The in vitro determination of the visual resolution in onchocercal nodules of bovine and human origin by a portable ophthalmologic ultrasound scanner.

A portable ophthalmologic real-time ultrasound linear scanner (Ophthascan) was used to determine the optic resolution of excised onchocercal nodules of Onchocerca volvulus and O. gibsoni origin. Fresh, thawed and fixed nodules were used. Following macroscopic and histologic examination it became apparent that the Ophthascan could clearly distinguish between echogenic worm coils and non-echogenic areas of necrosis. The fibrotic nodular capsule was more echogenic than the worm coils inside the nodule. The optic resolution did not permit to distinguish the internal organ structures within a worm segment. This in vitro determination of the visual resolution of an opthalmologic real-time ultrasound linear scanner is in accordance with in vivo results of an ongoing trial with a new macrofilaricide. Thus sonography can be used to visualise the interior of superficial onchocercal nodules in vivo and to follow their evolution with or without chemotherapy. The non-invasive diagnostic and sequential assessment of onchocercal nodules by sonography will be a valuable contribution in onchocerciasis, especially for the assessment of macrofilaricides.