Evaluation of Onchocerciasis Transmission in Tanzania: Preliminary Rapid Field Results in the Tukuyu Focus, 2015.

To compare diagnostic tests for onchocerciasis in a setting that has suppressed transmission, a randomized, age-stratified study was implemented in an area in Tanzania that had received 15 rounds of annual mass drug administration (MDA) with ivermectin. Study participants (N = 948) from 11 villages underwent a questionnaire, skin examination, skin snips, and blood draw. The burden of symptomatic disease was low. Ov-16 antibody rapid diagnostic test (RDT) results were positive in 38 (5.5%) participants, with 1 (0.5%), 1 (0.4%), and 2 (0.8%) in children aged 0-5, 6-10, and 11-15 years, respectively. Despite significant impact of MDA on transmission, the area would have failed to meet World Health Organization serologic criteria for stopping MDA if a full evaluation had been conducted. The specificity of the RDT, which is 97-98%, may result in the identification of a number of false positives that would exceed the current stop MDA threshold.