Successful Interruption of Transmission of Onchocerca volvulus in the Escuintla-Guatemala Focus, Guatemala

Rodrigo J Gonzalez,Eduardo Catú,Guillermo Zea-Flores,Jane Richards,Nancy Cruz-Ortiz,Nidia Rizzo,Alfredo Domínguez,Orlando Oliva,Frank O Richards,Mauricio Sauerbrey,Kim A Lindblade

doi:10.1371/journal.pntd.0000404

Abstract

BackgroundElimination of onchocerciasis (river blindness) through mass administration of ivermectin in the six countries in Latin America where it is endemic is considered feasible due to the relatively small size and geographic isolation of endemic foci. We evaluated whether transmission of onchocerciasis has been interrupted in the endemic focus of Escuintla-Guatemala in Guatemala, based on World Health Organization criteria for the certification of elimination of onchocerciasis.Methodology/Principal FindingsWe conducted evaluations of ocular morbidity and past exposure to Onchocerca volvulus in the human population, while potential vectors (Simulium ochraceum) were captured and tested for O. volvulus DNA; all of the evaluations were carried out in potentially endemic communities (PEC; those with a history of actual or suspected transmission or those currently under semiannual mass treatment with ivermectin) within the focus. The prevalence of microfilariae in the anterior segment of the eye in 329 individuals (≥7 years old, resident in the PEC for at least 5 years) was 0% (one-sided 95% confidence interval [CI] 0–0.9%). The prevalence of antibodies to a recombinant O. volvulus antigen (Ov-16) in 6,432 school children (aged 6 to 12 years old) was 0% (one-sided 95% IC 0–0.05%). Out of a total of 14,099 S. ochraceum tested for O. volvulus DNA, none was positive (95% CI 0–0.01%). The seasonal transmission potential was, therefore, 0 infective stage larvae per person per season.Conclusions/SignificanceBased on these evaluations, transmission of onchocerciasis in the Escuintla-Guatemala focus has been successfully interrupted. Although this is the second onchocerciasis focus in Latin America to have demonstrated interruption of transmission, it is the first focus with a well-documented history of intense transmission to have eliminated O. volvulus.

Highlights

Onchocerciasis is caused by a filarial nematode transmitted by black flies of the genus Simulium [1]
Brought to the Americas from Africa by the slave trade, onchocerciasis is present in six countries in Latin America
People living in the EscuintlaGuatemala focus, a region in Guatemala where the disease was common, have been taking ivermectin for many years

Summary

Introduction

Onchocerciasis (river blindness) is caused by a filarial nematode transmitted by black flies of the genus Simulium [1]. It is endemic to 6 countries in Latin America (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela). Foci of transmission in the Americas are relatively small and geographically delimited compared to areas of transmission in Africa [4]. In part due to the geographical isolation of foci, the goal of the Onchocerciasis Elimination Program of the Americas (OEPA) is both to eliminate ocular morbidity throughout the region, and to permanently interrupt transmission where possible [1,5]. Elimination of onchocerciasis (river blindness) through mass administration of ivermectin in the six countries in Latin America where it is endemic is considered feasible due to the relatively small size and geographic isolation of endemic foci. We evaluated whether transmission of onchocerciasis has been interrupted in the endemic focus of EscuintlaGuatemala in Guatemala, based on World Health Organization criteria for the certification of elimination of onchocerciasis

Methods

Results

Discussion

Conclusion