Dissertação
Epidemiologia molecular de surtos de Adenite equina no Rio Grande do Sul - Brasil
Fecha
2012-02-27Registro en:
LIBARDONI, Felipe. Molecular epidemiology of outbreaks strangles in Rio Grande do Sul - Brasil. 2012. 40 f. Dissertação (Mestrado em Medicina Veterinária) - Universidade Federal de Santa Maria, Santa Maria, 2012.
Autor
Libardoni, Felipe
Institución
Resumen
Strangles is an equine infectious disease that affects the upper respiratory tract, being
considered the main respiratory disease in horses. The etiologic agent is Streptococcus equi
subsp. equi (S. equi), responsible for approximately 30% of horse diseases worldwide
notifications. The clinical signs of strangles are fever, nasal secretion and lymph node
enlargement. The last one occurs due the incomplete phagocytosis of S. equi by defense cells
because the presence of hyaluronic acid capsule and M protein (SeM) on the bacteria. The
understanding of strangles epidemiology and its control is still limited. Molecular studies
demonstrate differences in the gene sequence that codify the N-terminal region of the M
protein (SeM) of S. equi. This gene region was already used in the differentiation of isolates
by characterization of different alleles. This thesis aims to analyze and differentiate 47 S. equi
isolates from equine clinical specimens from southern Brazil (15 Thoroughbred horses, 29
animals from the Crioula breed and three Brasileiro de Hipismo) through phylogenetic
analysis and differentiation of alleles based on sequencing of the N-terminal region of the
SeM protein. Samples were obtained from 31 outbreaks in 20 premises. Fifteen alleles were
identified being only one (allele 9), with 7 isolates (14.9%), was already available in the
PubMLST-SeM database (allele 61). Among the new identified alleles, the number 1 was the
most prevalent with 13 isolates (27.7%), followed by allele 3 with 10 isolates (21.3%). The
results demonstrate the great diversity of the amino acid sequence among the S. equi isolates
from the studied equine population. Therefore the N-terminal sequence of SeM gene of the S.
equi isolates is a useful tool in epidemiological investigation to differentiate isolates in
strangles outbreaks with the identification of alleles in horses population, and may represent
an alternative for to control the illness with guidance in selecting strains for production of
commercial and autogenous vaccines.