subcutaneous tissue; M. perstans in the peritoneum or pleura.
- Females release unsheathed microfilariae that circulate in the blood without marked periodicity.
- 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:

- [Ivermectin](https://durgical.com/en/pharmacology/ivermectin/)
- [Doxycycline](https://durgical.com/en/pharmacology/doxycycline/)

## Prevention

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

## In Colombia

M. ozzardi is endemic in the Colombian Amazon, especially in riverside Indigenous communities of Vaupés and Amazonas, where high prevalences have been described.

## Memory aid

The quiet filaria of the jungle: no sheath, no schedule, hardly any symptoms, yet there it is on the malaria smear.

## 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.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/microbiology/mansonella-ozzardi-mansonella-perstans/)

## Related

- [Wuchereria bancrofti / Brugia malayi](https://durgical.com/en/microbiology/wuchereria-bancrofti-brugia-malayi/)
- [Onchocerca volvulus](https://durgical.com/en/microbiology/onchocerca-volvulus/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Nematodes](https://durgical.com/en/microbiology/groups/nematodes/)

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](https://www.cdc.gov/dpdx/mansonellosis/index.html) (CDC, 2019); Parasitosis humanas (Corporación para Investigaciones Biológicas (CIB), 2019).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/mansonella-ozzardi-mansonella-perstans/