Reactivation of latent bovine herpesvirus type 5 in cattle with polioencephalomalacia induced by ammonium sulphate

Abstract

In the state Mato Grosso do Sul, Brazil, outbreaks of meningoencephalitis by BoHV-5 and polioencephalomalacia (PEM) display similar epidemiological features, suggesting that meningoencephalitis may be associated with reactivation of a latent BoHV-5 infection, during the development of PEM. To test this hypothesis, four 7-8 months old steers negative for BoHV-5 antibodies were inoculated intranasally with BoHV-5 and received amprolium from day 35 to day 105 after inoculation. Because PEM was not produced during this period, ammonium sulphate was given from day 114 to day 180 after inoculation. Two uninfected control steers received amprolium and ammonium sulphate for the same periods. All inoculated cattle developed antibodies against BoHV-5 after inoculation and the virus was isolated from nasal swabs, indicating that they were infected. Two inoculated steers had clinical signs of PEM after 118 and 146 days after virus inoculation. One was euthanized after a clinical manifestation period of seven days and had severe lesions of PEM and meningoencephalitis. BoHV-5 was isolated from the central nervous system of this animal. The other animal recovered but continued to manifest chronic signs of PEM and was euthanatized. On histological examination, the cerebral cortex, caudate nucleus and thalamus had multifocal areas of malacia and mild meningoencephalitis of the cortex. BoHV-5 was not isolated from the brain. One uninfected control steer had signs of neurological disease on day 158 and had lesions of PEM without meningoencephalitis at necropsy. The simultaneous production of PEM and diffuse meningoencephalitis, with isolation of BoHV-5, in one steer treated with ammonium sulphate, 118 days after BoHV-5 inoculation, suggests that latent BoHV-5 was reactivated in this animal submitted to experimental induction of PEM.INDEX TERMS: Polioencephalomalacia, bovine herpesvirus type 5, viral reactivation, cattle.

Polioencefalomalacia em ruminantes

“…No entanto BoHV-5 e BoHV-1 têm sido isolados de casos onde não se observam lesões inflamatórias significativas (Rissi et al 2008). Para complicar mais ainda a diferenciação entre essas doenças, uma teoria que une casos de polioencefalomalacia e infecção por BoHV-5 foi proposta (David et al 2007). Segundo ela, no Mato Grosso do Sul, surtos de meningoencefalite por BoHV-5 e PEM apresentam características epidemiológi-cas semelhantes, o que sugere, segundo os autores, que a meningoencefalite está associada à reativação de uma infecção latente por BoHV-5 em animais com PEM.…”

Meningoencefalite por herpesvírus bovino-5

“…A relação epidemiológica entre casos de meningoencefalite por BoHV-5 e polioencefalomalacia (PEM) é descrita no Mato Grosso do Sul, e evidências experimentais sugerem que agentes etiológicos da PEM possam reativar infecções latentes por BoHV-5 em bovinos (David et al 2007). Além disso, são descritos casos experimentais de infecção por BoHV-5 em que a infecção acidental pelo vírus da diarréia viral bovina (BVD) pode ter exacerbado os sinais clínicos da infecção por BoHV-5 e aumentado a quantidade de vírus excretado pela via nasal (Spilki et al 2006).…”

Polioencefalomalacia em bovinos: epidemiologia, sinais clínicos e distribuição das lesões no encéfalo

“…Em bovinos são descritos surtos da doença nos estados do Rio Grande do Sul (Santos et al 1983, Riet-Correa et al 1998, Motta et al 1999, Sanches et al 2000, Traverso et al 2001, Schild et al 2005, Minas Gerais (Ferreira et al 1986, Moro et al 1994, Pernambuco (Vieira et al 2007), Mato Grosso do Sul, São Paulo (Purisco 1982, Nakazato et al 2000, Gonçalves et al 2001, Lemos 2005, David et al 2007), Mato Grosso e Goiás (Grecco et al 2001, Lemos 2005.…”