Calabar swellings

Calabar Swellings

Calabar swellings are transient, localized subcutaneous swellings associated with Loa loa filariasis, a parasitic infection caused by the nematode worm Loa loa. These swellings are named after the city of Calabar in Nigeria, where they were first described. They are a hallmark of the disease and are caused by the migration of the adult worms through the subcutaneous tissues.

Clinical Presentation

Calabar swellings typically present as localized, non-painful, and non-erythematous swellings that appear suddenly and can last for several days before disappearing. They are most commonly found on the extremities, particularly the arms and legs, but can occur anywhere on the body. The swellings are often associated with itching and may recur in different locations over time.

Pathophysiology

The swellings are caused by the movement of adult Loa loa worms through the subcutaneous tissues. As the worms migrate, they cause localized inflammation and edema, leading to the characteristic swellings. The immune response to the worms and their secretions contributes to the development of these transient swellings.

Diagnosis

Diagnosis of Calabar swellings is primarily clinical, based on the characteristic appearance and history of the swellings. Laboratory confirmation can be obtained by identifying microfilariae in the blood, particularly during the daytime when they are most abundant. Serological tests and polymerase chain reaction (PCR) assays can also aid in diagnosis.

Treatment

The treatment of choice for Loa loa infection is diethylcarbamazine (DEC), which is effective in killing both adult worms and microfilariae. However, treatment must be approached with caution in patients with high microfilarial loads due to the risk of severe adverse reactions. In such cases, pretreatment with corticosteroids may be necessary to mitigate inflammatory responses.

Epidemiology

Calabar swellings are endemic in the rainforests of West and Central Africa, where the Chrysops fly, the vector for Loa loa, is prevalent. The disease primarily affects rural populations engaged in activities that expose them to the vector, such as farming and logging.

Prevention

Preventive measures include reducing exposure to the Chrysops fly through the use of insect repellents, protective clothing, and insecticide-treated nets. Community-based mass drug administration programs with DEC or ivermectin can also help reduce the prevalence of infection.

Also see

• Loa loa
• Filariasis
• Chrysops
• Diethylcarbamazine