Frequência e variabilidade genética de Giardia duodenalis em cães do município de Cuiabá - Mato Grosso, Brasil

Abstract

Giardia duodenalis is a unicellular, eukaryotic and flagellated protozoan. Two evolutionary forms are observed in the life cycle: trophozoite and cyst, the cyst being the infectious form. This protozoan is responsible for causing diarrhea in humans, dogs, cats, rodents and ungulate animals. Despite being morphologically equal, the isolates of G. duodenalis hide great genetic diversity and hinder the stability and unanimity of the taxonomic classification. So far, eight assemblages called A-H have been identified. Currently, multilocus genotyping is used for the molecular identification of Giardia species and / or genotypes. In order to identify the frequency of G. duodenalis in the feces of dogs domiciled in the city of Cuiabá, Mato Grosso, and to characterize the genetic variability of positive samples, fecal samples were collected

from 147 dogs. To perform screening, all samples were subjected to centrifugal- fluctuation examination for viewing under a microscopy. Of all samples collected, 26

dogs were infected with intestinal parasites, 38% (10) of whom were affected by G. duodenalis. The frequency of G. duodenalis in dogs was 6.8%. Other parasites have been observed, such as Cystoisospora sp. (15%) and Entamoeba sp. (2%), in addition to the Ancylostoma sp. (27%), Trichuris sp. (2%) and Toxocara sp. (1%). The positive samples for G. duodenalis were submitted to DNA extraction to perform the Chain Reaction by the Polymerase of the genes triosephosphate isomerase (tpi) and glutamate dehydrogenase (gdh) for amplification of the fragment of 530 and 659 bp, respectively, for genotypic characterization. The analysis of risk factors for dogs infected with G. duodenalis, was not significant regarding sex, breed, age, presence of diarrhea and diet. Only dogs with contacts were significantly positive for giardiasis. After molecular analysis of G. duodenalis isolates, only three samples amplified a fragment of the tpi gene showing 100% identity with Assemblage C. For genetic analysis of the sequences, the phylogenetic tree was built from the concatenated sequences of the gdh and tpi genes to determine the assemblage with greater precision.The sample identified in this study was grouped in the same clade as assemblage C, corroborating the sequence obtained by the tpi. Multilocus genotyping is the most reliable method for determining the assemblages of G. duodenalis, since discrepancies between the loci of the same isolate can occur due to mixed infections and/or heterozygosis.