Caracterização clinicopatológica da mamilite aguda em ovelhas lactantes infectadas experimentalmente com o herpesvírus bovino 2

Abstract

RESUMO.-A mamilite causada pelo herpesvírus bovino tipo 2 (BoHV-2) possui importante repercussão sanitária em gado leiteiro de alguns países, mas a sua patogenia permanece pouco conhecida. Este trabalho descreve a reprodução e caracterização da mamilite aguda em ovelhas lactantes inoculadas com o BoHV-2 na pele do úbe-re e dos tetos. is an important disease in dairy herds yet its pathogenesis remains largely unknown. This report describes the reproduction and characterization of acute mammillitis in lactating ewes inoculated with BoHV-2 in the skin of the udder and teats. Five out of eight inoculated ewes developed large plaques, with focal necrosis, small vesicles and crust formation in the inoculated areas. The lesions were first observed on day 4 post-inoculation (pi), progressed in size and severity up to days 7-8pi and subsided progressively thereafter. Infectious virus was isolated from the lesions at days 7 and 8pi. Viral antigens and herpesvirus-like particles were demonstrated by electron microscopy in lesions examined at days 5, 6 and 10pi. Histological findings included epithelial necrosis, erosions and ulcers, and formation of syncytial cells. Intranuclear inclusions bodies in epithelial, syncytial and inflammatory cells and lymphoplasmacytic inflammatory infiltrate in the dermis were also observed. In a second experiment, seven out of ten lambs inoculated into the nostrils and muzzle developed nasal hyperemia and discharge, vesicles, and erosions in the nose. Infectious virus was isolated from lesions during up to three days and all lambs seroconverted to BoHV-2. Attempts to reactivate the latent infection by dexamethasone administration on day 40pi failed, since virus shedding, clinical recrudescence or seroconversion were not observed. The reproduction of acute infection and mammillitis resembling that occurring in cattle paves the way for the use of sheep to study several aspects of the biology of BoHV-2 infection.

Pathogenesis of Bovine alphaherpesvirus 2 in calves following different routes of inoculation

“…The scarce knowledge about its biology, molecular biology and pathogenesis has somehow hampered its use as a model for human simplex viruses and as a vector for vaccine delivery, among others. Our group has long been interested in BoHV-2 epidemiology and pathogenesis (Almeida et al 2008, Torres et al 2010. More recently, we have focused our interest in the use of BoHV-2 for anti-viral drug testing and for development of vaccine platforms for antigen delivery.…”

“…1974, Castrucci et al 1978, Woods et al 1996, Kemp et al 2008 and animal models (Westbury 1981, Almeida et al 2008, Smee & Leonhardt 1994, Torres et al 2009a. A few experimental studies focusing on acute disease (Castrucci et al 1977, Castrucci et al 1982 or latent infection Probert & Povey (1975), Scott & Martin (1978), Letchworth & Carmichael (1982) introduced probably biases on data interpretation due to IV virus inoculation, an unlikely natural route of exposure.…”

“…The TD route was chosen because it would more closely resemble the natural route of infection. Using this protocol of virus inoculation, we have successfully reproduced udder and teat lesions typical of BHM in ewes (Almeida et al 2008). The IV route was employed trying to reproduce the virological findings of early studies which used this route (Castrucci et al1977, Castrucci et al 1978, Martin & Scott 1979.…”

“…These findings suggest that, like to other simplex viruses, BoHV-2 may circulate silently in susceptible host populations, occasionally producing clinical cases or outbreaks. This behavior may also explain findings of positive BoHV-2 serology in cattle populations with no evident, or scarce, history of compatible clinical disease (Almeida et al 2008, Torres et al 2009b.…”

“…Likewise, the sites in which the virus may remain latent remain unknown (Letchworth & Carmichael 1982). Pathogenesis studies were performed in animal models, with their inherent pitfalls and restrictions (Almeida et al 2008, Torres et al 2009a). Thus, a better understanding of BoHV-2 pathogenesis in their natural hosts is needed.…”