MACCHIONI AND OTHERS DRAMATIC DECREASE IN PREVALENCE OF SOIL-TRANSMITTED HELMINTHIASIS AND NEW INSIGHTS INTO INTESTINAL PROTOZOA IN CHILDREN LIVING IN THE CHACO REGION, BOLIVIA Short Report: Dramatic Decrease in Prevalence of Soil-Transmitted Helminths and New Insights Into Intestinal Protozoa in Children Living in the Chaco Region, Bolivia

We assessed the prevalence of intestinal parasites among 268 2–12-year-old children living in rural areas, small villages, and semi-urban areas of the Chaco region, south-eastern Bolivia. The overall parasitism was 69%. Only protozoa, helminths, or co-infections were observed in 89.2%, 5.9%, or 4.9% of the positive children, respectively. A significant progressive increase in overall parasite prevalence was found when passing from rural areas to small villages and semi-urban areas. The most commonly found species were Entamoeba coli (38.4%), Giardia intestinalis (37.7%), and Blastocystis spp. (16%). Hymenolepis nana was the most prevalent helminth (5.6%), followed by Ascaris lumbricoides and hookworms (1.5% and 0.4%) evidenced only in rural areas and in villages. Molecular diagnostics identified Blastocystis subtypes 4 and 5, and 5 infections by Entamoeba histolytica and 4 by Entamoeba dispar. The dramatic decrease in prevalence of soil-transmitted helminths with respect to that observed about 20 years ago (> 40%) evidences the success of the preventive chemotherapy intervention implemented in 1986. Health education and improved sanitation should be intensified to control protozoan infections. In developing countries the lack of access to safe water, sanitation, and hygiene are the key factors for the high prevalence of intestinal protozoa that, in infants and children, frequently have the clinical expression of malabsorption syndrome and gastrointestinal morbidity. 1 Moreover, Ascaris lumbricoides may contribute to nutritional deficiencies and even produce intestinal occlusion, whereas other soil-transmitted helminths (STHs) cause chronic intestinal blood loss that results in anemia, and impairing physical growth, cognition, learning and working capacities. 2 In the Santa Cruz Department (Plurinational State of Bolivia), studies conducted 40 years ago showed intestinal parasitism ranging from 85.4% to 99.5%, with 65% of polyparasitism. 3–5 A survey carried out in 1987 detected an overall value of 79%, with prevalence of STHs up to 64%. 6,7 Further investigations conducted in 1990 in children living in two rural communities showed prevalence of STH infections of 41% and 64%, respectively. 8 Starting in 1986, the Bolivian Ministry of Health developed a Parasitic Disease Control Program based on preventive chemotherapy with mebendazole that is still part of the Integral Attention to Prevalent Childhood Diseases Program (AIEPI).