Persistence of Trypanosoma cruzi vector-borne transmission among school-age children in the Bolivian Chaco documented by 24-month longitudinal serosurveillance.

BACKGROUND: Chagas disease represents a major public health concern in several Latin American countries, including Bolivia. METHODS: We present a longitudinal serosurvey for Trypanosoma cruzi antibodies among a cohort of 120 school-age children from rural communities in the Bolivian Chaco at three time points between 2017 and 2019. Serum samples extracted from dry blood spots collected on filter paper were tested for T. cruzi antibodies by enzyme-linked immunosorbent assay and rapid diagnostic test. RESULTS: T. cruzi antibodies were detected in 7/120 (5.8%), 8/120 (6.7%) and 11/120 (9.2%) samples in 2017, 2018 and 2019, respectively. An average incidence of 1.76 per 100 person-years was observed. CONCLUSIONS: Our findings support the persistence of vector-borne T. cruzi transmission in this area, highlighting the need for strengthening multidisciplinary efforts against Chagas disease.

Long-Standing International Cooperation in Parasitology Research: A Summary of 35 Years of Activities in the Bolivian Chaco.

The Bolivian Chaco is a semiarid region with a low population density, situated in the southeast part of the Plurinational State of Bolivia. Here, despite the improvements of the last 15 years, poverty remains high in rural areas, where social vulnerability is widespread. The Guaraní ethnic group often lives in isolated communities with a low standard of hygiene and sanitation. This epidemiological scenario favors the spread of transmissible diseases, including several parasitic infections belonging to the neglected tropical diseases (NTDs) group. In this area, a long-standing research activity, built upon the synergism between local and foreign institutions, has been established since the late 1980s and helps to fill in the knowledge gap about the epidemiology dynamics of soil-transmitted helminths, vector-borne parasites, and other parasitic diseases. A 35-year history of cooperation programs in parasitology research has contributed to informing local health authorities of the NTD burden in the Bolivian Chaco and, ultimately, supports local healthcare providers in the management of parasitic diseases.

Feasibility of a Combined Mobile-Health Electrocardiographic and Rapid Diagnostic Test Screening for Chagas-Related Cardiac Alterations.

BACKGROUND: Chronic Chagas cardiomyopathy (CChC) is the most common cause of death related to Chagas disease (CD). The aim of this study was to assess the feasibility of a combined rapid diagnostic test (RDT) and electrocardiographic (ECG) screening in a remote rural village of the Bolivian Chaco, with a high prevalence of CChC. METHODS: Consecutive healthy volunteers > 15 years were enrolled in the community of Palmarito (municipality of Gutierrez, Santa Cruz Department, Bolivia) in February 2019. All patients performed an RDT with Chagas Stat-Pak® (CSP, Chembio Diagnostic System, Medford, NY, USA) and an ECG by D-Heart® technology, a low-cost, user-friendly smartphone-based 8-lead Bluetooth ECG. RDTs were read locally while ECGs were sent to a cardiology clinic which transmitted reports within 24 h from recording. RESULTS: Among 140 people (54 men, median age 38(interquartile range 23-54) years), 98 (70%) were positive for Trypanosoma cruzi infection, with a linear, age-dependent, increasing trend (p < 0.001). Twenty-five (18%) individuals showed ECG abnormalities compatible with CD. Prevalence of ECG abnormalities was higher in infected individuals and was associated with higher systolic blood pressure and smoking. Following screening, 22 (16%) individuals underwent clinical evaluation and chest X-ray and two were referred for further evaluation. At multivariate analysis, positive CSP results (OR = 4.75, 95%CI 1.08-20.96, p = 0.039) and smoking (OR = 4.20, 95%CI 1.18-14.92, p = 0.027) were independent predictors of ECG abnormalities. Overall cost for screening implementation was <10 $. CONCLUSIONS: Combined mobile-Health and RDTs was a reliable and effective low-cost strategy to identify patients at high risk of disease needing cardiologic assessment suggesting potential future applications.

Cross-sectional study on intestinal parasite infections in different ecological zones of the Department of La Paz, Bolivia.

We performed a cross-sectional parasitological survey to assess the prevalence of protozoa and helminth infection among 275 school-age children (SAC) living in rural and peri-urban areas located in different ecological zones of the Department of La Paz, Bolivia. Public health activities for the control of STH, based on the biannual administration of mebendazole to preschool and school children are implemented at national level since 1986. We found an overall prevalence of 82.2% for intestinal parasites, including protozoa (80%) and helminths (23.3%). Blastocystis and Entamoeba coli were the most prevalent protozoa (found in 44% and 20.7% of the SAC enrolled); as for helminths, Ascaris lumbricoides and Hymenolepis nana were diagnosed in 14.5% and 3.3% of the children, respectively, followed by Trichuris trichiura 1.4%, Enterobius vermicularis 1.4%, Strongyloides stercoralis 0.7% and hookworms 0.7%. Molecular characterization of Blastocystis positive samples evidenced three different subtypes (ST1, ST2, ST3) highlighting the risk of transmission also from animal reservoir. We found a significant difference in the distribution of intestinal parasitic infection (IPIs) by ecological zone (44/74. 59% in Andean highlands, 94/170, 88% in tropical lowlands and 88/94, 94% in the Yungas, p < 0.001). Access to potable water (OR 0.1 95%CI 0.02-0.5, p = 0.004) and the habit of boiling drinking water (OR 0.3, 95% CI 0.2-0.7, p = 0.004) showed an independent association with a lower risk of all IPIs and STHs, respectively. The very low prevalence of STH infections of moderate heavy intensity demonstrate that periodical deworming has been successful in reducing the morbidity due to these parasites, however the high prevalence of protozoa demonstrate that sanitation is still problematic and there is a relevant contamination of the environment with human faeces. Significant efforts are still needed to reduce IPIs transmission and to improve health and sanitation in this area.

Trypanosoma cruzi infection in the human population of the Bolivian Chaco: four serosurveys over a 26-year period (1987-2013).

INTRODUCTION: Chagas disease (CD) remains a public health concern in several Latin American countries. At global level, Bolivia has the highest CD burden and the Chaco region, in the southeast of the country, is the most affected area. We report the results of four serosurveys for Trypanosoma cruzi antibodies, carried out approximately ten years apart from each other, during the lapse 1987-2013, in different localities of the Bolivian Chaco. METHODOLOGY: Four cross-sectional surveys were conducted in various localities, mostly rural, of the Bolivian Chaco, during the period 1987-2013. RESULTS: Although a reliable analysis of CD epidemiological trend is challenging, a partial reduction of anti-T. cruzi seroprevalence over the past four decades in the Bolivian Chaco may be assumed. In particular, in 1987 the exposure to T. cruzi in rural setting was universal since the first years of life, while it resulted gradually lower and age-dependent thereafter. Moreover, T. cruzi seroprevalence among women of reproductive age (15-45 years) has been persistently high in rural areas. CONCLUSIONS: T. cruzi transmission is still active and CD remains a concern throughout the Bolivian Chaco. More efforts are needed in order to achieve a sustainable interruption of vector-borne CD transmission in this area.

Seroprevalence of West Nile and dengue virus in the human population of the Bolivian Chaco.

To determine the seroprevalence of antibodies against dengue virus (DENV) and West Nile virus (WNV) in the human population of the Bolivian Chaco, we tested 256 inhabitants of two rural communities. The seroprevalence, confirmed by plaque reduction neutralization test, was 7.8% and 2.7% for DENV and WNV, respectively.

Canine Trypanosoma cruzi infection in the Bolivian Chaco.

A cross-sectional study on Trypanosoma cruzi was carried out in 2013 to evaluate the role of dogs as possible source of infection for humans in two rural communities of the highly endemic Bolivian Chaco (Bartolo, Chuquisaca Department, n = 57 dogs; and Ivamirapinta, Santa Cruz Department, n = 48 dogs). Giemsa-stained thick and thin smears, rapid immunochromatographic test (ICT) (Chagas Quick test, Cypress Diagnostic, Belgium) and polymerase chain reaction for T. cruzi on dried blood spots were performed. All smears proved negative by microscopic examination, whereas 23/103 (22%) were positive by ICT and 5/105 (5%) blood samples contained T. cruzi DNA, evidencing the potential role of dogs in the domestic transmission of the parasite.

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

Tropical anemia can have multiple causes, whether socioeconomic, dietary, or infectious. In the Bolivian Chaco, soil-transmitted helminthiases (STH), malaria, and Chagas disease are potential infectious causes of anemia among school-aged children (SAC). Following years of preventive chemotherapy with mebendazole, the prevalence of STH among SAC living in that area is now negligible, whereas protozoan infections are still highly prevalent (81%); Hymenolepis nana is the most frequent intestinal helminth (∼13%). We present results of hemoglobin (Hb) assessment and the association between parasitic infections and Hb levels of that SAC population. Overall, 511 SAC (girls:boys ratio 1:1, mean age 9.4 years [95% confidence interval {CI}: 9.3-9.5]) had Hb levels measured by using a point of care testing (HemoCue® Hb 301 System; HemoCue, Angelhome, Sweden). The prevalence of anemia was 23% (117/511), with mean and median Hb level = 12.2 g/dL (95% CI: 12.1-12.3; range 9.2-15.4 g/dL). By multivariate analysis, H. nana infection was associated with an increased risk of anemia (odds ratio 2.9, 95% CI: 1.5-5.7, P = 0.002). Two samples (0.5%) were positive for Trypanosoma cruzi and none for Plasmodium spp. by polymerase chain reaction of the 439 children tested. Anemia is still a concern among SAC living in the Bolivian Chaco. Our findings call for a greater attention to fecal-oral emerging pathogens, such as H. nana, and highlight the importance of water, sanitation, and hygiene improvements for disadvantaged population such as those living in the Bolivian Chaco.

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

OBJECTIVE: Preventive chemotherapy is the WHO-recommended control method for soil-transmitted helminthiases. In the Bolivian Chaco, 6-monthly single-dose mebendazole delivery to school-age children achieved a dramatic decrease in soil-transmitted helminthiases prevalence between 1987 and 2013. Consequently, in September 2016, preventive chemotherapy delivery was interrupted in nine rural communities. In compliance with WHO recommendations, we intensified surveillance to monitor soil-transmitted helminthiases prevalence and detect potential changes that would require interventions. METHODS: We conducted two cross-sectional parasitology surveys 12 months apart (September 2016-2017) among school-age children living in the communities where preventive chemotherapy delivery had been halted. Study design, methods of sampling and sample analysis technique (direct microscopy, Kato-Katz technique) followed WHO recommendations, aiming to obtain data representative of the Bolivian Chaco ecological zone. RESULTS: We collected 426 samples in 2016 and 520 in 2017. Soil-transmitted helminthiasis prevalence was unremarkable: 0.7% (95% CI 0-1.5%) in 2016 and 0.8% (0-1.5%) in 2017. Conversely, the prevalence of tapeworms (13% in 2016, 12% in 2017) and intestinal protozoan infections (81% in 2016 and 75% in 2017) continued to be high. CONCLUSIONS: 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.

Seroprevalence of Hepatitis A Virus, Hepatitis E Virus, and Helicobacter pylori in Rural Communities of the Bolivian Chaco, 2013.

In the Bolivian Chaco, south-east of Bolivia, studies conducted over the past three decades reported hepatitis A virus (HAV) and Helicobacter pylori seroprevalences above 90% and 60%, respectively. Hepatitis E virus (HEV) prevalence was previously found to be 6-7% but is probably an underestimate because of the poor sensitivity of the assays used. In November 2013, we conducted a cross-sectional study of 263 healthy volunteers from two rural communities of the Bolivian Chaco, aiming to reassess HAV, HEV, and H. pylori seroprevalence 10-20 years following the previous surveys. Hepatitis A virus seroprevalence was 95%, with universal exposure after the first decade of life; HEV seroprevalence was considerably higher (31-35%) than that previously reported; H. pylori seroprevalence was 59%, with an age-dependent distribution. The high prevalence of these infections suggests that major efforts are still needed to reduce fecal-oral transmission and to improve human health in the Bolivian Chaco.

Seroepidemiological trend of strongyloidiasis in the Bolivian Chaco (1987-2013) in the absence of disease-specific control measures.

OBJECTIVES: The prevalence of Strongyloides stercoralis infections is grossly underestimated because infections go mostly undetected, although they can persist for a lifetime due to the auto-infective cycle. In the Bolivian Chaco, the prevalence of soil-transmitted nematodes dropped dramatically in the past 25 years, but the mebendazole used for preventive chemotherapy has no effect on S. stercoralis. Meanwhile, the prevalence of intestinal protozoan infections remains unchanged. We compared S. stercoralis seroprevalence in rural communities of the Bolivian Chaco from 1987 to 2013. METHODS: Sera collected during two previous serosurveys, conducted in the Chaco region in 1987 and 2013, were tested for S. stercoralis using a commercial assay (Bordier-ELISA, Bordier Affinity Products, Switzerland). RESULTS: Overall, 355 sera were analysed, 122 from the 1987 survey and 233 from the 2013 survey. Seropositivity for S. stercoralis was significantly more prevalent in 1987 (19/122, 16% in 1987 vs. 15/233, 6% in 2013, P = 0.006), accounted for by a drop from 17% to 3% in people under 26 years of age. Multivariate analysis showed a significant association between seropositivity for S. stercoralis and age in the 2013 population (OR 1.03 for each one-year increase, 95%CI 1.00-1.05, P = 0.04), but none in 1987. CONCLUSIONS: The significant reduction in S. stercoralis seroprevalence in Bolivian Chaco cannot be explained by preventive chemotherapy or improved social-sanitary conditions. As the drop is seen in younger generations, it is consistent with little transmission occurring. However, the risk of transmission still exists, as prevalence is persistently high in older individuals, who present a potential reservoir due to the lifelong nature of S. stercoralis infections.

Intestinal parasitic infections and associated epidemiological drivers in two rural communities of the Bolivian Chaco.

INTRODUCTION: In 2013 a coproparasitological survey was carried out in two rural communities of the Bolivian Chaco to determine the prevalence of intestinal parasitic infections (IPIs) and to investigate on possible infection drivers through a questionnaire interview. METHODOLOGY: Faecal samples were examined by microscopy. Samples positive for Entamoeba histolytica complex and Blastocystis were molecularly examined to identify the species/subtypes involved. RESULTS: The overall infection rate was 86%, identical in both communities and mostly due to protozoa. Soil-transmitted helminths were detected in <3% of children and adults. DISCUSSION: The protozoa detected, including Blastocystis subtypes, indicate faecal contamination of the environment by both humans (as confirmed by the presence of Hymenolepis nana) and animals. Nested-PCR identified E. histolytica, thus signalling the possible occurrence of invasive amoebosis. Lack of safe water, environmental contamination, poor sanitation and hygiene, shared by both communities, are the main drivers of IPIs. In addition, unlike gender and socioeconomic factors, childhood (only for some species), crowding and cohabitation with animals proved to be further significant protozoon infection risk factors. CONCLUSIONS: These results highlight the need for the promotion of access to clean water, improved sanitation and better hygiene, thus reducing the frequency of preventive chemotherapy for STHs while continuing to monitor the population for possible recrudescence.

Human Babesiosis, Bolivia, 2013.

To investigate human babesiosis in the Bolivian Chaco, in 2013 we tested blood samples from 271 healthy persons living in 2 rural communities in this region. Microscopy and PCR indicated that 3.3% of persons were positive for Babesia microti parasites (US lineage); seroprevalence was 45.7%. Appropriate screening should mitigate the risk for transfusion-associated babesiosis.

High prevalence of acquired antimicrobial resistance unrelated to heavy antimicrobial consumption.

In a very remote rural Bolivian community where the use of antimicrobials has been minimal and where exchanges with the exterior are very limited, 67% of subjects were found to be carriers of fecal Escherichia coli with acquired resistance to >/=1 antimicrobial agent(s); the highest rates were observed for tetracycline (64%), ampicillin (58%), trimethoprim-sulfamethoxazole (50%), and chloramphenicol (41%). The most relevant implication of these findings is that, in certain settings, the spread and maintenance of antimicrobial resistance can occur, regardless of whether selective pressure generated by the use of antimicrobials is present.

Seroprevalence of varicella zoster and rubella antibodies among rural populations of the Chaco region, south-eastern Bolivia.

OBJECTIVE: To determine the seroprevalence of antibodies against varicella zoster virus (VZV) and rubella virus among the population of two rural areas, Camiri and Villa Montes, Chaco region, south-eastern Bolivia. METHODS: In a cross-sectional study, serum samples from randomly selected subjects were screened for VZV- and rubella antibodies using enzyme-linked immunosorbent assay (ELISA). RESULTS: The prevalence of VZV antibodies was 80% (391 of 489). No significant differences were observed between genders and study areas. The prevalence increased with age with a seropositivity rate of 21.2% in the 1-4-year-old children, 56.9% in the 5-9 age group and 83.7% in the 10-14 age group, and reached 98.2% in over 45-year olds. The prevalence of rubella virus antibodies was 76.9% (377 of 490), without significant differences between genders and study areas. Similar to the trend observed for VZV antibodies, the seroprevalence increased with age with a seropositivity rate of 18.1% in the 1-4-year-old children, 53.9% in the 5-9 age group and 78.4% in the 10-14 age group, and reached 94.7% in over 45-year-old subjects. Among the 95 women of childbearing age (15-44 years) the susceptibility rate was 11.6%. CONCLUSIONS: A common seroimmunological profile was evidenced for the two infections. The age-specific profile of VZV seropositivity differs from that reported for other tropical countries where higher median age of seroconversion and lower seroprevalence among adults are observed. Data concerning the prevalence of immunity to rubella may be useful to evaluate the impact of the recently introduced rubella immunization programme.

Anticuerpos contra Trichinella spiralis en la población rural de la provincia Cordillera, Bolivia / Seroprevalence of antibodies to Trichinella spiralis among rural residents of Cordillera province, Bolivia

Se realizó un estudio seroepidemiológico para determinar la prevalencia de anticuerpos contra Trichinella spiralis en el área rural de la provincia Cordillera del Departamento de Santa Cruz en Bolivia. Se examinaron 234 muestras de suero mediante el ensayo de inmunoabsorción enzimática (ELISA) y se detectaron los anticuerpos en siete muestras (3 por cien). Los resultados documentan por primera vez la presencia de infestación humana por Trichinella en Bolivia y sugieren la necesidad de fortalecer la vigilancia sanitaria de la triquinosis en los mataderos municipales, impedir la faena clandestina de animales y, sobre todo, lograr que los productores y pobladores tomen conciencia de los peligros de esta zoonosis

A seroepidemiological study was conducted to determine the prevalence of antibodies to Trichinella spiralis among rural residents of Cordillera province, Santa Cruz Department, Bolivia. Using the enzyme-linked immunosorbent assay (ELISA), 234 serum samples were examined, and antibodies were detected in seven of the samples (3%). The results document for the first time the presence of human infestation with Trichinella in Bolivia and suggest the need to strengthen trichinelosis surveillance in the municipal slaughterhouses, to prevent the clandestine slaughter of animals, and particularly to ensure that residents and meat producers in the area become aware of the dangers of this zoonosis