Diagnóstico histopatológico, imuno-histoquímico e molecular das principais causas infecciosas de aborto em bovinos de Minas Gerais

Abstract

Cattle breeding plays an important role in Brazil's economy, and the diseases associated with reproductive failure always resulted in a substantial cost to the producer. Thus, the loss of an animal due to an infectious abortion is worrisome because it involves not only the loss of that animal, but the health of the pregnant female. Furthermore, when dealing with an infectious agent, the possibility of it spreading in the herd and, in some cases, affecting the health of the human being, should also be considered. Unfortunately, the etiology of abortion often remains unclear despite extensive efforts to reaching a diagnosis. In Brazilian herds, due to the diversity of the breeding, and often the lack of information of some producers, little is known about the real frequency of the abortions agents. Therefore, this study aims to contribute in the knowledge of the main etiological agents involved in bovine abortions in the state of Minas Gerais, Brazil. In order to do this, we performed a 10 year retrospective study of abortions received by the Veterinary Pathology Sector of the Universidade Federal de Lavras, along with performing necropsies of fetuses forwarded for diagnosis in a period of two and a half years (2011-2013). The abortions were classified as abortions by protozoan, by virus or of bacterial origin, according to the predominant microscopic lesions. Posteriorly, we performed immunohistochemical studies on 30 fetuses, and molecular studies on 11 fetuses. The results were divided into two papers. The first paper presents the Neospora caninum as the main abortion agent, responsible for 31.66% of the bovine abortions. When excluding the fetuses improper for the exam due to accentuated autolysis or those without microscopic lesions, the abortions caused by N. caninum reach 63.3%. This paper also presents the cardiac and skeletal muscles as the locations of largest lesion frequency caused by this protozoan, and presents the efficiency of the immunohistochemical and molecular tests in the success of the diagnosis. The second paper reports the bacterial and viral agents associated with bovine abortion diagnosed in this study. Among them we found the bovine herpes virus and the bacteria Brucella sp, Leptospira sp and Staphylococcus sp. The results of this study highlight the N. caninum as an important agent of bovine abortion in Southern Minas Gerais, followed by the bacterial and viral agents. Furthermore, it reinforces that the molecular diagnosis was more sensitive in comparison to the immunohistochemical diagnosis.