, pela orientação dedicada ao desenvolvimento do presente trabalho, pela amizade, paciência e atenção que sempre teve comigo. Por ser um ótimo amigo e professor, tendo me estimulado e acreditado no meu potêncial, desde o 6º semestre de faculdade. Por ter sido um espelho, me fazendo querer sempre seguir em frente nas pesquisas e procurar melhorar cada vez mais e principalmente, amar a Patologia Veterinária. Às pessoas que fazem parte do Laboratório de Patologia Veterinária da Universidade de Brasília, pelo apoio, amizade e compreensão. Aos meus pais, familiares e amigos, pelo apoio, orações e incentivos de sempre seguir em frente e fazer o melhor possível. Ao meu querido João Carlos, por todo o apoio durante todos os anos juntos, pelo amor, amizade, atenção, incentivo e muita paciência. Ao Professor Edson Moleta, pelas amostras coletadas e enviadas ao Laboratório de Patologia Veterinária da UnB.

ABSTRACT.-Eloi R.S.A., Marçola T.G., Paludo G.R., Araújo R.R., Colodel E.M., Lima E. Malignant catarrhal fever (MCF) is a disease caused by bovine infection with ovine herpesvirus type 2 (OvHV-2) and responsible for economic losses in different Brazilian regions. This paper describes the molecular detection of OvHV-2 by nested-PCR (nPCR) in nasal secretion/exfoliation samples and blood cell fraction (BCF) of sheep from 8 properties in the Federal District. Among the 188 nasal samples, 88 (41.5%) were positive to OvHV-2. Pregnant ewe presented no differences at the infection rate in comparison with parous females. Newly calved sheep showed higher OvHV-2 infection rate than female over 60 days of calving. Nasal samples allowed the detection of infected animals by nPCR with efficiency about twice than that in the blood cell fraction samples. In Brazil, epidemiological information about OvHV-2 infection in sheep flocks and factors involved in emergence of FCM outbreaks in cattle are still scarce. This study may provide support for elucidating some characteristics of the disease and for further epidemiological studies in the Federal District and other Brazilian States.

Background: Brachiaria spp. is the main pasture for ruminant productions in Brazil, but the limiting factor for its use is the toxicity due to the presence of steroidal saponins. Chronic ingestion of Brachiaria spp. by cattle may cause liver changes such as fibrosis, bile duct proliferation and clusters of foamy macrophages in the hepatic parenchyma. The main objective of the present study was to evaluate the most frequent histological changes and their frequencies in livers collected in abattoirs in Brazil from beef cattle raised exclusively on Brachiaria spp. and compare them with those observed in animals kept in Andropogon spp. grass and native pastures in Rio Grande do Sul. Materials, Methods & Results: Liver samples without macroscopic changes were collected in abattoirs from 561 healthy Nelore and Nelore crossbred cattle raised in Brachiaria spp. pastures from Mato Grosso (MT), Mato Grosso do Sul (MS), Minas Gerais (MG) and Pará (PA) States. Liver samples from 84 Angus cattle (Bos taurus) kept on native pastures in Rio Grande do Sul (RS) and from 60 Nelore and Nelore crossbreed cattle raised in Andropogon spp. pastures in Tocantins State (TO) were collected as control. Semi-quantitative analysis of the histopathological changes were proceeded: (-) = no change; (+) = slight or discreet change; (++) = moderate change and (+++) = marked change.The main histopathological changes evaluted in the liver samples were the presence of foamy macrophages and its location, parenchymal fibrosis and its location, proliferation of bile ducts, periportal mononuclear infiltrate, presence of crystals in macrophages and within the bile ducts. Foamy macrophages clusters in the liver parenchyma were the most frequent histological changes exclusively observed in samples of animals kept in Brachiaria spp. and it was more frequent in cattle from MS State (P < 0.0001). The periportal hepatic fibrosis was another relevant finding in cattle kept in Brachiaria spp. and was also more frequent in MS animals (P ≤ 0.0001), and was not present in control groups. Proliferation of the bile ducts rate was similar between animals raised in Brachiaria spp. (P > 0.05), though it was higher in cattle kept on native pasture in RS (P < 0.0001). The mononuclear periportal inflammatory infiltrate was more frequent in MS and MG samples than in MT and PA (P < 0.0002). Discussion: The most significant histopathological changes observed in liver samples of cattle from the states of MT, MS, PA and MG kept in Brachiaria spp. pastures from the birth to slaughter, was the presence of foamy macrophages in quantities and variables distribution showing the strengthen association between clusters of foamy macrophages in the liver parenchyma and grazing on this grass. These macrophages could be found in healthy animals kept in Brachiaria spp. pastures and in intoxicated animals. This change was considered frequent and characteristic in animals kept in pastures containing steroidal lithogenic saponins in its composition, and it was frequently observed in ruminants...