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Epidemiology of bovine brucellosis using Real-time PCR from whole blood samples in Colombia's leading dairy region.
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  • Olga Herrán Ramirez,
  • Huarrisson Azevedo Santos,
  • Patricia Gonzaga Paulino,
  • Carolina Soares Van De Meer,
  • Jose Rodriguez Bautista,
  • Ingrid Jaramillo Delgado,
  • Juliana Gonzales Obando,
  • René Ramírez Garcia,
  • Isabele da Costa Angelo
Olga Herrán Ramirez
Federal Rural University of Rio de Janeiro
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Huarrisson Azevedo Santos
Federal Rural University of Rio de Janeiro
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Patricia Gonzaga Paulino
Federal Rural University of Rio de Janeiro
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Carolina Soares Van De Meer
Federal Rural University of Rio de Janeiro
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Jose Rodriguez Bautista
Federal Rural University of Rio de Janeiro
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Ingrid Jaramillo Delgado
TESTMOL molecular research and diagnostic center
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Juliana Gonzales Obando
University of Antioquia
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René Ramírez Garcia
CES University
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Isabele da Costa Angelo
Federal Rural University of Rio de Janeiro

Corresponding Author:[email protected]

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Abstract

A cross-sectional study was conducted in Antioquia, Colombia, the country’s leading dairy region, currently under brucellosis quarantine declaration, to recover Brucella spp. DNA from bovine whole-blood samples through Probe-based Real-time PCR (Probe-qPCR) detection. The associated factors for the presence of Brucella-DNA at the animal and herd levels were reported and evaluated using logistical regression models. A total of 656 random cows from 40 herds were selected. Template DNA was obtained based on not organic salting-out protocol modified. The Probe- qPCR assay using bcsp31 gene amplification had an efficiency of 92.35%, with a slope of -3.52 reached in the standard curve. The qPCR assay detected 9.5% (n = 62/656; 95% CI: 7.3,12.0) of the animals with Brucella-DNA presence, and 62.5% (n = 25/40; 95% CI: 45.8,77.3) of the herds with Brucella-DNA presence. Using SNP-based assay, all positive samples were identified as field Brucella strains. In the final regression model at the animal-level, five variables were associated with Brucella-DNA presence: the use of bulls for mating recorded history of reproductive problems, pregnant cows, parlor milking, and cows belonging to farms ≤ 200 m from the main road. At the herd-level, two variables were associated with Brucella-DNA presence: recorded history of reproductive problems and bulls’ use for mating. Given the fluctuant brucellosis prevalence in endemic areas, updated local epidemiological studies are necessary to evaluate if established prevention and control measures have been effective or need to be adjusted. The Probe-qPCR assay was able to detect Brucella-DNA from whole blood samples in cows. Once adequately validated, qPCR could be used as an additional tool to verify latent or acute infection states in individual animals when the antibody response is not yet evident. The current research highlights that management practices, mainly associated with reproduction, favors Brucella infection and propagation in livestock in Antioquia, Colombia.