Epidemiologia, sinais clínicos e distribuição das lesões encefálicas em bovinos afetados por meningoencefalite por herpesvírus bovino-5

Abstract

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.

Histopathological, immunohistochemical, and molecular study of BHV-5 infection in the central nervous system of experimentally infected calves

“…Edema was the most common finding, corroborating with others studies where the authors suggested that edema could contribute to the development of malacia due to ischemia (Rissi et al 2006, Rissi et al 2008.…”

“…Region 1 included the olfactory bulb and telencephalon; region 2 included the basal nucleus, thalamus, midbrain, pons, and medulla oblongata. et al , Elias et al 2004, Rissi et al 2006, Ferrari et al 2007, Rissi et al 2008. The absence of lesions in the cervical spinal cord, cerebellum, and Gasserian ganglia has been previously reported (Rissi et al 2008).…”

“…All 108 CNS samples were evaluated for 12 parameters: vascular changes (edema, congestion, and hemorrhagic changes), nervous tissue changes (number and degree of perivascular cuffing, neuronal necrosis, intranuclear inclusion bodies, diffuse or focal gliosis, malacia with presence of Gitter cells, inflammatory foci in the neuropil, and neuronophagia) and leptomeningeal changes (meningitis) (Rissi et al 2006, Sant'ana et al 2009). All parameters were scored as 0 (absence), 1 (mild), 2 (moderate), or 3 (severe).…”

“…This virus is involved in cases of nonsuppurative meningoencephalitis in cattle (Roizmann et al 1992). Meningoencephalitis mainly occurs in calves and causes individual deaths or outbreaks with low morbidity and high mortality (Rissi et al 2006, Rissi et al 2008. The disease has no seasonal pattern or predilection for breed or gender .…”

Uso de la inmunohistoquímica como herramienta epidemiológica para el diagnóstico de rabia bovina a partir de casos no conclusivos

“…Respecto a los diagnósticos diferenciales en los casos negativos y con base en alteraciones histopatológicas observadas en la coloración de rutina Hematoxilina-Eosina (H&E) de los tejidos evaluados, se consideró en algunos casos, compatibilidad con la meningoencefalitis causada por el Herpes Virus Bovino 5 (BoHV-5), agente recientemente descrito en Colombia (14), siendo que estos casos mostraron, gliosis, manguitos perivasculares, malacia y células gitter, considerados característicos de este tipo de infección (15). Es importante no dejar de lado otras causas de meningitis inespecíficas, como las de origen bacterial (por Listeria spp), envenenamiento por consumo de plantas tóxicas, intoxicación por plomo, polioencefalomalacia por deficiencia de tiamina y botulismo entre otros (16,17).…”