Prevalence of zoonotic and non-zoonotic genotypes of Giardia intestinalis in cats: a systematic review and meta-analysis.

There are no meta-analyses specifically describing the prevalence of zoonotic and non-zoonotic genotypes of Giardia intestinalis in cats, which would be useful in defining the importance of cats as a source of zoonotic transmission. We performed a systematic review of the literature in three databases (PubMed, Scopus and SciELO) to assess the proportion of cats that were infected with specific G. intestinalis genotypes. A meta-analysis using a random effects model was performed to calculate the pooled prevalence and 95% confidence intervals (95%CI). A 2-tailed alpha level of 5% was used for hypothesis testing. Measures of heterogeneity, including Cochran's Q statistic, the I2 index, and the tau-squared test, were estimated and reported. Subgroup analyses were conducted by geographic area and animal origin, as well as coinfection. Publication bias was assessed using a funnel-plot. Up to November 1, 2015, the literature search yielded 780 articles, of which 29 studies were valid for analysis. The pooled prevalence rate was higher for genotype F (19 studies, n=368 cats) with 55.8% [95%CI (42.8%-68.7%), τ2=0.0463]. For genotype A (21 n=409) it was 38.7% [95%CI (29.0%-48.4%), τ2=0.0527], for genotype D (7, n=276) 8.9% [95%CI (2.1%-15.8%), τ2=0.0024], for genotype C (2, n=212) 3.1% [95%CI (2.5%-3.5%), τ2=0.0001], for genotype E (3, n=187) 2.9% [95%CI (0.0%-8.1%), τ2=0.0009], and for genotype B (4, n=230) it was 2.8% [95%CI (0.0%-5.7%), τ2=0.0002]. Genotypes A and B of G. intestinalis are present in a wide range of hosts, including humans and cats, whilst genotype E has been reported in bovines, ovines, caprine and porcine animals, as well as in dogs and cats; and genotype F is almost exclusive to cats. Thus genotypes A and B are the most important for zoonotic transmission. In this study, after genotype F (55.5%), genotype A yielded more than 38% in cats (95%CI 29-48). This has interesting possible implications in zoonotic transmission of giardiasis between cats and humans.