Molecular analysis of a fragment of bovine leukemia virus env gene by Nested-PCR in dairy cows from Pasto, Nariño

Abstract

<em>Introduction</em>: Routine diagnosis for bovine leukemia is performed using indirect serologic tests, although it is recommended to use polymerase chain reaction (PCR), which allows a reliable diagnosis in early stages and in young animals. Moreover, by amplifying the DNA, it is possible to sequence fragments of the virus, which allows to identify genotypes and to construct phylogenetic trees. <em>Objective</em>: To analyze a fragment of the env gene of bovine leukemia virus (BLV) isolated from indirect ELISA-positive animals in dairy farms in the municipality of Pasto (Nariño). <em>Materials and methods</em>: Once the presence of BLV was established in 48 animals over two years old in seven dairy farms in the municipality of Pasto by indirect ELISA test, a nested PCR test was performed to confirm diagnosis and to sequence a fragment of the <em>env</em> gene in positive animals and their daughters. The sequences obtained were compared with the seven genotypes described worldwide by MEGA 6 program. <em>Results</em>: The sequences of the compared fragments do not differ from those described but they allow their grouping into different clusters according to their similarity. The genotypes found in these farms correspond to genotype 1 and 2 described in the literature. <em>Conclusions</em>: Only one genotype was found on farms with proper recovery and adequate biosecurity measures, and on farms with less control in management and recovery practices, both genotypes described for the region were evident.