Onchocerciasis in Ecuador. II. Epidemiology of the endemic foci in the province of Esmeraldas.

The epidemiology of infection was studied in all endemic foci of onchocerciasis in the province of Esmeraldas in Ecuador. The incidence of infection and the density of microfilariae in the skin, both greater in males than females, increased with age, reaching highest levels at 40-45 years in males and at 60 years and older in females. In the hyperendemic area males and females had the same rate of infection, but the microfilarial density in males exceeded that in females. In the hypoendemic areas males had a higher infection rate than females, but females registered a higher density of microfilariae in the skin. The incidence and location of the onchocercal nodules correlated closely with the density of microfilariae. Adults, aged 50-54 had the highest prevalence of onchocercal nodules, which occurred primarily in the thorax and pelvic regions. Children aged 0-14 years showed a low prevalence of nodules, the head region being the primary site. Of the two diagnostic methods used to detect the presence of microfilariae, most of the diagnoses (85.6%) were made by skin biopsies as compared to those made by the Mazzotti test (14.4%).