Clarification of Toxocara canis in dog in Viet Nam by molecular biology method

Abstract

Toxocara canis species causing toxocariasis in dog is a zoonosis. Mitochondrial gene segment-atp6 (598 bp) and nuclear gene segment-ITS2 (333 bp) of 14 Toxocara sp strains were obtained from the raising dogs in Thuong Tin and Thanh Oai districts, Ha Noi city. The result of comparison on similarity level between the above atp6 and ITS2 nucleotide sequences of Toxocara sp in dogs of Viet Nam and those of other Toxocara species was determined. The details were as follows: when comparing with T. cati species, the similarity rate between the 2 above gene segments (atp6, ITS2) and the respective gene segments of this species was 98.2-99.7% and 95.6%-100%; similarly, this rate was 88.5%-89.1% and 76.7%-79.7% when comparing with T. malaysiensis species; and 83.2-88.1% and 80.2%-80.6% when comparing with T.vitulorum species.Phylogenetic analysis basing on the genetic markers of atp6 and ITS2 genes indicated that there were 5 distinct Toxocara groups. Of which, the T. canis group included the Toxocara sp group in dogs of Viet Nam and the reference T. canis strains; The 4 other remaining groups including T. cati, T. malaysiensis, T. vitulorum, and Toxascaris leonina (outside groups) were completely different from the T. canis group. Thus, 14 Toxocara strains in dogs in Viet Nam in this study were identified to belong to T. canis species. The result of this study provided further understandings for the Toxocara species in dogs. It is a basis for epidemiological surveillance of this zoonotic toxocariasis in the community in Viet Nam.