Fifteen outbreaks of bovine herpesvirus-type 5 (BHV-5) infection were diagnosed from August 1993 to December 1996. Fourteen outbreaks occurred in the State of Mato Grosso do Sul and one in the State of São Paulo. Cattle 6 to 60 months old were affected. Morbidity reached 0.05% to 5% and case fatality rate was nearly 100%. The disease occurred in different municipalities and at different times of the year. Clinical signs were exclusively nervous, and the clinical course varied from 1 to 15 days. The main histologic lesions were meningitis, diffuse encephalitis and necrosis of the cerebral cortex with intranuclear inclusion bodies in astrocytes and neurons. BHV-5 was isolated from 11 out of 12 brains of infected animals inoculated in calf testis cells and MDBK cells. The virus was identified by immunoperoxidase staining with use of monoclonal specific antibodies. Outbreaks of infection by BHV-5 represent 5% of the total number of bovine cases submitted for diagnosis to the Clinical Hospital of the University of Mato Grosso do Sul. These results indicate the importance of the disease in Mato Grosso do Sul and the need for its differentiation from other diseases which affect the nervous system. INDEX TERMS: Meningoencephalitis, bovine herpesvirus-5, BHV-5, cortical cerebral necrosis, cattle, Mato Grosso do Sul.1 Aceito para publicação em 6 de março de 1998. Os sinais clínicos foram exclusivamente nervosos e o curso da enfermidade variou de 1 a 15 dias. As principais lesões histológicas detectadas foram meningite e encefalite difusa com malacia do córtex cerebral e presença de corpúsculos de inclusão intranucleares em astrócitos e neurônios. O vírus foi isolado do cérebro de 11 de um total de 12 animais, e sua identidade confirmada por imunoperoxidase, utilizando-se anticorpos monoclonais específicos. Os surtos de encefalite por BHV-5 representam 5% dos diagnósticos realizados em bovinos pelo Hospital Veterinário da Universidade Federal do Mato Grosso do Sul. Os resultados deste trabalho evidenciam a importância da doença no Mato Grosso do Sul e indicam a necessidade de incluir a encefalite por BHV-5 no diagnóstico diferencial de outras doenças do sistema nervoso de bovinos frequentes no Estado. TERMOS DE INDEXAÇÃO: Meningoencefalite, herpesvírus bovino-5, BHV-5, polioencefalomalacia, bovinos, Mato Grosso do Sul.
Seven outbreaks and an isolated case of meningoencephalitis caused by bovine herpesvirus-5 (BoHV-5) in cattle in Rio Grande do Sul, Brazil, occurring in 2002-2004, are described. From a total population at risk of 1,359 cattle, 54 1-18-month-old calves from both sexes and several breeds were affected and 50 died spontaneously or were euthanatized while moribund. The highest frequency of cases was in recently weaned calves or calves submitted to other stressing factors. General rates of morbidity, mortality and lethality were respectively 3.97, 3.67 and 92.59%. Clinical courses varied from 3-10 days and included depression, nasal and ocular discharge, grinding of teeth, circling, blindness, fever, nistagmus, trembling, anorexia, dysphagia, drooling, incoordination, head pressing, rough hair coat, tachycardia, tachypnea, abdominal pain, melena, falls, recumbency, opisthotonus, convulsions and paddling. Nineteen calves were necropsied. Necropsy findings were characterized by hyperemia of leptomeninges, swollen rostral portions of the telencephalon, and flattening of frontal lobes gyri; frequently in these frontal areas there were segmental brown-yellow discoloration and softening (malacia) of the cortex. In cases with more protracted clinical courses there were extensive swelling, softening and hemorrhaging of the telencephalic frontal lobes. Microscopically, all affected cattle had a necrotizing non-suppurative meningoencephalitis with variable distribution among the 19 cases and among the various telencephalic regions of the same case. The severity of these changes were more marked, in decreasing order of intensity, in the telencephalic frontal cortex, basal ganglia (nuclei), thalamus, brain stem, parietal telencephalic cortex, occipital telencephalic cortex and cerebellum. Perivascular inflammatory infiltrate consisted predominantly of lymphocytes, plasm cells, and less frequently of neutrophils. Additional microscopic findings included variable degrees of gliosis, edema, neuronal necrosis in the telencephalic cortex characterized by shrinking and eosinophilia of perikaria and nuclear picnosis (red neuron); basophilic intranuclear inclusion bodies in astrocytes and neurons (21.05% of the cases); sattelitosis; and neuronophagia. The areas of softening in the cortical substance consisted of necrosis of the neuroctodermal elements with maintenance of mesenchymal structures (vessels and microglia), infiltrate of Gitter cells, and, in more severe cases, extensive hemorrhages. In chronic cases, only vascular structures and a few Gitter cells remained in the cortical area leaving a cavity between white matter and leptomeninges (residual lesion).INDEX TERMS: Bovine herpesvirus-5, BoHV-5, encephalitis, diseases of cattle, viral diseases, neuropathology.
Dois surtos de fotossensibilização foram observados em ovinos em pastagens de Brachiaria decumbens no Estado de Mato Grosso do Sul. O quadro clínico incluía edema e dermatite da face, orelhas e pálpebras, conjuntivite, descarga ocular, cegueira e aumento nos níveis séricos de ASTe GT. Alguns ovinos recuperaram-se e outros morreram em 3-7 dias. O fígado apresentou leve aumento de volume e consistência e coloração amarelo-esbranquiçada ou marrom-amarelada. Os ductos biliares e a vesícula biliar estavam dilatados. A principal alteração histológica foi a presença de cristais birrefringentes, eticamente ativos nos ductos biliares e no citoplasma de hepatócitos periportais. Necrose do epitélio dos ductos biliares, fibrose periportal com infiltração de células inflamatórias e proliferação de ductos biliares também foram observadas. Grupos de células grandes com núcleo excêntrico e citoplasma espumoso ocorriam nas regiões periportal e centrolobular. Numerosos grupos destas células também foram observadas no córtex e na medula dos linfonodos hepáticos. Não foram encontradas quantidades contáveis de esporos de Pithomyces chartarum nas amostras da pastagem onde estavam os ovinos; de 30 culturas de P. chartarum isoladas dessas amostras, apenas uma produziu esporidesmina. Conclui-se que a intoxicação foi causada pela ação tóxica de Brachiaria decumbens.
Brachiaria species are the most important grasses for cattle production in Brazil. However, a limiting factor for the use of Brachiaria spp. is their toxicity. Most outbreaks of hepatogenous photosensitization are caused by B. decumbens; however B. brizantha, B. humidicola and B. ruziziensis can also cause poisoning. The poisoning affects cattle, sheep, goats and buffalo. Sheep are more susceptible than other animal species and the young are more susceptible than adults. There are differences in susceptibility among animals of the same species and it has been suggested that this resistance is genetic. Also has been suggested that buffalo and probably some sheep are resilient, i.e. when poisoned these animals have histologic lesions and high GGT serum concentrations, but do not show clinical signs. In general, saponin concentrations are higher in growing plants, but outbreaks occur all over the year, probably due to unexplained rise in saponin concentration in the plant. A clinical syndrome of progressive weight loss and death, without photosensitization, has been reported in cattle poisoned by B. decumbens. Main preventive measures are based on the selection of resistant or resilient animals and on the development of Brachiaria species or varieties with low saponin concentration.
An outbreak of hepatogenous photosensitization is reported in a flock of 28 sheep grazing Brachiaria decumbens in Mato Grosso do Sul State, Central-Western Brazil. Seven lambs and an adult sheep were affected and 6 of them died. Two surviving affected lambs and one lamb without clinical signs had increased serum values of gamma glutamyltransferase, bilirubin, and cholesterol. In two adult unaffected sheep those parameters were within normal values. An adult sheep submitted to necropsy presented moderate body condition, unilateral corneal opacity, drying of the muzzle, moderate jaundice, increased lobular pattern of the liver, and a distended gallbladder. Histological lesions were epithelial degeneration, necrosis, and hyperplasia of small bile ducts. Mild amounts of foamy macrophages were observed, mainly in the centroacinar zone. Diffuse swelling and vacuolation were observed in hepatocytes. Crystal negative images were found within bile ducts, foamy macrophages, and the lumen of some renal tubules. The heart showed multifocal areas of degeneration and necrosis of the muscle fibers. Pasture samples (Brachiaria decumbens) contained 2.36% of protodioscin. No Pithomyces chartarum spores were found in the pasture. Samples from a similar neighboring B. decumbens pasture grazed by cattle without photosensitization contained 1.63% of protodioscin isomers. Outbreaks of photosensitization caused by Brachiaria spp. are common in cattle in the Brazilian Cerrado (savanna) with about 51 million hectares of Brachiaria spp pastures. Sheep farming has been recently developed in this region, and the number of sheep is increasing significantly. Because sheep are more susceptible than cattle to lithogenic saponins, poisoning by Brachiaria should be an important limiting factor for the sheep industry.
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