Subarachnoid neurocysticercosis in a rural area of the Bolivian Chaco. A population-based survey through the use of a novel urine antigen assay

Neurocysticercosis (NCC) is a major public health concern in low-middle-income countries. Subarachnoid NCC (SANCC), a less frequent form of NCC, is characterized by severe clinical evolution, high mortality and impactful neurological sequelae in survivors. However, due to a long pre-clinical period, early diagnosis and treatment of SANCC would likely improve the clinical course and reduce the occurrence of complications. To date, data on the prevalence of SANCC in endemic settings are scant, and there are no commercially available tests for SANCC screening in at-risk populations. Between October 2023 and May 2024, we conducted a population-based cross-sectional study aimed at implementing a non-invasive screening for SANCC in a low-resource area of the Plurinational State of Bolivia, using a home-made Ag-ELISA urine assay based on the monoclonal antibody set TsW5-TsW8. Questionnaires were also administered to the study population to assess the presence of behaviors and risk factors for active transmission of Taenia solium in the area. The study involved 1,232 subjects aged ≥10 years, 1,130 of whom delivered a urine sample. Among them, a median age of 27.4 years was observed, with 38.1% of subjects being males. Overall, 7 subjects with positive urine antigen test, confirmed on two different samples, were identified and underwent magnetic resonance imaging. The diagnosis of SANCC was radiologically confirmed in 4/7 subjects, for a prevalence of SANCC in the enrolled population of 3.54/1,000. The antigen assay showed a positive predictive value for SANCC of 57.1%. Risk factors for active transmission of T. solium, such as lack of access to adequate sanitation and the widespread practice of domestic pig breeding and sacrifice, were frequent. While further studies are needed to better define the diagnostic performance of the employed urine assay, this study confirms the presence of SANCC in the study area, consistent with evidence from similar endemic settings.