Caracterização fenotípica e genotípica de animais da raça Hereford criados na região sul do estado do Rio Grande do Sul durante surtos de Ceratoconjuntivite Infecciosa Bovina

Abstract

This dissertation was divided into four chapters, with the following main objectives: i) to carry out the bacteriological identification of the agents involved in Infectious Bovine Keratoconjunctivitis (IBK) by means of different techniques: morpho-tintorial and biochemical analysis, mass spectrometry with ionization source and matrixassisted laser desorption and time-of-flight mass analyzer (MALDI-TOF), polymerase chain reaction (PCR) and sequencing. ii) to evaluate the genetic diversity of Moraxella bovis and Moraxella bovoculi bacteria isolated from IBK outbreaks between 2015 and 2017, using ERIC-PCR (enterobacterial repetitive intergenic consensus), RAPD-PCR (random amplification of polymorphic DNA) and a variation of the RAPD-PCR with primers JWP1 and JWOPA07. iii) to estimate the genetic parameters and values through the traditional evaluation by the animal model for the incidence of IBK. iv) carry out genome association study (GWAS) to identify genomic regions and most representative SNPs for susceptibility to IBK. At the beginning of the outbreak of IBK samples of ocular and nasal secretions were collected from Hereford cattle to enable the identification of the bacteriological agent causing the disease, thus confirming the IBK outbreak. The animals came from five farms, located in the southern of Rio Grande do Sul state. Four evaluations were performed, with an average interval of 30 days. The purpose of the monitoring was to perform the phenotyping with regard to susceptibility to the disease, by monitoring the evolution of IBK outbreaks in the properties, from the attribution of ocular lesion scores. Scores were assigned to IBK lesions for each eye on a scale of zero to four, in which zero indicated the normal eye and four the most advanced stage of the disease, implying ocular loss. The best concordances obtained between the methods of bacteriological identification studied were the identification by MALDI-TOF and the molecular identification (PCR), confirmed by sequencing, from the DNA extracted from the colonies of Moraxella spp. In addition, the existence of genetic variability between Moraxella bovis and Moraxella bovoculi strains isolated from Hereford cattle, affected by IBK, belonging to five different municipalities located in the state of Rio Grande do Sul was confirmed. The predicted heritability coefficients were 0.14, 0.096 and 0.099 for the categories (c2, c3 and c9) for incidence at IBK. GWAS studies showed significant genomic windows on chromosomes 3, 11, 14, 18, 26 and 27 associated with IBK. Functional enrichment analyzes revealed eight significant (p <0.05) terms associated with IBK susceptibility: Babesia, Plasmodium vivax, Babesiosis, Bood bactericidal activity, Retinal cone photorecptor cells, Animal nutritional physiological phenomena, COS cells e 5 Flanking region. The terms MeSH, point to important biological processes that are related to the phenotypic expression of the lesions occurred by IBC. In conclusion, the phenotypic and genomic analyzes carried out throughout this study may help in the design of strategies for prevention and treatment against CIB, and may collaborate with selection strategies for CIB resistant animals.