Evaluation of Ultrasonography for the Detection of Drug-induced Changes in Onchocercal Nodules

Clinical trials of macrofilaricidal drugs against Onchocerca volvulus are impeded due to the lack of means for assessing in vivo drug-induced changes in the onchocercomas. The application of ultrasonography in the sequential monitoring of morphologic alterations of onchocercal nodules after six weeks of suramin therapy was evaluated in 20 male patients from Ghana with a total of 64 nodule sites. After each follow-up session, a number of onchocercal nodules were extirpated so that by the end of one year, all nodules had been removed for histologic examination. The sonomorphologic changes observed and their time of appearance correlated well with the histologic findings of the onchocercomas. Eighty-three percent of the onchocercal nodules became hyperechogenic and 22% developed echo-free areas at the end of the follow-up period. Absence of the lateral acoustic shadow increased by more than 30% and the lack of differentiation of the worm center from the capsule and the nodule from its surrounding tissue increased by the end of one-year posttreatment to 100% and 91%, respectively. A mean reduction of nodule size of 27% was also documented. The histologic studies revealed that the proportion of the dead female worms increased from 17% at the end of the suramin therapy to 48% six months later and reached 61% at one year. It is concluded that ultrasonographic monitoring of onchocercomas can provide essential information on drug effects and facilitate clinical trials of macrofilaricidal drugs, limiting histologic evaluation to a few objectively selected onchocercomas.