Commercial vaccine against pseudorabies virus: A hidden health risk for dogs.

Pseudorabies virus (PRV) is considered as an infectious agent with a wide of host range, causing considerable economic losses in animal husbandry. Although the commercial vaccine against PRV plays an critical role in control of this disease in swine industry, the potential risk of commercial vaccines against PRV for other host is unclear. Here, we report that the commercial vaccine against PRV is a hidden health risk for dogs. We found that different attenuated PRV strains in commercial vaccines possess different tissue tropism, and that the attenuated PRV strains are lethal to dogs, and that the attenuated PRV strain possesses the ability to spread horizontally among the dogs. Collectively, our findings provide clues that the commercial vaccine against PRV is a hidden risk for dogs, even for the owner of pet dogs to take seriously.

From mouse to pig: Is PRV vaccine safe across two species?

Pseudorabies (PR) is an economically important viral disease of pigs which can infect numerous species of mammals including rodents. Commercial PR vaccines have been widely used worldwide to control and eradicate this disease. However, some PRV vaccines such as Bartha-K61 were occasionally reported to be lethal to mice. Since mice are commonly found in pig farms, the safety issue of PRV live vaccine across different species was never addressed. In this study, PRV vaccine strain Bartha-K61 was in vivo propagated in mice for five passages. The mortality of mice ranged from 80%-100% at each passage of PRV infection. The fifth passage of PRV was used to infect piglets to test its virulence on this species. The infected piglets clinically behaved normally and survived by the end of study (terminated at 10days post-infection). Histopathologically, there was infiltration of eosinophile granulocyte in tonsil and lung and no other changes were observed in other organs of infected pigs. Immunohistochemistry staining results showed that PRV antigen was only found in lung sample of one piglet. Therefore, the above results suggested there was no safety concern of Bartha-K61 PRV vaccine on pigs after the vaccine virus was passaged in mice for 5 times. The result of this study may suggest that mice may play a minimal role in the derivation of PRV vaccine-like field viruses that are believed to cause disease in young pigs.

A recombinant pseudorabies virus expressing rabies virus glycoprotein: safety and immunogenicity in dogs.

Several recombinant vaccines expressing the rabies virus glycoprotein have been developed, particularly for the oral vaccination of wildlife. While these vaccines induce protective immunity in some animal species such as foxes, they are less effective in others. Pseudorabies virus (PRV) has been licensed for use as a live vaccine in pigs and possesses an excellent safety and efficacy record. We have used it to construct a recombinant virus, rPRV/eGFP/rgp, expressing the rabies virus glycoprotein. This recombinant virus has been shown to be safe for dogs by oral and intramuscular routes of inoculation and was demonstrated to induce immune responses against both pseudorabies and rabies in dogs after a single oral dose of 2 x 10(7.0) plaque forming units (PFU). Neutralizing antibody titers against rabies reached > 0.5 IU/ml and 1:64-1:128 against pseudorabies by 5 weeks post-vaccination in all dogs, indicating that the pseudorabies virus vector infected dogs and replicated in vivo, and that the rabies virus glycoprotein had been expressed and an effective immune response elicited. Antibody titers were maintained for over 6 months. This suggests that pseudorabies virus could be an effective live vector for recombinant rabies oral vaccination.