Patogenia da infecção pelo herpesvírus bovino tipo 5 em caprinos e coelhos

Abstract

This study describes aspects of the pathogenesis of bovine herpesvirus-5 (BoHV-5) infection in goats and rabbits. The study performed in goats was aimed at investigating the susceptibility of this species to BoHV-5 infection, due its potential role as a virus reservoir. Young goats were inoculated intranasally with three Brazilian BoHV-5 isolates (SV-507, G1; SV-609, G2; and EVI-88, G3) and monitored thereafter regarding to virus shedding, clinical signs and antibody response. The acute infection was characterized by virus shedding in nasal secretions for up to 14 days post-inoculation (pi) in titers reaching up to 105.97 TCID50/mL, mild respiratory signs and seroconversion. At day 60 pi, two animals of each group were euthanized for tissue collection to search viral DNA. The remaining animals were submitted to dexamethasone (Dx) administration to reactivate latent infection. Dx treatment resulted in virus reactivation in 75% (9/12) animals, as ascertained by virus shedding (8/12), and/or seroconversion (3/12). Latent viral DNA was detected in the trigeminal ganglia (TG) and/or in the main olfactory bulb (MOB) of all goats euthanized at days 60 pi and 40 post-dexamethasone. These results demonstrate that goats are susceptible to BoHV-5 acute and latent infection and may shed virus upon reactivation of latency. Thus, this species should be considered a potential reservoir for BoHV-5 in areas where goats and cattle are raised in close contact. The second experiment was aimed at investigating the role of the olfactory pathway in the transport of BoHV-5 to the brain of rabbits. For this, thirty days-old rabbits had the MOB surgically removed and were subsequently inoculated intranasally (IN) or conjunctivally (IC) with the strain SV-507 of the BoHV-5. Intranasal inoculation resulted in neurological disease in 100% of the control animals (with MOB), with clinical signs starting between days 5 and 10 pi; in the group submitted to MOB ablation only one animal (9.1%) developed neurological signs (started at day 17 pi). Following IC inoculation 10/12 (83.3%) control rabbits (with MOB) developed neurological disease with clinical signs starting between days 11 and 20 (mean 15.3 days). Furthermore, 10/12 rabbits lacking the MOB also developed neurological disease starting between days 9 and 15 pi (mean 12.5 days). These results demonstrate that both the olfactory and the trigeminal pathways may be used by BoHV-5 to invade the brain of rabbits after experimental infection. The transport by the olfactory pathway is faster and more efficient, while the trigeminal transport is slower and less efficient. These results add important information to the knowledge about the neuropathogenesis of alphaherpesvirus infection.