La brucelosis bovina y sus factores de riesgo: evaluación a nivel mundial y en Colombia

Abstract

Bovine brucellosis is a zoonotic disease, with great importance in public health and in the livestock sector due to the direct economic losses it causes and, specially, due to the commercial restrictions for both the infected animals as well as their products. The knowledge of the health status of the disease, its evolution over time and the factors that influence its presentation is of great importance for the appropriate application of sanitary measures in a country. In this sense, four studies, fulfilling the proposed objectives, were formulated. The first study analyzes the evolution of bovine brucellosis in the world. Data were taken from 156 OIE member countries for the period between the years 1996 and 2014. The countries were classified into three groups according to their sanitary situation a) Enzootic: countries infected, which can have been free of brucellosis but for periods of less than 3 years. b) Non-enzootic: countries where the disease was present, but there was at least a 3-year period without the disease, and c) Free: countries where the disease remained absent during the whole period. The countries were compared by means of the Kruskall-Wallis and Mann-Whitney non-parametric tests, and the Spearman correlation coefficient for two quantitative variables. In this last case, if the relation was significant, a lineal or cubic regression model was made to better describe the tendency. A relationship was found between the status of the disease and the availability of economic resources; thus, countries with a high GDP per capita tended to be free from bovine brucellosis. Countries with a greater bovine census showed a greater probability to have the disease present. The most affected regions were Central and South America, Africa and parts of Asia. The next studies were focused on the epidemiology of the disease in Colombia. The first one intended to estimate the evolution of the bovine brucellosis control in Colombia over a seven years period (2006-2012). A univariate analysis was carried out, then a principal components analysis was performed for each year separately. The results indicated that, during the years of the study, prevalence remained practically unvaried (farms went from 22% to 23%, and animals varied between 4.7% and 4.6% between 2006 and 2012, respectively). Three different areas were defined according to brucellosis status and surveillance. In the second study, movements of the domestic animal species in Colombia (cattle and buffaloes, pigs, horses, goats and sheep) were analyzed over a period of nine years (2006-2014). The association between the disease prevalence and the animal movement was analyzed using a network analysis; subsequently, Multiple Linear Regressions (MLR) and ANOVA test were developed to analyze the relation between the health situation and the movement of animals. The results indicate the possible role of equine movements in the brucellosis spread between departments. Finally, the objective of the third study of Colombian data, was the identification of the risk factors associated with re-infection of Brucella abortus in cattle farms. A case-control study was performed in which 98 case-farms (herds were brucellosis was re-introduced) were compared to 93 control farms (without re-introduction of the disease). A bivariate analysis and a logistic regression model were done. The results indicated that the replacement animals, natural matting and contact with infected farms or with unknown sanitary status, were risk factors for the re-introduction of the disease.

Date of Award	17 Jan 2018
Original language	Spanish
Supervisor	Jordi Casal i Fabrega (Director)