Risk Factors Associated With the Presence of Mycobacterium Bovis in Macroscopic Lesions Suspected as Being Caused by Bovine Tuberculosis Detected in Slaughterhouses

Abstract

Mycobacterium bovis is a bacterium belonging to the Mycobacterium tuberculosis complex that causes tuberculosis in cattle and in other domestic and wild animals, as well as in humans. Disease control measures are carried out by slaughtering animals tested positive in the intradermal tuberculinization test and sanitation of their original living spaces, in addition to epidemiological surveillance carried out through the sanitary inspection of bovine carcasses in slaughterhouses. In the latter, official inspection services collect samples from macroscopic lesions suspected of bovine tuberculosis, which are then sent for laboratory analysis. Knowledge concerning the variables associated with the occurrence of M. bovis can aid in decision-making regarding control and disease eradication efforts. In this context, the aim of this study was to identify the risk factors for a positive M. bovis diagnosis in suspected bovine tuberculosis lesions obtained during epidemiological surveillance activities in the state of Mato Grosso, Brazil. A total of 105 suspicious lesions were analyzed using the Nested Polymerase Chain Reaction (nested q-PCR) method, of which 14 (13.33%) tested positive for M. bovis. Univariate and bivariate statistical analyses indicated that the variable “animal slaughter” was the only risk factor presenting statistical significance associated with the diagnosis of M. bovis (p < 0.05), demonstrating that macroscopic lesions suspected as being caused by bovine tuberculosis from animals with an in vivo diagnosis were 2.82 - fold more likely to result in a positive M. bovis diagnosis by molecular tests.

Genomic analysis of Mycobacterium tuberculosis variant bovis strains isolated from bovine in the state of Mato Grosso, Brazil

“…All were submitted and confirmed by this q-PCR, and four strains were selected for sequencing to represent two livestock circuits in the state of Mato Grosso, not only within a single circuit, in addition to selecting strains of M. tuberculosis var. bovis , which in previous studies were more prevalent ( 33 , 34 ).…”

“…bovis were obtained. Of these 23 isolates, four were selected as representatives of the regions studied, adopting criteria referring to representing the main livestock circuits that had shown higher prevalence in previous studies in the state of Mato Grosso ( 33 , 34 ).…”

“…Four strains were selected for genome sequencing based on each different livestock circuits in the state of Mato Grosso ( 20 ). These livestock circuits were previously established due to the higher prevalence of M. bovis in the state ( 33 , 34 ). The state of Mato Grosso is divided into four regions, called livestock circuits (CP), according to the bovine production that is predominant in that region.…”