Global molecular prevalence of Giardia duodenalis in pigs (Sus domesticus): A systematic review and meta-analysis

Giardia duodenalis is one of the common intestinal parasites causing diarrhea in humans and livestock, including pigs. Thus, a healthy livestock would result in a clean environment, which benefits humans. In the present study, the global molecular prevalence of G. duodenalis infection was determined in pig populations, through systematic exploration of 4 international databases (MEDLINE/PubMed, Scopus, Web of Science, and Google Scholar) until March 4th, 2022. A random-effects meta-analysis model was used to estimate the overall and subgroup-based pooled prevalence of G. duodenalis, and I(2) index was used for the evaluation of the heterogeneity. Altogether, 42 datasets from 18 papers examined 7272 pigs across 12 nations, showing a 9.1% (95% CI: 5.6–14.3%) pooled molecular prevalence. Sensitivity analysis demonstrated no remarkable variation in the reported total prevalence upon removing individual studies. It was found that 6 Giardia assemblages (A-F) are capable to infect pigs around the world, including assemblage E [16 datasets, 41.1% (95% CI: 24.8–59.6%)], B [8 datasets, 28.2% (95% CI: 12.2–52.6%)], D [3 datasets, 16.2% (95% CI: 10.6–24.1%)], C [3 datasets, 11.6% (95% CI: 7.3–17.9%)], and A [11 datasets, 9.9% (95% CI: 5.6–16.9%)]. Of note, assemblage F was only reported in one study. Meta-regression analysis showed that publication year was not significantly associated with the Giardia prevalence in swine population, in contrast to the sample size. Substantially, animals in weaner and fattener stages were more prone to giardiasis. Assemblages A and B are of utmost zoonotic significance for humans, while assemblages C, D and F have, also, been found in dogs and cats. Still, little is known on the prevalence and distribution of Giardia assemblages in pigs and requires more extensive and detailed studies.