Aujeszky's Disease Virus Infection Research Articles

Natto extract inhibits infection caused by the Aujeszky's disease virus in mice.

Aujeszky's disease virus (ADV), also known as Suid alphaherpesvirus 1, which mainly infects swine, causes life-threatening neurological disorders. This disease is a serious global risk factor for economic losses in the swine industry. The development of new anti-ADV drugs is highly anticipated and required. Natto, a traditional Japanese fermented food made from soybeans, is a well-known health food. In our previous study, we confirmed that natto has the potential to inhibit viral infections by severe acute respiratory syndrome coronavirus 2 and bovine alphaherpesvirus 1 through their putative serine protease(s). In this study, we found that an agent(s) in natto functionally impaired ADV infection in cell culture assays. In addition, ADV treated with natto extract lost viral infectivity in the mice. We conducted an HPLC gel-filtration analysis of natto extract and molecular weight markers and confirmed that Fraction No. 10 had ADV-inactivating ability. Furthermore, the antiviral activity of Fraction No. 10 was inhibited by the serine protease inhibitor 4-(2-Aminoethyl) benzene sulfonyl fluoride hydrochloride (AEBSF). These results also suggest that Fraction No. 10, adjacent to the 12.5 kDa peak of the marker in natto extract, may inactivate ADV by proteolysis. Our findings provide new avenues of research for the prevention of Aujeszky's disease.

Dynamics of Aujeszky's disease virus infection in wild boar in enzootic scenarios.

Aujeszky's disease (AD) virus is enzootic in Iberian wild boar, thus posing a threat to the official eradication of AD on extensive domestic pig farms in Spain. Understanding the dynamics and drivers of ADV infection in wild boar will help prevent viral transmission at the wild boar-pig interface. This study analyses the dynamics of ADV infection in wild boar and tests relevant hypotheses in order to identify drivers of ADV infection dynamics. Wild boar sera (N=971) and oropharyngeal tonsils (TN, N=549) collected over 11 consecutive years in south-western Spain were tested for ADV antibodies and DNA, respectively. We tested the hypotheses that population immunity modulates the risk of ADV infection (H1 ) and that detecting ADV DNA in TN is a good proxy of the annual ADV infection pressure (H2 ). This was done by building logistic regression models that were subsequently employed to test the influence of a series of host population and host individual factors-including predictors of ADV immunity in the population-on the annual risk of new ADV infections and on the presence of ADV DNA in TN. The premise of H1 was that there would be a negative association between the proportion of ADV antibody-positive wild boar in a given year and the risk of ADV infection of naïve individuals. There was, however, a positive association, and H1 was, therefore, rejected. If detecting ADV in TN had been a good indicator of ADV infection pressure, a positive association with the proportion of ADV antibody-positive wild boar would have been found. However, this was not the case and H2 was also rejected. We confirmed that ADV infection is a dynamic phenomenon. The risk of infection with ADV can change considerably between consecutive years, and these changes are positively associated with the proportion of infected wild boar in the population.

Detection of Aujeszky's disease virus DNA and antibody in swine oral fluid specimens.

Aujeszky's disease virus (ADV) continues to circulate in commercial swine populations in many regions and in feral swine populations in most parts of the world, that is, ADV continues to present a risk to pork producers everywhere. Current DIVA vaccines and assays are highly effective in the control and/or eradication of ADV, but detection of wild-type ADV infection relies on testing individual pig specimens, for example, serum or muscle exudate ("meat juice"). Oral fluid specimens have been shown to be highly effective for the surveillance of a variety of swine pathogens and could offer the means to improve the efficiency of ADV surveillance in the field. In this study, the temporal patterns of ADV DNA and antibody detection in oral fluid and serum specimens were established in ADV-inoculated pigs (n=14) using gB and gE PCRs, virus neutralization (VN) and three commercial serum antibody ELISAs (gB bELISA, gI bELISA and ADV iELISA). ADV DNA was detected in oral fluid samples (20% to 100%) from 3 to 21days postinoculation (DPI), but not in serum. ADV antibody was detected in oral fluid specimens at DPI ≥ 10 with the gB bELISA (36% to 79%) and ADV iELISA (29% to 100%), but not the gI bELISA. These results suggest that oral fluid could be used as an alternative to individual pig sampling for ADV surveillance using PCR- and/or antibody-based assays.

Aujeszky's Disease (Pseudorabies). An old threat in current pig industry? Part II. Epidemiology, Immunity, Prevention and the current situation in Greece

Aujeszky's disease (AD) (or Pseudorabies) is an important viral disease of swine causing neurological signs in neonatal pigs, respiratory problems in fatteners and reproductive disorders in breeding stock. Swine is the only natural host of Aujeszky's disease virus (ADV) and the only species that can survive its infection. Its transmission is mainly through nose-to-nose contact, but several other ways may apply. Both antibody- and cell-mediated immune responses occur following ADV infection, while maternal immunity can protect the pigs depending on their level and the virulence of the infecting strain. Virus glycoproteins may, also, play a role in immunity with that of gC and gD being the most important. Prevention and control of ADV is based on proper vaccination and biosecurity measures, while eradication has been practiced in various ways depending on the situation. The current vaccines are based on deletion of certain proteins and are effective. Despite the fact that the disease has been eradicatedfrom many developed countries, AD is still endemic in Greece. Findings of recent emergence of AD in Greek farms and the possibility of its eradication are discussed.

An oral Aujeszky's disease vaccine (YS-400) induces neutralizing antibody in pigs.

PurposeAujeszky's disease (AD) is an economically important disease affecting both wild and domestic pigs of the species Sus scrofa. A previous study yielded serological evidence of AD in Korean wild boars, which could spread AD to other animals. A new Aujeszky's disease virus (ADV) bait vaccine is required to prevent AD outbreaks in swine. In the present study, we investigated the safety and immunogenicity of a gE-deleted marker vaccine, strain YS-400, in young domestic pigs.Materials and MethodsThe YS-400 strain was propagated in Vero cells, and the trial ADV bait vaccine (a vaccine blister in a matrix including an attractant) was prepared. Pigs were orally immunized with the vaccine (2 mL, 107.5 TCID50/mL) delivered using a syringe or in the bait vaccine. The animals were observed for 9 weeks after vaccination, and immunogenicity was assessed using a virus neutralization (VN) test and enzyme linked immunosorbent assay.ResultsThe YS-400 strain was non-pathogenic to pigs when given orally and induced high VN titers (1:32-1:128) 6 weeks post-administration. Of the pigs given the ADV bait vaccine twice or three times, 40% were seropositive by 2 weeks, and 100% were seropositive by 7 weeks after the first dose. Pigs that consumed the AD bait vaccine three times developed VN titers that were slightly higher than those of pigs given the vaccine twice.ConclusionDomestic pigs given the trial ADV bait vaccine exhibited no adverse effects and developed high VN titers against ADV, indicating that the YS-400 strain is safe and can prevent ADV infection in domestic pigs.

A long-term serological survey on Aujeszky's disease virus infections in wild boar in East Germany

Between 1985 and 2008, a total of 102,387 wild boar sera originating from Eastern Germany covering an area of 108 589 km2 were tested for the presence of Aujeszky's disease virus (ADV)-specific antibodies. From 1985 until 1991 and from 1992 until 2008, wild boar sera were exclusively investigated using either conventional seroneutralization assays (n=39 621) or commercial gB and full antigen ELISAs (n=62,766), respectively. Spatial-temporal analysis revealed an increasing ADV seroprevalence from 0·4% to 15·9%, on average, during the 24-year observation period that went along with a continuous spread of the infection in a western direction. During 2006 and 2008, 18% of the 66 affected districts had ADV seroprevalences >30%. There was a significant correlation between ADV seroprevalence and the hunting index of population density (HIPD) of wild boar in the entire study area, although this did not hold true for some regions. Seroprevalences did not differ between sexes but were age-dependent. East Germany has been officially free of Aujeszky's disease (pseudorabies) in domestic pigs since 1985. Although a risk for domestic pigs cannot be completely ruled out, experience has shown that ADV in domestic pigs could be eliminated although the virus was present in the wild boar population. Despite increasing ADV seroprevalence in the East German wild boar population no spillover infections from wild boar to domestic pigs have been reported. To further trace ADV infections in the wild boar population in Germany, a nationwide serological monitoring programme should be implemented.

Aujeszky's disease virus infection patterns in European wild boar

Evidence of exposure (i.e. seroprevalence) to Aujeszky's disease virus (ADV) is high among wild boars from south-central Spain. This research aims to determine the presence of ADV by molecular detection, and to describe the patterns of ADV infection in wild boars. Tonsils (TN) and trigeminal ganglia (TG) for ADV molecular detection, and sera were collected from wild boars ( n = 192) in 39 hunting estates from south-central Spain (2004/2005). A nested polymerase chain reaction (PCR) for a fragment of the ADV surface glycoprotein B was performed on collected tissues. Individual status of presence of viral DNA was tested against explanatory variables by means of a Generalized Linear Mixed Model (GLIMMIX) analysis. Viral detection prevalence was 30.6 ± 6.7%. Although there was an increasing pattern with age and females presented higher prevalences, no statistically significant influence of sex and age was found for viral presence. Molecular testing in TN and TG allowed classifying infection status into (i) ADV negative (in both TN and TG), (ii) only positive in TN, (iii) only positive in TG and (iv) positive in both TN and TG. ADV DNA was statistically more frequently evidenced in TN in females than in males. With the exception of one individual, all wild boars with presence of ADV DNA in TN and TG or only in TG reacted positive in the ELISA. In contrast, animals with only ADV DNA in TN serorreacted positively and negatively. Interestingly, 45% of the PCR positive wild boars ( n = 59) were seronegative in the serological test, all of them with viral DNA only in TN. Our results provide evidence for latency of ADV in wild boars and stress the fact that antibody detection based tests may fail to detect a proportion of recently infected animals. This is of great concern since current management schemes in our study promote animal translocation for hunting purposes, with the associated risk of under-detecting ADV infected individuals when using serology to screen for ADV infection.

Presence of Antibodies Against Aujeszky's Disease Virus in Wild Boar (Sus scrofa) in Slovenia

Serum samples from 427 hunter-killed wild boar (Sus scrofa) from Slovenia were tested for antibodies to Aujeszky's disease virus (ADV). Samples were collected throughout Slovenia and corresponded to 6.2% of the total harvest. Antibodies against ADV were detected in 111 sera (26%) using a commercial enzyme-linked immunosorbent assay (ELISA). Antibody prevalence increased significantly with age. This report describes the first evidence of ADV infection in wild boar populations in Slovenia.

Aujeszky's disease virus eradication campaign successfully heading for last stage in the Netherlands

Summary The Aujeszky's disease virus (ADV) eradication campaign in the Netherlands is based on compulsory vaccination and certification of ADV‐free herds and consists of three stages: reduction of transmission of ADV, tracing and elimination of remaining sources of ADV, and, in the last stage prohibition of vaccination. This paper summarizes the progress made in the first two stages of the eradication. Between 1994–1999, ADV seroprevalence decreased sharply in all four regions in the Netherlands, both in the sow and the finishing pig population. In the sow population, the mean ADV prevalence in the northern, eastern and western regions decreased to less than 0.5% in the first quarter of 1998, and to approximately 1% in the southern region. For the finishing pig population, the mean ADV prevalence decreased to less than 0.6% in all fourregions in the first quarter of 1998. The proportion of sow herds that were certified ADV‐free increased steadily from approximately 40% in the last quarter of 1996 to 96% in the first quarter of 1999. The proportion of finishing pig herds that were certified ADV‐free showed the same spectacular increase as in the sow population: from approximately 14% in the last quarter of 1996 to 90% in the first quarter of 1999. It is anticipated that the last stage of the ADV eradication campaign, stopping vaccination, will be achieved very soon. Monitoring wild boars for ADV between 1994 and 1999 indicated that ADV is uncommon within the wild boar population. Therefore, it seems that ADV infection in the wild boar population is not an important reservoir in the Netherlands.

Risk factors of new Aujeszky's disease virus infection in swine herds in Brittany (France)

Risk factors of new Aujeszky's disease virus infection in swine herds in Brittany (France)

Development of DNA probe for detection of Aujeszky's disease virus

A DNA hybridization dot-blot assay using a radioactive and a non-radioactive probe has been developed for the detection of Aujeszky's disease virus (ADV). The Bam H I 7 fragment of ADV genomic DNA was labeled by nick translation using 32P-dCTP and the 196bp polymerase chain reaction (PCR) gG glycoprotein gene amplified fragment was also labeled by nick translation but using biotin d-7-dATP. This technique provides a fast and effective means of detecting acute cases of ADV infection but it was unable to detect ADV nucleic acid sequences in trigeminal nerve ganglia of latent infected pigs and mice.

Diagnosis of Aujeszky's Disease Virus Infection in Dogs by Use of Immunohistochemistry andIn‐SituHybridization

Aujeszky's disease (AD) was diagnosed in seven dogs by histological examination, immunohistochemistry and DNA in-situ hybridization. All dogs which lived on two swine farms died spontaneously showing an acute neurological syndrome (hypersalivation, vomiting, pruritus, depression and coma). The most significant histopathological lesion was a non-suppurative encephalitis located in the brain stem, mainly near the floor of the IVth ventricle. Aujeszky's disease virus (ADV) antigen and ADV nucleic acid distribution coincided with the histopathological lesions. However, little ADV antigen and ADV nucleic acid was found in severely damaged areas. A few neurons stained intensely by immunohistochemistry and in-situ hybridization in non-inflammatory areas. Both immunohistochemistry and in-situ hybridization techniques are valid techniques to confirm ADV infection in paraffin-embedded tissues and will be useful for characterizing the pathogenesis of ADV in the central nervous system (CNS) in carnivores.

Immunohistopathological characterization of pig pneumonia caused by a combined Aujeszky's disease virus and Actinobacillus pleuropneumoniae infection

Nine pigs were inoculated endobronchially with Actinobacillus pleuropneumoniae serotype 1 (App-1) 6 days after infection with Aujeszky's disease virus (ADV); four died within 3 days and the remainder were killed after 1-6 days. Immunohistopathologically, there were two types of pneumonic lesion: pleuropneumonia, characterized by coagulative necrosis, oedema and fibrinous thrombosis; and necrotizing interstitial pneumonia, characterized by bronchitis, bronchiolitis and alveolitis. The former type of lesion was associated with App-1 antigen, and the latter with ADV antigen. These results indicated that a combined ADV and App-1 infection produced severe haemorrhagic pleuropneumonia; and that ADV and App-1 each produced a characteristic pneumonic lesion.

Factors associated with the seroprevalence of Aujeszky's disease virus in seropositive breeding herds of Northern Germany during area-wide compulsory vaccination

In January 1990, a programme to eliminate Aujeszky's disease virus (ADV) infection from the swine herds of a pig-dense area of Northern Germany was initiated. The programme was based on intensive compulsory vaccination, with gI-deleted vaccines, of all pigs in the area. The objective of this study was to identify factors which were associated with the odds of gI-seropositive (gI+) versus gI-seronegative breeding female pigs (i.e. pigs with versus those without serological evidence of wild-type ADV infection), in a cross-section of seropositive farrow-to-feeder and farrow-to-finish herds, in the early 2 years of the programme. The study population included a random sample of 170 643 (26.5%) farrow-to-feeder and 79 315 (25%) farrow-to-finish herds in the project area. The within-herd seroprevalence and consequently, the odds of gI+ breeding females were higher in farrow-to-finish than farrow-to-feeder herds. Associations between the odds of gI + females and possible risk factors for each type of herd were evaluated in logistic-binomial regression models. The results of our study demonstrated a beneficial effect of mandatory vaccination of all pigs on the odds of gI + females in both types of herds. The pattern of reduction with time in the odds of gI + females in farrow-to-feeder herds was linear. By contrast, the reduction with time in the odds of gI + females in farrow-to-finish herds was more rapid in the early period of the programme. In farrow-to-feeder herds, there was a negative association between increasing herd size and the odds of gI + females. In farrow-to-finish herds, the odds of gI + females were associated positively with concurrent seropositivity in finishing pigs of the herd and with the density of pigs of the county in which the herd was located.

Factors associated with circulation of Aujeszky's disease virus in fattening herds of an intensively vaccinated area of Northern Germany

In January 1990, a programme to eliminate Aujeszky's disease virus (ADV) infection from the pig farms of an endemically infected, pig-dense area of Northern Germany was initiated. The programme was based on intensive compulsory vaccination (with killed and attenuated glycoprotein (gI)-deleted vaccines) of all pigs in the area. The objective of this study was to determine herd factors associated with the circulation of field strains of ADV in fattening pigs of feeder-to-finish and fattening units of farrow-to-finish herds during the early phase of the campaign. The study reports on data collected in the period June 1990 to November 1991. The study population comprised 391 (74.8%) feeder-to-finish and 132 (25.2%) fattening units of farrow-to-finish herds—a random sample of the total 1048 fattening herds in the area. Forty-six (8.9%) herds had >/ 1 gI-seropositive pigs in the sample (gI + herds). The association between the gI status of the herd and possible risk factors obtained from a questionnaire was assessed by unconditional maximum-likelihood logistic regression. Herd type (feeder-to-finish or farrow-to-finish), pig density of the county in which the herd was located (number of pigs weighing >/ 25 kg km −2, problems with clinical pneumonia, and time since initiation of vaccination in the area were factors significantly ( P < 0.1) associated with ADV infection of the herd. The probability of viral circulation in the herd was inversely related, in a curvilinear fashion, to time between initiation of vaccination in the area and sampling date. The risk of viral circulation decreased rapidly in the first year of the vaccination programme and at a lower rate in the second year. Fattening units of farrow-to-finish herds were three times more likely to have viral circulation among the fattening pigs than feeder-to-finish herds. Herds in counties with more than 320 pigs km −2 had significantly higher odds of showing gI-seropositivity than herds in counties with less than 217 pigs km −2. Also, the respective likelihood of gI-seropositivity was 2 or 2.2 times higher in herds which had reported moderate or severe problems of clinical pneumonia than in herds with no pneumonia problems.

Presence of wild type Aujeszky's disease virus in swine identified as subclinical low-prevalent serological test reactors within qualified virus-negative herds

Subclinical low-prevalent Aujeszky's disease (AD) serological test reactors test reactors are defined as those few swine within a qualified AD virus (ADV)-negative herd that have antibodies to wild type virus. However, clinical signs of the associated diease are not observed in these putatively infected swine or elsewhere in the herd. Twelve such animals, including 7 previously vaccinated with a genetically modified ADV, were identified in Illinois (USA) during a 2.5 year period. The humoral immune responses of the 5 nonvaccinated swine were assessed by an enhanced virus neutralization test and a radioimmunoassay. Anti-ADV antibodies were determined to be present in the serum from 4 of these swine. Attempts to isolate ADV by in vitro and in vivo inculations of cell cultures and weanling mice, respectively, of tonsillar and trigeminal nerve ganglionic tissue preparations from each animal (vaccinated and nonvaccinated) were unsuccessful. Tonsillar and trigeminal nerve ganglionic tissues of each animal were screened for the presecence of wild type and/or vaccine viral genomes by a soluble polymerase chain reaction (PCR) coupled with Southern hybridization. Unique PCR primers were used distinguish between wild type and vaccine viral DNAs. Additional PCR procedure, which amplifiers a portion of the essential and highly conserved viral gp50 gene, also was employed in an effort to detect viral genomes. Wild type viral DNA was found in the tissues from at least 5 of the vaccinated and 3 of the nonvaccinated swine. These results indicate that such animals should be considered as being infected with ADV. Further, these findings emphasize the need to develope highly specific and sensitive antemortem testing methods for accurate assessment of ADV infection in herds containing such subclinical, yet serologically positive, swine.

Spread of Aujeszky's disease virus within pig herds in an intensively vaccinated region.

An intensive vaccination programme with the glycoprotein I (gI) and thymidine kinase-deleted vaccine strain 783 was applied on all the pig farms in a region with a high pig density. To monitor the spread of Aujeszky's disease virus within breeding herds in that region, all the breeding stock in nine herds were examined for antibodies to gI six times at intervals of four months. The prevalence of gI-seropositive sows decreased greatly in all nine herds. The mean percentage of gI-seropositive sows decreased from 56.4 per cent (range 80.0 to 13.6 per cent) at the start, to 20.3 per cent (range 29.1 to 1.6 per cent) after two years. Nevertheless, seroconversions to gI were detected in all the herds, and in six out of the nine breeding herds even during the second year of the study. The intensive regional vaccination apparently did not completely prevent Aujeszky's disease virus infections within these herds. The source of the virus responsible for these infections was not identified. However, because in most herds only a few sows seroconverted, the virus either circulated at a low level within the herds, or its introduction or reactivation did not lead to an extensive spread of the virus.

Herd risk factors for serological evidence of Aujeszky's disease virus infection of breeding sows in northern Germany (1990-1991).

The distribution of herd risk factors with respect to serological evidence of Aujeszky's disease virus (ADV) infection in breeding sows was studied using samples collected in the early phase of an area-wide eradication programme in two districts of Northern Germany (Schleswig-Flensburg and Nordfriesland). The odds of seropositivity in breeding females were 6.5-times higher for herds that purchased replacement gilts compared with herds that introduced gilts from their own inventory. Herds in which confirmed clinical Aujeszky's disease (AD) had occurred during the 1980s had 4.2-times higher odds of seropositive test results compared with herds without clinical outbreaks of AD. The log-odds of a herd having seropositive females increased, in a curvilinear pattern, with increasing herd size. The slope of the log-transformed herd-size line suggested that wind-borne transmission may have been an important route for among-herd transmission of ADV. It was concluded that, in areas with endemically-infected swine herds, the expected level of ADV infection will be highest in regions with large herds and previous clinical outbreaks of AD. This should be taken into account in the design of future area-wide AD-eradication campaigns.

Immunopathology in Aujeszky's disease virus-infected pigs exposed to fluctuating temperatures

Pigs exposed to fluctuating temperatures (high, 30±2°C; low, 4±1°C) were intranasally inoculated with Aujeszky's disease virus (ADV). ADV-infected pigs, exposed to the fluctuating temperatures, showed severe clinical signs and ADV in the nasal secretions persisted longer than in the ADV-infected control pigs kept at the normal temperature (20±2°C). High concentrations of ADV were isolated from nasal secretions on the 1st day after inoculation of the virus. Pathologically, all ADV-infected pigs had non-suppurative encephalitis and trigeminal ganglionitis. The lesions were more widely distributed in pigs exposed to fluctuating temperatures than in infected control pigs. Two infected pigs given the stress had severe malacic foci in the frontal lobe and four of them had prominent interstitial pneumonia. In the pigs exposed to fluctuating temperatures, a significant number of immunoglobulin-containing cells, especially IgM-containing cells, did not respond to ADV infection. A significant ( P<0·01) difference in the number of IgG- and IgM-containing cells was observed between the ADV-infected pigs exposed to the fluctuating temperature and ADV-infected control pigs, respectively. These results demonstrated that the stress of fluctuating temperatures enhanced the susceptibility to ADV infection.

Multiplication and immunogenicity of a temperature-sensitive and thymidine kinase-deficient strain of Aujeszky's disease virus in pigs.

Hysterectomy-produced colostrum-deprived 5- and 27-day-old pigs were inoculated intramuscularly (IM) or intranasally (IN) with the temperature-sensitive and thymidine kinase-deficient ZHtsTK- strain of Aujeszky's disease virus (ADV), and the nasal swabs and organs of the pigs were periodically collected for virus isolation. No abnormal clinical signs were observed in these pigs, except for a mild febrile response. Viral shedding in the nasal swabs with low titers was detected in the pigs inoculated IN between postinoculation day (PID) 1 and 5, but not in those of the pigs inoculated IM. No contact infection, however, occurred in the cohabiting pigs. Viruses with low titers were isolated only from the muscles and lymph nodes at the site of inoculation in the pigs inoculated IM on PID 2 and 4, but not from any organs of the pigs inoculated IN. To investigate the ability of the ZHtsTK- strain to establish a latent infection in pigs, the pigs inoculated IM or IN with the ZHtsTK- strain were treated with prednisolone. No virus was detected in the trigeminal ganglia or the nasal swabs collected after prednisolone treatment by the cocultivation method. The immunological evaluation demonstrated that immunization of pigs with this strain was effective in preventing clinical signs caused by ADV infection. The duration of virus shedding was markedly shortened in immunized pigs, particularly in those immunized twice and the total quantity of virus recovered from immunized pigs was reduced in comparison with unimmunized pigs.