Guide to detecting a potential recrudescence of onchocerciasis during the posttreatment surveillance period: the American paradigm.

Control and elimination of human onchocerciasis using mass drug administration of ivermectin (Mectizan®) has proceeded with marked gains over the past 10 years, more so in the Americas than in Africa. In the Americas, the initial focus on elimination of ocular morbidity has shifted to interruption of transmission, and the program has refined both the process leading up to interruption of transmission as well as the critical period following cessation of mass drug administration to document that there is no recrudescence of transmission. This is called the post-treatment surveillance (PTS) period. This report describes the aims, phases, and methodology of PTS as operationalized by the endemic countries and the Onchocerciasis Elimination Program for the Americas. Successful completion of the PTS period without signs of recrudescence leads to a country request for certification of elimination by the World Health Organization. As elimination of onchocerciasis in the Americas proceeds and emphasis in Africa switches from control to elimination, the PTS guide should prove invaluable to those programs going forward.