Abstract
Background Giardia duodenalis infects humans and other mammals by ingestion of cysts in contaminated water or food, or directly in environments with poor hygiene. Eight assemblages, designated A–H, are described for this species.Methodology/Principal FindingsWe investigated by microscopy or by direct immunofluorescence technique the occurrence of G. duodenalis in 380 humans, 34 animals, 44 samples of water and 11 of vegetables. G. duodenalis cysts present in samples were genotyped through PCR-RFLP of β giardin and glutamate dehydrogenase (gdh) genes and sequencing of gdh. The gdh gene was amplified in 76.5% (26/34) of the human faeces samples with positive microscopy and in 2.9% (1/34) of negative samples. In 70.4% (19/27) of the positive samples were found BIV assemblage. In two samples from dogs with positive microscopy and one negative sample, assemblages BIV, C, and D were found. Cysts of Giardia were not detected in water samples, but three samples used for vegetable irrigation showed total coliforms above the allowed limit, and Escherichia coli was observed in one sample. G. duodenalis BIV was detected in two samples of Lactuca sativa irrigated with this sample of water. BIV was a common genotype, with 100% similarity, between different sources or hosts (humans, animals and vegetables), and the one most often found in humans.Conclusions/SignificanceThis is the first study in Brazil that reports the connection among humans, dogs and vegetables in the transmission dynamics of G. duodenalis in the same geographic area finding identical assemblage. BIV assemblage was the most frequently observed among these different links in the epidemiological chain.
Highlights
An important aspect of the epidemiology of giardiasis is to understand the potential of cross-transmission among hosts that harbour different genotypes of Giardia, the risk and environmental factors involved in exposure to this pathogen and its zoonotic potential
We investigated the occurrence of Giardia duodenalis and their genotypes in humans, animals, water and vegetables, to check the relationship among them in the epidemiological chain of an urban area of Southern Brazil
In Brazil there have been no studies reporting the relationship between different links in the epidemiological chain of G. duodenalis, in the same focus of endemicity, using molecular techniques
Summary
Giardia duodenalis infects humans and other mammals by ingestion of cysts in contaminated water or food, or directly in environments with poor hygiene. We investigated by microscopy or by direct immunofluorescence technique the occurrence of G. duodenalis in 380 humans, 34 animals, 44 samples of water and 11 of vegetables. In two samples from dogs with positive microscopy and one negative sample, assemblages BIV, C, and D were found. BIV was a common genotype, with 100% similarity, between different sources or hosts (humans, animals and vegetables), and the one most often found in humans. This is the first study in Brazil that reports the connection among humans, dogs and vegetables in the transmission dynamics of G. duodenalis in the same geographic area finding. BIV assemblage was the most frequently observed among these different links in the epidemiological chain
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