Scaling down of a deworming programme among school‐age children after a thirty‐year successful intervention in the Bolivian Chaco

Abstract

Our findings support the role of preventive chemotherapy in reducing soil-transmitted helminthiases transmission, as otherwise poor hygienic and health conditions persist in the Bolivian Chaco. A national survey, involving areas from all the ecological zones of Bolivia, is now warranted.

Decline in Total Serum IgE and Soluble CD30 in the Context of Soil-Transmitted Helminth Decline in Bolivia

“…These changes paralleled an impressive drop in STH prevalence in this area, from more than 50% to < 1%, likely the result of 30 years of PC. 8 Of note, no STH infections were identified in Ivamirapinta in 2013 during a parasitological survey, which involved 111 inhabitants (median age 30 years, range 1-73). 15 During the same period, a significant decrease in seroprevalence was documented also for S. stercoralis, although no large-scale control measures potentially affecting strongyloidiasis were implemented.…”

“…Two years later, surveillance confirmed the sustained STH reduction (< 1%) in the entire ecological zone. 8 Concomitantly, a serosurvey evidenced a drop of anti-S. stercoralis antibody prevalence from 1987 to 2013 (from 16% to 6%), although PC is not effective against this parasite. 9 Conversely, protozoan parasitic infections did not show any substantial decreasing.…”

Hymenolepis nana—An Emerging Intestinal Parasite Associated with Anemia in School Children from the Bolivian Chaco

“…7 At that time, STH infections were highly prevalent (41.0% to 64.5%), with hookworm prevalence reaching 50%, 5.6% of which of heavy or moderate intensity (> 2000 eggs per gram), and T. trichiura prevalence ranged from 14.5 to 19.3% (all of light intensity) 8. Today, STH prevalence is <1%, yet this dramatic decrease does not seem to have modified the risk of anaemia in school-age children in the past three decades (16% in 1990 vs. 23% 2016, Pearson's chi-squared test p= 0.20), possibly because STH infections were of low intensity in 1990 4. Yet, still today more than 80% of children have at least one intestinal parasitic infection and nearly 60% have two or more, essentially protozoa; about every other child is infected with Blastocystis spp, and one in four is infected with an Entamoeba species.…”

“…In September 2016, 519 SAC from 9 rural communities of the Bolivian Chaco, a semi-arid and sparsely populated region, located in the south-east of the Plurinational State of Bolivia (longitude 64°30’ - 58°50’ west; latitude 17°58’ - 22°20’ south), were enrolled in a cross-sectional parasitological survey, whose methodology and results have been previously described in detail 4. Briefly, a minimum of 50 third- to fifth-graders, usually 8–11 years old, was enrolled in each school.…”

“…Regular deworming through preventive chemotherapy (PC) of at-risk groups (preschool and school children and women of reproductive age) is expected to reduce worm burden and STH-induced morbidity in the infected individuals as well as overall prevalence 3. In the Bolivian Chaco, a recent cross-sectional survey found that the prevalence of hookworm infection in school-age children has dropped from 50% in the 1990’s to 0.7% in 2016, and no cases of A. lumbricoides and T. trichiura – likely the result of 30 years of PC 4. This, all the while protozoan infections continue to be prevalent (81% of children had at least one), and the minute tapeworm Hymenolepis nana having become the most frequent helminthic infection (~13%).…”