Mansonella streptocerca

Mansonella streptocerca LifeCycle

Mansonella streptocerca is a parasitic nematode that causes a disease known as streptocerciasis in humans. This condition is one of the lesser-known tropical diseases, primarily affecting skin and causing dermatitis, pruritus (itching), and skin lesions. Mansonella streptocerca is transmitted through the bites of infected Culicoides midges, small flying insects that are common in certain tropical and subtropical regions.

Life Cycle

The life cycle of Mansonella streptocerca involves two hosts: humans, where the adult worms reside, and the Culicoides midges, which act as vectors. The adult female worms produce microfilariae, which are the larval form of the parasite. These microfilariae circulate in the peripheral blood of the infected host but are primarily found in the skin. When a Culicoides midge bites an infected person, it ingests the microfilariae, which then develop into infective larvae within the midge. Upon biting another human, the midge transmits these larvae, which migrate to the skin and mature into adult worms, thus completing the cycle.

Distribution

Mansonella streptocerca is predominantly found in certain forested areas of West and Central Africa. The distribution of the disease is closely related to the habitat of the Culicoides vectors, which prefer humid, tropical environments.

Clinical Manifestations

Infection with Mansonella streptocerca often results in dermatological symptoms, including itching, rashes, and skin lesions. Unlike other filarial infections, it rarely causes significant systemic illness or severe complications. Many infections are asymptomatic, with the disease being discovered incidentally through skin snips or blood tests.

Diagnosis and Treatment

Diagnosis of streptocerciasis is typically made by identifying microfilariae in skin snips or biopsy samples. Blood tests are generally not useful due to the low concentration of microfilariae in the bloodstream. Treatment options include antiparasitic medications, such as ivermectin, which is effective in reducing the microfilarial load and alleviating symptoms.

Prevention

Preventive measures against Mansonella streptocerca infection are primarily aimed at reducing human contact with the Culicoides vectors. This can be achieved through the use of insect repellents, protective clothing, and insecticide-treated nets or screens to decrease midge bites.

Public Health Importance

Although Mansonella streptocerca does not cause severe disease, it is of public health importance in endemic areas due to its contribution to skin morbidity and potential to impair quality of life. Control efforts are focused on reducing vector populations and providing treatment to affected individuals to decrease the prevalence of infection.