The airborne excretion by pigs of swine vesicular disease virus

The air of loose-boxes holding pigs affected with swine vesicular disease was sampled for virus. In the multistage impinger virus to a titre of 10^2·6 TCID 50 was associated with particles greater than 6 μm., 10^1·6 with particles 3-6 μm. and 10^1·4 or less with particles less than 3 μm. In the noses of workers in contact with the pigs for periods not less than 5 min., virus to a titre of 10^2·4 TCID 50 was found. Virus was recovered from the air for 2-3 days during the disease and maximum titre in pigs infected by injection or by contact occurred on the second to third day after generalization of the lesions. The amounts of virus were about 160-fold less than those recovered from pigs affected with foot-and-mouth disease, and the quantity and time of excretion suggest that the source of swine vesicular disease virus in the aerosol may be from the lesions and skin rather than from the respiratory tract.     

防控甲型H1N1流感要有较长时期的思想准备

最近曾光教授提出针对甲型H1N1流感要做好秋季流感大流行的准备.WHO官员也提出警告,对流感疫情不要盲目乐观.甲型H1N1流感正在继续传播,存在巨大不确定因素.     

人感染猪流感

通常猪流感病毒是指在猪群中流行的流感病毒,或从病毒基因进化分析上类似于以往分离的猪流感病毒.1930年Shope和Lemis[1]首次从猪体内分离出流感病毒.1974年Smith等[2]从人体肺组织中分离出猪流感病毒,初次证实猪流感可以跨越种属屏障感染人.自1958年12月至2009年2月,全球共报道至少60例人感染猪流感病例[3,4],多数为散发病例.     

In vivo and in vitro studies on temperature-sensitive mutants of swine vesicular disease virus.

Two temperature-sensitive mutants of the Ukg 27/72 strain of swine vesicular disease virus were isolated in tissue culture and a third was derived following adaptation in mice. All three were found to have similar growth restrictive temperatures, but varied considerably in their virulence when administered to pigs. The route of inoculation appeared to exert a considerable influence on the apparent degree of attenuation, the antibody titre engendered and the transmission of disease to pigs held in contact with inoculated animals. One strain appeared almost totally attenuated when inoculated animals. One strain appeared almost totally attenuated when inoculated into pigs but spread to animals in contact causing severe disease. Virus re-isolated from one such animal was found to have retained its temperature sensitive phenotype, suggesting that virulence in this case was not directly related to temperature sensitivity. Pigs with high antibody titres were found to be susceptible when placed in contact with challenge animals, although the lesions which developed were mild.     

Viral meningitis epidemics and a single,recent, recombinant and anthroponotic origin of swine vesicular disease virus

Background and objectives: Swine vesicular disease virus (SVDV) is a close relative of the human Enterovirus B serotype, coxsackievirus B5. As the etiological agent of a significant emergent veterinary disease, several studies have attempted to explain its origin. However, several key questions remain, including the full biological ancestry of the virus, and its geographical and temporal origin.Methodology: We sequenced near-complete genomes of 27 SVDV and 13 coxsackievirus B5 samples, all originally isolated between 1966 and 2006, and analysed these in conjunction with existing sequences and historical information.Results: While analyses incorporating 24 additional near-complete SVDV genomic sequences indicate clear signs of within-SVDV recombination, all 51 SVDV isolates remain monophyletic. This supports a hypothesis of a single anthroponotic transfer origin. Analysis of individual coding and non-coding regions supports that SVDV has a recombinant origin between coxsackievirus B5 and another Enterovirus B serotype, most likely coxsackievirus A9. Extensive Bayesian sequence-based analysis of the time of the most recent common ancestor of all analysed sequences places this within a few years around 1961. Epidemiological evidence points to China as an origin, but there are no available samples to test this conclusively.Conclusions and implications: Historical investigation and the clinical aspects of the involved Enterovirus B serotypes, makes the current results consistent with a hypothesis stating that SVDV originated through co-infection, recombination, and a single anthroponotic event, during large viral meningitis epidemics around 1960/1961 involving the ancestral serotypes. The exact geographical origin of SVDV may remain untestable due to historical aspects.     

Isotype specific ELISAs to detect antibodies against swine vesicular disease virus and their use in epidemiology

Isotype specific ELISAs to detect antibodies against swine vesicular disease, which may help to estimate the moment of infection, were developed and validated on sera from pigs experimentally infected with four different isolates of swine vesicular disease virus. Virus specific IgM antibodies could be detected from days 3-49 and occasionally up to day 91 after infection. IgG1 antibodies were first detected at day 8 and IgG2 at day 11. IgA antibodies coincided with IgG1 antibodies, but antibody titres varied widely. From the results obtained with the sera from the experimentally infected pigs, we calculated the day at which 50% of the pigs had become positive (D50). A D50 of 5, 4, 12, 12 and 24 days was calculated, respectively, for the appearance of antibodies in the virus neutralization test, the IgM, total IgG, IgG1 and IgG2 ELISA. A D50 of 49 days was calculated for the disappearance of IgM antibodies. The isotype specific ELISAs proved to be valuable tools to study the epidemiology of the disease.     

Prior infection with an H1N1 swine influenza virus partially protects pigs against a low pathogenic H5N1 avian influenza virus

Most humans lack virus neutralizing (VN) and haemagglutination inhibition (HI) antibodies to H5N1 avian influenza viruses (AIVs), but cross-reactive neuraminidase inhibition (NI) antibodies and cell-mediated immune (CMI) responses are common. These immune responses result largely from infections with seasonal human H1N1 influenza viruses, but the protective effect of H1N1 infection-immunity against H5N1 infection has never been examined. To this purpose, we have used the pig model of influenza and a low pathogenic (LP) H5N1 AIV. Pigs were inoculated intranasally with sw/Belgium/1/98 (H1N1) 4 weeks before challenge with duck/Minnesota/1525/81 (H5N1). While the viruses failed to cross-react in HI and VN tests, the H1N1 infection induced high levels of H5N1 cross-reactive NI antibodies. Cross-reactive CMI was demonstrated by measurements of lymphoproliferation and IFN-γ secretion after in vitro restimulation of peripheral blood mononuclear cells. All control pigs showed clinical signs and H5N1 virus isolation from the respiratory tract post-challenge. The H1N1-immune pigs, in contrast, showed a complete clinical protection and only 3 pigs out of 10 were H5N1 virus-positive. In a second and smaller experiment, H1N1 virus infection also conferred cross-protection against a LP H5N2 AIV, while cross-reactive immunity was solely detected in tests for CMI. Our data further support the notion that immunity induced by seasonal human H1N1 influenza virus infection may provide some protection against H5N1 or other H5 AIVs in the absence of neutralizing H5 antibodies. Further studies should reveal whether cross-protection holds against H5N1 viruses that are better adapted to replicate in mammals or with a more distantly related N1.     

Innate immune responses following emergency vaccination against foot-and-mouth disease virus in pigs

Inactivated "emergency" foot-and-mouth disease virus (FMDV) vaccine of high potency will induce early protection against the disease, implying a critical role for innate immune defences. At 3 and 6 days post-vaccination (dpv), there was no evidence of vaccine-induced specific anti-FMDV antibodies (Abs), nor enhanced uptake and destruction of opsonised virus by macrophages. Sera from vaccinates and control animals showed similar capacity to neutralise the virus, and were not different from the pre-vaccination sera. There were also no distinguishable changes in the distribution of the different peripheral blood leucocyte (PBL) subpopulations. Nor was any vaccine-induced increase in production of acute phase proteins noted. In contrast, chemotaxis assays identified an increase in PBL migratory activity which was vaccine-related. Furthermore, sera from 3 days post-vaccination contained elevated chemotactic potential. These results demonstrate that enhanced chemotaxis of cells of the innate immune defences, could play an important role during the early protection induced by emergency FMDV vaccines.     

Swine vesicular disease: pathways of infection.

The pathways of infection in swine vesicular disease have been studied by (i) an estimation of the amounts of virus required to produce infection by different artificial inoculation procedures; (ii) the distribution and amounts of virus in various tissues of pigs killed at intervals after contact infection; (iii) an investigation of the susceptibility to virus infection of pig tissue explants. The results show that pigs can be infected by a number of pathways and that the skin, as the most susceptible tissue, is probably the most frequent route of infection.     

Assessment of a novel recombinant vesicular stomatitis virus with triple mutations in its matrix protein as a vaccine for pigs

Vesicular stomatitis virus (VSV) causes a serious vesicular disease responsible for economic losses in the livestock industry. Currently, there are no suitable vaccines to prevent VSV infection. Although the structural matrix (M) protein of VSV has been shown to be a virulence factor in rodent models, its role in the pathogenicity of VSV infection in livestock species is unknown. We hypothesized that VSV with mutations in the M protein represents a novel live attenuated vaccine candidate. To test this, we introduced mutations into VSV M protein using reverse genetics and assessed their attenuation both in vitro and in pigs, an important natural host of VSV. A recombinant VSV with a triple amino acid mutation in M protein (VSV_MT) demonstrated a significantly reduced ability to inhibit the type I interferon (IFN) signaling pathway and to shutoff host gene expression compared to WT-VSV and a mutant virus with a single amino acid deletion (VSV_ΔM51). Inoculation of pigs with VSV_MT induced no apparent vesicular lesions but stimulated virus-neutralizing antibodies and animals were protected against virulent VSV challenge infection. These data demonstrate that the M protein is an important virulence factor for VSV in swine and VSV_MT represents a novel vaccine candidate for VSV infections in pigs.     

The effect of relative humidity on swine vesicular disease virus in dried films before and during formaldehyde fumigation.

Swine Vesicular Disease virus (SVDV) did not survive drying at high relative humidities (r.h.) but there was little virus loss at low r.h. Purified virus dried in films was inactivated by formaldehyde fumigation only at high r.h. Inactivation was also influenced by the suspending medium from which the virus was dried. Purified virus resuspended in distilled water and then dried, was rapidly killed, but that in tissue culture fluid survived.     

Seasonal infection of Culex mosquitos and swine with Japanese encephalitis virus

A year-round study of the infection rates of JE virus in Culex mosquitos was made during 1970-71 in 2 hamlets in Taoyuan County, China (Province of Taiwan). JE virus was recovered from 5 of 314 pools of C. annulus, and from 1 of 22 pools of C. tritaeniorhynchus; these recoveries occurred during a 14-day period in July 1971. None of the 288 pools of C. p. fatigans, which had been collected between October and April, was positive. In addition, sentinel swine were assessed for antibody and virus. All the pigs became highly immune by 23 July; in each hamlet all the pigs had become infected within 1 week, virus being detected in them for only 1-2 weeks. Virus-positive mosquitos appeared to have obtained their infections at about the time that viraemia was occurring in the sentinel swine. These observations illustrate once again the lower infection rate and shorter duration of virus-positive mosquitos in China (Province of Taiwan) as compared with Japan.     

Lack of significant person-to-person spread of swine influenza-like virus following fatal infection in an immunocompromised child

In February 1982, a four-year-old Nevada girl with acute lymphoblastic leukemia in remission was hospitalized with fulminant pneumonia and died eight days later at a hospital in California. An influenza virus was the only pathogen detected, and was present in both antemortem and postmortem specimens. The virus was closely related antigenically to A/New Jersey/8/76 (H1N1) and had a genome very similar to a contemporary enzootic swine influenza virus. The patient had had no known contact with swine, and the source of infection could not be determined. Only five possible secondary cases could be detected by retrospective investigation of 62 contacts, and there was no evidence of spread to the general community. Swine influenza viruses circulate among pigs in the United States annually, and it is likely that sporadic transmissions to humans will continue to be detected. Nevertheless, person-to-person spread under these circumstances appears to be limited.     

Vaccination of pigs two weeks before infection significantly reduces transmission of foot-and-mouth disease virus

The objective of this study was to investigate whether and at what time interval could vaccination reduce transmission of foot-and-mouth disease virus (FMDV) among pigs. Reduction of virus transmission by vaccination was determined experimentally. Transmission of FMDV was studied in three groups of ten pigs: one non-vaccinated group and two groups that were vaccinated 7 days (-7 dpi) and 14 days before inoculation (-14 dpi), respectively. Five randomly selected pigs from each group were inoculated with FMDV type O Taiwan, while the other five pigs left in the groups were exposed to the inoculated pigs by direct contact. Clinical signs were recorded, virus isolation and RT-PCR were carried out on oropharyngeal fluid (OPF), and the neutralizing antibody titres and the antibody response against non-structural (NS) proteins of FMDV were determined. No virus transmission was observed in the -14 dpi group, whereas virus transmission was observed in all contact pigs affecting both the non-vaccinated and the -7 dpi group. The reproduction ratio R in the -14 dpi vaccinated group was significantly lower than that of the non-vaccinated group. This study confirms the potential of vaccination as an important tool to reduce transmission of FMDV.     

Vaccine-mediated protection of pigs against infection with pandemic H1N1 2009 swine influenza A virus requires a close antigenic match between the vaccine antigen and challenge virus

Swine influenza A virus (SwIV) infection has considerable economic and animal welfare consequences and, because of the zoonotic potential, can also have public health implications. The 2009 pandemic H1N1 ‘swine-origin’ infection is now endemic in both pigs and humans. In Europe, avian-like H1_avN1, human-like H1_huN2, human-like swine H3N2 and, since 2009, pandemic H1N1 (pH1N1) lineage viruses and reassortants, constitute the dominant subtypes. In this study, we used a swine pH1N1 challenge virus to investigate the efficacy of whole inactivated virus vaccines homologous or heterologous to the challenge virus as well as a commercial vaccine. We found that vaccine-mediated protection was most effective when vaccine antigen and challenge virus were homologous and correlated with the specific production of neutralising antibodies and a cellular response to the challenge virus. We conclude that a conventional whole inactivated SwIV vaccine must be antigenically matched to the challenge strain to be an effective control measure.     

上海地区猪戊型肝炎感染状况及病毒序列分析

[目的] 调查上海地区猪戊型肝炎感染现况,掌握上海市猪感染戊型肝炎病毒的型别,以进一步探讨猪戊型肝炎感染与病人感染的可能关系。[方法]采集上海市3个区的不同季度的3月龄猪血样,用ELISA法检测抗-HEV 特异性抗体水平,并用RT-nPCR方法检测猪粪便中HEV病毒,进行RNA核酸序列分析和基因进化树分析。 [结果] 共检测猪血清标本1 798份,HEV抗体阳性率为89．38％;44份猪粪便样品中17份RT、-nPCR为阳性,HEV RNA阳性率为38．64％,病毒序列经同源性分析,与戊型肝炎病毒I、Ⅱ、Ⅲ、Ⅳ型的同源性分别为78．5％-84．0％、76．5％-80．7％、 77．3％-82．7％、84．6％-90．7％,基因进化树的分析显示,病毒序列与HEVⅣ型的ⅣA形成同一分支。[结论] 上海地区的猪戊型肝炎感染率较高,戊型肝炎病毒型别属基因型Ⅳ型。     

Nipah virus infection of pigs in peninsular Malaysia

Between late 1998 and 1999, the spread of a new disease of pigs, characterized by a pronounced respiratory and neurological syndrome, sometimes accompanied by the sudden death of sows and boars, was recorded in pig farms in peninsular Malaysia. The disease appeared to have a close association with an epidemic of viral encephalitis among workers on pig farms. A previously unrecognised paramyxovirus was later identified from this outbreak; this virus was related to, but distinct from, the Hendra virus discovered in Australia in 1994. The new virus was named 'Nipah' and was confirmed by molecular characterization to be the agent responsible for the disease in both humans and pigs. The name proposed for the new pig disease was 'porcine respiratory and neurological syndrome' (also known as 'porcine respiratory and encephalitis syndrome'), or, in peninsular Malaysia, 'barking pig syndrome'. The authors describe the new disease and provide the epidemiological findings recorded among infected pigs. In addition, the control programmes which were instituted to contain the virus in the national swine herd are outlined.