# Prevalence and genotyping of Giardia duodenalis infections in humans in Thailand: a systematic review and meta-analysis

## TL;DR

This study estimates the prevalence of Giardia duodenalis infections in Thailand and identifies the most common genetic assemblages to guide control strategies.

## Contribution

The study provides the first comprehensive meta-analysis of G. duodenalis prevalence and assemblage distribution in Thailand.

## Key findings

- Prevalence of G. duodenalis varied by diagnostic method, with molecular techniques showing the highest rate at 8.98%.
- Assemblage B was the most common (55.0%), followed by Assemblage A (32.5%).
- High-risk populations like orphans and preschool children had disproportionately higher infection rates.

## Abstract

Giardia duodenalis remains a neglected parasitic infection in Thailand, with uncertain national prevalence and limited data on genetic assemblages. This systematic review and meta-analysis aimed to estimate the pooled prevalence of G. duodenalis infections in Thailand and assess the distribution of assemblages to inform surveillance and control strategies.

The protocol for this study was registered in PROSPERO (CRD42024629406). A comprehensive search was conducted across six databases: EMBASE, Ovid, PubMed, Scopus, Nursing & Allied Health Premium, and the Thai-Journal Citation Index (TCI). The methodological quality of included studies was assessed using the Joanna Briggs Institute (JBI) critical appraisal checklist for observational studies. A meta-analysis using random-effects models estimated the pooled prevalence of G. duodenalis infections and the distribution of assemblages.

Sixty-three studies comprising of 47,989 participants were included. The prevalence of G. duodenalis infection varied substantially by diagnostic method, ranging from 1.40% using direct smear microscopy to 1.99% using concentration techniques, 3.66% with culture-based methods, 13.44% with immunoassays, and 8.98% with molecular techniques (P < 0.0001). Prevalence also differed geographically, with the highest estimates in Western Thailand (12.22%) and the lowest in Northeastern Thailand (0.54%). Vulnerable groups, including orphans (15.14%) and preschool children (11.73%), carried a disproportionate burden of infection. Among the 240 samples analyzed by molecular methods, Assemblage B was the most common (55.0%), followed by Assemblage A (32.5%), mixed A/B infections (12.08%), and a single case of Assemblage F (0.42%).

G. duodenalis remains endemic in Thailand, with transmission concentrated in socially vulnerable groups and regions with higher environmental risk. The predominance of Assemblage B and the underuse of molecular diagnostics highlight critical gaps in understanding transmission pathways. These findings suggest that control strategies in Thailand should prioritize high-risk populations and incorporate molecular epidemiology into routine surveillance to more effectively guide prevention efforts.

Not applicable.

The online version contains supplementary material available at 10.1186/s12879-025-12372-6.