Ocorrência de tuberculose bovina no Estado do Rio Grande do Norte, Brasil.

Abstract

This dissertation is made up of two chapters. In the first chapter, the objective was to determine the occurrence of tuberculosis by Mycobacterium bovis in cattle slaughtered in two public slaughterhouses of the Central Potiguar mesorregion, state of Rio Grande do Norte, Brazil. In the period from November 2017 to August 2018, 11616 carcasses had a routine inspection, where lesions suggestive of tuberculosis were observed in one animal (0.009%). Samples of tissues located from the lung, heart and spleen were submitted to bacteriological culture and molecular diagnosis. The omentum was used for histopathological examination and Ziehl-Neelsen staining. The lesions were cultured for 90 days in Stonebrink medium, but there was no growth. When nested-PCR was used, lung, heart and spleen samples were positive. The histopathological exam of the omentum showed the presence of multiple granulomas of necrotic center and areas of mineralization and when it was submitted to the staining of Ziehl-Neelsen, the presence of acid-fast bacilli was detected. Microbiological culture, despite being considered gold standard, may present false negative results, besides being a time-consuming technique, making it difficult to use for surveillance in slaughterhouses. The presence of a positive animal in the study represents a serious public health problem, especially for breeders, scavengers, technicians and the end consumer. Nested-PCR and histopathology present fast and effective results for the diagnosis of the disease. Therefore, one of the essential systems applied to the control of bovine tuberculosis is the epidemiological surveillance of animals in slaughterhouses. The objective of chapter II was to determine the frequency of positive animals for bovine tuberculosis in the state of Rio Grande do Norte. The data were provided by the Institute of Defense and Agricultural Inspection of Rio Grande do Norte (IDIARN) and come from its Local Animal and Plant Health Units (ULSAV'S) collected from the monthly reports issued by veterinarians authorized to work under the National Program of the Control and Eradication of Brucellosis and of Animal Tuberculosis (PNCEBT), covering the period from June 2012 to June 2018. For the diagnosis, the simple cervical test and the cervical comparative test were used as the screening test. In total, 16889 cattle were tested, of which 44 animals (0,26%) presented a positive result. There was no significant difference (P <0,05) in the frequency of positivity between females (0,25%) and males (1,16%). In view of this result and considering the importance of local bovine farming to the economy, it is important to conduct measures that include producers' awareness, sanitary control in the acquisition and sale of matrices, inspection of sanitary barriers and periodic surveys of the epidemiological situation of this disease, especially in the units with the highest frequency of positive animals, with the aim of avoiding, or at least minimizing, the spread of the agent.