Detection of wild-type Aujeszky's disease virus by polymerase chain reaction in sheep vaccinated with a modified live vaccine strain

Pseudorabies Virus Associations in Wild Animals: Review of Potential Reservoirs for Cross-Host Transmission

Pseudorabies virus (PRV) has received widespread attention for its potential health effects on humans, wildlife, domestic animals, and livestock. In this review, we focus on PRV dynamics in wildlife, given the importance of wild-origin PRV transmission to domestic and farm animals. Wild boars, pigs, and raccoons can serve as reservoirs of PRV, with viral transmission to domestic livestock occurring via several routes, such as wild herd exposure, contaminated meat consumption, and insect vector transmission. Many endangered feline and canine species can be infected with PRV, with acute disease and death within 48 h. The first confirmed human case of PRV infection in mainland China was reported in 2017. Thus, PRV exhibits potentially dangerous cross-host transmission, which is likely associated with inappropriate vaccination, poor awareness, and insufficient biosecurity. Currently, no vaccine provides full protection against PRV in all animals. Here, we summarize the epidemiology and pathogenesis of PRV infection in wild, domestic, and farmed animals, which may facilitate the design of novel therapeutics and strategies for controlling PRV infection and improving wildlife protection in China.

Investigation of the molecular detection of vaccine-derived equine herpesvirus type 1 in blood and nasal secretions from horses following intramuscular vaccination

The objective of this study was to investigate whether intramuscular vaccination of healthy adult horses with a killed or a modified live equine herpesvirus type 1 (EHV-1) vaccine could induce transient positive PCR results in either blood or secretions collected on a nasopharyngeal swab. Four horses in each group received either a single killed or a modified-live vaccine intramuscularly. Two local commingled and 2 distant nonvaccinated controls were included for each group. All horses were observed daily for evidence of clinical abnormalities throughout the study periods. Blood and nasopharyngeal swabs were collected twice before vaccination and once weekly for 4 weeks after vaccination and submitted for PCR testing for EHV-1 by 2 independent laboratories using different real-time PCR methodologies. Serum samples collected from all horses on the vaccination day and 21 days later were tested for antibodies against EHV-1 using a serum neutralization test. Whereas the 2 vaccine strains tested positive in both EHV-1 PCR assays, nasopharyngeal swabs and whole blood collected from vaccinated and control horses had negative PCR test results for EHV-1 during the entire study period. Serum neutralization testing revealed a 2- to 4-fold increase in titers for all vaccinated horses, whereas titers in control horses were largely unchanged. The use of seropositive horses before immunization and the sampling frequency of 7 days may have prevented the occasional molecular detection of the vaccine virus in whole blood and nasopharyngeal secretions. However, the study results demonstrate that detection of EHV-1 DNA by PCR in vaccinated and unvaccinated healthy horses is not a common event.

Viral diseases of the ruminant nervous system

This article presents the etiology, epidemiology, clinical features,and diagnosis of the primary viral neurologic diseases observed in ruminants. In general, these viral neurologic diseases are uncommon but often fatal. Rabies virus is perhaps the most important cause of encephalitis in cattle because of the public health implications. Other viral encephalitis diseases in ruminants include bovine herpesvirus encephalomyelitis, pseudorabies, malignant catarrhal fever, ovine and caprine lentiviral encephalitis, West Nile virus encephalitis, Borna disease, paramyxoviral sporadic bovine encephalomyelitis,and ovine encephalomyelitis (louping-ill).

Detection of pseudorabies virus DNA in individual single-reactor pigs found in certified pseudorabies-free herds

During monitoring of certified pseudorabies (PRV)-free herds to confirm their PRV -free status, occasional individual gE-seropositive pigs are detected. These single-reactor pigs remain gE-seropositive when further serum samples are collected and tested. For the eradication programme to proceed, it is important to determine whether these pigs are only false positives or are; in fact, infected with field PRV. The purpose of this study was to determine whether the polymerase chain reaction (PCR) could detect field PRVDNA in single-reactor pigs and so confirm positive reactions in the serologic monitoring programme. First, DNA samples of various tissues from 15 single-reactor pigs all from different herds were examined for field PRV by PCR. Additionally, serum samples from these pigs were analyzed in a gE-confirmation enzyme linked immunosorbent assay (gE-confirmation ELISA). PCR detected PRVDNA in five of the 15 pigs, and these results were confirmed by the gE-confirmation ELISA. The remaining 10 pigs that tested negative in the PCR also tested negative in the gE- confirmation ELISA. We conclude that PCR can be used to discriminate between true and false serological positive single-reactor pigs and, moreover, that the gE-confirmation ELISA confirms these PCR results.