Abstract
Intestinal worms, or soil-transmitted helminths (STHs), affect hundreds of millions of people in all tropical and subtropical regions of the world. The most prevalent STH is Ascaris lumbricoides. Through large-scale deworming programs, World Health Organization aims to reduce morbidity, caused by moderate-to-heavy intensity infections, below 2%. In order to monitor these control programs, stool samples are examined microscopically for the presence of worm eggs. This procedure requires well-trained personnel and is known to show variability between different operators interpreting the slides. We have investigated whether ABA-1, one of the excretory-secretory products of A. lumbricoides can be used as a coproantigen marker for infection with this parasite. Polyclonal antibodies were generated and a coproantigen ELISA was developed. Using this ELISA, it was found that ABA-1 in stool detected Ascaris infection with a sensitivity of 91.5% and a specificity of 95.3%. Our results also demonstrate that there is a correlation between ABA-1 levels in stool and A. lumbricoides DNA detected in stool. Using a threshold of 18.2 ng/g stool the ABA-1 ELISA correctly assigned 68.4% of infected individuals to the moderate-to-heavy intensity infection group, with a specificity of 97.1%. Furthermore, the levels of ABA-1 in stool were shown to rapidly and strongly decrease upon administration of a standard anthelminthic treatment (single oral dose of 400 mg albendazole). In an Ascaris suum infection model in pigs, it was found that ABA-1 remained undetectable until day 28 and was detected at day 42 or 56, concurrent with the appearance of worm eggs in the stool. This report demonstrates that ABA-1 can be considered an Ascaris -specific coproantigen marker that can be used to monitor infection intensity. It also opens the path for development of point-of-care immunoassay-based tests to determine A. lumbricoides infection in stool at the sample collection site.
Highlights
According to the World Health Organization (WHO), approximately 1.5 billion people, or 24% of the world’s population, are infected with soil-transmitted helminths (STH) worldwide [1]
We have investigated the possibility of using ABA-1, an abundantly secreted protein from the worm, as a biomarker in stool of infected individuals
We have developed an ELISA and using this assay determined that ABA-1 as stool biomarker had a sensitivity of 91.5% and a specificity of 95.3% to detect infection with A. lumbricoides
Summary
According to the World Health Organization (WHO), approximately 1.5 billion people, or 24% of the world’s population, are infected with soil-transmitted helminths (STH) worldwide [1]. This group of parasites comprises the intestinal worms Ascaris lumbricoides, Trichuris trichiura, and the hookworm species Ancylostoma duodenale and Necator americanus. Children and women of childbearing age are at highest risk of developing morbidity, which is mainly associated with moderate-toheavy intensity (M&HI) infections [2] It is the goal of the WHO to reduce the prevalence of preschool and school-aged children with STH infections of M&HI below 2% by 2030 [3]. Global control efforts for soiltransmitted helminthiasis are an essential part of the Sustainable Development Goals (SDGs) put forward by the WHO where it contributes to achieve goal # 3: good health and well-being
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