Giardia duodenalis in Rodents: A Global Systematic Review and Meta-Analysis

Giardia duodenalis (also known as G. lamblia or G. intestinalis) is a globally distributed protozoan with zoonotic potential. This systematic review and meta-analysis aimed to determine the global molecular prevalence and genotypic distribution of G. duodenalis in rodents, based exclusively on studies using molecular diagnostic techniques.

A comprehensive literature search up to 15 October 2024, identified 23 eligible studies encompassing 54 datasets and 5971 rodent samples from 10 countries across three continents. Prevalence estimates were pooled using a random-effects model, and heterogeneity was assessed via the I² statistic. Assemblage and sub-assemblage distributions were analysed across rodent species and geographic regions.

The pooled molecular prevalence of G. duodenalis in rodents was 7.4% (95% CI: 4.8-11.4%), with chinchillas (36.9%) and porcupines (23.1%) showing the highest infection rates. Rodents were found to harbour six assemblages (A-E, G) and four sub-assemblages (AI, AII, BIII, BIV) of G. duodenalis, with marked geographic variation. The highest pooled prevalence was observed in Europe (17.9%; 95% CI: 9.8-30.5), where assemblages C, D, G, and most occurrences of E, B, and A were reported. Assemblages C and D were entirely absent in Asia. In contrast, most reports of the rodent-specific assemblage G originated from Asia. South America (represented solely by Brazil) reported only assemblage A. China contributed the largest dataset (n = 25) and sample size (n = 4009), exhibiting high genetic diversity (A, B, E, G). Belgium also showed notable diversity (A, B, C, E), with assemblage B being the most prevalent in both countries. Assemblage D was found exclusively in Romania, while assemblage C was reported only in Belgium and Italy. Notably, the highest assemblage diversity was observed in chinchillas (five: A-E), squirrels (four: A, B, E, G), and rats (three: A, B, G).

Although various rodent species, especially chinchillas, mice, porcupines, rats, squirrels, and voles, carry G. duodenalis zoonotic assemblages (A and B), the overall molecular prevalence in rodents remains relatively low. Due to significant limitations in sampling design, methodological heterogeneity, limited ecological data, and unknown host health status, current evidence is insufficient to confirm rodents as major zoonotic reservoirs. Standardised, large-scale molecular studies are needed to clarify the epidemiological role of rodents in G. duodenalis transmission.