Ocorrência e diversidade genética de Babesia bovis em bovinos de corte amostrados no Pantanal sul matogrossense
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Data
2019-03-01
Autores
Mendes, Natalia Serra [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Babesia bovis é um agente etiológico da babesiose bovina, enfermidade transmitida por carrapatos da espécie Rhipicephalus microplus, que afeta a saúde do gado em regiões tropicais e subtropicais do mundo, causando perdas significativas na produção de carne e leite. O presente trabalho objetivou verificar, por meio de técnicas moleculares, a ocorrência e a diversidade genética de B. bovis com base nos genes que codificam antígenos de superfície de merozoíto (MSAs) em uma população de 400 bovinos de corte (Bos indicus) da raça Nelore amostrados em propriedades no Pantanal do Estado do Mato Grosso do Sul, centro-oeste brasileiro. Dezoito (4,5%) bovinos mostraram-se positivos em ensaios de nested PCR para B. bovis com base no gene spherical body protein (sbp-2). Destes, 77,7% (14/18) e 66,6% (12/18) mostraram-se positivos para B. bovis em ensaios de cPCR baseados nos genes msa-2b e msa-2c, respectivamente. Análises filogenéticas baseadas no método de Máxima Verossimilhança utilizando 14 sequências de clones de msa-2b e 13 sequências de clones de msa-2c mostraram uma clara distribuição das sequências detectadas neste estudo em diferentes clados do filograma. Esses achados corroboraram com a análise de diversidade das mesmas sequências, a qual revelou a presença de 14 e 11 haplótipos dos genes msa-2b e msa-2c, respectivamente. Ainda, as análises de entropia das sequências de aminoácidos MSA-2B e MSA-2C revelaram a presença de 78 e 44 picos de alta entropia, com valores variando entre 0,25 a 1,53 e 0,27 a 1,09 para MSA-2B e MSA-2C, respectivamente. O presente estudo mostrou uma baixa ocorrência molecular de B. bovis em bovinos de corte amostrados no Pantanal brasileiro. Apesar disso, um alto grau de diversidade genética foi encontrado na população de B. bovis analisada, com a possível presença de diferentes genótipos coexistentes em um mesmo animal e/ou no mesmo rebanho estudado.
Babesia bovis is the etiological agent of bovine babesiosis, a disease transmitted by Rhipicephalus microplus, which affects cattle herds in tropical and subtropical regions of the world, causing significant economic losses due to decreasing meat and milk yield. This study used molecular techniques to determine the occurrence and genetic diversity of B. bovis, based on the genes encoding the merozoite surface antigens (MSAs), in a herd of 400 Nellore (Bos indicus) sampled from beef cattle farms in the Pantanal region, in Mato Grosso do Sul, Midwestern Brazil. The results of the nested PCR assays based on the spherical body protein (sbp-2) gene indicated that 18 (4.5%) calves were positive for B. bovis, of the 18, 77.7% (14/18) were positive for the B. bovis msa-2b fragment while 66.6% (12/18) were positive for the msa-2c fragment. The phylogenetic analysis based on the Maximum Likelihood method using 14 sequences from msa-2b clones and 13 sequences from msa-2c clones indicated that the sequences detected in this study are clearly distributed in different cladograms. These findings corroborated the diversity analysis of the same sequences, which revealed the presence of 14 and 11 haplotypes of the msa-2b and msa-2c genes, respectively. Furthermore, the entropy analyses of the MSA-2B and MSA-2C amino acid sequences revealed 78 and 44 high entropy peaks with values ranging from 0.25 to 1.53 and from 0.27 to 1.09 for MSA -2B and MSA-2C, respectively. Therefore, the results indicate a low molecular occurrence of B. bovis in beef cattle sampled in the Brazilian Pantanal. Despite this, a high degree of genetic diversity was found in the analyzed B. bovis population, with possibly different genotypes coexisting in the same animal and/or in the same studied herd.
Babesia bovis is the etiological agent of bovine babesiosis, a disease transmitted by Rhipicephalus microplus, which affects cattle herds in tropical and subtropical regions of the world, causing significant economic losses due to decreasing meat and milk yield. This study used molecular techniques to determine the occurrence and genetic diversity of B. bovis, based on the genes encoding the merozoite surface antigens (MSAs), in a herd of 400 Nellore (Bos indicus) sampled from beef cattle farms in the Pantanal region, in Mato Grosso do Sul, Midwestern Brazil. The results of the nested PCR assays based on the spherical body protein (sbp-2) gene indicated that 18 (4.5%) calves were positive for B. bovis, of the 18, 77.7% (14/18) were positive for the B. bovis msa-2b fragment while 66.6% (12/18) were positive for the msa-2c fragment. The phylogenetic analysis based on the Maximum Likelihood method using 14 sequences from msa-2b clones and 13 sequences from msa-2c clones indicated that the sequences detected in this study are clearly distributed in different cladograms. These findings corroborated the diversity analysis of the same sequences, which revealed the presence of 14 and 11 haplotypes of the msa-2b and msa-2c genes, respectively. Furthermore, the entropy analyses of the MSA-2B and MSA-2C amino acid sequences revealed 78 and 44 high entropy peaks with values ranging from 0.25 to 1.53 and from 0.27 to 1.09 for MSA -2B and MSA-2C, respectively. Therefore, the results indicate a low molecular occurrence of B. bovis in beef cattle sampled in the Brazilian Pantanal. Despite this, a high degree of genetic diversity was found in the analyzed B. bovis population, with possibly different genotypes coexisting in the same animal and/or in the same studied herd.
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Palavras-chave
Babesiose bovina, Babesia bovis, Diversidade genética, MSA, Pantanal