ABSTRACT
A clinical and serological epidemiological study done on a yaws focus in the Santiago Basin area, province of Esmeraldas, showed a prevalence of 11.3% for active clinical lesions and a seropositivity of 94.9%. The Rio Santiago was hyperendemic for yaws (prevalence, 17.9%; seropositivity, 98.0%) while Rio Zapallito was found to be mesoendemic and the Rio Cayapas and Rio Onzoles hypoendemic. Active and latent evidence of yaws was found only in the black race. Children, ages 5-12 year, were found to have the highest incidence (55.8%) of clinical lesions, with the majority found on the legs (64.2%). Papilloma was the most prevalent lesion (55.4%). Mass treatment of the basin using benzathine penicillin G was done according to WHO recommendation.