Mansonella perstans

A parasitic nematode causing mansonelliasis

Mansonella perstans is a parasitic nematode that causes the disease known as mansonelliasis. It is one of the three species of the genus Mansonella that infect humans, the others being Mansonella ozzardi and Mansonella streptocerca. M. perstans is primarily found in sub-Saharan Africa and parts of Central and South America.

Morphology

Mansonella perstans is a small filarial worm. The adult worms reside in the body cavity of the human host, particularly in the peritoneal cavity and pleural cavity. The microfilariae, which are the larval stage, are unsheathed and measure approximately 200 micrometers in length. They can be found in the bloodstream of the host.

Life Cycle

The life cycle of Mansonella perstans involves two hosts: a human host and an insect vector. The adult worms produce microfilariae that circulate in the blood. These microfilariae are ingested by a biting insect, typically a Culicoides midge, during a blood meal. Inside the midge, the microfilariae develop into infective larvae. When the midge bites another human, the larvae are transmitted and develop into adult worms in the new host.

Epidemiology

Mansonella perstans is endemic in many parts of sub-Saharan Africa, including countries such as Uganda, Nigeria, and Cameroon. It is also found in some regions of Central and South America. The prevalence of infection can be high in endemic areas, with some communities showing infection rates of over 50%.

Clinical Manifestations

Infection with Mansonella perstans is often asymptomatic, but it can cause a range of symptoms in some individuals. These may include:

• Angioedema
• Pruritus
• Arthralgia
• Fever
• Headache

In rare cases, more severe manifestations such as pericarditis and pleuritis have been reported.

Diagnosis

The diagnosis of Mansonella perstans infection is primarily based on the detection of microfilariae in the blood. Blood samples are typically collected during the day, as the microfilariae do not exhibit periodicity. Microscopic examination of stained blood smears can reveal the presence of the characteristic unsheathed microfilariae.

Treatment

Treatment of Mansonella perstans infection can be challenging. The drug diethylcarbamazine (DEC) is not effective against this species. Ivermectin has been used with some success, but it may not completely clear the infection. Albendazole has also been used, sometimes in combination with ivermectin, to improve treatment outcomes.

Prevention

Preventive measures focus on reducing exposure to the insect vectors. This includes the use of insect repellent, wearing protective clothing, and using insecticide-treated bed nets. Control of the midge population through environmental management can also help reduce transmission.

Related pages

• Mansonelliasis
• Nematode
• Parasitic disease
• Vector (epidemiology)