Understanding Calabar swellings: Assessing subcutaneous loiasis using ultrasound.

Area of Science:

• Parasitology
• Medical Ultrasound
• Tropical Medicine

Background:

• Loiasis, caused by Loa loa filariae, manifests as eyeworm and Calabar swellings.
• Calabar swellings are itchy, painful edemas causing significant morbidity.
• The exact migration pathways and tissue tropism of adult Loa loa remain unclear.

Purpose of the Study:

• To characterize Calabar swellings using portable ultrasound.
• To elucidate the pathophysiology of Loa loa-associated swellings and nodules.

Main Methods:

• Ultrasound imaging was performed on 22 individuals with Calabar swellings in the Republic of Congo.
• Participants completed questionnaires and underwent physician examination.
• Ultrasound videos were analyzed for characteristic findings.

Main Results:

• Typical Calabar swellings showed nonspecific angioedema.
• Subcutaneous nodules revealed trans-fascial fluid-filled retentions with hyperechoic structures.
• These structures exhibited movement and measured consistent with Loa loa macrofilariae.

Conclusions:

• Ultrasound findings suggest trans-fascial migration of adult Loa loa filariae.
• This migration is associated with fascial lesions and fluid retention, leading to Calabar swellings.
• The destructive nature of Loa loa migration necessitates further research and public health interventions.