Febre catarral maligna em bovinos no norte de Mato Grosso - Brasil / Malignant catarrhal fever in cattle in the northern region of Mato Grosso - Brazil

ABSTRACT

Background: Malignant catarrhal fever is an infectious pan-systemic viral disease, worldwide distribuition and highly fatal. The disease is described in many ruminant species, manly bovine. The lesions produced by malignant catarrhal fever in catlle affect upper respiratory and digestive tracts, lymph nodes, brain, eyes, kidney and urinary bladder. Affected animals present fever, depression, ocular and nasal discharge, erosions and ulcerations in the respiratory tract, keratoconjunctivitis, lymph node enlargement, hemorrhagic enteritis, encephalitis and arteritis. Four viruses are described as agents implicated on malignant catarrhal fever, although in Brazil, only ovine herpesvirus-2 has been described. Malignant catarrhal fever occurs in several regions of Brazil, including Mato Grosso state, where it was already reported in its southern region. The aim of this study was to describe the occurrence of malignant catarrhal fever in cattle in the northern region of the state of Mato Grosso. Case Two affected bovine were necropsied. Tissue fragments were fixed with buffered formalin 10% and the hematoxylineosin sections were submitted to histopathology examination. Bovine DNA samples were extracted from paraffin embedded tissue fragments and submitted to nested PCR detection of ovine herpesvirus-2. The disease affected two bovine, one became clinically sick in October 2009 and the other one in November 2010, in a dairy cattle farm where sheep and cows were raised together in the same feedlot. Disease occurrence was coincident with a four-month period after sheep's parturition. Clinical signs included apathy, decreased appetite, fever, nasal and vulvar discharge, recumbence, opisthotonos and death within four days. Necropsy revealed corneal opacity, multiple white foci in kidneys, crusts distributed over nasal and vulvar mucosa, catarrhal discharge and small erosions. Major histopathological findings had variable intensity and distribution and included perivascular inflammatory infiltrate, fibrinoid degeneration of arterial and arteriolar layers and epithelial necrosis with inflammatory infiltrate. Vascular histopathological findings included lymphocytic perivascular infiltrate with hyalinization, and a lymphoplasmocytic inflamatory infiltrated associated with histiocytes in the tunica media and vascular adventitia. Molecular examination detected ovine herpesvirus-2 DNA amplification. Discussion: In this study, malignant catarrhal fever diagnosis based on epidemiological, macroscopic, microscopic and molecular findings. Macroscopic and microscopic lesions observed are similar to those described in the literature. The disease occurs in a sporadic pattern, affecting few animals or as epizootic outbreaks affecting many bovines in a same herd. Four outbreaks were recorded in the southern region of Mato Grosso (Pantanal and Cerrado regions), three in a sporadic pattern and one as an epizootic outbreak. In the present study, the disease is reported in the northern region of the state (Amazonic region) as a sporadic form affecting two animals in the same farm. Histological examination is a valuable tool to diagnose malignant catarrhal fever; however rete miriabile should be carefully evaluated, once in this disease, vasculitis is a distinctive finding. PCR examination is an important tool to aid the diagnosis.