Validity of nodule palpation in a Simulium neavei-transmitted onchocerciasis area in Uganda

The objective of this study was to evaluate the prevalence of palpable nodules as a rapid indicator for onchocerciasis endemicity in at-risk communities where Simulium neavei s.s. is the transmitting vector. We used data collected from 13 villages in Uganda to determine the validity of this rapid assessment method. The prevalence of palpable nodules was closely associated with the microfilarial prevalence (R2 = 0.603, P = 0.002), with the community filarial load (R2 = 0.620, P = 0.001) and with the prevalence of onchodermatitis. Nodule palpation in males more than 20 years old, using a cut-off point of 40% and higher for the nodule prevalence, had a sensitivity of 92% and a specificity of 100% in correctly identifying communities in need of urgent intervention with ivermectin mass treatment. Cut-off points were based on World Health Organization recommendations. Thus, nodule palpation can replace skin snipping to identify communities at serious risk of S. neavei-transmitted onchocerciasis.