新型猪细小病毒感染的分子流行病学调查

近几年来,世界范围内的猪群出现了多种新型猪细小病毒(porcine parvovirus,PPV)的感染,其中我国南方地区的猪群也出现了不同程度的感染。本研究利用PCR方法对实验室保存的2008—2013年期间的送检病料,进行猪细小病毒2型(PPV2)、PPV3、PPV4、猪类博卡病毒(PBo-likeV)和猪博卡病毒(PBoV)感染的分子流行病学调查,结果显示阳性率依次为46.4%、21.1%、6.8%、12.3%和5.5%。结合PRRSV和PCV2检测结果,并对新型细小病毒与这2种病毒共感染情况进行初步分析,结果显示PPV3和PRRSV、PBo-likeV和PCV2混合感染的几率较高,提示它们在感染过程中可能存在着协同作用。本研究为细小病毒流行病学和致病机理的研究奠定了一定的基础。     

Epidemiologic investigation of an outbreak of goose parvovirus infection in Sweden

An outbreak of goose parvovirus (GPV) infection on a Swedish goose farm in the spring of 2004 increased the mortality rates from 2% in the early unaffected hatches to 90% and 99% respectively in the two hatches following virus introduction and 40% in goslings hatched later in the same breeding season. In this paper we describe the clinical observations, diagnostic procedures, and epidemiologic investigation carried out to elucidate the source of the infection. The diagnosis was confirmed by serology, virus isolation, and sequence analysis of a 493-bp-long fragment of the VP1 gene. Phylogenetically the causative virus was closely related to pathogenic GPV strains isolated in 2003 and 2004 from Poland and the United Kingdom, respectively. The Swedish isolate exhibited less homology with pathogenic strains from Hungary and Asia and with attenuated vaccine strains. The epidemiologic investigation showed that the virus was first introduced to a contract farm (farm A) and then was transferred with newly hatched goslings to the farm that had submitted the birds for necropsy (index farm). The exact time and source of the virus introduction to farm A could not be determined with absolute certainty. Possible sources of the infection included backyard goose eggs that had been delivered to farm A for subcontract incubation and hatching, wild geese that frequented the flock of breeding geese on pasture on farm A, and a clutch of Canada goose eggs (Branta canadensis) that had been produced by wild geese and was hatched in the same machine as the eggs produced by farm A.     

1起猪细小病毒病的PCR诊断与防制

2005年10月,郑州市某猪场发生了一种以初产母猪流产、死产为特征的疾病,经PCR检测猪细小病毒阳性,结合病史和临床症状,诊断为猪细小病毒病。对该猪场采取了综合防制措施,取得了较好的效果。     

Pathogenesis of in utero infection: experimental infection of eight- and ten-week-old porcine fetuses with porcine parvovirus.

Selected numbers of fetuses in each of 4 pregnant gilts were exposed to a porcine parvovirus by injecting the virus into the allantoic fluid at gestation day 56 or 70. The fetuses were examined on postexposure day 7 or 14. When pregnancy was terminated, 2 of 15 exposed fetuses were dead. Several fetuses tested at post-exposure day 14 had hemagglutination-inhibiting antibodies to porcine parvovirus. Virus was detected most frequently and in highest concentration in the parenchymatous organs of thorax and abdomen of fetuses exposed on gestation day 56. A small amount of antigen was in neurons and capillary endothelium of cerebral and cerebellar cortexes.     

人工感染猪胎儿猪细小病毒的强毒复壮及其在猪肾原代细胞上的增殖

猪细小病毒(PPV)强毒，在1～5日龄仔猪肾原代细胞上传代，传至20代左右毒力下降。为保持PPV强毒的毒力，我们用一头妊娠母猪(妊娠48d)做剖腹术。用大剂量的PPV细胞培养物注入猪胎儿的羊膜腔内，人工感染猪胎儿，病毒通过猪胎儿体内的组织进行复制，使毒力增强。术后12d迫杀母猪，取胎儿分离PPV强毒。     

Hormonal changes in sows after induced porcine parvovirus infection in early pregnancy

Hormonal changes, lesions, and virus isolation studies were determined in sows after uterine artery inoculation with porcine parvovirus [( PPV], strain NADL-8) in early pregnancy. Two sows were given PPV on days 14 or 16 and were euthanatized and necropsied on day 35 after twice daily plasma collection for hormone measurement. Parvovirus was given to 4 sows on day 14 and to 4 sows on day 21 with 5 times daily plasma samples collected for 1 week. Sows were examined on days 21 and 28, respectively. Four control sows in each group on days 14 and 21 were given a placebo injection and were similarly studied. All embryos in all but 1 sow given PPV were in various stages of resorption at necropsy. Normal embryos were present in all control sows. Estrone sulfate values increased logarithmically, progesterone values remained stable, and concentrations of 13, 14-dihydro-15-keto-prostaglandin (PG) F2 alpha (PGFM), a PGF2 alpha metabolite, were less than 200 ng/ml for sows given a placebo. In contrast, sows with resorbing embryos did not have an increase in estrone sulfate values. A decrease in plasma progesterone values occurred in 9 of 10 sows inoculated with PPV; this decrease was accompanied by greater than or equal to 1 marked increase in PGFM concentrations. Quantitative assessment of the uterus revealed significantly greater cytoplasmic density in endometrial and glandular cell (P less than 0.01), a greater glandular epithelium height (P less than 0.05), and twice the number of glands (P less than 0.05) in control sows, compared with values in sows inoculated with PPV.(ABSTRACT TRUNCATED AT 250 WORDS)     

一例猪细小病毒病的诊断

从取自某猪场表现初产母猪流产胎儿的肾脏、脾脏、肠系膜淋巴结组织,进行研磨后接种猪原代肾细胞,成功分离到一株病毒。该病毒的豚鼠红细胞血凝活性为27,用针对猪细小病毒结构蛋白VP2的特异性引物对分离病毒进行扩增,将扩增结果进行克隆测序,结果经BLAST分析后,证实分离到一株猪细小病毒。     

Reproduction of postweaning multisystemic wasting syndrome in pigs by prenatal porcine circovirus 2 infection and postnatal porcine parvovirus infection or immunostimulation

Postweaning multisystemic wasting syndrome (PMWS) was reproduced in prenatally porcine circovirus 2 (PCV2)-infected pigs by either postnatal infection with porcine parvovirus (PPV) or by immunostimulation. Twenty-four randomly selected piglets from 3 sows, which had been experimentally infected during gestation with PCV2, were randomly divided into 3 groups; group 1 (prenatal PCV2 infection, with postnatal PPV infection), group 2 (prenatal PCV2 infection, with postnatal keyhole limpet hemocyanin, emulsified in incomplete Freund's adjuvant [KLH/ICFA] injection), and group 3 (prenatal PCV2 infection only). Twenty-four randomly selected piglets from 3 uninfected sows were randomly divided into 3 groups; group 4 (no prenatal infection, with postnatal PCV2 and PPV infection), group 5 (no prenatal infection, with postnatal PCV2 infection), and group 6 (negative control pigs). Body weight in negative control pigs (group 6) was increased significantly compared with pigs in groups 1, 2, and 4 at 49, 52, 56, 59, and 63 days of age. The granulomatous inflammatory reaction and lymphoid depletion that are typical lesions in pigs with PMWS were observed in the lymph node of piglets in groups 1, 2, and 4 at 63 days of age. Pigs in group 3 had significantly fewer PCV2-positive cells than those from groups 1, 2, 4, or 5. When the prenatally PCV2-infected pigs were infected with PPV or injected with immunostimulant in the postnatal period, they developed PMWS. Thus, factors that potentiate the progression of prenatal PCV2 infection to PMWS are postnatal infection with PPV or immune stimulation.     

Experimental in utero infection of pig foetuses with porcine parvovirus (PPV).

Pig foetuses of various gestational ages were exposed to experimental infection with porcine parvovirus (PPV) in utero. Inoculation of 40-, 50- and 60-day-old foetuses with PPV caused foetal death and mummification and spread of the infection to non-inoculated foetuses. Inoculation at 80 and 100 days gestation caused pathological lesions of various degrees whereas spread of infection occurred only sporadically. Serological examinations of foetuses of different ages suggest that immunocompetence for PPV develops before 70 days gestation. The present results strongly indicate that intrauterine spread of PPV is a route of transmission of this virus between pig foetuses.     

Acute reproductive losses due to porcine parvovirus infection in a swine herd: Herd observations and economic analysis of the losses

An acute outbreak of reproductive failure associated with porcine parvovirus (PPV) infection occurred in a swine herd with a group-farrowing system. In Group A, of 35 bred females, 17 (49%) farrowed. Mummification was the predominant sign, increasing from an endemic level of 0.22 per litter in previous farrowing groups to 4.10. Diagnosis of PPV was made from abnormal fetuses in Group A. In the next group (Group B), only 8 of 35 (23%) females bred and farrowed, and they averaged 0.25 mummified fetuses per litter. Remaining sows did not farrow as scheduled and indicated a high incidence of early embryonic resorption. In Group C, 19 females farrowed out of 35 bred (54%), and averaged 0.32 mummified fetuses per litter. Clinical patterns and size of mummified fetuses suggested that PPV infection occurred in Group A during the second third of pregnancy, in Group B during the first third and in Group C prior to mating. An estimation of the net opportunity cost experienced due to this outbreak ($7260.000) is made to emphasize the importance of instituting and maintaining an effective preventive medicine program.     

Experimental infection of 3-week-old conventional colostrum-fed pigs with porcine circovirus type 2 and porcine parvovirus

This report describes an experimental infection with porcine circovirus type 2 (PCV2) in combination with porcine parvovirus (PPV) in 3-week-old conventional colostrum-fed pigs with maternal antibodies to both viruses. Two groups of four pigs each were inoculated with PCV2 and PPV. One of the groups received also a commercial inactivated vaccine against porcine pleuropneumonia to evaluate possible effects of the stimulation of the immune system of pigs on the infection. Another group of four pigs was kept as uninfected control. Clinical signs, rectal temperatures and body weights were recorded. Serum antibody titers to PCV2 and PPV were determined at weekly intervals. Pigs were killed 42 days after inoculation and tissue samples were examined for the presence of gross and microscopic lesions. Tissues were also analyzed for the presence of PCV2 and PPV DNA by PCR, and for the presence of PCV2 antigen by immunohistochemistry (IHC). All the pigs had serum antibodies to PCV2 and PPV at the beginning of the trial. None of them developed clinical symptoms or pathological lesions typical of post-weaning multisystemic wasting syndrome (PMWS), a disease associated to PCV2 infection. However, IHC and/or PCR analyses showed that clinically silent PCV2 infection developed in five of the eight inoculated pigs, regardless of the administration of the vaccine. In particular, PCV2 DNA and/or antigen were detected in most of the tissues examined in the two pigs with the lowest titer of maternal PCV2 antibodies at the beginning of the trial. PPV DNA was not detected in any of the samples examined. The five pigs with PCR and/or IHC evidence of PCV2 infection had a mean weight gain during the experiment lower than that of the inoculated PCR-negative pigs considered together and that of the control pigs. In conclusion, it would appear that passive immunity against PCV2 can play a role in preventing the development of PMWS, but is not able to prevent the establishing of clinically silent PCV2 infections. The dissemination and persistence of the virus in the tissues may depend on the level of PCV2 antibodies at the time of inoculation.     

Interepizootic survival of porcine parvovirus

Porcine parvovirus (PPV) was transmitted by direct contact between experimentally infected and susceptible pigs at 1 and 2 weeks, but not at 4, 8, 16, or 25 weeks, after experimental infection. In contrast, PPV was found to remain infectious for at least 14 weeks in uncleaned rooms previously vacated by experimentally infected pigs. These findings suggest that facilities contaminated by secretions and excretions of infected pigs may provide the major means by which PPV survives between episodes of acute infection.     

Efficacy of porcine parvovirus vaccines

Three inactivated porcine parvovirus vaccines were tested for efficacy in 66 susceptible gilts. The gilts were challenged with virulent virus on the 40th day of gestation. All the vaccines provided excellent protection against fetal mortality despite insignificant serological responses to one of them. Good protection was obtained with two of the vaccines even when the dose was substantially reduced. Unvaccinated controls had very few viable fetuses.     

The effect on reproductive performance of porcine parvovirus infection in a susceptible pig herd

An acute episode of reproductive failure occurred following natural introduction of porcine parvovirus to a susceptible herd of 48 breeding sows. Serological data gave a close estimate of the time that infection spread through the herd, and enabled a correct forecast of the reproductive failure that followed. Severe fetal mummification was seen over a three-week period. Epidemiological data is presented strongly linking in utero parvovirus infection with the mummification that occurred, and the significance of this data is discussed in connection with the present knowledge of transplacental porcine parvovirus infection.     

Clinical, virologic, and histopathologic observations of induced porcine parvovirus infection in boars

Twelve 8- to 12-month-old crossbred boars were inoculated with a virulent strain (NADL-8) of porcine parvovirus (PPV). Hemicastrations were performed on 6 boars 3, 7, 10, 14, 21, and 28 days after an IM injection of 10(8) median cell culture infectious dose (CCID50) of PPV (n = 3) or injection of 10(7.4) CCID50 given intratesticularly (IT, n = 3). Noninfected cell culture medium (0.25 ml) was injected into each testicle of a 7th boar (IT inoculated control). Virus or viral antigen was detected in testicular and epididymal tissues up to 14 days after inoculation. Direct immunofluorescence indicated that viral antigen was mainly associated with the vasculature of the interstitium. Microscopic lesions were not evident in the testicles and epididymides of IM inoculated boars. Acute-to-chronic testicular degeneration was evident in the IT inoculated boars, as well as in the IT inoculated control boar. Six boars were inoculated IM or orally/nasally with 10(7.9) CCID50 of PPV. Semen was collected twice weekly for 8 weeks after inoculation. Virus was not detected in any ejaculates. Semen also was collected from 4 boars for 5 weeks before inoculation, and preinoculation and post-inoculation semen quality was compared. Pronounced changes in sperm output, ejaculate volume, motility, or morphologic defects were not observed. The reproductive consequences of experimental PPV infection in boars were minimal because reproductive function was unaffected and venereal transmission of PPV was not detected.     

Outbreaks of porcine parvovirus disease in Panama

Summary The first recorded isolation of porcine parvovirus (PPV) in Panama is described. The outbreaks of PPV disease were characterised by a high prevalence of mummified foetuses, stillborn and weak pigs and a common source of exposure. Diagnosis was based on virus isolation and by demonstrating viral antigen in lungs of affected foetuses. Six farms in four different provinces were involved. Rapid control of the epizootic was achieved through the use of an inactivated PPV vaccine in the affected farms.

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Resumen Se describe el primer aislamiento de parvovirus porcino (PVP) en Panamá. Los brotes se caracterizaron por una prevalencia alta de fetos momificados, mortinatos y recién nacidos débiles; todos tuvieron una fuente común de exposición. El diagóstico se basó en el aislamiento del virus y en la demostración del antígeno viral en pulmones de los fetos abortados. Seis porquerizas en cuatro provincias differentes estuvieron involucradas. La enfermedad se controló rápidamente en las granjas problema, mediante el use de una vacuna inactivada de PVP.

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Résumé Pour la première fois l'isolation d'un parvovirus porcin au Panama est décrite. Les foyers de cette affection ont été caractérisés par la présence, en grand nombre, de foetus momifiés, de porcelets mort-nés ou très fragiles et une origine commune de contamination. Le diagnostic a reposé sur l'isolement du virus et la reconnaissance de l'antigène viral dans les poumons des foetus. Six élevages dans quatre provinces différentes ont été touchés. L'épizootie a été rapidement ma?trisée grace à l'emploi d'un vaccin parvovirus porcin dans les élevages atteints.

     

Some epidemiological features and effects on reproductive performance of endemic porcine parvovirus infection

The time of development of demonstrable antibody to porcine parvovirus (PPV) was determined for 661 gilts entering the breeding herd in a 2800 sow intensive piggery; 13.2% of these gilts did not have detectable antibody to PPV when first introduced into the breeding herd at 25 to 26 weeks of age. Exposure to PPV was found to vary in different sheds and even in different areas within a shed. Gilts that developed antibody to PPV during the first third of pregnancy were not adversely affected. Those that developed antibody during the middle third of pregnancy had fewer piglets born alive, more stillborn piglets and more mummified foetuses.     

Canine parvovirus infection

Extract

Sir — Referring to M. H. Blunt's letter to the Journal for December, 1980 regarding canine parvovirus disease, I would like to take issue with several points.