This scoping review follows the methodological framework proposed by Arksey and O’Malley [30], with enhancements by Levac et al [31], and guidance from the Joanna Briggs Institute (JBI) [32]. Reporting adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) [33], and the search strategy is reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Reporting of Systematic Searches (PRISMA-S) [34]. The completed PRISMA-ScR checklist is provided as a supplementary file. The protocol was registered prospectively on the Open Science Framework (osf.io/qv27y)

This review aimed to map the existing literature on Cryptosporidium in Southeast Asia and was guided by the following research questions: (1) What is the reported prevalence of Cryptosporidium across human, animal, and environmental domains in Southeast Asian countries? (2) What diagnostic methods have been used across the regional literature, and how does diagnostic heterogeneity affect species-level resolution and transmission inference? (3) To what extent do studies integrate evidence across human, animal, and environmental domains within a One Health framework? (4) What environmental, food-related, and socioeconomic risk factors have been quantitatively assessed in association with Cryptosporidium infection or detection in the region?

Studies were included if they reported primary data on Cryptosporidium in human or animal populations within one or more of the 11 Southeast Asian countries: Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, Timor-Leste, and Vietnam. Eligible studies had to provide information on prevalence, diagnostic methods, or risk factors related to environmental, food, or socioeconomic domains. Only English-language publications were considered.

Studies were excluded if they were not primary research (eg, reviews, editorials, letters, or conference abstracts), were conducted outside the defined geographic region, or did not report on Cryptosporidium in human, animal, or environmental samples.

We searched five databases: PubMed, Embase, CABI Digital Library, Cochrane Library, and Index Medicus for the South-East Asia Region (IMSEAR). The strategy combined organism-specific terms (eg, “Cryptosporidium,” “Cryptosporidiosis,” “C. parvum,” “C. hominis”) with geographic terms (eg, country names and “Southeast Asia,” “ASEAN”). Searches were designed to maximize inclusivity and minimize missed studies. Full search strategies for each database are provided in Multimedia Appendix 1, reported in accordance with PRISMA-S [34].

Backward citation tracking was performed by reviewing reference lists of included studies and relevant reviews. Targeted searches of organizational websites (eg. World Health Organization, WHO, Food and Agriculture Organization of the United Nations, FAO) were also conducted. No formal gray literature search was performed.

All search results were imported into EndNote 21 (Clarivate, Philadelphia, PA) for deduplication. Title and abstract screening, followed by full-text review, was conducted in the Covidence Systematic Review Software (Veritas Health Innovation, Melbourne, Australia) using predefined inclusion and exclusion criteria. Each article was independently screened by two reviewers, with discrepancies resolved by a third reviewer.

Data extraction was performed by a single reviewer using a standardized form developed in Covidence. Due to the large number of included studies, dual extraction was not feasible within a reasonable timeframe. To ensure consistency, the form was piloted on ten records, revised based on identified inconsistencies, and the ten piloted records were re-extracted in full before proceeding with the remainder of the dataset. Extracted variables included study metadata (authors, year, country), study design and setting, host population (human, animal, environmental, or mixed), sample type and size, diagnostic methods, species/genotypes, prevalence, study limitations, and reported environmental, food-related, and socioeconomic risk factors. The data dictionary is provided in Multimedia Appendix 2 and is available through OSF (Open Science Framework).

A descriptive synthesis will summarize findings across the included studies. Data will be organized thematically across four domains corresponding to the research questions outlined above: prevalence distribution, diagnostic methods and species resolution, One Health domain integration, and transmission risk factors. Findings will be presented in tables, charts, and maps to illustrate trends in publication volume, geographic distribution, diagnostic approaches, prevalence estimates, species and genotype distribution, and associated risk factors. Descriptive statistics and visualizations will be generated using RStudio (version 2023.09.1+494; R Foundation for Statistical Computing).

Findings will be interpreted with attention to the One Health domain from which data were derived. Prevalence estimates from human, animal, and environmental studies reflect structurally different sampling frames and diagnostic contexts and will not be aggregated across domains. Studies using microscopy-only methods and those using genotyping-based methods yield epidemiologically non-comparable outputs and will be analyzed and presented separately where relevant, as species-level identification is required to distinguish anthroponotic from zoonotic transmission pathways.

No meta-analysis will be conducted. The heterogeneity of diagnostic methods, study populations, and case definitions across the included literature precludes meaningful pooling of prevalence estimates, and formal quantitative synthesis is inconsistent with scoping review methodology as outlined by the Joanna Briggs Institute [32]. No formal risk-of-bias assessment will be performed, consistent with the scoping review methodology.

Results will be disseminated through a peer-reviewed publication targeting journals in the fields of neglected tropical diseases and parasitology. All extracted data and synthesis outputs will be made available in CSV format on the OSF project page [35] in accordance with FAIR (Findable, Accessible, Interoperable, Reusable) principles. No embargo is planned.

This scoping review will provide a comprehensive synthesis of literature on Cryptosporidium in Southeast Asia, mapping research across human, animal, and environmental domains. It will identify geographic and thematic gaps, examine diagnostic practices, and assess the degree of One Health integration. These anticipated findings would extend prior regional syntheses that identified Southeast Asia as a high-priority context for Cryptosporidium burden but did not examine diagnostic heterogeneity, One Health integration, or surveillance utility across the regional literature [13,28].

Special attention will be given to diagnostic diversity, including reliance on microscopy versus molecular techniques such as polymerase chain reaction and sequencing, which enables species- and genotype-level identification critical for understanding zoonotic potential. The review will also characterize environmental surveillance efforts, including studies on water and food contamination, and highlight gaps in monitoring systems.

Findings will inform research priorities, support integrated surveillance strategies, and encourage multidisciplinary collaboration under the One Health framework. All extracted data and synthesis outputs will be shared publicly on the OSF in accordance with FAIR principles, ensuring transparency and enabling future meta-analyses and regional comparisons.

Strengths of this review include the pre-registered search strategy, dual-reviewer screening, and cross-domain scope encompassing human, animal, and environmental studies within a single synthesis. Limitations include restriction to English-language publications and single-reviewer data extraction, the latter mitigated by use of a structured extraction form piloted on ten records before full extraction.

This scoping review will provide a systematic, cross-domain evidence base to support more coordinated and interdisciplinary research on Cryptosporidium in Southeast Asia. The findings aim to inform future surveillance strategies, strengthen regional capacity for zoonotic disease prevention, and advance One Health approaches that address the complex drivers of transmission. Ultimately, this work supports the development of context-specific interventions and contributes to broader efforts in health systems resilience.